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Wang Y, Liu Z, Zhou W, Wang J, Li R, Peng C, Jiao L, Zhang S, Liu Z, Yu Z, Sun J, Deng Q, Duan S, Tan W, Wang Y, Song L, Guo F, Zhou Z, Wang Y, Zhou L, Jiang H, Yu L. Mast cell stabilizer, an anti-allergic drug, reduces ventricular arrhythmia risk via modulation of neuroimmune interaction. Basic Res Cardiol 2024; 119:75-91. [PMID: 38172251 DOI: 10.1007/s00395-023-01024-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 11/26/2023] [Accepted: 11/27/2023] [Indexed: 01/05/2024]
Abstract
Mast cells (MCs) are important intermediates between the nervous and immune systems. The cardiac autonomic nervous system (CANS) crucially modulates cardiac electrophysiology and arrhythmogenesis, but whether and how MC-CANS neuroimmune interaction influences arrhythmia remain unclear. Our clinical data showed a close relationship between serum levels of MC markers and CANS activity, and then we use mast cell stabilizers (MCSs) to alter this MC-CANS communication. MCSs, which are well-known anti-allergic agents, could reduce the risk of ventricular arrhythmia (VA) after myocardial infarction (MI). RNA-sequencing (RNA-seq) analysis to investigate the underlying mechanism by which MCSs could affect the left stellate ganglion (LSG), a key therapeutic target for modulating CANS, showed that the IL-6 and γ-aminobutyric acid (GABA)-ergic system may be involved in this process. Our findings demonstrated that MCSs reduce VA risk along with revealing the potential underlying antiarrhythmic mechanisms.
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Affiliation(s)
- Yuhong Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Zhihao Liu
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Wenjie Zhou
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Jun Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Rui Li
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Chen Peng
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Liying Jiao
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Song Zhang
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Zhihao Liu
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Zhongyang Yu
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Ji Sun
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Qiang Deng
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Shoupeng Duan
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Wuping Tan
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Yijun Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Lingpeng Song
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Fuding Guo
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Zhen Zhou
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Yueyi Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Liping Zhou
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China
| | - Hong Jiang
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China.
| | - Lilei Yu
- Department of Cardiology, Renmin Hospital of Wuhan University, Hubei Key Laboratory of Autonomic Nervous System Modulation, Cardiac Autonomic Nervous System Research Center of Wuhan University, Taikang Center for Life and Medical Sciences of Wuhan University, Hubei Key Laboratory of Cardiology, Cardiovascular Research Institute of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, 430060, Hubei Province, People's Republic of China.
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Sinn M, Stanoppi M, Hauth F, Fleming JR, Funck D, Mayans O, Hartig JS. Guanidino acid hydrolysis by the human enzyme annotated as agmatinase. Sci Rep 2022; 12:22088. [PMID: 36543883 PMCID: PMC9772407 DOI: 10.1038/s41598-022-26655-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022] Open
Abstract
Guanidino acids such as taurocyamine, guanidinobutyrate, guanidinopropionate, and guanidinoacetate have been detected in humans. However, except for guanidionacetate, which is a precursor of creatine, their metabolism and potential functions remain poorly understood. Agmatine has received considerable attention as a potential neurotransmitter and the human enzyme so far annotated as agmatinase (AGMAT) has been proposed as an important modulator of agmatine levels. However, conclusive evidence for the assigned enzymatic activity is lacking. Here we show that AGMAT hydrolyzed a range of linear guanidino acids but was virtually inactive with agmatine. Structural modelling and direct biochemical assays indicated that two naturally occurring variants differ in their substrate preferences. A negatively charged group in the substrate at the end opposing the guanidine moiety was essential for efficient catalysis, explaining why agmatine was not hydrolyzed. We suggest to rename AGMAT as guanidino acid hydrolase (GDAH). Additionally, we demonstrate that the GDAH substrates taurocyamine, guanidinobutyrate and guanidinopropionate were produced by human glycine amidinotransferase (GATM). The presented findings show for the first time an enzymatic activity for GDAH/AGMAT. Since agmatine has frequently been proposed as an endogenous neurotransmitter, the current findings clarify important aspects of the metabolism of agmatine and guanidino acid derivatives in humans.
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Affiliation(s)
- Malte Sinn
- grid.9811.10000 0001 0658 7699Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - Marco Stanoppi
- grid.9811.10000 0001 0658 7699Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - Franziskus Hauth
- grid.9811.10000 0001 0658 7699Department of Chemistry, University of Konstanz, Konstanz, Germany ,grid.9811.10000 0001 0658 7699Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Konstanz, Germany
| | - Jennifer R. Fleming
- grid.9811.10000 0001 0658 7699Department of Biology, University of Konstanz, Konstanz, Germany
| | - Dietmar Funck
- grid.9811.10000 0001 0658 7699Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - Olga Mayans
- grid.9811.10000 0001 0658 7699Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Konstanz, Germany ,grid.9811.10000 0001 0658 7699Department of Biology, University of Konstanz, Konstanz, Germany
| | - Jörg S. Hartig
- grid.9811.10000 0001 0658 7699Department of Chemistry, University of Konstanz, Konstanz, Germany ,grid.9811.10000 0001 0658 7699Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Konstanz, Germany
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3
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Events Occurring in the Axotomized Facial Nucleus. Cells 2022; 11:cells11132068. [PMID: 35805151 PMCID: PMC9266054 DOI: 10.3390/cells11132068] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/26/2022] [Accepted: 06/27/2022] [Indexed: 01/27/2023] Open
Abstract
Transection of the rat facial nerve leads to a variety of alterations not only in motoneurons, but also in glial cells and inhibitory neurons in the ipsilateral facial nucleus. In injured motoneurons, the levels of energy metabolism-related molecules are elevated, while those of neurofunction-related molecules are decreased. In tandem with these motoneuron changes, microglia are activated and start to proliferate around injured motoneurons, and astrocytes become activated for a long period without mitosis. Inhibitory GABAergic neurons reduce the levels of neurofunction-related molecules. These facts indicate that injured motoneurons somehow closely interact with glial cells and inhibitory neurons. At the same time, these events allow us to predict the occurrence of tissue remodeling in the axotomized facial nucleus. This review summarizes the events occurring in the axotomized facial nucleus and the cellular and molecular mechanisms associated with each event.
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Abstract
SummaryThe present study was conducted to investigate whether several GABAergic drugs could affect immobility in the behavioral “despair” test (swimming test). The subacute (3 injections) treatment with the GABA-B agonist baclofen 0.5 mg/kg (BC05) partially antagonised the antiimmobility action of imipramine (IMI), whereas muscimol 0.00125 mg/kg (MU ; GABA-A agonist) did not affect the imipramine effect on immobility. The highest doses of baclofen alone increased immobility time, and no effect of muscimol alone was observed on this measure. Other experiments indicated that different doses of δ-α-aminovaleric acid (a GABA-B antagonist and GABA-A agonist) or progabide (a GABA A/B agonist with clinical antidepressive properties) did not modify immobility time. On the other hand, sodium valproate (VPA), chronically administered, was effective in reducing the time of immobility of rats in the swimming test, at doses which did not alter motor activity in an open field test. Since there is evidence indicating that valproate can be considered as a GABA-mimetic agent, the present data is consistent with other results showing an antidepressant-like activity of agents which enhance GABAergic transmission.
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Abstract
Here, I recount some adventures that I and my colleagues have had over some 60 years since 1957 studying the effects of drugs and neurotransmitters on neuronal excitability and ion channel function, largely, but not exclusively, using sympathetic neurons as test objects. Studies include effects of centrally active drugs on sympathetic transmission; neuronal action and neuroglial uptake of GABA in the ganglia and brain; the action of muscarinic agonists on sympathetic neurons; the action of bradykinin on neuroblastoma-derived cells; and the identification of M-current as a target for muscarinic action, including experiments to determine its distribution, molecular composition, neurotransmitter sensitivity, and intracellular regulation by phospholipids and their hydrolysis products. Techniques used include electrophysiological recording (extracellular, intracellular microelectrode, whole-cell, and single-channel patch-clamp), autoradiography, messenger RNA and complementary DNA expression, antibody injection, antisense knockdown, and membrane-targeted lipidated peptides. I finish with some recollections about my scientific career, funding, and changes in laboratory life and pharmacology research over the past 60 years.
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Affiliation(s)
- David A. Brown
- Departments of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, United Kingdom
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Villar-Briones A, Aird SD. Organic and Peptidyl Constituents of Snake Venoms: The Picture Is Vastly More Complex Than We Imagined. Toxins (Basel) 2018; 10:E392. [PMID: 30261630 PMCID: PMC6215107 DOI: 10.3390/toxins10100392] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 09/18/2018] [Accepted: 09/20/2018] [Indexed: 12/24/2022] Open
Abstract
Small metabolites and peptides in 17 snake venoms (Elapidae, Viperinae, and Crotalinae), were quantified using liquid chromatography-mass spectrometry. Each venom contains >900 metabolites and peptides. Many small organic compounds are present at levels that are probably significant in prey envenomation, given that their known pharmacologies are consistent with snake envenomation strategies. Metabolites included purine nucleosides and their bases, neurotransmitters, neuromodulators, guanidino compounds, carboxylic acids, amines, mono- and disaccharides, and amino acids. Peptides of 2⁻15 amino acids are also present in significant quantities, particularly in crotaline and viperine venoms. Some constituents are specific to individual taxa, while others are broadly distributed. Some of the latter appear to support high anabolic activity in the gland, rather than having toxic functions. Overall, the most abundant organic metabolite was citric acid, owing to its predominance in viperine and crotaline venoms, where it chelates divalent cations to prevent venom degradation by venom metalloproteases and damage to glandular tissue by phospholipases. However, in terms of their concentrations in individual venoms, adenosine, adenine, were most abundant, owing to their high titers in Dendroaspis polylepis venom, although hypoxanthine, guanosine, inosine, and guanine all numbered among the 50 most abundant organic constituents. A purine not previously reported in venoms, ethyl adenosine carboxylate, was discovered in D. polylepis venom, where it probably contributes to the profound hypotension caused by this venom. Acetylcholine was present in significant quantities only in this highly excitotoxic venom, while 4-guanidinobutyric acid and 5-guanidino-2-oxopentanoic acid were present in all venoms.
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Affiliation(s)
- Alejandro Villar-Briones
- Division of Research Support, Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan.
| | - Steven D Aird
- Division of Faculty Affairs and Ecology and Evolution Unit, Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan.
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Response of the GABAergic System to Axotomy of the Rat Facial Nerve. Neurochem Res 2017; 43:324-339. [PMID: 29164431 DOI: 10.1007/s11064-017-2427-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 09/24/2017] [Accepted: 10/21/2017] [Indexed: 12/31/2022]
Abstract
The responses of inhibitory neurons/synapses to motoneuron injury in the cranial nervous system remain to be elucidated. In this study, we analyzed GABAA receptor (GABAAR) and GABAergic neurons at the protein level in the transected rat facial nucleus. Immunoblotting revealed that the GABAARα1 protein levels in the axotomized facial nucleus decreased significantly 5-14 days post-insult, and these levels remained low for 5 weeks. Immunohistochemical analysis indicated that the GABAARα1-expressing cells were motoneurons. We next examined the specific components of GABAergic neurons, including glutamate decarboxylase (GAD), vesicular GABA transporter (VGAT) and GABA transporter-1 (GAT-1). Immunoblotting indicated that the protein levels of GAD, VGAT and GAT-1 decreased transiently in the transected facial nucleus from 5 to 14 days post-insult, but returned to the control levels at 5 weeks post-insult. Although GABAARα1 protein levels in the transected nucleus did not return to their control levels for 5 weeks post-insult, the administration of glial cell line-derived neurotrophic factor at the cut site significantly ameliorated the reductions. Through these findings, we verified that the injured facial motoneurons suppressed the levels of GABAARα1 protein over the 5 weeks post-insult, presumably due to the deprivation of neurotrophic factor. On the other hand, the levels of the GAD, VGAT and GAT-1 proteins in GABAergic neurons were transiently reduced in the axotomized facial nucleus at 5-14 days post-insult, but recovered at 4-5 weeks post-insult.
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Brown DA. Norman Bowery's discoveries about extrasynaptic and asynaptic GABA systems and their significance. Neuropharmacology 2017; 136:3-9. [PMID: 29128306 DOI: 10.1016/j.neuropharm.2017.11.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 11/04/2017] [Indexed: 11/26/2022]
Abstract
Before discovering the GABA-B receptor, Norman Bowery completed a series of studies on an extrasynaptic or asynaptic "GABA system" in the rat superior cervical sympathetic ganglion. First, he discovered an uptake system for GABA in neuroglial cells in the ganglia and in peripheral nerves, with a different substrate specificity than that in neurons. Second, he showed that accumulated GABA in sympathetic glial cells was metabolized to succinate by a transaminase enzyme. Third, he provided detailed structure-activity information about compounds activating an extrasynaptic GABA-A receptor on neurons in the rat sympathetic ganglion. Fourth, he showed that some amino acid substrates for the neuroglial transporter could indirectly stimulate neurons by releasing GABA from adjacent glial cells, and that GABA could also be released from neuroglial cells by membrane depolarization. In this review, these discoveries are briefly described and updated and some of their implications assessed. This article is part of the "Special Issue Dedicated to Norman G. Bowery".
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Affiliation(s)
- David A Brown
- Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK.
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The influence of midazolam on heart rate arises from cardiac autonomic tones alterations in Burmese pythons, Python molurus. Auton Neurosci 2017; 208:103-112. [PMID: 29104018 DOI: 10.1016/j.autneu.2017.10.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 10/25/2017] [Accepted: 10/25/2017] [Indexed: 11/22/2022]
Abstract
The GABAA receptor agonist midazolam is a compound widely used as a tranquilizer and sedative in mammals and reptiles. It is already known that this benzodiazepine produces small to intermediate heart rate (HR) alterations in mammals, however, its influence on reptiles' HR remains unexplored. Thus, the present study sought to verify the effects of midazolam on HR and cardiac modulation in the snake Python molurus. To do so, the snakes' HR, cardiac autonomic tones, and HR variability were evaluated during four different experimental stages. The first stage consisted on the data acquisition of animals under untreated conditions, in which were then administered atropine (2.5mgkg-1; intraperitoneal), followed later by propranolol (3.5mgkg-1; intraperitoneal) (cardiac double autonomic blockade). The second stage focused on the data acquisition of animals under midazolam effect (1.0mgkg-1; intramuscular), which passed through the same autonomic blockade protocol of the first stage. The third and fourth stages consisted of the same protocol of stages one and two, respectively, with the exception that atropine and propranolol injections were reversed. By comparing the HR of animals that received midazolam (second and fourth stages) with those that did not (first and third stages), it could be observed that this benzodiazepine reduced the snakes' HR by ~60%. The calculated autonomic tones showed that such cardiac depression was elicited by an ~80% decrease in cardiac adrenergic tone and an ~620% increase in cardiac cholinergic tone - a finding that was further supported by the results of HR variability analysis.
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Trist DG, Kenakin TP, Blackburn TP. In memory of Norman Bowery (1944-2016). Curr Opin Pharmacol 2017; 35:89-93. [PMID: 28864032 DOI: 10.1016/j.coph.2017.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 05/25/2017] [Accepted: 05/25/2017] [Indexed: 11/25/2022]
Abstract
This article is in memory of Professor Norman Bowery (1944-2016). Norman was a pharmacologist who spent most of his career researching the pharmacology of γ-aminobutyric acid (GABA). He discovered a novel metabotropic receptor subtype, GABAB, that is pharmacologically, and structurally different from the original ionotropic receptor now designated as GABAA. In his research he also studied the neurotransmitters glutamate and substance P, two molecules whose release in parts of the spinal cord is inhibited by baclofen a GABAB receptor agonist. Norman was interested in the therapeutic potential of interacting with the GABAB receptor, in particular spasticity, pain and absence epilepsy.
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Affiliation(s)
| | - Terry P Kenakin
- Department of Pharmacology, 120 Mason Farm Road, 4009 Genetic Medicine Bldg, Campus Box 7365, UNC-Chapel Hill, Chapel Hill, NC 27599-7365, United States
| | - Thomas P Blackburn
- TPBioventures Ltd., Turnpike House, 1208/1210 London Road, Leigh on Sea, Essex, England SS9 2UA, UK
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Assessment of Methods for the Intracellular Blockade of GABAA Receptors. PLoS One 2016; 11:e0160900. [PMID: 27501143 PMCID: PMC4976935 DOI: 10.1371/journal.pone.0160900] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 07/26/2016] [Indexed: 12/11/2022] Open
Abstract
Selective blockade of inhibitory synaptic transmission onto specific neurons is a useful tool for dissecting the excitatory and inhibitory synaptic components of ongoing network activity. To achieve this, intracellular recording with a patch solution capable of blocking GABAA receptors has advantages over other manipulations, such as pharmacological application of GABAergic antagonists or optogenetic inhibition of populations of interneurones, in that the majority of inhibitory transmission is unaffected and hence the remaining network activity preserved. Here, we assess three previously described methods to block inhibition: intracellular application of the molecules picrotoxin, 4,4’-dinitro-stilbene-2,2’-disulphonic acid (DNDS) and 4,4’-diisothiocyanostilbene-2,2’-disulphonic acid (DIDS). DNDS and picrotoxin were both found to be ineffective at blocking evoked, monosynaptic inhibitory postsynaptic currents (IPSCs) onto mouse CA1 pyramidal cells. An intracellular solution containing DIDS and caesium fluoride, but lacking nucleotides ATP and GTP, was effective at decreasing the amplitude of IPSCs. However, this effect was found to be independent of DIDS, and the absence of intracellular nucleotides, and was instead due to the presence of fluoride ions in this intracellular solution, which also blocked spontaneously occurring IPSCs during hippocampal sharp waves. Critically, intracellular fluoride ions also caused a decrease in both spontaneous and evoked excitatory synaptic currents and precluded the inclusion of nucleotides in the intracellular solution. Therefore, of the methods tested, only fluoride ions were effective for intracellular blockade of IPSCs but this approach has additional cellular effects reducing its selectivity and utility.
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Bowery NG, Doble A, Hill DR, Hudson AL, Shaw J, Turnbull MJ. A Novel Gaba Receptor on Central Neurones. Scott Med J 2016. [DOI: 10.1177/003693308002500436] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The features of γ-aminobutyric acid (GABA) as an inhibitory neurotransmitter are described, together with those of its receptor as defined by both iontophoretic and radiolabelled ligand binding techniques. Evidence is presented supporting the existence of a second GABA receptor at both peripheral nerve endings and within the CNS. At the classical receptor, GABA can produce a depolarisation of the ganglion cell body or mediate hyperpolarisation within the CNS by increasing membrane conductance to chloride ions. At this second receptor GABA acts in a bicuculline-insensitive manner to reduce neurotransmitter outflow. Many GABA analogues active at the classical receptor are inactive at the second receptor but by contrast baclofen which is inactive at the classical receptor is a potent agonist at the novel site.
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Affiliation(s)
- N. G. Bowery
- Department of Pharmacology, St. Thomas's Hospital Medical School, London SE1 7EH and Biology Department, ICI Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG
| | - A. Doble
- Department of Pharmacology, St. Thomas's Hospital Medical School, London SE1 7EH and Biology Department, ICI Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG
| | - D. R. Hill
- Department of Pharmacology, St. Thomas's Hospital Medical School, London SE1 7EH and Biology Department, ICI Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG
| | - A. L. Hudson
- Department of Pharmacology, St. Thomas's Hospital Medical School, London SE1 7EH and Biology Department, ICI Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG
| | - J. Shaw
- Department of Pharmacology, St. Thomas's Hospital Medical School, London SE1 7EH and Biology Department, ICI Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG
| | - M. J. Turnbull
- Department of Pharmacology, St. Thomas's Hospital Medical School, London SE1 7EH and Biology Department, ICI Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG
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Bowery NG. Reflections on more than 30 years association with Hanns. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2015; 73:1-11. [PMID: 25637435 DOI: 10.1016/bs.apha.2014.11.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
I first met Hanns in 1977 and soon learnt of his extraordinary ability as a researcher. He became a friend as well as a mentor providing enthusiasm for my own research. I watched closely over the years how his research uncovered details of the association of the benzodiazepines and GABA and delineated the structural composition of the GABAA receptor associated with the action of individual drugs such as antianxiety and antiepileptic agents. His work produced many important contributions to medicine notable of which was the discovery of the first benzodiazepine antagonists, which are now routinely used in clinical practice. But for me his most important contribution was the discovery of the benzodiazepine receptor. During this time, my group uncovered a novel receptor for GABA and my progress in this work was encouraged and enhanced by discussions with Hanns.
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Affiliation(s)
- Norman G Bowery
- Department of Pharmacology, University of Birmingham Medical School, Edgbaston, United Kingdom.
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Mortensen M, Iqbal F, Pandurangan AP, Hannan S, Huckvale R, Topf M, Baker JR, Smart TG. Photo-antagonism of the GABAA receptor. Nat Commun 2014; 5:4454. [PMID: 25072879 PMCID: PMC4124873 DOI: 10.1038/ncomms5454] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 06/19/2014] [Indexed: 11/23/2022] Open
Abstract
Neurotransmitter receptor trafficking is fundamentally important for synaptic transmission and neural network activity. GABAA receptors and inhibitory synapses are vital components of brain function, yet much of our knowledge regarding receptor mobility and function at inhibitory synapses is derived indirectly from using recombinant receptors, antibody-tagged native receptors and pharmacological treatments. Here we describe the use of a set of research tools that can irreversibly bind to and affect the function of recombinant and neuronal GABAA receptors following ultraviolet photoactivation. These compounds are based on the competitive antagonist gabazine and incorporate a variety of photoactive groups. By using site-directed mutagenesis and ligand-docking studies, they reveal new areas of the GABA binding site at the interface between receptor β and α subunits. These compounds enable the selected inactivation of native GABAA receptor populations providing new insight into the function of inhibitory synapses and extrasynaptic receptors in controlling neuronal excitation.
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Affiliation(s)
- Martin Mortensen
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Favaad Iqbal
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
| | - Arun P. Pandurangan
- Institute of Structural and Molecular Biology, Crystallography/Department of Biological Sciences, Birkbeck College, University of London, London WC1E 7HX, UK
| | - Saad Hannan
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Rosemary Huckvale
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
| | - Maya Topf
- Institute of Structural and Molecular Biology, Crystallography/Department of Biological Sciences, Birkbeck College, University of London, London WC1E 7HX, UK
| | - James R. Baker
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
| | - Trevor G. Smart
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
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Adkins DE, McClay JL, Vunck SA, Batman AM, Vann RE, Clark SL, Souza RP, Crowley JJ, Sullivan PF, van den Oord EJ, Beardsley PM. Behavioral metabolomics analysis identifies novel neurochemical signatures in methamphetamine sensitization. GENES, BRAIN, AND BEHAVIOR 2013; 12:780-91. [PMID: 24034544 PMCID: PMC3922980 DOI: 10.1111/gbb.12081] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 07/22/2013] [Accepted: 08/29/2013] [Indexed: 12/17/2022]
Abstract
Behavioral sensitization has been widely studied in animal models and is theorized to reflect neural modifications associated with human psychostimulant addiction. While the mesolimbic dopaminergic pathway is known to play a role, the neurochemical mechanisms underlying behavioral sensitization remain incompletely understood. In this study, we conducted the first metabolomics analysis to globally characterize neurochemical differences associated with behavioral sensitization. Methamphetamine (MA)-induced sensitization measures were generated by statistically modeling longitudinal activity data for eight inbred strains of mice. Subsequent to behavioral testing, nontargeted liquid and gas chromatography-mass spectrometry profiling was performed on 48 brain samples, yielding 301 metabolite levels per sample after quality control. Association testing between metabolite levels and three primary dimensions of behavioral sensitization (total distance, stereotypy and margin time) showed four robust, significant associations at a stringent metabolome-wide significance threshold (false discovery rate, FDR <0.05). Results implicated homocarnosine, a dipeptide of GABA and histidine, in total distance sensitization, GABA metabolite 4-guanidinobutanoate and pantothenate in stereotypy sensitization, and myo-inositol in margin time sensitization. Secondary analyses indicated that these associations were independent of concurrent MA levels and, with the exception of the myo-inositol association, suggest a mechanism whereby strain-based genetic variation produces specific baseline neurochemical differences that substantially influence the magnitude of MA-induced sensitization. These findings demonstrate the utility of mouse metabolomics for identifying novel biomarkers, and developing more comprehensive neurochemical models, of psychostimulant sensitization.
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Affiliation(s)
- Daniel E. Adkins
- Center for Biomarker Research and Personalized Medicine, Virginia Commonwealth University, Richmond VA, USA
| | - Joseph L. McClay
- Center for Biomarker Research and Personalized Medicine, Virginia Commonwealth University, Richmond VA, USA
| | - Sarah A. Vunck
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond VA, USA
| | - Angela M. Batman
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond VA, USA
| | - Robert E. Vann
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond VA, USA
| | - Shaunna L. Clark
- Center for Biomarker Research and Personalized Medicine, Virginia Commonwealth University, Richmond VA, USA
| | - Renan P. Souza
- Laboratory of Neurosciences, Universidade do Extremo Sul Catarinense, Criciúma, Brazil
| | - James J. Crowley
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill NC, USA
- Institute for Pharmacogenomics and Individualized Therapy, University of North Carolina at Chapel Hill, Chapel Hill NC, USA
| | - Patrick F. Sullivan
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill NC, USA
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
| | - Edwin J.C.G. van den Oord
- Center for Biomarker Research and Personalized Medicine, Virginia Commonwealth University, Richmond VA, USA
| | - Patrick M. Beardsley
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond VA, USA
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Frølund S, Holm R, Brodin B, Nielsen CU. The proton-coupled amino acid transporter, SLC36A1 (hPAT1), transports Gly-Gly, Gly-Sar and other Gly-Gly mimetics. Br J Pharmacol 2011; 161:589-600. [PMID: 20880398 DOI: 10.1111/j.1476-5381.2010.00888.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The intestinal proton-coupled amino acid transporter, SLC36A1, transports zwitterionic α-amino acids and drugs such as vigabatrin, gaboxadol and δ-aminolevulinic acid. We hypothesize that SLC36A1 might also transport some dipeptides. The aim of the present study was to investigate SLC36A1-mediated transport of Gly-Gly and Gly-Gly mimetics, and to investigate Gly-Sar transport via SLC36A1 and the proton-coupled dipeptide/tripeptide transporter, SLC15A1 in Caco-2 cells. EXPERIMENTAL APPROACH Transport of a compound via SLC36A1 was determined by its ability to induce an increase in the inward current of two-electrode voltage clamped SLC36A1 cRNA-injected Xenopus laevis oocytes. SLC36A1-mediated L-[³H]Pro uptake in Caco-2 cells was measured in the absence and presence of Gly-Gly or Gly-Sar. In addition, apical [¹⁴C]Gly-Sar uptake was measured in the absence and presence of the SLC36A1 inhibitor 5-hydroxy-L-tryptophan (5-HTP) or the SLC15A1 inhibitor L-4,4'-biphenylalanyl-L-proline (Bip-Pro). KEY RESULTS In SLC36A1-expressing oocytes, an inward current was induced by Gly-Sar, Gly-Gly, δ-aminolevulinic acid, β-aminoethylglycine, δ-aminopentanoic acid, GABA, Gly and Pro, whereas Val, Leu, mannitol, 5-HTP and the dipeptides Gly-Ala, Gly-Pro and Gly-Phe did not evoke currents. In Caco-2 cell monolayers, the apical uptake of 30 mM Gly-Sar was inhibited by 20 and 22% in the presence of 5-HTP or Bip-Pro, respectively, and by 48% in the presence of both. CONCLUSION AND IMPLICATIONS Our results suggest that whereas Gly-Gly amid bond bioisosteres are widely accepted by the hPAT1 carrier, dipeptides in general are not; and therefore, Gly-Sar might structurally define the size limit of dipeptide transport via SLC36A1.
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Affiliation(s)
- S Frølund
- Department of Pharmaceutics and Analytical Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Copenhagen, Denmark
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Bowery N. Historical Perspective and Emergence of the GABAB Receptor. GABABRECEPTOR PHARMACOLOGY - A TRIBUTE TO NORMAN BOWERY 2010; 58:1-18. [DOI: 10.1016/s1054-3589(10)58001-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Takemura M, Sugiyo S, Moritani M, Kobayashi M, Yonehara N. Mechanisms of orofacial pain control in the central nervous system. ACTA ACUST UNITED AC 2006; 69:79-100. [PMID: 16819148 DOI: 10.1679/aohc.69.79] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Recent advances in the study of pain have revealed somatotopic- and modality-dependent processing and the integration of nociceptive signals in the brain and spinal cord. This review summarizes the uniqueness of the trigeminal sensory nucleus (TSN) in structure and function as it relates to orofacial pain control. The oral nociceptive signal is primarily processed in the rostral TSN above the obex, the nucleus principalis (Vp), and the subnuclei oralis (SpVo) and interpolaris (SpVi), while secondarily processed in the subnucleus caudalis (SpVc). In contrast, the facial nociceptive signal is primarily processed in the SpVc. The neurons projecting to the thalamus are localized mostly in the Vp, moderately in the SpVi, and modestly in the ventrolateral SpVo and the SpVc. Orofacial sensory inputs are modulated in many different ways: by interneurons in the TSN proper, through reciprocal connection between the TSN and rostral ventromedial medulla, and by the cerebral cortex. A wide variety of neuroactive substances, including substance P, gamma-aminobutyric acid, serotonin and nitric oxide (NO) could be involved in the modulatory functions of these curcuits. The earliest expression of NO synthase (NOS) in the developing rat brain is observed in a discrete neuronal population in the SpVo at embryonic day 15. NOS expression in the SpVc is late at postnatal day 10. The neurons receiving intraoral signals are intimately related with the sensorimotor reflexive function through the SpVo. In summary, a better understanding of the trigeminal sensory system--which differs from the spinal system--will help to find potential therapeutic targets and lend to developing new analgesics for orofacial-specific pain with high efficacy and fewer side effects.
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Affiliation(s)
- Motohide Takemura
- Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Yamadaoka, Suita, Japan.
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Lang EJ, Sugihara I, Llinás R. Olivocerebellar modulation of motor cortex ability to generate vibrissal movements in rat. J Physiol 2005; 571:101-20. [PMID: 16357010 PMCID: PMC1805652 DOI: 10.1113/jphysiol.2005.102764] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The vibrissal movements known as whisking are generated in a pulsatile, or non-continuous, fashion and comprise sequences of brief regularly spaced movements. These rhythmic timing sequences imply the existence of periodically issued motor commands. As inferior olivary (IO) neurones generate periodic synchronous discharges that could provide the underlying timing signal, this possibility was tested by determining whether the olivocerebellar system modulates motor cortex (MCtx)-triggered whisker movements in rats. Trains of current pulses were applied to MCtx, and the resulting whisker movements were recorded using a high speed video camera. The evoked movement patterns demonstrated properties consistent with the existence of an oscillatory motor driving rhythm. In particular, movement amplitude showed a bell-shaped dependence on stimulus frequency, with a peak at 11.5+/-2.3 Hz. Moreover, movement trajectories showed harmonic and subharmonic entrainment patterns within specific stimulus frequency ranges. By contrast, movements evoked by facial nerve stimulation showed no such frequency-dependent properties. To test whether the IO was the oscillator in question, IO neuronal properties were modified in vivo by intra-IO picrotoxin injection, which enhances synchronous oscillatory IO activity and reduces its natural frequency. The ensuing changes in the evoked whisker patterns were consistent with these pharmacological effects. Furthermore, in cerebellectomized rats, oscillatory modulation of MCtx-evoked movements was greatly reduced, and intra-IO picrotoxin injections did not affect the evoked movement patterns. Additionally, multielectrode recording of Purkinje cell complex spikes showed a temporal correlation of olivocerebellar activity during MCtx stimulus trains to evoked movement patterns. In sum, the results indicate that MCtx's ability to generate movements is modulated by an oscillatory signal arising in the olivocerebellar system.
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Affiliation(s)
- Eric J Lang
- Department of Physiology and Neuroscience, New York University Medical Center, 550 First Avenue, New York, NY 10016, USA.
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Abstract
In the immature brain, GABA (gamma-aminobutyric acid) is excitatory, and GABA-releasing synapses are formed before glutamatergic contacts in a wide range of species and structures. GABA becomes inhibitory by the delayed expression of a chloride exporter, leading to a negative shift in the reversal potential for choride ions. I propose that this mechanism provides a solution to the problem of how to excite developing neurons to promote growth and synapse formation while avoiding the potentially toxic effects of a mismatch between GABA-mediated inhibition and glutamatergic excitation. As key elements of this cascade are activity dependent, the formation of inhibition adds an element of nurture to the construction of cortical networks.
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Affiliation(s)
- Yehezkel Ben-Ari
- Institut de Neurobiologie de la Méditerranée (INMED), INSERM Unit 29, Parc Scientifique de Luminy, 13273 Marseille Cedex 09, France.
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Kaczyńska K, Szereda-Przestaszewska M. Apnoeic response to stimulation of peripheral GABA receptors in rats. Respir Physiol Neurobiol 2002; 131:189-97. [PMID: 12126920 DOI: 10.1016/s1569-9048(02)00021-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Respiratory effects of intracarotid injection of gamma-amino-butyric acid (GABA) were investigated in two groups of rats. In the first group of 12 rats the effects of GABA were checked in the intact state, following bilateral vagotomy and GABA receptor blockade. The second group consisted of five initially vagotomized rats, challenged with GABA prior to and after bilateral carotid chemodenervation (CSN-cut). All rats were urethane and chloralose anaesthetized and spontaneously breathing. Injection of 39 micromol/kg GABA prior to and after vagotomy induced an expiratory apnoea of, respectively 5.5+/-0.84 sec and 3.9+/-0.6 sec duration (mean+/-S.E.M.), P>0.05 in all 12 rats. In breaths that followed the apnoea tidal volume increased above the control level by 23.3% (P<0.01) and 25.6% (P<0.01) pre- and post-vagotomy, respectively. Blockade of GABA receptors with bicuculline and picrotoxin abolished the inhibition of breathing. In five vagotomized rats with intact carotid sinus nerves (CSNs) intracarotid GABA challenge increased tidal volume by 39% compared with baseline breathing (P<0.05). Section of the CSNs precluded the occurrence of apnoea and undergoing respiratory changes evoked by GABA. Intracarotid GABA caused significant decrease in the mean blood pressure independent of the neural state, but the fall was delayed by CSNs neurotomy. Results of this study indicate that GABA given systemically induces apnoea followed by post-apnoeic hyperventilation. Carotid bodies are required for the ventilatory response to GABA; vagal afferents are not involved in this response.
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Affiliation(s)
- Katarzyna Kaczyńska
- Laboratory of Respiration Physiology, Department of Neurophysiology, Polish Academy of Sciences Medical Research Centre, 5 Pawińskiego Street, 02-106, Warsaw, Poland.
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Koga T, Bradley RM. Biophysical properties and responses to neurotransmitters of petrosal and geniculate ganglion neurons innervating the tongue. J Neurophysiol 2000; 84:1404-13. [PMID: 10980013 DOI: 10.1152/jn.2000.84.3.1404] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The properties of afferent sensory neurons supplying taste receptors on the tongue were examined in vitro. Neurons in the geniculate (GG) and petrosal ganglia (PG) supplying the tongue were fluorescently labeled, acutely dissociated, and then analyzed using patch-clamp recording. Measurement of the dissociated neurons revealed that PG neurons were significantly larger than GG neurons. The active and passive membrane properties of these ganglion neurons were examined and compared with each other. There were significant differences between the properties of neurons in the PG and GG ganglia. The mean membrane time constant, spike threshold, action potential half-width, and action potential decay time of GG neurons was significantly less than those of PG neurons. Neurons in the PG had action potentials that had a fast rise and fall time (sharp action potentials) as well as action potentials with a deflection or hump on the falling phase (humped action potentials), whereas action potentials of GG neurons were all sharp. There were also significant differences in the response of PG and GG neurons to the application of acetylcholine (ACh), serotonin (5HT), substance P (SP), and GABA. Whereas PG neurons responded to ACh, 5HT, SP, and GABA, GG neurons only responded to SP and GABA. In addition, the properties of GG neurons were more homogeneous than those of the PG because all the GG neurons had sharp spikes and when responses to neurotransmitters occurred, either all or most of the neurons responded. These differences between neurons of the GG and PG may relate to the type of receptor innervated. PG ganglion neurons innervate a number of receptor types on the posterior tongue and have more heterogeneous properties, while GG neurons predominantly innervate taste buds and have more homogeneous properties.
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Affiliation(s)
- T Koga
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109-1078, USA
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Malatynska E, Crites GJ, Harrawood D, Goldenberg R, Matheson GK. Antidepressant effects on GABA-stimulated 36Cl(-) influx in rat cerebral cortex are altered after treatment with GABA(A) receptor antisense oligodeoxynucleotides. Brain Res 2000; 869:78-84. [PMID: 10865061 DOI: 10.1016/s0006-8993(00)02354-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Antidepressants act at the GABA(A) receptor to inhibit GABA-stimulated 36Cl(-) influx and GABA reduction of [35S]TBPS binding. This study examined how selective knock-down (via antisense oligodeoxynucleotides, aODNs) of GABA(A) receptor subunits modified antidepressant activity. The specific aODNs used were for the alpha1, beta1, beta2 or gamma2 subunits of the GABA(A) receptor. The aODN microinjections reduced corresponding GABA(A) receptor subunit mRNA levels by 30-40% as assessed by RT-PCR. The inhibitory effect of the antidepressants amitriptyline and mianserin on GABA-stimulated 36Cl(-) influx was decreased after microinjections of alpha1, beta1, or beta2 subunit aODNs but potentiated after microinjections of gamma2 subunit aODNs. This pattern of aODNs effect on amitriptyline and mianserin modulation of GABA-stimulated 36Cl(-) influx was the same for both antidepressants and similar to GABA but different than that of diazepam and bicuculline. We conclude that multiple subunits of the GABA(A) receptor regulate the effect of amitriptyline and mianserin on the GABA(A) receptor chloride ionophore complex. However, the exact identity of the subunit mediating the direct or allosteric modulation of the antidepressant effect on GABA-stimulated 36Cl(-) influx remains unclear.
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Affiliation(s)
- E Malatynska
- Indiana University School of Medicine, Department of Pharmacology and Toxicology, 8600 University Boulevard, Evansville, IN 47712, USA.
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Abstract
1. Imidazole 4-acetic acid (IMA) is a naturally occurring metabolite in brain, although it is unclear what biochemical pathways are involved in its biosynthesis and breakdown. Some evidence, however, suggests that IMA is an oxidation product of histamine. 2. The compound has pronounced neuropharmacological properties, many of which are consistent with an activation of GABA(A) receptors. Indeed, IMA is able to displace [3H]GABA from GABA(A) sites in a potent manner. 3. IMA displays definite partial agonist characteristics as an enhancer of benzodiazepine binding to the GABA(A) receptor complex in membrane preparations. In addition, it has an affinity for GABA(C) receptors, where it seems to act as an antagonist, and perhaps as a weak partial agonist. A third recognition site for IMA in brain is the I1-imidazoline receptor. 4. Parenteral administration to experimental animals leads to a sleep-like state which can often be accompanied by seizures. In addition, central application of IMA has been associated with a dose-related reduction in arterial pressure and sympathetic nervous discharge. 5. No specific receptor site or uptake system for IMA has yet been discovered, adding uncertainty to its role in central nervous system function. Yet the possibility cannot be overlooked that IMA plays a role in regulating blood pressure.
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Affiliation(s)
- G Tunnicliff
- Laboratory of Neurochemistry, Indiana University School of Medicine, Evansville 47712, USA.
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Tohda Y, Ohkawa K, Kubo H, Muraki M, Fukuoka M, Nakajima S. Role of GABA receptors in the bronchial response: studies in sensitized guinea-pigs. Clin Exp Allergy 1998; 28:772-7. [PMID: 9677144 DOI: 10.1046/j.1365-2222.1998.00289.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Gamma-aminobutyric acid (GABA), an important inhibitory neurotransmitter in the mammalian central nervous system, is also found in peripheral tissues, including the lung. GABA has recently been shown to modulate the contraction of airway smooth muscle. OBJECTIVE We studied the effect of GABA on the contractile properties of tracheal smooth muscle by measuring the tension of the trachea isolated from non-sensitized and ovalbumin (OA)-sensitized guinea-pigs under isometric conditions. METHODS Guinea-pigs were sensitized by intraperitoneal doses of OA to prepare a bronchial asthma model. Tracheal spiral rings were prepared from the OA-sensitized as well as normal, non-sensitized guinea-pigs. Using the tracheal preparations, the effects of GABA and GABAa and GABAb receptor agonists (muscimol and baclofen) and antagonists (bicuculline and saclofen) on the basal tone of the trachea and on tracheal contraction induced by electrical field stimulation (EFS) were determined. The effect of GABA on tracheal contraction induced by exogenous acetylcholine was also studied. RESULTS GABA and GABA agonists and antagonists had no effect on the basal tone of normal guinea-pig tracheae. Both GABAa and GABAb receptor agonists, as well as GABA, suppressed EFS-induced contraction of normal guinea-pig tracheae in a reversible, dose-dependent manner. Moreover, this suppression was reserved to the control level by either GABAa and GABAb receptor antagonists. In tracheal spiral ring prepared from OA-sensitized guinea-pigs, GABA and baclofen caused a smaller reversible inhibition of EFS-induced contraction than in normal tracheal spiral ring, while muscimol inhibited EFS-induced tracheal contraction to a similar extent to that observed in normal tracheae. GABA had no effect on the tracheal contractile response to acetylcholine. CONCLUSION The results suggest that there may be a biological mechanism mediated by prejunctional GABAb receptors which attenuates cholinergic contraction of airway smooth muscle and that dysfunction of the receptors may underlie the airway obstruction in asthmatics.
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Affiliation(s)
- Y Tohda
- Fourth Department of Internal Medicine, Kinki University School of Medicine, Osakasayama, Osaka, Japan
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Bowery NG, Hill DR, Hudson AL. Characteristics of GABAB receptor binding sites on rat whole brain synaptic membranes. 1983. Br J Pharmacol 1997; 120:452-67; discussion 450-1. [PMID: 9142424 PMCID: PMC3224330 DOI: 10.1111/j.1476-5381.1997.tb06835.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Saturable binding of (±)-[3H]-baclofen and [3H]-γ-aminobutyric acid ([3H]-GABA) to rat brain crude synaptic membranes has been examined by means of a centrifugation assay. The binding of [3H]-baclofen could be detected in fresh or previously frozen tissue and was dependent on the presence of physiological concentrations of Ca2+ or Mg2+ although a lower affinity Na+-dependent component could also be observed. Both components probably reflect binding to receptor recognition sites. The saturable portion of bound [3H]-baclofen formed 20.3 ± 6.9% of total bound ligand. This could be displaced by GABA (IC50 = 0.04 μm), (–)-baclofen (0.04 μm) and to a much lesser extent by (+)-baclofen (33 μm). Isoguvacine, piperidine-4-sulphonic acid and bicuculline methobromide were inactive (up to 100 μm) and muscimol was only weakly active (IC50 = 12.3 μm). Saturable binding of [3H]-GABA increased on adding CaCl2 or MgSO4 (up to 2.5 Mm and 5.0 Mm respectively) to the Tris-HCl incubation solution. This binding (GABAB site binding) was additional to the bicuculline-sensitive binding of GABA (GABAA site binding) and could be completely displaced by (–)-baclofen (IC50 = 0.13 μm). Increasing the Ca2+ concentration (0 to 2.5 Mm) increased the binding capacity of the membranes without changing their affinity for the ligand. The binding of [3H]-GABA to GABAB sites could be demonstrated in fresh as well as previously frozen membranes with a doubling of the affinity being produced by freezing. Further incubation with the non-ionic detergent Triton-X-100 (0.05% v/v) reduced the binding capacity by 50%. The pharmacological profile of displacers of [3H]-GABA from GABAB sites correlated well with that for [3H]-baclofen displacement. A correlation with data previously obtained in isolated preparations of rat atria and mouse vas deferens was also apparent. It is concluded that [3H]-baclofen or [3H]-GABA are both ligands for the same bicuculline-insensitive, divalent cation-dependent binding sites in the rat brain.
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Bowery N, Hill D, Hudson A. Characteristics of GABAB receptor binding sites on rat whole brain synaptic membranes. Br J Pharmacol 1997. [DOI: 10.1111/j.1476-5381.1997.tb06834.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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29
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Mitchell CK, Redburn DA. GABA and GABA-A receptors are maximally expressed in association with cone synaptogenesis in neonatal rabbit retina. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1996; 95:63-71. [PMID: 8873977 DOI: 10.1016/0165-3806(96)00064-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Previous studies have shown the cone photoreceptors form reciprocal synapses with horizontal cells during the first week after birth in rabbits. These synapses constitute pioneering elements of the developing outer plexiform layer. We now report that antibodies against the alpha-1 and against the beta-2/3 subunits of the GABA-A receptor label a highly restricted sublamina in the developing outer plexiform layer known to contain nascent cone photoreceptor terminals. Staining is relatively weak at birth, increases to maximal levels between postnatal days 5 and 7, and is significantly reduced in the adult. These results support recent calcium imaging studies which have shown that the activation of GABA-A receptors causes an increase in intracellular free calcium in cones, an effect which is observed only at 3-9 days after birth. The transient expression of GABA-A receptors in this region coincides with the period of peak expression of GABA immunoreactivity in horizontal cells. A direct functional link between GABAergic transmission and cone synaptogenesis is suggested by previous reports that GABA-A receptor antagonists cause disruption of cone synaptogenesis. Together these findings support the notion that GABA functions as a developmental neurotransmitter which is produced by horizontal cells and interacts with developing cone axons in order to facilitate synaptic linkage between these two cells types.
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Affiliation(s)
- C K Mitchell
- Department of Opthalmology and Visual Science, University of Texas-Houston Medical School 77030, USA
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30
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Mitchell CK, Rowe-Rendleman CL, Ashraf S, Redburn DA. Calbindin immunoreactivity of horizontal cells in the developing rabbit retina. Exp Eye Res 1995; 61:691-8. [PMID: 8846841 DOI: 10.1016/s0014-4835(05)80020-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Horizontal cells are retinal interneurons that establish inhibitory feedback loops within the outer plexiform layer of the primary visual pathway. Most mammalian retinas contain two types of horizontal cells. A-type horizontal cells have neuritic branches that contact cone photoreceptors exclusively, while the B-type horizontal cells have dendritic branches that contact cones, in addition to axons that form synapses with rod photoreceptors. Immunoreactivity for calbindin, a calcium binding protein involved in calcium transport, was used as a marker for horizontal cells during post-natal development of the rabbit retina. On post-natal days 1, 3 and 5, calbindin immunoreactivity is limited to a single population of A-type horizontal cells. They appear as a monolayer of cells with broad tapering processes, establishing the proximal border of the nascent outer plexiform layer and forming a target for ingrowing cone photoreceptor terminals. The size and density of the cell bodies and the length of neuritic processes are essentially unchanged during this period, which corresponds to the time of peak expression of GABAergic markers in horizontal cells. Coincident with a decrease in GABAergic markers and the completion of cone-to-horizontal cell synaptogenesis by day 7, changes within the horizontal cell mosaic are detected morphometrically. A delayed phase of overall cell growth results in a 70% increase in average somal diameter (representing a 3.7-fold increase in spherical volume), a six-fold increase in mean neurite length and a decrease in cell density to one-third of that found in the newborn. We conclude that the process of terminal differentiation of horizontal cells is not complete until some time after the second post-natal week. Furthermore, the expression of GABAergic markers is associated primarily with early maturational events, whereas expression of calbindin is sustained throughout post-natal development, suggesting a prominent role for calcium dependent mechanisms at all development stages.
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Affiliation(s)
- C K Mitchell
- Department of Ophthalmology and Visual Science, University of Texas-Houston Medical School 77030, USA
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31
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Kitayama S, Nakatsukasa Y, Morita K, Dohi T, Tsujimoto A. Pharmacological evidence for the possible involvement of repetitive action potentials in facilitation by GABA of catecholamine secretion in bovine adrenal chromaffin cells. Br J Pharmacol 1995; 102:706-10. [PMID: 1364842 PMCID: PMC1917939 DOI: 10.1111/j.1476-5381.1991.tb12237.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. gamma-Aminobutyric acid (GABA) evokes catecholamine (CA) secretion and enhances the stimulation-evoked CA secretion via facilitation of Ca2+ entry in a Cl(-)-dependent manner. The present study was designed to investigate further the ionic mechanism of modulation by GABA of CA secretion from adrenal medulla, using a primary culture of bovine chromaffin cells. 2. Tetrodotoxin (TTX), a voltage-sensitive Na+ channel blocker, reduced GABA-evoked CA secretion. 3. Inhibition of the sodium pump by ouabain or removal of extracellular K+ enhanced GABA-evoked CA secretion in a TTX-sensitive manner. 4. Tetraethylammonium (TEA) and cesium, which are known to block some types of K+ channels, markedly enhanced GABA-evoked CA secretion in a concentration-related fashion. TEA-induced enhancement of the GABA-evoked CA secretion was attenuated by TTX or replacement of extracellular Na+ by choline. On the other hand, ouabain accelerated the effect of TEA. 5. TEA and ouabain also enhanced GABA-induced Ca2+ influx and accumulation of cytosolic Ca2+, assessed with 45Ca2+ uptake and quin2 fluorescence. 6. Veratridine increased accumulation of cytosolic Ca2+ in a TTX-sensitive manner. GABA facilitated the veratridine-induced elevation of cytosolic Ca2+ even when the GABA-induced rise of cytosolic Ca2+ levelled off. 7. These results suggest the involvement of repetitive action potentials in modulation of GABA by Ca2+ mobilization and, as a consequence, of the CA secretion in chromaffin cells.
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Affiliation(s)
- S Kitayama
- Department of Pharmacology, Hiroshima University School of Dentistry, Japan
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32
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González Burgos GR, Biali FI, Nicola Siri LC, Cardinali DP. Effect of gamma-aminobutyric acid on synaptic transmission and long-term potentiation in rat superior cervical ganglion. Brain Res 1994; 658:1-7. [PMID: 7834329 DOI: 10.1016/s0006-8993(09)90002-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The effect of gamma-aminobutyric acid (GABA) on synaptic transmission in rat superior cervical ganglion (SCG) was assessed in vitro by extracellular recording. Postganglionic compound action potentials (CAPs) triggered by preganglionic stimulation were blocked in a reversible and concentration-dependent fashion by short, 60 s long, superfusion with GABA (IC50 = 39.3 microM), with the GABAA agonist muscimol (IC50 = 8.7 microM) or with the GABAB agonist baclofen (IC50 = 145 microM). Responses to GABA and muscimol, but not to baclofen, exhibited desensitization after 5 min long superfusions with the drugs. In a long-term potentiation (LTP) paradigm, the degree of potentiation found 30 min after a tetanic train of stimuli (20 Hz for 20 s) was strongly inhibited by GABA (100-250 microM), when superfused at the time of tetanic stimulus or shortly thereafter. The effect of GABA on SCG LTP was mimicked by muscimol but not by baclofen. The results are compatible with the view that GABA exerts overall inhibitory effects in rat SCG, including transmission blockade of single impulses (through activation of GABAA and GABAB receptors) and impairment of activity-dependent potentiation of nicotinic transmission (through activation of GABAA receptors).
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Affiliation(s)
- G R González Burgos
- Departamento de Fisiología, Facultad de Medicina, Unidersidad de Buenos Aires, Argentina
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33
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Ault B, Hildebrand LM. GABAA receptor-mediated excitation of nociceptive afferents in the rat isolated spinal cord-tail preparation. Neuropharmacology 1994; 33:109-14. [PMID: 8183434 DOI: 10.1016/0028-3908(94)90104-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Algogens such as capsaicin, bradykinin, acetylcholine, 5-hydroxytryptamine and potassium ions applied to exposed tail skin of the rat isolated spinal cord-tail preparation evoke a ventral root response consisting of depolarization and spiking activity. L-glutamate and kainate also evoke similar reflexes. All these compounds evoke depolarization of afferent axons or dorsal root ganglion cells. Since GABA depolarizes unmyelinated afferent fibers, the ability of GABA receptor agonists to activate cutaneous nociceptive afferents has been examined. GABA superfused over exposed tail skin evoked a ventral root reflex essentially identical to that produced by capsaicin (3 microM). The EC50 was 27 microM. Muscimol, 3-aminopropane sulphonate, isoguvacine and beta-alanine had effects comparable to GABA, with EC50 values of 9.6, 26, 56 and 870 microM respectively. Baclofen (100 microM) or glycine (10 mM) had no effect. Bicuculline applied to the tail competitively antagonized GABA (Schild slope = -1.03) with a pA2 of 5.8. Spinal application of 1 microM morphine blocked the actions of GABA and capsaicin. These data indicate that GABAA receptors can depolarize and excite nociceptive afferents. GABA could be involved in nociception by contributing to firing of C-fibres, or by analogy to presynaptic inhibition in the spinal cord, may act to decrease neuropeptide transmitter release in cutaneous tissue.
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Affiliation(s)
- B Ault
- Department of Neurosciences, Sterling Winthrop Pharmaceuticals Research Division, Collegeville, PA 19426-0900
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34
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Wolff JR, Joó F, Kása P. Modulation by GABA of neuroplasticity in the central and peripheral nervous system. Neurochem Res 1993; 18:453-61. [PMID: 8474568 DOI: 10.1007/bf00967249] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Apart from being a prominent (inhibitory) neurotransmitter that is widely distributed in the central and peripheral nervous system, gamma-aminobutyric acid (GABA) has turned out to exert trophic actions. In this manner GABA may modulate the neuroplastic capacity of neurons and neuron-like cells under various conditions in situ and in vitro. In the superior cervical ganglion (SCG) of adult rat, GABA induces the formation of free postsynaptic-like densities on the dendrites of principal neurons and enables implanted foreign (cholinergic) nerves to establish functional synaptic contacts, even while preexisting connections of the preganglionic axons persist. Apart from postsynaptic effects, GABA inhibits acetylcholine release from preganglionic nerve terminals and changes, at least transiently, the neurochemical markers of cholinergic innervation (acetylcholinesterase and nicotinic receptors). In murine neuroblastoma cells in vitro, GABA induces electron microscopic changes, which are similar in principle to those seen in the SCG. Both neuroplastic effects of GABA, in situ and in vitro, could be mimicked by sodium bromide, a hyperpolarizing agent. In addition, evidence is available that GABA via A- and/or B-receptors may exert direct trophic actions. The regulation of both types of trophic actions (direct, receptor-mediated vs. indirect, bioelectric activity dependent) is discussed.
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Affiliation(s)
- J R Wolff
- Department of Anatomy, University of Göttingen, Federal Republic of Germany
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35
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Newland CF, Cull-Candy SG. On the mechanism of action of picrotoxin on GABA receptor channels in dissociated sympathetic neurones of the rat. J Physiol 1992; 447:191-213. [PMID: 1317428 PMCID: PMC1176032 DOI: 10.1113/jphysiol.1992.sp018998] [Citation(s) in RCA: 159] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
1. The mechanism of action of picrotoxin on GABA receptor channels in rat sympathetic neurones has been investigated with whole-cell clamp. In addition, the action of picrotoxin on single GABA channels has been examined in outside-out membrane patches from these cells. 2. Picrotoxin, at concentrations which dramatically reduced the amplitude of whole-cell GABA currents, did not alter the spectral time constants or single-channel conductance estimated by analysis of GABA-activated current noise. This was observed at potentials both negative and positive to the GABA reversal potential (i.e. for both inward and outward GABA currents). In control conditions, the slow and fast time constants from GABA noise were 40 +/- 14 ms and 2 +/- 0.4 ms, while the estimated single-channel conductance was 14 +/- 2 pS. In the presence of picrotoxin, the time constants and estimated single-channel conductance were 41 +/- 5 ms, 2.7 +/- 0.6 ms and 15 +/- 2.3 pS. 3. Picrotoxin did not alter the shape of the whole-cell GABA current-voltage relationship, indicating that the steady-state block was not voltage dependent. The lack of effect of picrotoxin on the GABA noise spectra and the lack of outward rectification makes it unlikely that picrotoxin acts by a simple voltage-dependent (or voltage-independent) channel blocking mechanism. In the presence of picrotoxin the reversal potential for GABA remained at approximately 0 mV in symmetrical chloride. 4. Distributions of total burst durations, obtained from single-channel records with low concentrations of GABA, were fitted with three or four exponential components. Picrotoxin had no consistent effect on the time constants of the total burst length distributions. It also did not alter the amplitude of the main conductance state. However, picrotoxin did reduce the frequency of channel openings. 5. The application of brief ionophoretic pulses of GABA, to cells under whole-cell voltage clamp, revealed that the rate of onset of block by picrotoxin was accelerated in the presence of GABA. In the absence of agonist, picrotoxin produced a more slowly equilibrating block. 6. Our data are consistent with a mechanism whereby picrotoxin binds preferentially to an agonist bound form of the receptor and stabilizes an agonist-bound shut state. This could, for example, mean that picrotoxin enhances the occurrence of a desensitized state or an allosterically blocked state.
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Affiliation(s)
- C F Newland
- Department of Pharmacology, University College London
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36
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Okada Y. The distribution and function of gamma-aminobutyric acid (GABA) in the superior colliculus. PROGRESS IN BRAIN RESEARCH 1992; 90:249-62. [PMID: 1631301 DOI: 10.1016/s0079-6123(08)63617-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Laminer analysis of the distribution of GABA and GAD in the superior colliculus has shown that the distribution pattern of GABA within the SC is similar in rabbit, cat, and guinea pig. The highest levels of GABA were found in the superficial gray layer (SGL), averaging 37-40 mmol/kg dry weight. The GABA concentrations in the deep layers were each only half that of the levels in the SGL. The concentrations of both GABA and GAD in the upper half of SGL are the same as those in the substantia nigra and medial forebrain bundle which have the highest amounts of GABA in the CNS. Denervation studies of the fibers projecting to SGL suggest that the GABA concentrated in the SGL is intrinsic to the layer. The results obtained from immunohistochemical and electron microscopic studies on the localization of GABA neurons corresponds well with the regional distribution pattern of GABA and GAD reported here. However, pharmacological and electrophysiological studies do not necessarily accord well with the GABA distribution studies because they indicate that there are many GABA sensitive neurons in both the SGL and DGL. To investigate the role of GABA in the SGL, the effect of GABA and its agonists and antagonists on neurotransmission in SGL has been studied in SC slices in a perfusion system. Bath applied GABA (100 microM to 1 mM) enhanced the amplitude of postsynaptic field potentials (PSP) in SGL in a dose-dependent fashion and at concentrations above 1 mM it depressed the PSP in a dose-dependent fashion. A similar response pattern was obtained with muscimol (0.1-10 microM excitation; greater than 10 microM inhibition). However (-)-baclofen only inhibited the PSP. Bicuculline (1 microM) shifted the dose-response inhibitory curve of GABA to the right, while the excitatory effect was enhanced. These results indicate that GABA has an excitatory and inhibitory action on neurotransmission in the SGL. The nigro-tectal GABAergic fibers terminate in the intermediate and deep layers of SC. Inhibition of GABAergic activity in the SC causes irrepressible saccades made toward the center of the movement field while GABA activation delays and slows saccadic eye movements. Thus, GABA in the SC plays an important role in the control of eye movements. The same GABAergic projection is also related to the propagation of generalized seizures. There exist collicular neurons which suppress the propagation of seizures.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- Y Okada
- Department of Physiology, School of Medicine, Kobe University, Japan
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37
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Friedman DL, Redburn DA. Evidence for functionally distinct subclasses of gamma-aminobutyric acid receptors in rabbit retina. J Neurochem 1990; 55:1189-99. [PMID: 2168933 DOI: 10.1111/j.1471-4159.1990.tb03124.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
gamma-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the mammalian retina, where it serves many roles in establishing complex response characteristics of ganglion cells. We now provide biochemical and physiological evidence that at least three subclasses of GABA receptors (A1, A2, and B) contribute to different types of synaptic integration. Receptor binding studies indicate that approximately three-fourths of the total number of [3H]GABA binding sites in retina are displaced by the GABAA receptor antagonist, bicuculline, whereas one-fourth are displaced by the GABA-B receptor agonist, baclofen. GABAA receptors can be described by a three-site binding model with KD values of 19 nM, 122 nM, and 5.7 microM. Benzodiazepines and barbiturates potentiate binding to the GABAA site, which suggests that significant numbers of GABAA receptors are coupled to regulatory sites for these compounds and thus are classified as GABAA1 receptors. The response to pentobarbital appears to involve a conversion of low-affinity sites to higher-affinity sites, and is reflected in changes in the densities of sites at different affinities. Functional studies were used to establish which of the different receptor subclasses regulate release from cholinergic amacrine cells. Our results show that GABA suppresses light-evoked [3H]acetylcholine release via GABAA2 receptors not coupled to a benzodiazepine or barbiturate regulatory site, and enhances release via GABAB receptors. GABAA1 sites do not appear to control acetylcholine release in rabbit retina.
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Affiliation(s)
- D L Friedman
- Department of Neurobiology and Anatomy, University of Texas Medical School, Houston 77225
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38
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Kitayama S, Morita K, Dohi T, Tsujimoto A. GABAergic modulation of catecholamine release from cultured bovine adrenal chromaffin cells. Evidence for the involvement of Cl(-)-dependent Ca2+ entry. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1990; 341:419-24. [PMID: 1694971 DOI: 10.1007/bf00176334] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The mode by which GABA facilitates the basal and stimulation-evoked catecholamine (CA) release from cultured bovine adrenal chromaffin cells was investigated. Muscimol, a GABAA receptor agonist, facilitated 45Ca uptake in a concentration-related manner. When GABA and acetylcholine (ACh) were simultaneously applied, additive increase in 45Ca uptake was observed. Similar effect on 45Ca uptake was observed in the presence of GABA and veratridine, although 45Ca uptake induced by a rather low concentration of veratridine was more than additively enhanced by GABA. GABA-evoked CA release was also more than additively enhanced by BayK 8644 whereas there was only an additive effect on 45Ca uptake. Substitution of extracellular Cl- by sucrose ("low Cl- medium") during the stimulation with GABA enhanced GABA-evoked CA release. Substitution of extracellular Cl- for more than 1 h abolished GABA-evoked CA release and 45Ca uptake. At this time, the concentration-response curve for veratridine-evoked CA release was shifted to left and GABA no longer enhanced veratridine-evoked CA release at any concentration of veratridine. GABA-induced facilitation of 45Ca uptake in the presence of low concentration of veratridine was also inhibited by long-term treatment with low Cl- medium. These results suggest that the Cl(-)-dependent process linked to GABAA receptor acts on voltage-sensitive Ca2+ channels in chromaffin cells to elicit and modulate CA release.
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Affiliation(s)
- S Kitayama
- Department of Pharmacology, Hiroshima University, School of Dentistry, Japan
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Lim DY, Suh J, Yoo HJ, Kim WS, Kim SB, Lee SK, Lee SI, Hong SP. Influence of gamma-aminobutyric acid on the changes of blood pressure in rats. Korean J Intern Med 1990; 5:23-33. [PMID: 2271508 PMCID: PMC4534999 DOI: 10.3904/kjim.1990.5.1.23] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
This is an attempt to investigate the effect of gamma-aminobutyric acid (GABA), a well-known major inhibitory neurotransmitter in the central nervous system, on the blood pressure response in rats and to elucidate the mechanism of its action. GABA injected into a femoral vein of the rat produced a dose-related fall in blood pressure followed by a secondary pressor response. The depressor response evoked by GABA was clearly blocked by pretreatment with chlorisondamine, diazepam and picrotoxin but was unaffected by atropine, prazosin and debrisoquin. GABA-induced pressor responses were significantly attenuated by pretreatment with prazosin or picrotoxin, while not affected by atropine, diazepam, debrisoquin and chlorisondamine. These experimental data suggest that GABA causes biphasically depressor and pressor responses in rats, and that the hypotensive activity evoked by GABA may be exerted through activation of GABAergic receptors and hypertensive activity due to stimulation of the adrenergic alpha-receptors, which appears to be associated with GABAergic receptors.
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Affiliation(s)
- D Y Lim
- Department of Pharmacology, College of Medicine, Chosun University, Kwang Joo, Korea
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40
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Barbier AJ, Guenaneche F, Lefebvre RA. Influence of GABA and ethylenediamine in the guinea-pig duodenum. JOURNAL OF AUTONOMIC PHARMACOLOGY 1989; 9:279-91. [PMID: 2549072 DOI: 10.1111/j.1474-8673.1989.tb00218.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. GABA induced concentration-dependent transient contractions of the guinea-pig duodenum, but only occasionally evoked small relaxatory responses. The GABA-induced contractions were blocked by atropine and tetrodotoxin but were not influenced by hexamethonium; during electrically evoked twitch contractions, GABA had a concentration-dependent inhibitory effect. 2. The concentration-response curve for the contractile effect of GABA was shifted to the right in a dose-dependent manner by bicuculline and picrotoxin, with a clear reduction of the maximal effect in the presence of picrotoxin. 3. Homotaurine and delta-aminovaleric acid but not baclofen mimicked the GABA-induced contractions; the responses induced by these GABAA receptor agonists were antagonized by atropine, tetrodotoxin and bicuculline. Baclofen concentration-dependently inhibited electrically evoked twitch contractions. 4. Ethylenediamine also had a GABA-like effect, and cross-desensitization developed between GABA and ethylenediamine. 5. The ethylenediamine-induced contractions were not antagonized by thiosemicarbazide; they were reduced by 3-mercaptopropionic acid but the GABA-induced contractions were reduced to the same extent. 6. It is concluded that GABA induces contraction of the guinea-pig duodenum by excitation of GABAA receptors on postganglionic cholinergic neurones; a GABAB receptor-mediated inhibitory effect can be observed during electrically evoked twitch contractions. Ethylenediamine mimicks the GABAA receptor-mediated effect probably by a direct effect on the GABAA receptors.
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Affiliation(s)
- A J Barbier
- Heymans Institute of Pharmacology, University of Gent Medical School, Belgium
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41
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Owen WG, Hare WA. Signal transfer from photoreceptors to bipolar cells in the retina of the tiger salamander. NEUROSCIENCE RESEARCH. SUPPLEMENT : THE OFFICIAL JOURNAL OF THE JAPAN NEUROSCIENCE SOCIETY 1989; 10:S77-87. [PMID: 2594256 DOI: 10.1016/0921-8696(89)90011-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Under conditions of dark-adaptation, in response to weak stimuli, the distal retina behaves as a linear system. During the process of voltage transfer from the rods to the bipolar cells the information encoded in the rod responses is spatially filtered. The spatial filtering is determined by the spatial properties of the receptive field of the bipolar cell. These, in turn, depend upon the spatial properties of three syncytia, those of the receptors, the horizontal cells and the bipolar cells themselves. The response of the bipolar cell to these weak stimuli is a linear difference of two components; a component generated by the receptive field center and a component generated by the receptive field surround. The receptive field surround is misnamed since it extends throughout the receptive field center and contributes to the response of the bipolar cell to stimuli located anywhere within the receptive field. The receptive field surround has the spatial properties that would be expected if it were generated by an input from the horizontal cells to the receptive field center of the bipolar cell. The cellular pathway mediating this input remains unclear though we have evidence that it involves, at least in part, a feedforward pathway from horizontal cells to bipolar cells. If a feedback pathway also exists it is not mediated by the GABAA synapse on the synaptic terminals of the cones.
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Affiliation(s)
- W G Owen
- Department of Biophysics & Medical Physics, University of California, Berkeley 94720
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42
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Arakawa T, Okada Y. Excitatory and inhibitory action of GABA on synaptic transmission in slices of guinea pig superior colliculus. Eur J Pharmacol 1988; 158:217-24. [PMID: 2855312 DOI: 10.1016/0014-2999(88)90070-2] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The laminar distribution of gamma-aminobutyric acid (GABA) in the superior colliculus of the guinea pig was analyzed. The superficial gray layer, especially the upper half, was found to contain the highest amount, 37.4 +/- 1.1 mmol/kg dry. To investigate the role of GABA in the superficial gray layer, the effect of GABA on neurotransmission in the superficial gray layer was studied in superior colliculus slices in a perfusion system. Bath-applied GABA, 100 microM-1 mM, enhanced the amplitude of the postsynaptic field potential (PSP) in the superficial gray layer dose dependently and at concentrations above 1 mM it depressed the PSP dose dependently. A similar response pattern was obtained with muscimol (0.1-10 microM, enhancement; greater than 10 microM, depression). However, (-)-baclofen only inhibited the PSP dose dependently (0.1-1 microM). The excitatory effect of GABA was enhanced at concentrations of nipecotic acid less than 0.5 mM. Bicuculline 1 microM shifted the dose-response curve of GABA to the right and the excitatory effect was also enhanced. These results indicate that GABA has a dual action on neurotransmission in the superficial gray layer: an excitatory effect, possibly mediated by GABAA receptors and an inhibitory effect mediated by both GABAA and GABAB receptors.
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Affiliation(s)
- T Arakawa
- Department of Physiology, Kobe University School of Medicine, Japan
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Kása P, Joó F, Dobó E, Wenthold RJ, Ottersen OP, Storm-Mathisen J, Wolff JR. Heterogeneous distribution of GABA-immunoreactive nerve fibers and axon terminals in the superior cervical ganglion of adult rat. Neuroscience 1988; 26:635-44. [PMID: 3173691 DOI: 10.1016/0306-4522(88)90170-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The distribution of axons and axon varicosities containing GABA was studied in the superior cervical ganglion of rat by light and electron microscopic immunohistochemistry. Two different polyclonal antibodies were used, which had been made against GABA conjugated by glutardialdehyde to bovine serum albumin. GABA-like immunoreactivity occurred in many axons within the cervical sympathetic trunk and in axons and axon varicosities around the principal nerve cells in the superior cervical ganglion. GABA-positive axons were intermingled with non-stained axons, except for a small group of fibers in the trunk where the staining was absent. The rostral part of the ganglion and some scattered patches were more densely innervated by GABA-positive axons than the middle and caudal parts. Within dense areas, some of the large ganglion cells were abundantly surrounded by GABA-positive nerve fibers, while the vicinity of others was devoid of any immunoreactive axon terminals. None of the principal ganglion cells contained GABA-like immunoreactivity, although a class of small cells scattered within the ganglion was stained. Transection of the cervical sympathetic trunk for 11 days caused the disappearance of GABA-like positivity from most of the fibers, and only very little GABA-like staining was revealed in some small cells, which resembled satellite cells. Ultrastructurally, the GABA-positive nerve fibers were unmyelinated. However, their terminal branches and varicosities accumulated around the perikarya and dendrites of certain principal ganglion cells were partly wrapped in glial processes. The present results provide evidence that the superior cervical ganglion of adult rat receives a significant number of GABA-positive axons from the cervical sympathetic trunk and that these axons provide an innervation which is heterogeneously distributed within the superior cervical ganglion and on ganglionic cells. The source and function of the GABA-positive axons remain to be elucidated.
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Affiliation(s)
- P Kása
- Central Research Laboratory, Medical University, Szeged, Hungary
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Schwarz M, Klockgether T, Wüllner U, Turski L, Sontag KH. Delta-aminovaleric acid antagonizes the pharmacological actions of baclofen in the central nervous system. Exp Brain Res 1988; 70:618-26. [PMID: 3384060 DOI: 10.1007/bf00247610] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The action of delta-aminovaleric acid (AVA) on the muscle relaxant properties of baclofen, a GABAB receptor agonist, was investigated in two experimental models: (1) the pathologically increased muscle tone of the gastrocnemius muscle in spastic mutant Han-Wistar rats and (2) the Hoffmann (H)-reflex recorded from plantar foot muscles after electrical stimulation of the tibial nerve in barbiturate (60 mg/kg) anaesthetized rats. In both paradigms coadministration of AVA (500 nmol/5 microliter) antagonized the muscle relaxant action of intrathecally applied baclofen (0.2-2 nmol), but failed to affect the muscle relaxant effects of intrathecally injected muscimol (2-20 nmol). In contrast, coadministration of bicuculline (1 nmol) did block the muscle relaxant action of muscimol, but failed to alter the effects of baclofen. When administered alone, bicuculline (1 nmol), or AVA (500 nmol-2 mumol) were without intrinsic action in both paradigms. In an additional series of experiments we investigated the action of AVA on a supraspinal effect of baclofen. Coadministration of AVA (12.5 nmol/0.5 microliter) in the ventromedial thalamic nucleus antagonized the catalepsy induced by baclofen (ED50 10 pmol/0.5 microliter), as indicated by an increase in ED50 of baclofen by a factor of 4.835 and a parallel shift of the probit-log dosage regression line to the right. The parallel shift seems to be consistent with a competitive mechanism of action of AVA. This study presents evidence that AVA antagonizes central pharmacological actions of baclofen at both spinal and supraspinal sites without affecting the actions of a GABAA agonist, muscimol.
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Affiliation(s)
- M Schwarz
- Max-Planck-Institute for Experimental Medicine, Göttingen, Federal Republic of Germany
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Wüllner U, Klockgether T, Schwarz M, Sontag KH. Behavioral actions of baclofen in the rat ventromedial thalamic nucleus: antagonism by delta-aminovalerate. Brain Res 1987; 422:129-36. [PMID: 3676775 DOI: 10.1016/0006-8993(87)90547-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Baclofen, an agonist at GABAB receptors injected locally into the rat ventromedial thalamic nucleus (VM) induced catalepsy in a dose-dependent, stereospecific and site-specific way. Baclofen-induced catalepsy was accompanied by tonic activity in the electromyogram (EMG) recorded from the gastrocnemius muscle, which is considered to be a measure of limb rigidity. delta-Aminovalerate (delta-AVA) coadministered with baclofen into the VM prevented the development of both catalepsy and limb rigidity. delta-AVA injected alone into the VM was devoid of depressant or stimulating behavioral effects. In contrast to delta-AVA, bicuculline, a GABAA antagonist, failed to antagonize baclofen-induced catalepsy. On the other hand, catalepsy due to local injection of a GABAA agonist, muscimol into the VM was antagonized by bicuculline, but not by delta-AVA. The present results suggest that delta-AVA may be useful as an antagonist of central pharmacological actions of baclofen.
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Affiliation(s)
- U Wüllner
- Max-Planck-Institute for Experimental Medicine, Göttingen, F.R.G
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Eugène D. Fast non-cholinergic depolarizing postsynaptic potentials in neurons of rat superior cervical ganglia. Neurosci Lett 1987; 78:51-6. [PMID: 3039421 DOI: 10.1016/0304-3940(87)90560-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
After the blockade of cholinergic transmission, stimulation of the preganglionic sympathetic trunk elicited fast depolarizing postsynaptic potentials (PSPs) in rat superior cervical ganglia. At 50 min, their amplitude measured intracellularly was 6.9 +/- 1.7 mV and their duration 25.9 +/- 7.6 ms (mean +/- S.D., n = 9 ganglia). The extracellular electrical activity recorded from the postganglionic internal carotid nerve was monophasic and equal to 4.0 +/- 2.2% of the normal activity (mean +/- S.D., n = 12 ganglia). The effects on these PSPs of some postsynaptic receptor antagonists have been tested. Bicuculline decreased the amplitude of the PSPs as well as that of the monophasic extracellular activity, suggesting that GABA could mediate these non-cholinergic synaptic potentials.
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Hills JM, Jessen KR, Mirsky R. An immunohistochemical study of the distribution of enteric GABA-containing neurons in the rat and guinea-pig intestine. Neuroscience 1987; 22:301-12. [PMID: 2819777 DOI: 10.1016/0306-4522(87)90220-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
gamma-Aminobutyric acid (GABA) antiserum was applied to sections of rat and guinea-pig intestine which were subsequently processed to reveal any immunoreactivity using either fluorescence or peroxidase techniques. Immunopositive fibres were demonstrated in stomach, duodenum, ileum and colon of rat and guinea-pig intestine. Myenteric ganglia and nerve bundles in the circular muscle contained immunopositive nerve fibres, while the longitudinal muscle, submucosa and mucosa were only rarely innervated. In favourable sections, immunopositive fibres could be seen running from the myenteric plexus into the circular muscle, thus suggesting that the GABA-immunopositive nerves in the circular muscle originate from neurons in the myenteric plexus. In both rat and guinea-pig, immunoreactive nerve cell bodies were most numerous in the myenteric plexus of the colon. In the rat, immunopositive fibres in the circular muscle were most abundant in the ileum, whereas in the guinea-pig it was the colon circular muscle that was most richly innervated. The results demonstrate that neurons which show GABA immunoreactivity are present along the length of the gastrointestinal tract. Their distribution in both myenteric ganglia and circular muscle is heterogeneous both within and between the two species studied. It is probable that this heterogeneity reflects the diversity and specificity of function of this class of enteric neurons.
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Squires RF, Saederup E. GABAA receptor blockers reverse the inhibitory effect of GABA on brain-specific [35S]TBPS binding. Brain Res 1987; 414:357-64. [PMID: 3040167 DOI: 10.1016/0006-8993(87)90017-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Thirteen substances previously reported to antagonize the electrophysiological effects of gamma-aminobutyric acid (GABA) on neurons also reversed the inhibitory effects of GABA on specific [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to sites on rat brain membranes in vitro with a rank-order of potencies similar to those found in electrophysiological systems (R 5135 greater than pitrazepin greater than bicuculline greater than SR 95103 greater than securinine) confirming the earlier conclusion that GABA inhibits [35S]TBPS binding by acting allosterically on physiologically relevant GABAA receptors. Pitrazepin is the most potent of a series of mono N-aryl piperazines that block GABAA receptors. The new aryl amino pyridazine GABA derivative SR 95531 was about 3-fold more potent than bicuculline and 39-fold more potent than the structurally related SR 95103. Four known GABA antagonists have the same rank orders of potencies as convulsants and as reversers of GABA's inhibitory action on [35S]TBPS binding (bicuculline greater than securinine greater than theophylline greater than caffeine). Reversal of GABA-induced suppression of [35S]TBPS binding provides a simple method for further characterizing GABAA receptors linked to TBPS binding sites, and facilitates identification of convulsants and novel, perhaps selective, GABA antagonists.
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Randle JC, Renaud LP. Actions of gamma-aminobutyric acid on rat supraoptic nucleus neurosecretory neurones in vitro. J Physiol 1987; 387:629-47. [PMID: 3656185 PMCID: PMC1192523 DOI: 10.1113/jphysiol.1987.sp016592] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
1. Intracellular recordings were obtained from thirty-eight rat supraoptic nucleus (s.o.n.) neurosecretory neurones in perfused hypothalamic explants. Changes in membrane potential and conductance were monitored following application of gamma-aminobutyric acid (GABA), and related agonists and antagonists. 2. GABA depressed action potential discharge of all of thirty-five s.o.n. neurones tested and induced either membrane hyperpolarization or depolarization. Neurones that displayed membrane hyperpolarization in response to lower GABA concentrations (30-300 microM) demonstrated a biphasic membrane voltage change with a later depolarizing phase as a response to higher concentrations (up to 3000 microM). 3. GABA (10-3000 microM) induced a prominent concentration-dependent increase in membrane conductance in all neurones. The critical slope for the log-log plot of [GABA] vs. GABA-induced membrane conductance was 1.7, indicating co-operativity in the GABA receptor-induced conductance change. 4. Muscimol (0.3-30 microM) potently mimicked all the effects of GABA. Bicuculline (1-100 microM) antagonized the effects of GABA and muscimol in a competitive manner. 5. Glycine and taurine (1-10 mM) had weak effects, although comparatively similar to those of GABA. These actions were blocked both by bicuculline (100 microM) and by strychnine (1 microM). At higher concentrations (greater than 10 microM), strychnine also antagonized the actions of GABA. 6. In recordings with potassium-acetate-filled micropipettes, the reversal potential of hyperpolarizing membrane voltage responses to GABA was -72.5 +/- 1.5 mV in close agreement (+/- 5 mV) with the reversal potential of inhibitory post-synaptic potentials (i.p.s.p.s) recorded in the same neurones. Depolarizing responses to GABA reversed polarity at -50 +/- 1.6 mV. In recordings with KCl-filled micropipettes, voltage responses to GABA were always depolarizing and reversed near -40.0 +/- 4.3 mV. Similarly, reduction of the concentration of chloride ions in the perfusion medium from 134 to 10.4 mM induced a positive shift of the GABA reversal potential by 40-50 mV. 7. From measurements of input resistance (Rin) and cell time constant (tau O), input capacitance (Cin; representing total membrane capacitance) was calculated as 78.9 +/- 2.1 pF. During responses to GABA or muscimol, decreased Rin was accompanied by a linearly related decrease in tau o indicating that these substances had no effect on the membrane capacitance of s.o.n. neurones.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- J C Randle
- Neuroscience Unit, Montreal General Hospital, Quebec, Canada
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Conzelmann U, Meyer DK. Blockade of gamma-aminobutyric acid-receptors of the B-subtype inhibits the dopamine-induced enhancement of the release of cholecystokinin-like immunoreactivity from slices of rat dorsal caudatoputamen. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1987; 335:541-6. [PMID: 3039381 DOI: 10.1007/bf00169121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
When slices of rat dorsal caudatoputamen (= neostriatum) are incubated in vitro, cholecystokinin-like immunoreactivity (CCK-LI) is released upon addition of veratridine (3.75 mumol/l). This release is affected by dopamine and by gamma-aminobutyric acid (GABA)-receptor agonists. Dopamine enhances the release by stimulating dopamine D2-receptors and decreases it via D1-receptors. GABAA-receptor agonists enhance the veratridine-induced release of CCK-LI, while GABAB-receptor agonists decrease it. In the present investigation, it was examined whether GABA-receptors are involved in the effect which dopamine exerts via D2-receptors. The GABAA-receptor antagonist bicuculline (10 mumol/l) and the blocker of the GABAA-receptor ionophore picrotoxin (1 mumol/l) did not affect the dopamine (0.1 mumol/l)-induced increase in the release of CCK-LI. However, the GABAA-receptor agonist muscimol (1 mumol/l) not only enhanced the release of CCK-LI, but also prevented a further enhancement by dopamine (0.1 mumol/l). This effect of muscimol was blocked by bicuculline (10 mumol/l). In the presence of delta-amino-n-valeric acid (0.1 mmol/l), which has been described to block GABAB-receptors, dopamine no longer enhanced the veratridine-induced release of CCK-LI. delta-Amino-n-valeric acid also inhibited the pronounced enhancement of the release of CCK-LI caused by dopamine (0.1 mumol/l and 1 mumol/l in the presence of the preferential D1-receptor antagonist SCH 23390. The effect of delta-amino-n-valeric acid persisted in the presence of bicuculline (10 mumol/l and 100 mumol/l).(ABSTRACT TRUNCATED AT 250 WORDS)
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