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Rice HC, de Malmazet D, Schreurs A, Frere S, Van Molle I, Volkov AN, Creemers E, Vertkin I, Nys J, Ranaivoson FM, Comoletti D, Savas JN, Remaut H, Balschun D, Wierda KD, Slutsky I, Farrow K, De Strooper B, de Wit J. Secreted amyloid-β precursor protein functions as a GABA BR1a ligand to modulate synaptic transmission. Science 2019; 363:eaao4827. [PMID: 30630900 PMCID: PMC6366617 DOI: 10.1126/science.aao4827] [Citation(s) in RCA: 186] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/30/2018] [Accepted: 11/14/2018] [Indexed: 12/16/2022]
Abstract
Amyloid-β precursor protein (APP) is central to the pathogenesis of Alzheimer's disease, yet its physiological function remains unresolved. Accumulating evidence suggests that APP has a synaptic function mediated by an unidentified receptor for secreted APP (sAPP). Here we show that the sAPP extension domain directly bound the sushi 1 domain specific to the γ-aminobutyric acid type B receptor subunit 1a (GABABR1a). sAPP-GABABR1a binding suppressed synaptic transmission and enhanced short-term facilitation in mouse hippocampal synapses via inhibition of synaptic vesicle release. A 17-amino acid peptide corresponding to the GABABR1a binding region within APP suppressed in vivo spontaneous neuronal activity in the hippocampus of anesthetized Thy1-GCaMP6s mice. Our findings identify GABABR1a as a synaptic receptor for sAPP and reveal a physiological role for sAPP in regulating GABABR1a function to modulate synaptic transmission.
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Affiliation(s)
- Heather C Rice
- VIB Center for Brain & Disease Research, Leuven, Belgium
- Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium
| | - Daniel de Malmazet
- Neuro-Electronics Research Flanders, Leuven, Belgium
- Department of Biology, Leuven Brain Institute, KU Leuven, Leuven, Belgium
| | - An Schreurs
- Brain & Cognition, KU Leuven, Leuven, Belgium
| | - Samuel Frere
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Inge Van Molle
- VIB-VUB Structural Biology Research Center, Brussels, Belgium
| | - Alexander N Volkov
- VIB-VUB Structural Biology Research Center, Brussels, Belgium
- Jean Jeener NMR Centre, VUB, Brussels, Belgium
| | - Eline Creemers
- VIB Center for Brain & Disease Research, Leuven, Belgium
- Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium
| | - Irena Vertkin
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Julie Nys
- VIB Center for Brain & Disease Research, Leuven, Belgium
- Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium
| | - Fanomezana M Ranaivoson
- Child Health Institute of New Jersey, Robert Wood Johnson Medical School, Rutgers University, NJ, USA
| | - Davide Comoletti
- Child Health Institute of New Jersey, Robert Wood Johnson Medical School, Rutgers University, NJ, USA
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, NJ, USA
| | - Jeffrey N Savas
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Han Remaut
- VIB-VUB Structural Biology Research Center, Brussels, Belgium
| | | | - Keimpe D Wierda
- VIB Center for Brain & Disease Research, Leuven, Belgium
- Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium
| | - Inna Slutsky
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Karl Farrow
- Neuro-Electronics Research Flanders, Leuven, Belgium
- Department of Biology, Leuven Brain Institute, KU Leuven, Leuven, Belgium
- VIB, Leuven, Belgium
- imec, Leuven, Belgium
| | - Bart De Strooper
- VIB Center for Brain & Disease Research, Leuven, Belgium.
- Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium
- UK-Dementia Research Institute at University College London, UK
| | - Joris de Wit
- VIB Center for Brain & Disease Research, Leuven, Belgium.
- Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium
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Corradini I, Focchi E, Rasile M, Morini R, Desiato G, Tomasoni R, Lizier M, Ghirardini E, Fesce R, Morone D, Barajon I, Antonucci F, Pozzi D, Matteoli M. Maternal Immune Activation Delays Excitatory-to-Inhibitory Gamma-Aminobutyric Acid Switch in Offspring. Biol Psychiatry 2018; 83:680-691. [PMID: 29146047 DOI: 10.1016/j.biopsych.2017.09.030] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 08/03/2017] [Accepted: 09/11/2017] [Indexed: 12/28/2022]
Abstract
BACKGROUND The association between maternal infection and neurodevelopmental defects in progeny is well established, although the biological mechanisms and the pathogenic trajectories involved have not been defined. METHODS Pregnant dams were injected intraperitoneally at gestational day 9 with polyinosinic:polycytidylic acid. Neuronal development was assessed by means of electrophysiological, optical, and biochemical analyses. RESULTS Prenatal exposure to polyinosinic:polycytidylic acid causes an imbalanced expression of the Na+-K+-2Cl- cotransporter 1 and the K+-Cl- cotransporter 2 (KCC2). This results in delayed gamma-aminobutyric acid switch and higher susceptibility to seizures, which endures up to adulthood. Chromatin immunoprecipitation experiments reveal increased binding of the repressor factor RE1-silencing transcription (also known as neuron-restrictive silencer factor) to position 509 of the KCC2 promoter that leads to downregulation of KCC2 transcription in prenatally exposed offspring. Interleukin-1 receptor type I knockout mice, which display braked immune response and no brain cytokine elevation upon maternal immune activation, do not display KCC2/Na+-K+-2Cl- cotransporter 1 imbalance when implanted in a wild-type dam and prenatally exposed. Notably, pretreatment of pregnant dams with magnesium sulfate is sufficient to prevent the early inflammatory state and the delay in excitatory-to-inhibitory switch associated to maternal immune activation. CONCLUSIONS We provide evidence that maternal immune activation hits a key neurodevelopmental process, the excitatory-to-inhibitory gamma-aminobutyric acid switch; defects in this switch have been unequivocally linked to diseases such as autism spectrum disorder or epilepsy. These data open the avenue for a safe pharmacological treatment that may prevent the neurodevelopmental defects caused by prenatal immune activation in a specific pregnancy time window.
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Affiliation(s)
- Irene Corradini
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy; Institute of Neuroscience - National Research Council, Milan, Italy
| | - Elisa Focchi
- Institute of Neuroscience - National Research Council, Milan, Italy; Department of Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Marco Rasile
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy; Hunimed University, Rozzano, Italy
| | - Raffaella Morini
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy
| | - Genni Desiato
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy; University of Milano-Bicocca, Milan, Italy
| | - Romana Tomasoni
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy
| | - Michela Lizier
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy; Institute for Genetic and Biomedical Research - National Research Council, Milan, Italy
| | - Elsa Ghirardini
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy; Department of Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Riccardo Fesce
- Hunimed University, Rozzano, Italy; Neuroscience Center, Dipartimento di Scienze Teoriche e Applicate, Insubria University, Busto Arsizio, Italy
| | - Diego Morone
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy
| | | | - Flavia Antonucci
- Department of Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Davide Pozzi
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy; Hunimed University, Rozzano, Italy
| | - Michela Matteoli
- Istituto di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano, Italy; Institute of Neuroscience - National Research Council, Milan, Italy.
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Imbrosci B, Mittmann T. Functional consequences of the disturbances in the GABA-mediated inhibition induced by injuries in the cerebral cortex. Neural Plast 2011; 2011:614329. [PMID: 21766043 PMCID: PMC3135051 DOI: 10.1155/2011/614329] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2011] [Accepted: 04/05/2011] [Indexed: 11/18/2022] Open
Abstract
Cortical injuries are often reported to induce a suppression of the intracortical GABAergic inhibition in the surviving, neighbouring neuronal networks. Since GABAergic transmission provides the main source of inhibition in the mammalian brain, this condition may lead to hyperexcitability and epileptiform activity of cortical networks. However, inhibition plays also a crucial role in limiting the plastic properties of neuronal circuits, and as a consequence, interventions aiming to reestablish a normal level of inhibition might constrain the plastic capacity of the cortical tissue. A promising strategy to minimize the deleterious consequences of a modified inhibitory transmission without preventing the potential beneficial effects on cortical plasticity may be to unravel distinct GABAergic signaling pathways separately mediating these positive and negative events. Here, gathering data from several recent studies, we provide new insights to better face with this "double coin" condition in the attempt to optimize the functional recovery of patients.
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Affiliation(s)
- Barbara Imbrosci
- Institute of Physiology and Pathophysiology, Medical Center of the Johannes Gutenberg University, Duesbergweg 6, 55128 Mainz, Germany.
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Theile JW, Morikawa H, Gonzales RA, Morrisett RA. Ethanol enhances GABAergic transmission onto dopamine neurons in the ventral tegmental area of the rat. Alcohol Clin Exp Res 2008; 32:1040-8. [PMID: 18422836 DOI: 10.1111/j.1530-0277.2008.00665.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Activation of the dopaminergic (DA) neurons of the ventral tegmental area (VTA) by ethanol has been implicated in its rewarding and reinforcing effects. At most central synapses, ethanol generally increases inhibitory synaptic transmission; however, no studies have explored the effect of acute ethanol on GABAergic transmission in the VTA. METHODS Whole-cell patch clamp recordings of inhibitory postsynaptic currents (IPSCs) from VTA-DA neurons in midbrain slices from young rats. RESULTS Acute exposure of VTA-DA neurons to ethanol (25 to 50 mM) robustly enhanced GABAergic spontaneous and miniature IPSC frequency while inducing a slight enhancement of spontaneous IPSC (sIPSC) amplitude. Ethanol (50 mM) enhanced paired-pulse depression of evoked IPSCs, further suggesting enhanced GABA release onto VTA-DA neurons. The frequency of sIPSCs was suppressed by the GABA(B) agonist, baclofen (1.25 microM) and enhanced by the antagonist, SCH50911 (20 microM); however, neither appeared to modulate or occlude the effects of ethanol on sIPSC frequency. CONCLUSIONS The present results indicate that ethanol increases postsynaptic GABA(A) receptor sensitivity, enhances action potential-independent GABA release onto VTA-DA neurons, and that this latter effect is independent of GABA(B) auto-receptor inhibition of GABA release.
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Affiliation(s)
- Jonathan W Theile
- Cell and Molecular Biology, The University of Texas at Austin, PHAR-Pharmacology, 1 University Station, A1915, Austin, TX 78712-0125, USA.
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Barbaresi P. Cellular and subcellular localization of the GABAB receptor 1a/b subunit in the rat periaqueductal gray matter. J Comp Neurol 2007; 505:478-92. [DOI: 10.1002/cne.21509] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Liu X, Tribollet E, Raggenbass M. GABA(B) receptor-activation inhibits GABAergic synaptic transmission in parvocellular neurones of rat hypothalamic paraventricular nucleus. J Neuroendocrinol 2006; 18:177-86. [PMID: 16454801 DOI: 10.1111/j.1365-2826.2005.01402.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The paraventricular nucleus of the hypothalamus contains three classes of neurones: (i) magnocellular and (ii) parvocellular neurosecretory neurones and (iii) nonendocrine projection neurones. The present study aimed to determine whether functional GABA(B) receptors are present on axon terminals that synapse with parvocellular neurosecretory and nonendocrine paraventricular neurones and to determine how activation of GABA(B) receptors control GABAergic input to these neurones. Whole-cell recordings were performed in coronal hypothalamic slices of the rat containing the paraventricular nucleus. GABA(A) receptor-mediated inhibitory postsynaptic currents (i.p.s.c.) were isolated pharmacologically in the presence of antagonists of glutamatergic ionotropic receptors. We found that baclofen, an agonist of GABA(B) receptors, decreased the frequency of spontaneous and miniature i.p.s.c. It also decreased the amplitude of evoked i.p.s.c. These effects were suppressed by CGP55845A, a competitive antagonist of GABA(B) receptors. CGP55845A also increased the frequency of miniature i.p.s.c. and the amplitude of evoked i.p.s.c., suggesting that, in physiological conditions, presynaptic GABA(B) receptors exert a tonic inhibition on GABA release. Baclofen had no effect on GABA-evoked postsynaptic currents, suggesting that the baclofen-dependent suppression of GABAergic i.p.s.c. was exclusively due to a presynaptic action of the agonist. Our data indicate that GABA(B) receptors are present on axon terminals of GABAergic presynaptic neurones contacting parvocellular neurosecretory and nonendocrine paraventricular neurones, and suggest that GABA(B) receptors exert a tonic inhibition of GABA release from GABAergic terminals. Activation of these receptors causes disinhibition of parvocellular neurosecretory and nonendocrine paraventricular neurones.
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Affiliation(s)
- X Liu
- Department of Basic Neuroscience, University Medical Centre, Geneva, Switzerland
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Giustizieri M, Bernardi G, Mercuri NB, Berretta N. Distinct mechanisms of presynaptic inhibition at GABAergic synapses of the rat substantia nigra pars compacta. J Neurophysiol 2005; 94:1992-2003. [PMID: 15944237 DOI: 10.1152/jn.00171.2005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the mechanisms of presynaptic inhibition of GABAergic neurotransmission by group III metabotropic glutamate receptors (mGluRs) and GABA(B) receptors, in dopamine (DA) neurons of the substantia nigra pars compacta (SNc). Both the group III mGluRs agonist L-(+)-2-amino-4-phosphonobutyric acid (AP4, 100 microM) and the GABA(B) receptor agonist baclofen (10 microM) reversibly depressed the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) to 48.5 +/- 2.7 and 79.3 +/- 1.6% (means +/- SE) of control, respectively. On the contrary, the frequency of action potential-independent miniature IPSCs (mIPSCs), recorded in tetrodotoxin (TTX, 1 microM) and cadmium (100 microM) were insensitive to AP4 but were reduced by baclofen to 49.7 +/- 8.6% of control. When the contribution of voltage-dependent calcium channels (VDCCs) to synaptic transmission was boosted with external barium (1 mM), AP4 became effective in reducing TTX-resistant mIPSCs to 65.4 +/- 3.9% of control, thus confirming a mechanism of presynaptic inhibition involving modulation of VDCCs. Differently from AP4, baclofen inhibited to 58.5 +/- 6.7% of control the frequency mIPSCs recorded in TTX and the calcium ionophore ionomycin (2 microM), which promotes Ca2+-dependent, but VDCC-independent, transmitter release. Moreover, in the presence of alpha-latrotoxin (0.3 nM), to promote a Ca2+-independent vesicular release of GABA, baclofen reduced mIPSC frequency to 48.1 +/- 3.2% of control, while AP4 was ineffective. These results indicate that group III mGluRs depress GABA release to DA neurons of the SNc through inhibition of presynaptic VDCCs, while presynaptic GABA(B) receptors directly impair transmitter exocytosis.
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Affiliation(s)
- Michela Giustizieri
- Centro Europeo di Ricerca sul Cervello Fondazione Santa Lucia Istituto di Ricovero e Cura a Carattere Scientifico, Via del Fosso di Fiorano, 64, 00143 Rome, Italy
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Bettler B, Kaupmann K, Mosbacher J, Gassmann M. Molecular structure and physiological functions of GABA(B) receptors. Physiol Rev 2004; 84:835-67. [PMID: 15269338 DOI: 10.1152/physrev.00036.2003] [Citation(s) in RCA: 640] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
GABA(B) receptors are broadly expressed in the nervous system and have been implicated in a wide variety of neurological and psychiatric disorders. The cloning of the first GABA(B) receptor cDNAs in 1997 revived interest in these receptors and their potential as therapeutic targets. With the availability of molecular tools, rapid progress was made in our understanding of the GABA(B) system. This led to the surprising discovery that GABA(B) receptors need to assemble from distinct subunits to function and provided exciting new insights into the structure of G protein-coupled receptors (GPCRs) in general. As a consequence of this discovery, it is now widely accepted that GPCRs can exist as heterodimers. The cloning of GABA(B) receptors allowed some important questions in the field to be answered. It is now clear that molecular studies do not support the existence of pharmacologically distinct GABA(B) receptors, as predicted by work on native receptors. Advances were also made in clarifying the relationship between GABA(B) receptors and the receptors for gamma-hydroxybutyrate, an emerging drug of abuse. There are now the first indications linking GABA(B) receptor polymorphisms to epilepsy. Significantly, the cloning of GABA(B) receptors enabled identification of the first allosteric GABA(B) receptor compounds, which is expected to broaden the spectrum of therapeutic applications. Here we review current concepts on the molecular composition and function of GABA(B) receptors and discuss ongoing drug-discovery efforts.
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Affiliation(s)
- Bernhard Bettler
- Pharmazentrum, Dept. of Clinical-Biological Sciences, Institute of Physiology, Univ. of Basel, Klingelbergstr. 50, CH-4056 Basel, Switzerland.
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Axmacher N, Stemmler M, Engel D, Draguhn A, Ritz R. Transmitter Metabolism as a Mechanism of Synaptic Plasticity: A Modeling Study. J Neurophysiol 2004; 91:25-39. [PMID: 13679396 DOI: 10.1152/jn.00797.2003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The nervous system adapts to experience by changes in synaptic strength. The mechanisms of synaptic plasticity include changes in the probability of transmitter release and in postsynaptic responsiveness. Experimental and neuropharmacological evidence points toward a third variable in synaptic efficacy: changes in presynaptic transmitter concentration. Several groups, including our own, have reported changes in the amplitude and frequency of postsynaptic (miniature) events indicating that alterations in transmitter content cause alterations in vesicular transmitter content and vesicle dynamics. It is, however, not a priori clear how transmitter metabolism will affect vesicular transmitter content and how this in turn will affect pre- and postsynaptic functions. We therefore have constructed a model of the presynaptic terminal incorporating vesicular transmitter loading and the presynaptic vesicle cycle. We hypothesize that the experimentally observed synaptic plasticity after changes in transmitter metabolism puts predictable restrictions on vesicle loading, cytoplasmic–vesicular transmitter concentration gradient, and on vesicular cycling or release. The results of our model depend on the specific mechanism linking presynaptic transmitter concentration to vesicular dynamics, that is, alteration of vesicle maturation or alteration of release. It also makes a difference whether differentially filled vesicles are detected and differentially processed within the terminal or whether vesicle filling acts back onto the terminal by presynaptic autoreceptors. Therefore, the model allows one to decide, at a given synapse, how transmitter metabolism is linked to presynaptic function and efficacy.
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Affiliation(s)
- Nikolai Axmacher
- Johannes-Müller-Institut für Physiologie, Humboldt-Universität Berlin, 10117 Berlin, Germany
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Chen R. Interactions between inhibitory and excitatory circuits in the human motor cortex. Exp Brain Res 2003; 154:1-10. [PMID: 14579004 DOI: 10.1007/s00221-003-1684-1] [Citation(s) in RCA: 353] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2003] [Accepted: 07/15/2003] [Indexed: 12/13/2022]
Abstract
Cortical activity depends on the balance between excitatory and inhibitory influences. Several different excitatory and inhibitory systems in the human motor cortex can be tested by transcranial magnetic stimulation (TMS). While considerable information is known about these different inhibitory and excitatory phenomena individually, how they are related to each other and how they interact is not well understood. Several recent studies have investigated the interactions between some of these circuits by applying them together. It has been found that short-interval intracortical inhibition (SICI) and long-interval intracortical inhibition (LICI) are mediated by different circuits. LICI appears to inhibit SICI, which may occur through presynaptic GABA(B) receptors. Interhemispheric inhibition elicited by stimulation of the contralateral motor cortex also inhibits SICI and may share inhibitory mechanisms with LICI. Long-interval afferent inhibition induced by median nerve stimulation inhibits LICI but does not interact with SICI. Based on these results, a model of interactions between different inhibitory systems that can be tested and refined in the future is proposed. Further studies of the interaction between different cortical inhibitory and excitatory circuits should improve our understanding of the functional organization of the motor cortex and allow better interpretation of abnormal findings in disease states. It may also be developed into a new way of studying the pathophysiology of diseases and the effects of intervention.
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Affiliation(s)
- Robert Chen
- Division of Neurology and Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Ontario, Canada.
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Kubota H, Katsurabayashi S, Moorhouse AJ, Murakami N, Koga H, Akaike N. GABAB receptor transduction mechanisms, and cross-talk between protein kinases A and C, in GABAergic terminals synapsing onto neurons of the rat nucleus basalis of Meynert. J Physiol 2003; 551:263-76. [PMID: 12815184 PMCID: PMC2343138 DOI: 10.1113/jphysiol.2003.046524] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The transduction mechanisms underlying presynaptic GABAB receptor-mediated inhibition of transmitter release have been characterized for a variety of synapses in the central nervous system (CNS). These studies have suggested a range of transduction mechanisms, including a role for second messengers such as protein kinases A (PKA) and C (PKC). In the present study, we have examined the intracellular signalling pathways underlying baclofen-induced inhibition of GABA release from terminals synapsing onto rat basalis of Meynert neurons using patch-clamp recordings. Baclofen, a selective GABAB receptor agonist, reversibly decreased both evoked and spontaneous, miniature, GABAergic inhibitory postsynaptic currents (eIPSCs and mIPSCs, respectively). Such baclofen actions were completely abolished by CGP55845A, a selective GABAB receptor antagonist, and by staurosporine, a non-selective PKA and PKC inhibitor. The mIPSC frequency was still decreased by baclofen even in the presence of 4 AP, a K+ channel blocker, and Cd2+, a voltage-dependent calcium channel blocker. Pharmacological activation or inhibition of PKC activity affected basal GABA release and mildly affected the response to baclofen. Inhibition of the cAMP/PKA cascade also affected basal GABA release and, in a subset of neurons, occluded the effects of baclofen, suggesting that the GABAB receptor-mediated inhibitory action on GABA release was mediated via decreases in PKA activity. In addition, PKA inhibition occluded the effects of PKC modulation on both basal GABA release and on the response to baclofen. Our results characterize the transduction pathway of baclofen at these nucleus basalis of Maynert (nBM) synapses and show, for the first time, some cross-talk between the cAMP/PKA and PKC pathways in mammalian presynaptic nerve terminals.
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Affiliation(s)
- Hisahiko Kubota
- Cellular and System Physiology, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Fukuoka 812-8582, Japan
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O'Shaughnessy TJ, Zim B, Ma W, Shaffer KM, Stenger DA, Zamani K, Gross GW, Pancrazio JJ. Acute neuropharmacologic action of chloroquine on cortical neurons in vitro. Brain Res 2003; 959:280-6. [PMID: 12493616 DOI: 10.1016/s0006-8993(02)03763-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Chloroquine, a common quinolone derivative used in the treatment of malaria, has been associated with neurologic side-effects including depression, psychosis and delirium. The neuropharmacologic effects of chloroquine were examined on cultured cortical neurons using microelectrode array (MEA) recording and the whole-cell patch clamp technique. Whole-cell patch clamp records under current-clamp mode also showed a chloroquine-induced depression of the firing rate of spontaneous action potentials by approximately 40%, consistent with the observations with the MEA recording, although no changes in either the baseline membrane potential or input resistance were observed. Voltage clamp recordings of spontaneous post-synaptic currents, recorded in the presence of tetrodotoxin, revealed no obvious changes in either the amplitude or rate of occurrence of inward currents with application of chloroquine at 10 microM, suggesting that the fundamental molecular mechanisms underlying spontaneous synaptic transmission may not be affected by acute application of the drug. In contrast, a concentration-dependent inhibition of whole-cell calcium current was observed in the presence of chloroquine. These acute neuropharmacologic changes were not accompanied by cytotoxic actions of the compound, even after exposure of up to 500 microM chloroquine for 7 h. These data suggest that chloroquine can depress in vitro neuronal activity, perhaps through inhibition of membrane calcium channels.
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Affiliation(s)
- Thomas J O'Shaughnessy
- Center for Bio/Molecular Science and Engineering, Code 6910, Naval Research Laboratory, Washington, DC 20375, USA
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Daskalakis ZJ, Christensen BK, Fitzgerald PB, Roshan L, Chen R. The mechanisms of interhemispheric inhibition in the human motor cortex. J Physiol 2002; 543:317-26. [PMID: 12181302 PMCID: PMC2290496 DOI: 10.1113/jphysiol.2002.017673] [Citation(s) in RCA: 341] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2002] [Accepted: 05/23/2002] [Indexed: 11/08/2022] Open
Abstract
Transcranial magnetic stimulation can be used to non-invasively study inhibitory processes in the human motor cortex. Interhemispheric inhibition can be measured by applying a conditioning stimulus to the motor cortex resulting in inhibition of the contralateral motor cortex. Transcranial magnetic stimulation can also be used to demonstrate ipsilateral cortico-cortical inhibition in the motor cortex. At least two different ipsilateral cortico-cortical inhibitory processes have been identified: short interval intracortical inhibition and long interval intracortical inhibition. However, the relationship between interhemispheric inhibition and ipsilateral cortico-cortical inhibition remains unclear. This study examined the relationship between interhemispheric inhibition, short interval intracortical inhibition and long interval intracortical inhibition. First, the effect of test stimulus intensity on each inhibitory process was studied. Second, the effects of interhemispheric inhibition on short interval intracortical inhibition and long interval intracortical inhibition on interhemispheric inhibition were examined. Motor evoked potentials were recorded from the right first dorsal interosseous muscle in 11 right-handed healthy volunteers. For interhemispheric inhibition, conditioning stimuli were applied to the right motor cortex and test stimuli to the left motor cortex. For short interval intracortical inhibition and long interval intracortical inhibition, both conditioning stimuli and test stimuli were applied to the left motor cortex. With increasing test stimulus intensities, long interval intracortical inhibition and interhemispheric inhibition decreased, while short interval intracortical inhibition increased. Moreover, short interval intracortical inhibition was significantly reduced in the presence of interhemispheric inhibition. Interhemispheric inhibition was significantly reduced in the presence of long interval intracortical inhibition when matched for test motor evoked potential amplitude but the difference was not significant when matched for test pulse intensity. These findings suggest that both interhemispheric inhibition and long interval intracortical inhibition are predominately mediated by low threshold cortical neurons and may share common inhibitory mechanisms. In contrast, the mechanisms mediating short interval intracortical inhibition are probably different from those mediating long interval intracortical inhibition and interhemispheric inhibition although these systems appear to interact.
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Abstract
Although studies in the visual cortex have found gamma-aminobutyric acid B (GABA(B)) receptor-mediated pre- and postsynaptic inhibitory effects on neurons, the subcellular localization of GABA(B) receptors in different types of cortical neurons and synapses has not been shown directly. To provide this information, we have used antibodies against the GABA(B) receptor (R)1a/b and GABA(B)R2 subunits and have studied the localization of immunoreactivities in rat visual cortex. Light microscopic analyses have shown that both subunits are expressed in cell bodies and dendrites of 65-92% of corticocortically projecting pyramidal neurons and in 92-100% of parvalbumin (PV)-, calretinin (CR)-, and somatostatin (SOM)-containing GABAergic neurons. Electron microscopic analyses of immunoperoxidase- and immunogold-labeled tissue revealed staining in the nucleus, cytoplasm and cell surface membranes with both antibodies. Colocalization of both subunits was observed in all of these structures. GABA(B)R1a/b and GABA(B)R2 were concentrated in excitatory and inhibitory synapses and in extrasynaptic membranes. In GABAergic synapses, GABA(B)R1a/b and GABA(B)R2 were more strongly expressed postsynaptically on pyramidal and nonpyramidal cells than presynaptically. In type 1 synapses GABA(B)R1a/b and GABA(B)R2 was found in pre- and postsynaptic membranes. The nuclear localization of GABA(B)R1 and GABA(B)R2 subunits suggests a novel role for neurotransmitter receptors in controlling gene expression. The synaptic colocalization of GABA(B)R1 and GABA(B)R2 indicates that subunits form heteromeric assemblies of the functional receptor in inhibitory and excitatory synapses. Subunit coexpression in GABAergic synapses that include PV-containing and PV-deficient terminals suggests that pre- and postsynaptic GABA(B) receptor activation is provided by several different types of interneurons. The coexpression of both subunits in excitatory synapses suggests a role for GABA(B) receptors in the regulation of glutamate release and raises the question how these receptors are activated in the absence of pre-or postsynaptic GABAergic synaptic inputs to excitatory synapses.
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Affiliation(s)
- Y Gonchar
- Department of Anatomy and Neurobiology, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
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A furosemide-sensitive K+-Cl- cotransporter counteracts intracellular Cl- accumulation and depletion in cultured rat midbrain neurons. J Neurosci 1999. [PMID: 10366603 DOI: 10.1523/jneurosci.19-12-04695.1999] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Efficacy of postsynaptic inhibition through GABAA receptors in the mammalian brain depends on the maintenance of a Cl- gradient for hyperpolarizing Cl- currents. We have taken advantage of the reduced complexity under which Cl- regulation can be investigated in cultured neurons as opposed to neurons in other in vitro preparations of the mammalian brain. Tightseal whole-cell recording of spontaneous GABAA receptor-mediated postsynaptic currents suggested that an outward Cl- transport reduced dendritic [Cl-]i if the somata of cells were loaded with Cl- via the patch pipette. We determined dendritic and somatic reversal potentials of Cl- currents induced by focally applied GABA to calculate [Cl-]i during variation of [K+]o and [Cl-] in the patch pipette. [Cl-]i and [K+]o were tightly coupled by a furosemide-sensitive K+-Cl- cotransport. Thermodynamic considerations excluded the significant contribution of a Na+-K+-Cl- cotransporter to the net Cl- transport. We conclude that under conditions of normal [K+]o the K+-Cl- cotransporter helps to maintain [Cl-]i at low levels, whereas under pathological conditions, under which [K+]o remains elevated because of neuronal hyperactivity, the cotransporter accumulates Cl- in neurons, thereby further enhancing neuronal excitability.
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Jarolimek W, Lewen A, Misgeld U. A furosemide-sensitive K+-Cl- cotransporter counteracts intracellular Cl- accumulation and depletion in cultured rat midbrain neurons. J Neurosci 1999; 19:4695-704. [PMID: 10366603 PMCID: PMC6782681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/1999] [Revised: 03/11/1999] [Accepted: 03/16/1999] [Indexed: 02/12/2023] Open
Abstract
Efficacy of postsynaptic inhibition through GABAA receptors in the mammalian brain depends on the maintenance of a Cl- gradient for hyperpolarizing Cl- currents. We have taken advantage of the reduced complexity under which Cl- regulation can be investigated in cultured neurons as opposed to neurons in other in vitro preparations of the mammalian brain. Tightseal whole-cell recording of spontaneous GABAA receptor-mediated postsynaptic currents suggested that an outward Cl- transport reduced dendritic [Cl-]i if the somata of cells were loaded with Cl- via the patch pipette. We determined dendritic and somatic reversal potentials of Cl- currents induced by focally applied GABA to calculate [Cl-]i during variation of [K+]o and [Cl-] in the patch pipette. [Cl-]i and [K+]o were tightly coupled by a furosemide-sensitive K+-Cl- cotransport. Thermodynamic considerations excluded the significant contribution of a Na+-K+-Cl- cotransporter to the net Cl- transport. We conclude that under conditions of normal [K+]o the K+-Cl- cotransporter helps to maintain [Cl-]i at low levels, whereas under pathological conditions, under which [K+]o remains elevated because of neuronal hyperactivity, the cotransporter accumulates Cl- in neurons, thereby further enhancing neuronal excitability.
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Affiliation(s)
- W Jarolimek
- I. Physiologisches Institut der Universität Heidelberg, D-69120 Heidelberg, Germany
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18
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Enhancement of neurotransmitter release induced by brain-derived neurotrophic factor in cultured hippocampal neurons. J Neurosci 1999. [PMID: 9852560 DOI: 10.1523/jneurosci.18-24-10231.1998] [Citation(s) in RCA: 229] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF), like other neurotrophins, has long-term effects on neuronal survival and differentiation; furthermore, recent work has shown that BDNF also can induce rapid changes in synaptic efficacy. We have investigated the mechanism(s) of these synaptic effects on cultured embryonic hippocampal neurons. In the presence of the GABAA receptor antagonist, picrotoxin, the application of BDNF (100 ng/ml) for 1-5 min increased the amplitude of evoked synaptic currents by 48 +/- 9% in 10 of 15 pairs of neurons and increased the frequency of EPSC bursts to 205 +/- 20% of the control levels. There was no detectable effect of BDNF on various measures of electrical excitability, including the resting membrane potential, input resistance, action potential threshold, and action potential amplitude. In addition, BDNF did not change the postsynaptic currents induced by the exogenous application of glutamate. BDNF did increase the frequency of miniature EPSCs (mEPSCs) (268.0 +/- 46.8% of control frequency), however, without affecting the mEPSC amplitude. The effect of BDNF on mEPSC frequency was blocked by the tyrosine kinase inhibitor K252a and also by the removal of extracellular calcium ([Ca2+]o). Fura-2 recordings showed that BDNF elicited an increase in intracellular calcium concentration ([Ca2+]c). This effect was dependent on [Ca2+]o; it was blocked by K252a and by thapsigargin, but not by caffeine. The results demonstrate that BDNF enhances glutamatergic synaptic transmission at a presynaptic locus and that this effect is accompanied by a rise in [Ca2+]c that requires the release of Ca2+ from IP3-gated stores.
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Li YX, Zhang Y, Lester HA, Schuman EM, Davidson N. Enhancement of neurotransmitter release induced by brain-derived neurotrophic factor in cultured hippocampal neurons. J Neurosci 1998; 18:10231-40. [PMID: 9852560 PMCID: PMC6793341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
Brain-derived neurotrophic factor (BDNF), like other neurotrophins, has long-term effects on neuronal survival and differentiation; furthermore, recent work has shown that BDNF also can induce rapid changes in synaptic efficacy. We have investigated the mechanism(s) of these synaptic effects on cultured embryonic hippocampal neurons. In the presence of the GABAA receptor antagonist, picrotoxin, the application of BDNF (100 ng/ml) for 1-5 min increased the amplitude of evoked synaptic currents by 48 +/- 9% in 10 of 15 pairs of neurons and increased the frequency of EPSC bursts to 205 +/- 20% of the control levels. There was no detectable effect of BDNF on various measures of electrical excitability, including the resting membrane potential, input resistance, action potential threshold, and action potential amplitude. In addition, BDNF did not change the postsynaptic currents induced by the exogenous application of glutamate. BDNF did increase the frequency of miniature EPSCs (mEPSCs) (268.0 +/- 46.8% of control frequency), however, without affecting the mEPSC amplitude. The effect of BDNF on mEPSC frequency was blocked by the tyrosine kinase inhibitor K252a and also by the removal of extracellular calcium ([Ca2+]o). Fura-2 recordings showed that BDNF elicited an increase in intracellular calcium concentration ([Ca2+]c). This effect was dependent on [Ca2+]o; it was blocked by K252a and by thapsigargin, but not by caffeine. The results demonstrate that BDNF enhances glutamatergic synaptic transmission at a presynaptic locus and that this effect is accompanied by a rise in [Ca2+]c that requires the release of Ca2+ from IP3-gated stores.
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Affiliation(s)
- Y X Li
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA
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20
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Chan PK, Leung CK, Yung WH. Differential expression of pre- and postsynaptic GABA(B) receptors in rat substantia nigra pars reticulata neurones. Eur J Pharmacol 1998; 349:187-97. [PMID: 9671097 DOI: 10.1016/s0014-2999(98)00194-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Whole-cell recordings were made from substantia nigra pars reticulata in rat midbrain slices to study the functional expression of pre- and postsynaptic GABA(B) receptors in GABA output neurones. Baclofen (up to 300 microM) dose-dependently activated a weak current which was insensitive to tetrodotoxin and Ca2+-free solution but blocked by Ba2+ and 2-OH-saclofen. The maximum current activated by baclofen (30 microM) was 43.0 +/- 4.5 pA (n = 27), representing only 23% of that in dopamine neurones. Baclofen (1-30 microM) also reduced the frequency of the GABA(A) receptor-mediated miniature inhibitory postsynaptic currents while the distribution of their amplitudes was unaffected. This presynaptic effect of baclofen, prominent at a concentration as low as 1 microM, was sensitive to 2-OH-saclofen and occluded by Cd2+, but was unaffected by Ba2+. The results suggest a predominant role of the presynaptic GABA(B) receptors in substantia nigra pars reticulata. The relative abundance of pre- and postsynaptic GABA(B) receptor subtypes in this brain region may also be important in mediating the anticonvulsant effect of baclofen in rats.
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Affiliation(s)
- P K Chan
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin
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21
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G-Protein-coupled modulation of presynaptic calcium currents and transmitter release by a GABAB receptor. J Neurosci 1998. [PMID: 9547222 DOI: 10.1523/jneurosci.18-09-03138.1998] [Citation(s) in RCA: 184] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Presynaptic GABAB receptors play a regulatory role in central synaptic transmission. To elucidate their underlying mechanism of action, we have made whole-cell recordings of calcium and potassium currents from a giant presynaptic terminal, the calyx of Held, and EPSCs from its postsynaptic target in the medial nucleus of the trapezoid body of rat brainstem slices. The GABAB receptor agonist baclofen suppressed EPSCs and presynaptic calcium currents but had no effect on voltage-dependent potassium currents. The calcium current-EPSC relationship measured during baclofen application was similar to that observed on reducing [Ca2+]o, suggesting that the presynaptic inhibition generated by baclofen is caused largely by the suppression of presynaptic calcium influx. Presynaptic loading of the GDP analog guanosine-5'-O-(2-thiodiphosphate) (GDPbetaS) abolished the effect of baclofen on both presynaptic calcium currents and EPSCs. The nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) suppressed presynaptic calcium currents and occluded the effect of baclofen on presynaptic calcium currents and EPSCs. Photoactivation of GTPgammaS induced an inward rectifying potassium current at the calyx of Held, whereas baclofen had no such effect. We conclude that presynaptic GABAB receptors suppress transmitter release through G-protein-coupled inhibition of calcium currents.
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Takahashi T, Kajikawa Y, Tsujimoto T. G-Protein-coupled modulation of presynaptic calcium currents and transmitter release by a GABAB receptor. J Neurosci 1998; 18:3138-46. [PMID: 9547222 PMCID: PMC6792650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Presynaptic GABAB receptors play a regulatory role in central synaptic transmission. To elucidate their underlying mechanism of action, we have made whole-cell recordings of calcium and potassium currents from a giant presynaptic terminal, the calyx of Held, and EPSCs from its postsynaptic target in the medial nucleus of the trapezoid body of rat brainstem slices. The GABAB receptor agonist baclofen suppressed EPSCs and presynaptic calcium currents but had no effect on voltage-dependent potassium currents. The calcium current-EPSC relationship measured during baclofen application was similar to that observed on reducing [Ca2+]o, suggesting that the presynaptic inhibition generated by baclofen is caused largely by the suppression of presynaptic calcium influx. Presynaptic loading of the GDP analog guanosine-5'-O-(2-thiodiphosphate) (GDPbetaS) abolished the effect of baclofen on both presynaptic calcium currents and EPSCs. The nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) suppressed presynaptic calcium currents and occluded the effect of baclofen on presynaptic calcium currents and EPSCs. Photoactivation of GTPgammaS induced an inward rectifying potassium current at the calyx of Held, whereas baclofen had no such effect. We conclude that presynaptic GABAB receptors suppress transmitter release through G-protein-coupled inhibition of calcium currents.
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Affiliation(s)
- T Takahashi
- Department of Neurophysiology, University of Tokyo Faculty of Medicine, Tokyo 113, Japan
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23
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Rohrbacher J, Sauer K, Lewen A, Misgeld U. Enhancement of synaptic excitation by GABAA receptor antagonists in rat embryonic midbrain culture. J Neurophysiol 1998; 79:1113-6. [PMID: 9463468 DOI: 10.1152/jn.1998.79.2.1113] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Alterations of synaptic excitation induced by exposure to gamma-aminobutyric acid-A (GABAA) receptor antagonists were investigated employing tight-seal whole cell recording from single neurons or pairs of neurons in rat embryonic midbrain culture. Application of GABAA receptor antagonists led to sustained depolarizations followed by synchronous paroxysmal depolarization shifts (PDSs). PDSs induced a transient increase in miniature excitatory postsynaptic currents in the presence as well as in the absence of a N-methyl-aspartate receptor antagonist. The increase in glutamate release supports the excitatory drive required to reinitiate PDSs from the quiescent interburst intervals. After washout of GABAA receptor antagonists, synaptic activity remained grouped, regardless of the presence or absence of PDS blockade by tetrodotoxin (TTX). Impediment of action potential-triggered transmitter release by Cd2+ or TTX also induced grouped activity. We conclude that changes in synaptic excitation are produced by the impaired GABAA inhibition per se and by the initiation of PDSs.
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Affiliation(s)
- J Rohrbacher
- Physiologisches Institut der Universität Heidelberg, D-69120 Heidelberg, Germany
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