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Yian Huang, Yuwen Zhang, Shuzhen Kong, Kai Zang, Shize Jiang, Li Wan, Lulan Chen, Guoxiang Wang, Min Jiang, Xin Wang, Jie Hu, Yun Wang
G protein-gated inwardly rectifying potassium (GIRK) channels are important inhibitory regulators of neuronal excitability in central nervous system, and the impairment of GIRK channel function has been reported to be associated with the susceptibility of epilepsy. However, the dynamics of GIRK channels in the pathogenesis of epilepsy are still unclear. In this study, our results showed that cyclothiazide, a potent convulsant, dose dependently increased the epileptiform bursting activities and suppressed the baclofen induced GIRK currents...
February 27, 2018: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Avia Rosenhouse-Dantsker
In recent years, it has become evident that cholesterol plays a direct role in the modulation of a variety of ion channels. In most cases, cholesterol downregulates channel activity. In contrast, our earlier studies have demonstrated that atrial G protein inwardly rectifying potassium (GIRK) channels are upregulated by cholesterol. Recently, we have shown that hippocampal GIRK currents are also upregulated by cholesterol. A combined computational-experimental approach pointed to putative cholesterol-binding sites in the transmembrane domain of the GIRK2 channel, the primary subunit in hippocampal GIRK channels...
2018: Lipid Insights
Josephine Herbst, Annabel Girke, Mohammad Reza Hajirezaei, Guy Hanke, Bernhard Grimm
Chlorophyll is synthesized from activated glutamate in the tetrapyrrole biosynthesis pathway through at least 20 different enzymatic reactions. Among these, the MgProto monomethylester (MgProtoME) cyclase catalyzes the formation of a fifth isocyclic ring to tetrapyrroles to form protochlorophyllide. The enzyme consists of two proteins. The CHL27 protein is proposed to be the catalytic component, while LCAA/YCF54 likely acts as a scaffolding factor. In comparison to other reactions of chlorophyll biosynthesis, this enzymatic step lacks clear elucidation and it is hardly understood, how electrons are delivered for the NADPH-dependent cyclization reaction...
February 14, 2018: Plant Journal: for Cell and Molecular Biology
Alessandra Porcu, Miriam Melis, Rostislav Turecek, Celine Ullrich, Ignazia Mocci, Bernhard Bettler, Gian Luigi Gessa, M Paola Castelli
Rimonabant is a potent and selective cannabinoid CB1 receptor antagonist widely used in animal and clinical studies. Besides its antagonistic properties, numerous studies have shown that, at micromolar concentrations rimonabant behaves as an inverse agonist at CB1 receptors. The mechanism underpinning this activity is unclear. Here we show that micromolar concentrations of rimonabant inhibited Gαi/o-type G proteins, resulting in a receptor-independent block of G protein signaling. Accordingly, rimonabant decreased basal and agonist stimulated [35S]GTPγS binding to cortical membranes of CB1- and GABAB-receptor KO mice and Chinese Hamster Ovary (CHO) cell membranes stably transfected with GABAB or D2 dopamine receptors...
January 27, 2018: Neuropharmacology
Reginald Cannady, Jennifer A Rinker, Sudarat Nimitvilai, John J Woodward, Patrick J Mulholland
Neural mechanisms underlying alcohol use disorder remain elusive, and this lack of understanding has slowed the development of efficacious treatment strategies for reducing relapse rates and prolonging abstinence. While synaptic adaptations produced by chronic alcohol exposure have been extensively characterized in a variety of brain regions, changes in intrinsic excitability of critical projection neurons are understudied. Accumulating evidence suggests that prolonged alcohol drinking and alcohol dependence produce plasticity of intrinsic excitability as measured by changes in evoked action potential firing and after-hyperpolarization amplitude...
January 28, 2018: Handbook of Experimental Pharmacology
Leif-Christopher Engel, Ulf Landmesser, Kevin Gigengack, Thomas Wurster, Constantina Manes, Georg Girke, Milosz Jaguszewski, Carsten Skurk, David M Leistner, Alexander Lauten, Andreas Schuster, Bernd Hamm, Rene M Botnar, Marcus R Makowski, Boris Bigalke
OBJECTIVES: This study sought to investigate the potential of the noninvasive albumin-binding probe gadofosveset-enhanced cardiac magnetic resonance (GE-CMR) for detection of coronary plaques that can cause acute coronary syndromes (ACS). BACKGROUND: ACS are frequently caused by rupture or erosion of coronary plaques that initially do not cause hemodynamically significant stenosis and are therefore not detected by invasive x-ray coronary angiography (XCA). METHODS: A total of 25 patients with ACS or symptoms of stable coronary artery disease underwent GE-CMR, clinically indicated XCA, and optical coherence tomography (OCT) within 24 h...
January 12, 2018: JACC. Cardiovascular Imaging
Allison Anderson, Kanchan Kulkarni, Ezequiel Marron Fernandez de Velasco, Nicholas Carlblom, Zhilian Xia, Atsushi Nakano, Kirill A Martemyanov, Elena G Tolkacheva, Kevin Wickman
The atrial G protein-gated inwardly rectifying K+ (GIRK) channel is a critical mediator of parasympathetic influence on cardiac physiology. Here, we probed the details and relevance of the GIRK channel in mouse ventricle. mRNAs for the atrial GIRK channel subunits (GIRK1, GIRK4), M2 muscarinic receptor (M2R), and RGS6, a negative regulator of atrial GIRK-dependent signaling, were detected in mouse ventricle at relatively low levels. The cholinergic agonist carbachol (CCh) activated small GIRK currents in adult wild-type ventricular myocytes that exhibited relatively slow kinetics and low CCh sensitivity; these currents were absent in ventricular myocytes from Girk1-/- or Girk4-/- mice...
January 19, 2018: Scientific Reports
Muriel Nobles, David Montaigne, Sonia Sebastian, Lutz Birnbaumer, Andrew Tinker
G-protein gated inwardly rectifying K+ (GIRK) channels are the major inwardly rectifying K+ currents in cardiac atrial myocytes and an important determinant of atrial electrophysiology. Inhibitory G-protein alpha subunits can both mediate activation via acetylcholine but can also supress basal currents in the absence of agonist. We studied this phenomenon using whole cell patch clamping in murine atria from mice with global genetic deletion of Gαi2, combined deletion of Gαi1/Gαi3 and littermate controls...
January 17, 2018: American Journal of Physiology. Cell Physiology
Juan A Estrada, Marc P Kaufman
Mu opioid G-protein coupled receptors (MOR) interact with ion channels to decrease neuronal excitability. In humans, intrathecal administration of the MOR agonist, fentanyl, inhibits the exercise pressor reflex, an effect that can be attributed to either the opening of inward rectifying potassium channels (GIRK) or the closing of N-type calcium channels. The purpose of this study was to determine if the highly selective MOR agonist DAMGO attenuates the exercise pressor reflex, and which of these two channels are responsible for this effect...
January 17, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Richard Ågren, Kristoffer Sahlholm, Johanna Nilsson, Peter Århem
The muscarinic M2 receptor (M2R) has been shown to display voltage-sensitive agonist binding, based on G protein-activated inward rectifier potassium channel (GIRK) opening and radioligand binding at different membrane voltages. A conserved aspartate in transmembrane segment (TM) II of M2R, D69, has been proposed as the voltage sensor. While a recent paper instead presented evidence of tyrosines in TMs III, VI, and VII acting as voltage sensors, these authors were not able to record GIRK channel activation by a D69N mutant M2R...
January 2, 2018: Biochemical and Biophysical Research Communications
Ikutaro Honda, Kimi Araki, Sokichi Honda, Fumio Soeda, Min-Chul Shin, Shogo Misumi, Ken-Ichi Yamamura, Kazuo Takahama
We previously reported that non-narcotic antitussives possessing inhibitory actions on G protein-coupled inwardly rectifying potassium (GIRK) channels have antidepressant-like effects in the forced swimming test in normal and adrenocoticotropic hormone (ACTH) treated rats. Furthermore, the antidepressant-like effects of the antitussives such as tipepidine were blocked by dopamine D1 receptor antagonist, and inhibitory actions on GIRK channels of dopamine neurons may be involved in the antidepressant-like effects of tipepidine...
February 5, 2018: Neuroscience Letters
Rafael Luján, Carolina Aguado, Francisco Ciruela, Javier Cózar, David Kleindienst, Luis de la Ossa, Bernhard Bettler, Kevin Wickman, Masahiko Watanabe, Ryuichi Shigemoto, Yugo Fukazawa
Metabotropic GABAB receptors mediate slow inhibitory effects presynaptically and postsynaptically through the modulation of different effector signalling pathways. Here, we analysed the distribution of GABAB receptors using highly sensitive SDS-digested freeze-fracture replica labelling in mouse cerebellar Purkinje cells. Immunoreactivity for GABAB1 was observed on presynaptic and, more abundantly, on postsynaptic compartments, showing both scattered and clustered distribution patterns. Quantitative analysis of immunoparticles revealed a somato-dendritic gradient, with the density of immunoparticles increasing 26-fold from somata to dendritic spines...
November 25, 2017: Brain Structure & Function
Jean-Didier Breton, Greg J Stuart
Classically, GABAB receptors are thought to regulate neuronal excitability via G-protein-coupled inwardly rectifying potassium (GIRK) channels. Recent data, however, indicate that GABAB receptors can also activate two-pore domain potassium channels. Here, we investigate which potassium channels are coupled to GABAB receptors in rat neocortical layer 5 and hippocampal CA1 pyramidal neurons. Bath application of the non-specific GIRK channel blocker barium (200 μm) abolished outward currents evoked by GABAB receptors in CA1 pyramidal, but only partially blocked GABAB responses in layer 5 neurons...
December 2017: European Journal of Neuroscience
Boris Mlinar, Alberto Montalbano, Jonas Waider, Klaus-Peter Lesch, Renato Corradetti
Firing activity of serotonergic neurons is under regulatory control by somatodendritic 5-HT1A autoreceptors (5-HT1A ARs). Enhanced 5-HT1A AR functioning may cause decreased serotonergic signaling in brain and has thereby been implicated in the etiology of mood and anxiety disorders. Tryptophan hydroxylase-2 knockout (Tph2-/- ) mice exhibit sensitization of 5-HT1A agonist-induced inhibition of serotonergic neuron firing and thus represents a unique animal model of enhanced 5-HT1A AR functioning. To elucidate the mechanisms underlying 5-HT1A AR supersensitivity in Tph2-/- mice, we characterized the activation of G protein-coupled inwardly-rectifying potassium (GIRK) conductance by the 5-HT1A receptor agonist 5-carboxamidotryptamine using whole-cell recordings from serotonergic neurons in dorsal raphe nucleus...
December 2017: European Neuropsychopharmacology: the Journal of the European College of Neuropsychopharmacology
Irene Sánchez-Rodríguez, Sara Temprano-Carazo, Alberto Nájera, Souhail Djebari, Javier Yajeya, Agnès Gruart, José M Delgado-García, Lydia Jiménez-Díaz, Juan D Navarro-López
The hippocampus plays a critical role in learning and memory. Its correct performance relies on excitatory/inhibitory synaptic transmission balance. In early stages of Alzheimer's disease (AD), neuronal hyperexcitability leads to network dysfunction observed in cortical regions such as the hippocampus. G-protein-gated potassium (GirK) channels induce neurons to hyperpolarize, contribute to the resting membrane potential and could compensate any excesses of excitation. Here, we have studied the relationship between GirK channels and hippocampal function in a mouse model of early AD pathology...
November 7, 2017: Scientific Reports
M Carola Zillikens, Serkalem Demissie, Yi-Hsiang Hsu, Laura M Yerges-Armstrong, Wen-Chi Chou, Lisette Stolk, Gregory Livshits, Linda Broer, Toby Johnson, Daniel L Koller, Zoltán Kutalik, Jian'an Luan, Ida Malkin, Janina S Ried, Albert V Smith, Gudmar Thorleifsson, Liesbeth Vandenput, Jing Hua Zhao, Weihua Zhang, Ali Aghdassi, Kristina Åkesson, Najaf Amin, Leslie J Baier, Inês Barroso, David A Bennett, Lars Bertram, Rainer Biffar, Murielle Bochud, Michael Boehnke, Ingrid B Borecki, Aron S Buchman, Liisa Byberg, Harry Campbell, Natalia Campos Obanda, Jane A Cauley, Peggy M Cawthon, Henna Cederberg, Zhao Chen, Nam H Cho, Hyung Jin Choi, Melina Claussnitzer, Francis Collins, Steven R Cummings, Philip L De Jager, Ilja Demuth, Rosalie A M Dhonukshe-Rutten, Luda Diatchenko, Gudny Eiriksdottir, Anke W Enneman, Mike Erdos, Johan G Eriksson, Joel Eriksson, Karol Estrada, Daniel S Evans, Mary F Feitosa, Mao Fu, Melissa Garcia, Christian Gieger, Thomas Girke, Nicole L Glazer, Harald Grallert, Jagvir Grewal, Bok-Ghee Han, Robert L Hanson, Caroline Hayward, Albert Hofman, Eric P Hoffman, Georg Homuth, Wen-Chi Hsueh, Monica J Hubal, Alan Hubbard, Kim M Huffman, Lise B Husted, Thomas Illig, Erik Ingelsson, Till Ittermann, John-Olov Jansson, Joanne M Jordan, Antti Jula, Magnus Karlsson, Kay-Tee Khaw, Tuomas O Kilpeläinen, Norman Klopp, Jacqueline S L Kloth, Heikki A Koistinen, William E Kraus, Stephen Kritchevsky, Teemu Kuulasmaa, Johanna Kuusisto, Markku Laakso, Jari Lahti, Thomas Lang, Bente L Langdahl, Lenore J Launer, Jong-Young Lee, Markus M Lerch, Joshua R Lewis, Lars Lind, Cecilia Lindgren, Yongmei Liu, Tian Liu, Youfang Liu, Östen Ljunggren, Mattias Lorentzon, Robert N Luben, William Maixner, Fiona E McGuigan, Carolina Medina-Gomez, Thomas Meitinger, Håkan Melhus, Dan Mellström, Simon Melov, Karl Michaëlsson, Braxton D Mitchell, Andrew P Morris, Leif Mosekilde, Anne Newman, Carrie M Nielson, Jeffrey R O'Connell, Ben A Oostra, Eric S Orwoll, Aarno Palotie, Stephen C J Parker, Munro Peacock, Markus Perola, Annette Peters, Ozren Polasek, Richard L Prince, Katri Räikkönen, Stuart H Ralston, Samuli Ripatti, John A Robbins, Jerome I Rotter, Igor Rudan, Veikko Salomaa, Suzanne Satterfield, Eric E Schadt, Sabine Schipf, Laura Scott, Joban Sehmi, Jian Shen, Chan Soo Shin, Gunnar Sigurdsson, Shad Smith, Nicole Soranzo, Alena Stančáková, Elisabeth Steinhagen-Thiessen, Elizabeth A Streeten, Unnur Styrkarsdottir, Karin M A Swart, Sian-Tsung Tan, Mark A Tarnopolsky, Patricia Thompson, Cynthia A Thomson, Unnur Thorsteinsdottir, Emmi Tikkanen, Gregory J Tranah, Jaakko Tuomilehto, Natasja M van Schoor, Arjun Verma, Peter Vollenweider, Henry Völzke, Jean Wactawski-Wende, Mark Walker, Michael N Weedon, Ryan Welch, H-Erich Wichmann, Elisabeth Widen, Frances M K Williams, James F Wilson, Nicole C Wright, Weijia Xie, Lei Yu, Yanhua Zhou, John C Chambers, Angela Döring, Cornelia M van Duijn, Michael J Econs, Vilmundur Gudnason, Jaspal S Kooner, Bruce M Psaty, Timothy D Spector, Kari Stefansson, Fernando Rivadeneira, André G Uitterlinden, Nicholas J Wareham, Vicky Ossowski, Dawn Waterworth, Ruth J F Loos, David Karasik, Tamara B Harris, Claes Ohlsson, Douglas P Kiel
A correction to this article has been published and is linked from the HTML version of this article.
November 7, 2017: Nature Communications
Erica S Levitt, John T Williams
Acute desensitization of mu opioid receptors is thought to be an initial step in the development of tolerance to opioids. Given the resistance of the respiratory system to develop tolerance, desensitization of neurons in the Kölliker-Fuse (KF), a key area in the respiratory circuit, was examined. The activation of G protein-coupled inwardly rectifying potassium current was measured using whole-cell voltage-clamp recordings from KF and locus coeruleus (LC) neurons contained in acute rat brain slices. A saturating concentration of the opioid agonist [Met5 ]-enkephalin (ME) caused significantly less desensitization in KF neurons compared with LC neurons...
January 2018: Molecular Pharmacology
Anna Tchenio, Salvatore Lecca, Kristina Valentinova, Manuel Mameli
Early-life stress, including maternal separation (MS), increases the vulnerability to develop mood disorders later in life, but the underlying mechanisms remain elusive. We report that MS promotes depressive-like symptoms in mice at a mature stage of life. Along with this behavioral phenotype, MS drives reduction of GABAB-GIRK signaling and the subsequent lateral habenula (LHb) hyperexcitability-an anatomical substrate devoted to aversive encoding. Attenuating LHb hyperactivity using chemogenetic tools and deep-brain stimulation ameliorates MS depressive-like symptoms...
October 26, 2017: Nature Communications
Dasiel O Borroto-Escuela, Caitlin M DuPont, Xiang Li, David Savelli, Davide Lattanzi, Ipsit Srivastava, Manuel Narváez, Michael Di Palma, Elisa Barbieri, Yuniesky Andrade-Talavera, Riccardo Cuppini, Yuji Odagaki, Miklos Palkovits, Patrizia Ambrogini, Maria Lindskog, Kjell Fuxe
The FGFR1-5-HT1A heteroreceptor complexes are involved in neuroplasticity in the rat hippocampus and in the mesencephalic raphe 5-HT nerve cells. There exists a 5-HT1A protomer enhancement of FGFR1 protomer signaling. Acute and 10 day treatment with intracerebroventricular (i.c.v.) FGF-2 and the 5-HT1A agonist 8-OH-DPAT produced enhanced antidepressant effects in the forced swim test (FST). We studied in the current work the disturbances in the FGFR1-5-HT1A heterocomplexes in a genetic rat model of depression, the Flinders sensitive line (FSL) rats of Sprague-Dawley (SD) origin, by means of neurochemical, neurophysiological and behavioral techniques...
2017: Frontiers in Cellular Neuroscience
Brian C Baculis, Amanda C Weiss, Weilun Pang, Han Gil Jeong, Jun Hee Lee, Dai-Chi Liu, Nien-Pei Tsai, Hee Jung Chung
Recurrent high-frequency epileptic seizures cause progressive hippocampal sclerosis, which is associated with caspase-3 activation and NMDA receptor-dependent excitotoxicity. However, the identity of caspase-3 substrates that contribute to seizure-induced hippocampal atrophy remains largely unknown. Here, we show that prolonged high-frequency epileptiform discharges in cultured hippocampal neurons leads to caspase-dependent cleavage of GIRK1 and GIRK2, the major subunits of neuronal G protein-activated inwardly rectifying potassium (GIRK) channels that mediate membrane hyperpolarization and synaptic inhibition in the brain...
September 26, 2017: Scientific Reports
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