DOCSLIB.ORG

University of Alberta the Effect of Benzodiazepines on GABA

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
University of Alberta the Effect of Benzodiazepines on GABA University of Alberta The Effect of Benzodiazepines on GABA, Receptor Homeostasis by Robert Andrew Holt O A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillrnent of the requirements for the degree of Doctor of Philosophy Department of Pharmacology Edmonton, Alberta Spring, 1998 National Library Bibliothéque nationale of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. nie Wellington ûttawaON K1AON4 Ottawa ON K 1A ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence dowing the exclusive permettant à la National Librq of Canada to Bibliothèque nationale du Canada de reproduce, loan, disîribute or sell reproduire, prêter, distribuer ou copies of ibis thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/nlm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copy~@t in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ABSTRACT The oven effects of Diazepam (Valiums), a comrnonly used anxiolytic and hypnotic drug, are produced through allostenc modulation of GABA, receptors. GABA, receptors are pentarnenc chloride channels that display extensive structural and functional heterogeneity based on the differential assembly of multiple subunit isoforms, each of which is encoded by a separate gene. In the present study, exposure of rats to daily doses of 15 mgKg diûzepam modified GABA, receptor a3-, a4-, a5-,p 1-. y2- and y3-subunit steady-state mRNA levels in a time- and brin region-specific rnanner. Diazeparn also modified transcription of the GABA, receptor @-subunit gene in rat brain in a manner consistent wiih the effects of this drug on @-subunit steady-state mRNA levels. suggesting a potentiai transcriptional basis for diazeparn-induced changes in GABA, receptor steady-state mEWA levels. Further, the benzodiazepine-site binding characteristics of native GABA, receptors in nt brain were modified by chronic diazepam in a manner consistent with the effects of this dmg on GABA, receptor steady-state mRNA levels. Reduced 'H-flunitrazepam but not 'H- Ro 15-45 13 binding was observed in cortical membranes denved from rats chronicaliy treated with diazepam, as was an increased ratio of zolpidem displaceable versus zolpidem non-displaceable 'H-flunitrazepam binding. Potentiation of 'H-flunitrazepam binding to nt brain membranes by GABA was reduced after a single diazepam dose, but this effect did not appear to be enhanced by chronic treatment and did not appear to be related to diazeparn-induced changes in GABA, receptor gene expression. Finally, the specific pattem of changes in GABA, receptor subunit rnRNA levels produced by chronic exposure to two subtype-specific benzodiazepine-site ligands, abeca.mil and zolpidem, which have Iower tolerance and dependence liability than diazepam, was different from the pattern produced by diazepam. The results of the present study are consistent with the hypothesis that benzodiazepine exposure evokes subtype-specific changes the population of GABA, receptors in rat brain as a homeostatic response. ACKNOWLEDGMENTS To my supervisors, Ian and Alan, for your guidance and inspiration. To my parents. Bob and Anne. You taught me perseverance which, more than any other factor, was necessary for the completion of this thesis. To my wife, Lea, for your constant suppon, understanding and heroic patience. TABLE OF CONTENTS PAGE CHAPTER 1 - Introduction General overview The benzodiazepines: their development and discovery of their mechanism of action Structural and functional characteristics of the GABA, receptor Benzodiazepine modulation of a variant GABA, receptors Benzodiazepine modulation of B variant GABA, receptors Benzodiazepine modulation of y variant GABA, receptors GABA, receptors containing other classes of subunits The native GABA, receptor Specific airns CHAPTER 2 - The effect of diazepam on GABA, receptor steady-state mRNA levels In traduction Materials and rnethods Dmg treatment Quantification of CNS diazepam levels by reversed-phase HPLC The solution hybridization assay - overview RNA preparation Oligonucleotide probe synthesis and purification PAGE Oligonucleotide labeling Solution hybridization Digestion of excess oligonucleotide probe Separation of protected oligonucleotides by denaturing polyacrylamide gel electrophoresis Detection of protected oligonucleotides by autoradiography Densitometric quantification of oligonucleotide band intensities Linearity and variability of the solution hybridization assay Results Diazeparn concentrations in rat brain following chronic exposure The effects of diazeparn on GABA, receptor mRNA ievels Discussion CHAPTER 3 - The effect of diazepam on transcription of the GABA, receptor y2-subunit gene. ln troduc tion Materials and rnethods Drug treatrnen t Isolation of nuclei Synthesis of nascent radiolabeled RNA Preparation of DNA probes Irnmobilization of probes on nylon membranes PAGE Hybridization of radiolabeled RNA to membrane-irnmobilized probes 57 Detection and quantification of nascent y2-subunit RNA 58 Resui ts Discussion CHAPTER 4 - The effect of diazepam on benzodiazepine-site binding characteristics PART 1: The effect of chronic diazepam on benzodiazepine recognition properties htroduction Materials and methods Dmg treatment Preparation of rat brain membranes Estimation of protein concentration in membrane preparations Single point 3~-flunitrazepamand 'H-RO15-45 13 binding assays Single point zolpidem displacement binding assays Results Discussion PART 2: The effect of diazeparn exposure on GABA enhancement of benzodiazepine binding Introduction PAGE iMaterials and meihods GABA shift binding assayç Results Discussion CHAPTER 5 - The effect of abecarnil and zolpidem on GABA, 90 receptor steady-state mRNA levels introduction Materials and methods Dm,= treatment Quantification of CNS drug bels by reversed-phase HPLC Quantification of GABA, receptor steady-state mRNA levels by solution hybridization Results Abecarnil and zolpidem concentrations in nt brain following chronic exposure The effects of abecarnil and zolpidem on GMA, receptor subunit mRNA levels Discussion CHAPTER 6 - General discussion Future directions Bibliography 116 LIST OF TABLES PAGE Table 2.1 Sequences of oligonucleotide probes used in solution 40 hybridization experiments Table 2.2 The effect of diazeparn on GABA, receptor steady-state 46 mRNA levels in nt cortex and hippocampus Table 5.1 nie effect of abecarnil on GABA, receptor steady-state 102 mRNA levels in rat cortex and hippocampus Table 5.2 The effect of zolpidern on GABA, receptor steady-state 104 mRNA levels in rat cortex LIST OF FIGURES PAGE Figure 2.1 The solution hybridization assay: relationship between radioactivity and measured band intensity Figure 2.2 The solution hybndization assay: relationship between input RNA and rneasured band intensity Figure 2.3 The solution hybridization assay: typical results Figure 2.4 Examples of subunit- and brain region-specific effects of diazeparn on GABA, receptor subunit rnRNA levels in rat brain Figure 2.5 Tirnecourse of diazepam-induced changes in GABA, receptor p 1 -subunit mRNA levels in rat cortex and hippocarnpus Figure 2.6 Association between the mean rnRNA levels of clustered GABA, receptor genes in rat brain following diazeparn exposure Figure 3.1 The effect of 14 days of diazepam exposure on transcription of the GABA, receptor @-subunit gene in rat cortex and cerebellum Figure 3.2 Transcription of the GABA, receptor $2-subunit gene in rat cortex and cerebellum 12 or 24 hours after a single diazepam dose Figure 3.3 Phospho-image illustrating the results of a typical nuclear run- off experiment. Figure 4.1 Total specific binding of 3~-flunitrazepamand 'H-RO 15-45 13 in nt cortex after chronic diazeparn exposure Figure 4.2 Ratio of 3~-flunitrazeparnto 'H-RO 15-45 13 binding in rat cortex after chronic diazeparn exposure Figure 4.3 Ratio of type BZII to type BZI binding in rat cortex after chronic diazepam exposure PAGE Figure 4.4 GABA potentiation of 3~-flunitrazepambinding in rat 87 cortex and cerebellum at various tirnepoints following a single diazepam dose Figure 4.5 GABA potentiation of 3~-flunitmzepambinding in rat cortex and cerebellum following chronic diazepam exposure Figure 4.6 The effect of chronic diazeparn exposure on GABA, receptor al-.P2-, and y2-subunit mRNA levels in rat cortex and cerebellum Figure 5.1 Differentid effects of chronic diazepam, abecamil and zolpidem treatment on GABA, receptor a3-.a5- and y3-subunit mRNA levels in rat cortex Figure 5.2 Association between the mean mRNA levels of clustered GABA, receptor genes in rat cortex following chronic diazepam, abecamil or zolpidem treatment LIST OF ABBREVIATIONS ATP adenosine triphosphate P-CCE ethyl P-carboline-3-carboxylate P-CCM methyl fi-carboline-3-carboxylate cDNA complimentary deoxyribonucleic acid CTP cytidine triphosphate DEPC diethy 1 pyrocarbonate DMCM methyl-6,7-dimethoxy-4-ethyl-P-carbol~e dP disintegrations per minute EC 50 agonist concentration that produces a half-maximal response EDTA ethylenediamine tetraace tic acid EGTA ethylene glycol-bis@-aminoethyl
Load more

Recommended publications
  • Molecular Dissection of G-Protein Coupled Receptor Signaling and Oligomerization
    MOLECULAR DISSECTION OF G-PROTEIN COUPLED RECEPTOR SIGNALING AND OLIGOMERIZATION BY MICHAEL RIZZO A Dissertation Submitted to the Graduate Faculty of WAKE FOREST UNIVERSITY GRADUATE SCHOOL OF ARTS AND SCIENCES in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Biology December, 2019 Winston-Salem, North Carolina Approved By: Erik C. Johnson, Ph.D. Advisor Wayne E. Pratt, Ph.D. Chair Pat C. Lord, Ph.D. Gloria K. Muday, Ph.D. Ke Zhang, Ph.D. ACKNOWLEDGEMENTS I would first like to thank my advisor, Dr. Erik Johnson, for his support, expertise, and leadership during my time in his lab. Without him, the work herein would not be possible. I would also like to thank the members of my committee, Dr. Gloria Muday, Dr. Ke Zhang, Dr. Wayne Pratt, and Dr. Pat Lord, for their guidance and advice that helped improve the quality of the research presented here. I would also like to thank members of the Johnson lab, both past and present, for being valuable colleagues and friends. I would especially like to thank Dr. Jason Braco, Dr. Jon Fisher, Dr. Jake Saunders, and Becky Perry, all of whom spent a great deal of time offering me advice, proofreading grants and manuscripts, and overall supporting me through the ups and downs of the research process. Finally, I would like to thank my family, both for instilling in me a passion for knowledge and education, and for their continued support. In particular, I would like to thank my wife Emerald – I am forever indebted to you for your support throughout this process, and I will never forget the sacrifices you made to help me get to where I am today.
    [Show full text]
  • GABA Receptors
    D Reviews • BIOTREND Reviews • BIOTREND Reviews • BIOTREND Reviews • BIOTREND Reviews Review No.7 / 1-2011 GABA receptors Wolfgang Froestl , CNS & Chemistry Expert, AC Immune SA, PSE Building B - EPFL, CH-1015 Lausanne, Phone: +41 21 693 91 43, FAX: +41 21 693 91 20, E-mail: [email protected] GABA Activation of the GABA A receptor leads to an influx of chloride GABA ( -aminobutyric acid; Figure 1) is the most important and ions and to a hyperpolarization of the membrane. 16 subunits with γ most abundant inhibitory neurotransmitter in the mammalian molecular weights between 50 and 65 kD have been identified brain 1,2 , where it was first discovered in 1950 3-5 . It is a small achiral so far, 6 subunits, 3 subunits, 3 subunits, and the , , α β γ δ ε θ molecule with molecular weight of 103 g/mol and high water solu - and subunits 8,9 . π bility. At 25°C one gram of water can dissolve 1.3 grams of GABA. 2 Such a hydrophilic molecule (log P = -2.13, PSA = 63.3 Å ) cannot In the meantime all GABA A receptor binding sites have been eluci - cross the blood brain barrier. It is produced in the brain by decarb- dated in great detail. The GABA site is located at the interface oxylation of L-glutamic acid by the enzyme glutamic acid decarb- between and subunits. Benzodiazepines interact with subunit α β oxylase (GAD, EC 4.1.1.15). It is a neutral amino acid with pK = combinations ( ) ( ) , which is the most abundant combi - 1 α1 2 β2 2 γ2 4.23 and pK = 10.43.
    [Show full text]
  • A 3-Fold Kernel Approach for Characterizing Late Onset Alzheimer’S Disease
    bioRxiv preprint doi: https://doi.org/10.1101/397760; this version posted August 22, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. A 3-fold kernel approach for characterizing Late Onset Alzheimer’s Disease Margherita Squillarioa,*, Federico Tomasia, Veronica Tozzoa, Annalisa Barlaa and Daniela Ubertib “for the Alzheimer’s Disease Neuroimaging Initiative**” aDIBRIS, University of Genoa, Via Dodecaneso 35, I-16146 Genova, Italy. E-mail address: {squillario, federico.tomasi, veronica.tozzo}@dibris.unige.it, [email protected] bDepartment of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy. E-mail address: [email protected] * Corresponding author and Lead Contact. Tel: +39-010-353-6707; Fax: +39-010-353- 6699. ** Data used in preparation of this article were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database (adni.loni.usc.edu). As such, the investigators within the ADNI contributed to the design and implementation of ADNI and/or provided data but did not participate in analysis or writing of this report. A complete listing of ADNI investigators can be found at: http://adni.loni.usc.edu/wp- content/uploads/how_to_apply/ADNI_Acknowledgement_List.pdf 1 bioRxiv preprint doi: https://doi.org/10.1101/397760; this version posted August 22, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.
    [Show full text]
  • GABA Receptor Crosstalk the Inhibitory Neurotransmitter GABA Activates Both Ionotropic
    RESEARCH HIGHLIGHTS IN BRIEF SYNAPTIC TRANSMISSION GABA receptor crosstalk The inhibitory neurotransmitter GABA activates both ionotropic type A GABA receptors (GABAARs) and metabotropic GABAB receptors (GABABRs). Two independent studies in rat brain slices now show that activation of postsynaptic GABABRs enhances signalling through extrasynaptic GABAARs. Activity-dependent changes in GABA concentration activate postsynaptic GABABRs leading to slow inhibition, whereas high-affinity GABAARs at extrasynaptic sites are activated tonically by ambient GABA. This tonic inhibitory tone has been implicated in synaptic integration, anxiety-related behaviours and seizure susceptibility. Tao et al. show that activation of postsynaptic GABABRs enhances GABAAR-mediated currents caused by exogenous GABA or the GABABR agonist baclofen in dentate gyrus granule cells (DGGCs) but not in CA1 pyramidal neurons or cortical layer 2/3 pyramidal neurons. Connelly et al. report similar crosstalk in thalamocortical neurons of the ventrobasal thalamus and cerebellar granule cells as well as in DGGCs. ORIGINAL RESEARCH PAPERS Tao, W. et al. Postsynaptic GABAB receptors enhance extrasynaptic GABAA receptor function in dentate gyrus granule cells. J. Neurosci. 33, 3738–3743 (2013) | Connelly, W. M. et al. GABAB receptors regulate extrasynaptic GABAA receptors. J. Neurosci. 33, 3780–3785 (2013) SIGNAL TRANSDUCTION JACOB reveals the origin of NMDAR signals Signalling through NMDA receptors (NMDARs) can trigger cell death or survival depending on whether activation of such receptors occurs at extrasynaptic or synaptic sites, respectively. It is unclear how these opposing signals are communicated to and discriminated by the nucleus, but the authors of this study show that differential phosphorylation of JACOB relays the origin of the NMDAR signal to the nucleus.
    [Show full text]
  • A Review of Glutamate Receptors I: Current Understanding of Their Biology
    J Toxicol Pathol 2008; 21: 25–51 Review A Review of Glutamate Receptors I: Current Understanding of Their Biology Colin G. Rousseaux1 1Department of Pathology and Laboratory Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada Abstract: Seventy years ago it was discovered that glutamate is abundant in the brain and that it plays a central role in brain metabolism. However, it took the scientific community a long time to realize that glutamate also acts as a neurotransmitter. Glutamate is an amino acid and brain tissue contains as much as 5 – 15 mM glutamate per kg depending on the region, which is more than of any other amino acid. The main motivation for the ongoing research on glutamate is due to the role of glutamate in the signal transduction in the nervous systems of apparently all complex living organisms, including man. Glutamate is considered to be the major mediator of excitatory signals in the mammalian central nervous system and is involved in most aspects of normal brain function including cognition, memory and learning. In this review, the basic biology of the excitatory amino acids glutamate, glutamate receptors, GABA, and glycine will first be explored. In the second part of this review, the known pathophysiology and pathology will be described. (J Toxicol Pathol 2008; 21: 25–51) Key words: glutamate, glycine, GABA, glutamate receptors, ionotropic, metabotropic, NMDA, AMPA, review Introduction and Overview glycine), peptides (vasopressin, somatostatin, neurotensin, etc.), and monoamines (norepinephrine, dopamine and In the first decades of the 20th century, research into the serotonin) plus acetylcholine. chemical mediation of the “autonomous” (autonomic) Glutamatergic synaptic transmission in the mammalian nervous system (ANS) was an area that received much central nervous system (CNS) was slowly established over a research activity.
    [Show full text]
  • Multi-Functionality of Proteins Involved in GPCR and G Protein Signaling: Making Sense of Structure–Function Continuum with In
    Cellular and Molecular Life Sciences (2019) 76:4461–4492 https://doi.org/10.1007/s00018-019-03276-1 Cellular andMolecular Life Sciences REVIEW Multi‑functionality of proteins involved in GPCR and G protein signaling: making sense of structure–function continuum with intrinsic disorder‑based proteoforms Alexander V. Fonin1 · April L. Darling2 · Irina M. Kuznetsova1 · Konstantin K. Turoverov1,3 · Vladimir N. Uversky2,4 Received: 5 August 2019 / Revised: 5 August 2019 / Accepted: 12 August 2019 / Published online: 19 August 2019 © Springer Nature Switzerland AG 2019 Abstract GPCR–G protein signaling system recognizes a multitude of extracellular ligands and triggers a variety of intracellular signal- ing cascades in response. In humans, this system includes more than 800 various GPCRs and a large set of heterotrimeric G proteins. Complexity of this system goes far beyond a multitude of pair-wise ligand–GPCR and GPCR–G protein interactions. In fact, one GPCR can recognize more than one extracellular signal and interact with more than one G protein. Furthermore, one ligand can activate more than one GPCR, and multiple GPCRs can couple to the same G protein. This defnes an intricate multifunctionality of this important signaling system. Here, we show that the multifunctionality of GPCR–G protein system represents an illustrative example of the protein structure–function continuum, where structures of the involved proteins represent a complex mosaic of diferently folded regions (foldons, non-foldons, unfoldons, semi-foldons, and inducible foldons). The functionality of resulting highly dynamic conformational ensembles is fne-tuned by various post-translational modifcations and alternative splicing, and such ensembles can undergo dramatic changes at interaction with their specifc partners.
    [Show full text]
  • A Physiological Role for GABAA Receptor Desensitization – Induction of Long-Term Potentiation at Inhibitory Synapses
    bioRxiv preprint doi: https://doi.org/10.1101/2020.06.02.128900; this version posted June 5, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. A physiological role for GABAA receptor desensitization – induction of long-term potentiation at inhibitory synapses Martin Field, Philip Thomas & Trevor G Smart Department of Neuroscience, Physiology & Pharmacology UCL Gower Street London WC1E 6BT bioRxiv preprint doi: https://doi.org/10.1101/2020.06.02.128900; this version posted June 5, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. Abstract GABAA receptors (GABAARs) are pentameric ligand-gated ion channels distributed throughout the brain where they mediate synaptic and tonic inhibition. Following activation, these receptors undergo desensitization which involves entry into long-lived agonist-bound closed states. Although the kinetic effects of this state are recognised and its structural basis has been uncovered, the physiological impact of desensitization on inhibitory neurotransmission remains unknown. Here we describe an enduring new form of long-term potentiation at inhibitory synapses that elevates synaptic current amplitude for 24 hrs following desensitization of GABAARs in response to prolonged agonist exposure or allosteric modulation. Using receptor mutants and allosteric modulators we demonstrate that desensitization of GABAARs facilitates their phosphorylation by PKC, which increases the number of receptors at inhibitory synapses. These observations provide a new physiological relevance to the desensitized state of GABAARs, acting as a signal to regulate the efficacy of inhibitory synapses during prolonged periods of inhibitory neurotransmission.
    [Show full text]
  • The Dynamic Modulation of Gabaa Receptor Trafficking and Its Role in Regulating the Plasticity of Inhibitory Synapses
    Physiol Rev 91: 1009–1022, 2011 doi:10.1152/physrev.00015.2010 THE DYNAMIC MODULATION OF GABAA RECEPTOR TRAFFICKING AND ITS ROLE IN REGULATING THE PLASTICITY OF INHIBITORY SYNAPSES Mansi Vithlani, Miho Terunuma, and Stephen J. Moss Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts; and Department of Neuroscience, Physiology, and Pharmacology, University College London, London, United Kingdom Vithlani M, Terunuma M, Moss SJ. The Dynamic Modulation of GABAA Receptor Trafficking and Its Role in Regulating the Plasticity of Inhibitory Synapses. Physiol Rev 91: 1009–1022, 2011; doi:10.1152/physrev.00015.2010.—Inhibition in the adult mammalian central nervous system (CNS) is mediated by ␥-aminobutyric acid (GABA). The fast inhibitory actions of GABA are mediated by GABA type A receptors (GABAARs); Lthey mediate both phasic and tonic inhibition in the brain and are the principle sites of action for anticonvulsant, anxiolytic, and sedative-hypnotic agents that include benzodiazepines, barbiturates, neurosteroids, and some general anesthetics. GABAARs are heteropentameric ligand-gated ion channels that are found concentrated at inhibitory postsynaptic sites where they mediate phasic inhibition and at extrasynaptic sites where they mediate tonic inhibition. The efficacy of inhibition and thus neuronal excitability is critically dependent on the accumulation of specific GABAAR subtypes at inhibitory synapses. Here we evaluate how neurons control the number of GABAARs on the neuronal plasma membrane together with their selective stabilization at synaptic sites. We then go on to examine the impact that these processes have on the strength of synaptic inhibition and behavior. I. INTRODUCTION 1009 slow and prolonged inhibitory responses (10). GABAARs II.
    [Show full text]
  • Glutamate Inhibits GABA Excitatory Activity in Developing Neurons
    The Journal of Neuroscience, December 15, 1998, 18(24):10749–10761 Glutamate Inhibits GABA Excitatory Activity in Developing Neurons Anthony N. van den Pol,1,2 Xiao-Bing Gao,1 Peter R. Patrylo,1 Prabhat K. Ghosh,1 and Karl Obrietan2 1Department of Neurosurgery, Yale University, New Haven, Connecticut 06520, and 2Department of Biological Sciences, Stanford University, Stanford, California 94305 In contrast to the mature brain, in which GABA is the major suggesting an ongoing spontaneous glutamate-mediated inhi- inhibitory neurotransmitter, in the developing brain GABA can bition of excitatory GABA actions in developing neurons. North- be excitatory, leading to depolarization, increased cytoplasmic ern blots revealed that many mGluRs were expressed early in calcium, and action potentials. We find in developing hypotha- brain development, including times of synaptogenesis. To- lamic neurons that glutamate can inhibit the excitatory actions gether these data suggest that in developing neurons gluta- of GABA, as revealed with fura-2 digital imaging and whole-cell mate can inhibit the excitatory actions of GABA at both pre- recording in cultures and brain slices. Several mechanisms for synaptic and postsynaptic sites, and this may be one set of the inhibitory role of glutamate were identified. Glutamate re- mechanisms whereby the actions of two excitatory transmit- duced the amplitude of the cytoplasmic calcium rise evoked by ters, GABA and glutamate, do not lead to runaway excitation in GABA, in part by activation of group II metabotropic glutamate the developing brain. In addition to its independent excitatory receptors (mGluRs). Presynaptically, activation of the group III role that has been the subject of much attention, our data mGluRs caused a striking inhibition of GABA release in early suggest that glutamate may also play an inhibitory role in stages of synapse formation.
    [Show full text]
  • Multifactorial Basis and Therapeutic Strategies in Metabolism-Related Diseases
    nutrients Review Multifactorial Basis and Therapeutic Strategies in Metabolism-Related Diseases João V. S. Guerra 1,2,† , Marieli M. G. Dias 1,3,† , Anna J. V. C. Brilhante 3,4, Maiara F. Terra 1,3, Marta García-Arévalo 1,* and Ana Carolina M. Figueira 1,* 1 Brazilian Center for Research in Energy and Materials (CNPEM), Brazilian Biosciences National Laboratory (LNBio), Polo II de Alta Tecnologia—R. Giuseppe Máximo Scolfaro, Campinas 13083-100, Brazil; [email protected] (J.V.S.G.); [email protected] (M.M.G.D.); [email protected] (M.F.T.) 2 Graduate Program in Pharmaceutical Sciences, Faculty Pharmaceutical Sciences, University of Campinas, Campinas 13083-970, Brazil 3 Graduate Program in Functional and Molecular Biology, Institute of Biology, State University of Campinas (Unicamp), Campinas 13083-970, Brazil; [email protected] 4 Brazilian Center for Research in Energy and Materials (CNPEM), Brazilian Biorenewables National Laboratory (LNBR), Polo II de Alta Tecnologia—R. Giuseppe Máximo Scolfaro, Campinas 13083-100, Brazil * Correspondence: [email protected] or [email protected] (M.G.-A.); ana.fi[email protected] (A.C.M.F.) † Both authors contributed equally to this work. Abstract: Throughout the 20th and 21st centuries, the incidence of non-communicable diseases (NCDs), also known as chronic diseases, has been increasing worldwide. Changes in dietary and physical activity patterns, along with genetic conditions, are the main factors that modulate the Citation: Guerra, J.V.S.; Dias, metabolism of individuals, leading to the development of NCDs. Obesity, diabetes, metabolic M.M.G.; Brilhante, A.J.V.C.; Terra, associated fatty liver disease (MAFLD), and cardiovascular diseases (CVDs) are classified in this M.F.; García-Arévalo, M.; Figueira, group of chronic diseases.
    [Show full text]
  • G-Protein Coupled Receptors Targeted by Analgesic Venom Peptides
    Review G-Protein Coupled Receptors Targeted by Analgesic Venom Peptides James T. Daniel and Richard J. Clark * School of Biomedical Sciences, University of Queensland, Brisbane, QLD 4072, Australia; [email protected] * Correspondence: [email protected]; Tel.: +61-7-3365-1527 Academic Editor: Stuart M. Brierley and Irina Vetter Received: 24 October 2017; Accepted: 13 November 2017; Published: 16 November 2017 Abstract: Chronic pain is a complex and debilitating condition associated with a large personal and socioeconomic burden. Current pharmacological approaches to treating chronic pain such as opioids, antidepressants and anticonvulsants exhibit limited efficacy in many patients and are associated with dose-limiting side effects that hinder their clinical use. Therefore, improved strategies for the pharmacological treatment of pathological pain are urgently needed. G-protein coupled receptors (GPCRs) are ubiquitously expressed on the surface of cells and act to transduce extracellular signals and regulate physiological processes. In the context of pain, numerous and diverse families of GPCRs expressed in pain pathways regulate most aspects of physiological and pathological pain and are thus implicated as potential targets for therapy of chronic pain. In the search for novel compounds that produce analgesia via GPCR modulation, animal venoms offer an enormous and virtually untapped source of potent and selective peptide molecules. While many venom peptides target voltage-gated and ligand-gated ion channels to inhibit neuronal excitability and blunt synaptic transmission of pain signals, only a small proportion are known to interact with GPCRs. Of these, only a few have shown analgesic potential in vivo. Here we review the current state of knowledge regarding venom peptides that target GPCRs to produce analgesia, and their development as therapeutic compounds.
    [Show full text]
  • GABA Receptors
    Tocris Scientific ReviewReview SeriesSeries Tocri-lu-2945 GABA Receptors Ian L. Martin, Norman G. Bowery Historical Perspective and Susan M.J. Dunn GABA is the major inhibitory amino acid transmitter of the Ian Martin is Professor of Pharmacology in the School of Life and mammalian central nervous system (CNS). Essentially all neurons Health Sciences, Aston University, Birmingham, UK. Norman in the brain respond to GABA and perhaps 20% use it as their 1 Bowery is Emeritus Professor of Pharmacology, University of primary transmitter. Early electrophysiological studies, carried Birmingham, UK. Susan Dunn is Professor and Chair at the out using iontophoretic application of GABA to CNS neuronal Department of Pharmacology, Faculty of Medicine and Dentistry, preparations, showed it to produce inhibitory hyperpolarizing 2 University of Alberta, Canada. All three authors share common responses that were blocked competitively by the alkaloid 3 interests in GABAergic transmission. E-mail: sdunn@pmcol. bicuculline. However, in the late 1970s, Bowery and his ualberta.ca colleagues, who were attempting to identify GABA receptors on peripheral nerve terminals, noted that GABA application reduced the evoked release of noradrenalin in the rat heart and that this Contents effect was not blocked by bicuculline. This action of GABA was Introduction ............................................................................................. 1 mimicked, however, by baclofen (Figure 1), a compound that was unable to produce rapid hyperpolarizing responses
    [Show full text]