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Szabadi E. Three paradoxes related to the mode of action of pramipexole: The path from D2/D3 dopamine receptor stimulation to modification of dopamine-modulated functions. J Psychopharmacol 2024; 38:581-596. [PMID: 39041250 DOI: 10.1177/02698811241261022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/24/2024]
Abstract
Pramipexole, a D2/D3 dopamine receptor agonist, is used to treat the motor symptoms of Parkinson's disease, caused by degeneration of the dopaminergic nigrostriatal pathway. There are three paradoxes associated with its mode of action. Firstly, stimulation of D2/D3 receptors leads to neuronal inhibition, although pramipexole does not inhibit but promotes some dopamine-modulated functions, such as locomotion and reinforcement. Secondly, another dopamine-modulated function, arousal, is not promoted but inhibited by pramipexole, leading to sedation. Thirdly, pramipexole-evoked sedation is associated with an increase in pupil diameter, although sedation is expected to cause pupil constriction. To resolve these paradoxes, the path from stimulation of D2/D3 receptors to the modification of dopamine-modulated functions has been tracked. The functions considered are modulated by midbrain dopaminergic nuclei: locomotion - substantia nigra pars compacta (SNc), reinforcement/motivation - ventral tegmental area (VTA), sympathetic activity (as reflected in pupil function) - VTA; arousal - ventral periaqueductal grey (vPAG), with contributions from VTA and SNc. The application of genetics-based molecular techniques (optogenetics and chemogenetics) has enabled tracing the chains of neurones from the dopaminergic nuclei to their final targets executing the functions. The functional neuronal circuits linked to the D2/D3 receptors in the dorsal and ventral striata, stimulated by inputs from SNc and VTA, respectively, may explain how neuronal inhibition induced by pramipexole is translated into the promotion of locomotion, reinforcement/motivation and sympathetic activity. As the vPAG may increase arousal mainly by stimulating cortical D1 dopamine receptors, pramipexole would stimulate only presynaptic D2/D3 receptors on vPAG neurones, curtailing their activity and leading to sedation.
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Affiliation(s)
- Elemer Szabadi
- Developmental Psychiatry, University of Nottingham, Nottingham, UK
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2
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Characterization of dopamine D 2 receptor coupling to G proteins in postmortem brain of subjects with schizophrenia. Pharmacol Rep 2021; 73:1136-1146. [PMID: 34196951 PMCID: PMC8413194 DOI: 10.1007/s43440-021-00305-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 06/16/2021] [Accepted: 06/24/2021] [Indexed: 11/04/2022]
Abstract
Background Alterations of dopamine D1 (D1R) and D2 receptor (D2R) are proposed in schizophrenia but brain neuroimaging and postmortem studies have shown controversial results in relation to D1R and D2R density. Besides, scarce information on the functionality of brain D1R and D2R is available. The present study characterized G-protein activation by D1R and D2R agonists in postmortem human brain. Furthermore, D2R functional status was compared between schizophrenia and control subjects. Methods G-protein receptor coupling was assessed in control caudate nucleus and frontal cortex by [35S]GTPγS-binding stimulation induced by increasing concentrations (10–10–10–3 M) of dopamine, and the selective dopaminergic agonists SKF38393 (D1R) and NPA (D2R). Concentration–response curves to NPA stimulation of [35S]GTPγS binding were analyzed in antipsychotic-free (n = 10) and antipsychotic-treated (n = 7) schizophrenia subjects and matched controls (n = 17). Results In caudate, [35S]GTPγS-binding responses to agonists were compatible with the existence of functional D2R. In contrast, stimulations in cortex showed responses that did not correspond to D1R or D2R. [35S]GTPγS-binding activation by NPA in caudate displayed biphasic curves with similar profile in schizophrenia (EC50H = 7.94 nM; EC50L = 7.08 μM) and control (EC50H = 7.24 nM; EC50L = 15.14 μM) subjects. The presence or absence of antipsychotic medication did not influence the pharmacological parameters. Conclusions Feasibility of functional evaluation of dopamine receptors in postmortem human brain by conventional [35S]GTPγS-binding assays appears to be restricted to signalling through inhibitory Gi/o proteins. These findings provide functional information about brain D2R status in subjects with schizophrenia and do not support the existence of D2R supersensitive in this mental disorder. Supplementary Information The online version contains supplementary material available at 10.1007/s43440-021-00305-4.
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Functional approaches to the study of G-protein-coupled receptors in postmortem brain tissue: [ 35S]GTPγS binding assays combined with immunoprecipitation. Pharmacol Rep 2021; 73:1079-1095. [PMID: 33876404 DOI: 10.1007/s43440-021-00253-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/16/2021] [Accepted: 03/19/2021] [Indexed: 10/21/2022]
Abstract
G-protein-coupled receptors (GPCRs) have an enormous biochemical importance as they bind to diverse extracellular ligands and regulate a variety of physiological and pathological responses. G-protein activation measures the functional consequence of receptor occupancy at one of the earliest receptor-mediated events. Receptor coupling to G-proteins promotes the GDP/GTP exchange on Gα subunits. Thus, modulation of the binding of the poorly hydrolysable GTP analog [35S]GTPγS to the Gα-protein subunit can be used as a functional approach to quantify GPCR interaction with agonist, antagonist or inverse agonist drugs. In order to determine receptor-mediated selective activation of the different Gα-proteins, [35S]GTPγS binding assays combined with immunodetection by specific antibodies have been developed and applied to physiological and pathological brain conditions. Currently, immunoprecipitation with magnetic beads and scintillation proximity assays are the most habitual techniques for this purpose. The present review summarizes the different procedures, advantages and limitations of the [35S]GTPγS binding assays combined with selective Gα-protein sequestration methods. Experience of functional coupling of several GPCRs to different Gα-proteins and recommendations for optimal performance in brain membranes are described. One of the biggest opportunities opened by these techniques is that they enable evaluation of biased agonism in the native tissue, which results in high interest in drug discovery. The available results derived from application of these functional methodologies to study GPCR dysfunctions in neuro-psychiatric disorders are also described. In conclusion, [35S]GTPγS binding combined with antibody-mediated immunodetection represents an useful method to separately evaluate the functional activity of drugs acting on GPCRs over each Gα-protein subtype.
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Preto AJ, Barreto CAV, Baptista SJ, Almeida JGD, Lemos A, Melo A, Cordeiro MNDS, Kurkcuoglu Z, Melo R, Moreira IS. Understanding the Binding Specificity of G-Protein Coupled Receptors toward G-Proteins and Arrestins: Application to the Dopamine Receptor Family. J Chem Inf Model 2020; 60:3969-3984. [PMID: 32692555 DOI: 10.1021/acs.jcim.0c00371] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
G-Protein coupled receptors (GPCRs) are involved in a myriad of pathways key for human physiology through the formation of complexes with intracellular partners such as G-proteins and arrestins (Arrs). However, the structural and dynamical determinants of these complexes are still largely unknown. Herein, we developed a computational big-data pipeline that enables the structural characterization of GPCR complexes with no available structure. This pipeline was used to study a well-known group of catecholamine receptors, the human dopamine receptor (DXR) family and its complexes, producing novel insights into the physiological properties of these important drug targets. A detailed description of the protein interfaces of all members of the DXR family (D1R, D2R, D3R, D4R, and D5R) and the corresponding protein interfaces of their binding partners (Arrs: Arr2 and Arr3; G-proteins: Gi1, Gi2, Gi3, Go, Gob, Gq, Gslo, Gssh, Gt2, and Gz) was generated. To produce reliable structures of the DXR family in complex with either G-proteins or Arrs, we performed homology modeling using as templates the structures of the β2-adrenergic receptor (β2AR) bound to Gs, the rhodopsin bound to Gi, and the recently acquired neurotensin receptor-1 (NTSR1) and muscarinic 2 receptor (M2R) bound to arrestin (Arr). Among others, the work demonstrated that the three partner groups, Arrs and Gs- and Gi-proteins, are all structurally and dynamically distinct. Additionally, it was revealed the involvement of different structural motifs in G-protein selective coupling between D1- and D2-like receptors. Having constructed and analyzed 50 models involving DXR, this work represents an unprecedented large-scale analysis of GPCR-intracellular partner interface determinants. All data is available at www.moreiralab.com/resources/dxr.
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Affiliation(s)
- A J Preto
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Casa Costa Alemão - Pólo II
- Rua Dom Francisco de Lemos, 3030-789 Coimbra, Portugal
| | - Carlos A V Barreto
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Casa Costa Alemão - Pólo II
- Rua Dom Francisco de Lemos, 3030-789 Coimbra, Portugal
| | - Salete J Baptista
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, ao Km 139,7, 2695-066 Bobadela, Portugal
| | - José Guilherme de Almeida
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,European Bioinformatics Institute EMBL-EBI, Hinxton, Cambridgeshire CB10 1SD, United Kingdom
| | - Agostinho Lemos
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,GIGA Cyclotron Research Centre In Vivo Imaging, University of Liège, Bâtiment B30, Allée du 6 Août, 8, 4000 Liège, Belgium
| | - André Melo
- REQUIMTE/LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua Campo Alegre 687, s/n, 4169-007 Porto, Portugal
| | - M Nátalia D S Cordeiro
- REQUIMTE/LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua Campo Alegre 687, s/n, 4169-007 Porto, Portugal
| | - Zeynep Kurkcuoglu
- Bijvoet Center for Biomolecular Research, Faculty of Science - Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Rita Melo
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, ao Km 139,7, 2695-066 Bobadela, Portugal
| | - Irina S Moreira
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Department of Life Sciences, University of Coimbra, Colégio de S. Bento, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
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Odagaki Y, Kinoshita M, Ota T. Dopamine-induced functional activation of Gα q mediated by dopamine D 1-like receptor in rat cerebral cortical membranes. J Recept Signal Transduct Res 2019; 39:9-17. [PMID: 31223051 DOI: 10.1080/10799893.2018.1562470] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Although multiple roles of dopamine through D1-like (D1 and D5) and D2-like (D2, D3, and D4) receptors are initiated primarily through stimulation or inhibition of adenylyl cyclase via Gs/olf or Gi/o, respectively, there have been many reports indicating diverse signaling mechanisms that involve alternative G protein coupling. In this study, dopamine-induced Gαq activation in rat brain membranes was investigated. Agonist-induced Gαq activation was assessed by increase in guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPγS) binding to Gαq determined by [35S]GTPγS binding/immunoprecipitation assay in rat brain membranes. Dopamine-stimulated Gαq functionality was highest in cortex as compared to hippocampus or striatum. In cerebral cortical membranes, this effect was mimicked by benzazepine derivatives with agonist properties at dopamine D1-like receptors, that is, SKF83959, SKF83822, R(+)-SKF81297, R(+)-SKF38393, and SKF82958, but not by the compounds with dopamine D2-like receptor agonist properties except for aripiprazole. Against expectation, stimulatory effects were also induced by SKF83566, R(+)-SCH23390, and pergolide. The pharmacological profiling by using a series of antagonists indicated that dopamine-induced response was mediated through dopamine D1-like receptor, which was distinct from the receptor involved in 5-HT-induced response (5-HT2A receptor). Conversely, the responses induced by SKF83566, R(+)-SCH23390, and pergolide were most likely mediated by 5-HT2A receptor, but not by dopamine D1-like receptor. Caution should be paid when interpreting the experimental data, especially in behavioral pharmacological research, in which SKF83566 or R(+)-SCH23390 is used as a standard selective dopamine D1-like receptor antagonist. Also, possible clinical implications of the agonistic effects of pergolide on 5-HT2A receptor has been mentioned.
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Affiliation(s)
- Yuji Odagaki
- a Department of Psychiatry, Faculty of Medicine , Saitama Medical University , Saitama , Japan
| | - Masakazu Kinoshita
- a Department of Psychiatry, Faculty of Medicine , Saitama Medical University , Saitama , Japan
| | - Toshio Ota
- a Department of Psychiatry, Faculty of Medicine , Saitama Medical University , Saitama , Japan
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Odagaki Y. Guanosine-5′-O-(3-[35S]thio)triphosphate ([35S]GTPγS) Binding/Immunoprecipitation Assay Using Magnetic Beads Coated with Anti-Gα Antibody in Mammalian Brain Membranes. CO-IMMUNOPRECIPITATION METHODS FOR BRAIN TISSUE 2019. [DOI: 10.1007/978-1-4939-8985-0_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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7
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Lassus B, Naudé J, Faure P, Guedin D, Von Boxberg Y, Mannoury la Cour C, Millan MJ, Peyrin JM. Glutamatergic and dopaminergic modulation of cortico-striatal circuits probed by dynamic calcium imaging of networks reconstructed in microfluidic chips. Sci Rep 2018; 8:17461. [PMID: 30498197 PMCID: PMC6265304 DOI: 10.1038/s41598-018-35802-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 11/07/2018] [Indexed: 11/21/2022] Open
Abstract
Although the prefrontal cortex and basal ganglia are functionally interconnected by parallel loops, cellular substrates underlying their interaction remain poorly understood. One novel approach for addressing this issue is microfluidics, a methodology which recapitulates several intrinsic and synaptic properties of cortico-subcortical networks. We developed a microfluidic device where cortical neurons projected onto striatal neurons in a separate compartment. We exploited real-time (low-resolution/high-output) calcium imaging to register network dynamics and characterize the response to glutamatergic and dopaminergic agents. Reconstructed cortico-striatal networks revealed the progressive appearance of cortical VGLUT1 clusters on striatal dendrites, correlating with the emergence of spontaneous and synchronous glutamatergic responses of striatal neurons to concurrent cortical stimulation. Striatal exposure to the NMDA receptor GluN2A subunit antagonist TCN201 did not affect network rhythm, whereas the GluN2B subunit antagonist RO256981 significantly decreased striatal activity. Dopamine application or the D2/D3 receptor agonist, quinpirole, decreased cortico-striatal synchrony whereas the D1 receptor agonist, SKF38393, was ineffective. These data show that cortico-striatal networks reconstructed in a microfluidic environment are synchronized and present characteristics close to those of their in situ counterparts. They should prove instructive for deciphering the molecular substrates of CNS disorders and evaluating the actions of novel therapeutic agents.
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Affiliation(s)
- Benjamin Lassus
- CNRS UMR 8256, Biological Adaptation and Ageing, Paris, 75005, France.,Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, 75005, Paris, France
| | - Jérémie Naudé
- CNRS UMR 8246, Neurosciences, Paris, 75005, France.,Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, 75005, Paris, France
| | - Philippe Faure
- CNRS UMR 8246, Neurosciences, Paris, 75005, France.,Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, 75005, Paris, France
| | - Denis Guedin
- Servier Biotechnology, Chemogenetic Laboratory @ ICM Brain & Spine Institue, Pitié-Salpétrière Hospital, 52 boulevard Vincent Auriol, 75013, Paris, France
| | - Ysander Von Boxberg
- CNRS UMR 8246, Neurosciences, Paris, 75005, France.,Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, 75005, Paris, France
| | - Clotilde Mannoury la Cour
- Centre for Therapeutic Innovation in Neuropsychiatry, Institut de Recherches Servier, Centre de Recherches de Croissy, 78290, Croissy-sur-Seine, France
| | - Mark J Millan
- Centre for Therapeutic Innovation in Neuropsychiatry, Institut de Recherches Servier, Centre de Recherches de Croissy, 78290, Croissy-sur-Seine, France
| | - Jean-Michel Peyrin
- CNRS UMR 8246, Neurosciences, Paris, 75005, France. .,Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, 75005, Paris, France.
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Odagaki Y, Kinoshita M, Ota T, Javier Meana J, Callado LF, García-Sevilla JA. Functional activation of Gαq coupled to 5-HT2A receptor and M1 muscarinic acetylcholine receptor in postmortem human cortical membranes. J Neural Transm (Vienna) 2017; 124:1123-1133. [DOI: 10.1007/s00702-017-1749-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 06/20/2017] [Indexed: 11/30/2022]
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9
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Frederick AL, Yano H, Trifilieff P, Vishwasrao HD, Biezonski D, Mészáros J, Sibley DR, Kellendonk C, Sonntag KC, Graham DL, Colbran RJ, Stanwood GD, Javitch JA, Javitch JA. Evidence against dopamine D1/D2 receptor heteromers. Mol Psychiatry 2015; 20:1373-85. [PMID: 25560761 PMCID: PMC4492915 DOI: 10.1038/mp.2014.166] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 10/24/2014] [Accepted: 10/27/2014] [Indexed: 02/07/2023]
Abstract
Hetero-oligomers of G-protein-coupled receptors have become the subject of intense investigation, because their purported potential to manifest signaling and pharmacological properties that differ from the component receptors makes them highly attractive for the development of more selective pharmacological treatments. In particular, dopamine D1 and D2 receptors have been proposed to form hetero-oligomers that couple to Gαq proteins, and SKF83959 has been proposed to act as a biased agonist that selectively engages these receptor complexes to activate Gαq and thus phospholipase C. D1/D2 heteromers have been proposed as relevant to the pathophysiology and treatment of depression and schizophrenia. We used in vitro bioluminescence resonance energy transfer, ex vivo analyses of receptor localization and proximity in brain slices, and behavioral assays in mice to characterize signaling from these putative dimers/oligomers. We were unable to detect Gαq or Gα11 protein coupling to homomers or heteromers of D1 or D2 receptors using a variety of biosensors. SKF83959-induced locomotor and grooming behaviors were eliminated in D1 receptor knockout (KO) mice, verifying a key role for D1-like receptor activation. In contrast, SKF83959-induced motor responses were intact in D2 receptor and Gαq KO mice, as well as in knock-in mice expressing a mutant Ala(286)-CaMKIIα that cannot autophosphorylate to become active. Moreover, we found that, in the shell of the nucleus accumbens, even in neurons in which D1 and D2 receptor promoters are both active, the receptor proteins are segregated and do not form complexes. These data are not compatible with SKF83959 signaling through Gαq or through a D1/D2 heteromer and challenge the existence of such a signaling complex in the adult animals that we used for our studies.
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Affiliation(s)
- Aliya L. Frederick
- Neuroscience Graduate Program, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Hideaki Yano
- Departments of Psychiatry and Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - Pierre Trifilieff
- Nutrition and Integrative Neurobiology, INRA UMR 1286; University of Bordeaux, F-33076, Bordeaux, France,Center for Neuroscience. Columbia University, Kolb Research Building, New York, NY10032, USA
| | - Harshad D. Vishwasrao
- Center for Neuroscience. Columbia University, Kolb Research Building, New York, NY10032, USA
| | - Dominik Biezonski
- Departments of Psychiatry and Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - József Mészáros
- Departments of Psychiatry and Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - David R. Sibley
- Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Christoph Kellendonk
- Departments of Psychiatry and Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York, USA,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York, USA
| | - Kai C. Sonntag
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA, USA
| | - Devon L. Graham
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Roger J. Colbran
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA,Vanderbilt Kennedy Center and Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Gregg D. Stanwood
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA,Vanderbilt Kennedy Center and Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Jonathan A. Javitch
- Departments of Psychiatry and Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York, USA,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York, USA
| | - J A Javitch
- Departments of Psychiatry and Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
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Hints on the Lateralization of Dopamine Binding to D1 Receptors in Rat Striatum. Mol Neurobiol 2015; 53:5436-45. [DOI: 10.1007/s12035-015-9468-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 09/29/2015] [Indexed: 10/23/2022]
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Odagaki Y, Kinoshita M, Toyoshima R. Functional activation of Gαq via serotonin2A (5-HT2A) and muscarinic acetylcholine M1 receptors assessed by guanosine-5׳-O-(3-[35S]thio)triphosphate ([35S]GTPγS) binding/immunoprecipitation in rat brain membranes. Eur J Pharmacol 2014; 726:109-15. [PMID: 24485888 DOI: 10.1016/j.ejphar.2013.12.040] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Revised: 12/10/2013] [Accepted: 12/30/2013] [Indexed: 11/29/2022]
Abstract
Functional coupling between serotonin2A (5-HT2A) receptors and Gαq proteins in native brain membranes has been sparsely reported thus far. In the present study, the guanosine-5׳-O-(3-[35S]thio)triphosphate ([35S]GTPγS) binding assay combined with immunoprecipitation using magnetic beads (Dynabeads Protein A) coated with anti-Gαq antibody was developed. Under experimental conditions optimised for assay constituents (GDP, MgCl2, and NaCl), for contents of membrane protein, anti-Gαq antibody, and Dynabeads Protein A, and for the incubation period, 5-HT stimulated specific [35S]GTPγS binding to Gαq in rat cerebral cortical membranes in a concentration-dependent and saturable manner, with a signal/noise ratio that was sufficiently high for further detailed pharmacological characterisation. This characterisation revealed an involvement of 5-HT2A receptors. Activation of Gαq proteins was also detectable by the addition of carbachol via muscarinic acetylcholine M1 receptors, (-)-epinephrine, and dopamine, but not by L-glutamate or (±)-baclofen. When 5-HT2A receptors and M1 receptors were stimulated simultaneously, there were non-additive effects, indicating that the two receptors were coupled to the same components of Gαq proteins in the rat cerebral cortex. This method will serve as an efficacious strategy for neurobiological investigations aimed at elucidating the physiological and pathological implications of signal transduction systems mediated via Gαq proteins coupled with 5-HT2A receptors and muscarinic acetylcholine M1 receptors.
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Dopamine and extinction: a convergence of theory with fear and reward circuitry. Neurobiol Learn Mem 2013; 108:65-77. [PMID: 24269353 DOI: 10.1016/j.nlm.2013.11.007] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 11/01/2013] [Accepted: 11/08/2013] [Indexed: 01/11/2023]
Abstract
Research on dopamine lies at the intersection of sophisticated theoretical and neurobiological approaches to learning and memory. Dopamine has been shown to be critical for many processes that drive learning and memory, including motivation, prediction error, incentive salience, memory consolidation, and response output. Theories of dopamine's function in these processes have, for the most part, been developed from behavioral approaches that examine learning mechanisms in reward-related tasks. A parallel and growing literature indicates that dopamine is involved in fear conditioning and extinction. These studies are consistent with long-standing ideas about appetitive-aversive interactions in learning theory and they speak to the general nature of cellular and molecular processes that underlie behavior. We review the behavioral and neurobiological literature showing a role for dopamine in fear conditioning and extinction. At a cellular level, we review dopamine signaling and receptor pharmacology, cellular and molecular events that follow dopamine receptor activation, and brain systems in which dopamine functions. At a behavioral level, we describe theories of learning and dopamine function that could describe the fundamental rules underlying how dopamine modulates different aspects of learning and memory processes.
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Díaz C, García C, Iturriaga-Vásquez P, Aguirre MJ, Muena JP, Contreras R, Ormazábal-Toledo R, Isaacs M. Experimental and theoretical study on the oxidation mechanism of dopamine in n-octyl pyridinium based ionic liquids–carbon paste modified electrodes. Electrochim Acta 2013. [DOI: 10.1016/j.electacta.2013.08.103] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Khawaja X, Dunlop J, Kowal D. Scintillation proximity assay in lead discovery. Expert Opin Drug Discov 2013; 3:1267-80. [PMID: 23496165 DOI: 10.1517/17460441.3.11.1267] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Scintillation proximity assay (SPA) is a homogeneous scintillant bead-based platform for the measurement of biological processes and plays an important role in the identification of active chemical entities in drug discovery. OBJECTIVE The design and development of solid-phase SPA approaches are examined and compared with alternative non-radiometric fluorescence-based technologies. METHODS This review provides background on the principle of SPA and its application to biomolecular interactions from a variety of biological sources. CONCLUSION The SPA approach is well suited to the demands of commercial high volume automation and assay miniaturization for target-based high-throughput screening campaigns on synthetic and natural product libraries as well as for benchtop characterization and confirmation studies. In the near future, innovations in the way SPA and fluorescence-based screening strategies are multiplexed will improve our comprehensive understanding of cellular system biology and dramatically advance the lead discovery process for the treatment of complex target-related disorders.
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Affiliation(s)
- Xavier Khawaja
- Depression and Anxiety, Neuroscience Discovery Research, Wyeth Research, Princeton, NJ 08543, USA +1 732 274 4382 ; +1 732 274 4020 ;
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Effects of protein kinase A inhibitor and activator on rewarding effects of SKF-82958 microinjected into nucleus accumbens shell of ad libitum fed and food-restricted rats. Psychopharmacology (Berl) 2012; 221:589-99. [PMID: 22143580 PMCID: PMC3310955 DOI: 10.1007/s00213-011-2602-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Accepted: 11/27/2011] [Indexed: 10/14/2022]
Abstract
RATIONALE Previous studies indicate that the rewarding effect of D-1 dopamine receptor stimulation in nucleus accumbens (NAc) shell is greater in food-restricted (FR) than in ad libitum fed (AL) rats. The D-1 receptor is positively coupled to adenylyl cyclase and activates protein kinase A (PKA). OBJECTIVES The purpose of this study was to determine whether PKA is involved in the rewarding effect of D-1 receptor stimulation and, if so, whether it is involved in the enhanced response of FR rats. MATERIALS AND METHODS Rats were stereotaxically implanted with microinjection cannulae in NAc shell and a stimulating electrode in lateral hypothalamus. The rewarding effects of SKF-82958 (1.5 or 3.0 μg, bilaterally) in the presence and absence of PKA inhibitor, Rp-cAMPS (8.9 μg), and PKA activator, Sp-cAMPS (8.9 μg), were assessed using the curve-shift method of intracranial self-stimulation (ICSS). Basal NAc levels of DARPP-32 phosphorylated on Thr34 and Thr75 were measured. RESULTS Rp-cAMPS increased the rewarding effect of SKF-82958 in AL but not FR rats, doubling the ICSS threshold-lowering effect of the 3.0-μg dose. Sp-cAMPS decreased the rewarding effect of SKF-82958 in FR but not AL rats. Levels of phospho-DARPP-32 (Thr75), which inhibits PKA, were higher in FR than AL rats. CONCLUSIONS Results indicate that inhibition of PKA enhances the unconditioned rewarding effect of D-1 receptor stimulation and that decreased PKA may be involved in the effect of FR on drug reward. Evidence for involvement of D-2 receptor-expressing neurons in the enhancing effect of PKA inhibition is discussed.
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Muscarinic acetylcholine receptor-mediated activation of G(q) in rat brain membranes determined by guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPγS) binding using an anti-G protein scintillation proximity assay. J Neural Transm (Vienna) 2011; 119:525-32. [PMID: 22127550 DOI: 10.1007/s00702-011-0742-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 11/20/2011] [Indexed: 10/15/2022]
Abstract
In the present study, we performed antibody-capture guanosine-5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPγS) scintillation proximity assay (SPA), in which immuno-capture of Gα subunits following [(35)S]GTPγS binding was combined with SPA technology, in rat brain membranes. Preliminary experiments using a series of agonists and commercially available anti-Gα antibodies indicated the increase in specific [(35)S]GTPγS binding to Gα(q) determined with the anti-Gα antibody sc-393 and evoked by carbamylcholine chloride (CCh) was pharmacologically relevant. The experimental conditions were optimized as for the concentrations of GDP, MgCl(2), and NaCl, the dilution of the anti-Gα(q) antibody, and membrane protein contents incubated. Under the optimized conditions, CCh-stimulated specific [(35)S]GTPγS binding to Gα(q) in a concentration-dependent and saturable manner with an EC(50) of around 10 μM in all of the membranes prepared from rat hippocampus, cerebral cortex, and striatum. The maximum responses were varied according to the brain regions, with the rank order in magnitude of hippocampus > cerebral cortex > striatum. The addition of MT-7, a snake toxin with high selectivity for M(1) over the other muscarinic acetylcholine receptors (mAChRs) (M(2)-M(5)), almost completely extinguished CCh-stimulated [(35)S]GTPγS binding to Gα(q), even at a concentration as low as 1 nM. These results indicate that the functional coupling between M(1) mAChR and Gα(q) can be investigated in rat native brain membranes by means of antibody-capture SPA/[(35)S]GTPγS binding assay. The assay developed in the present study would provide a useful strategy for investigation of possible pathophysiological alterations in neuropsychiatric disorders such as Alzheimer's disease and schizophrenia as well as for drug discovery.
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Hervé D. Identification of a specific assembly of the g protein golf as a critical and regulated module of dopamine and adenosine-activated cAMP pathways in the striatum. Front Neuroanat 2011; 5:48. [PMID: 21886607 PMCID: PMC3155884 DOI: 10.3389/fnana.2011.00048] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 07/20/2011] [Indexed: 11/16/2022] Open
Abstract
In the principal neurons of striatum (medium spiny neurons, MSNs), cAMP pathway is primarily activated through the stimulation of dopamine D1 and adenosine A2A receptors, these receptors being mainly expressed in striatonigral and striatopallidal MSNs, respectively. Since cAMP signaling pathway could be altered in various physiological and pathological circumstances, including drug addiction and Parkinson’s disease, it is of crucial importance to identify the molecular components involved in the activation of this pathway. In MSNs, cAMP pathway activation is not dependent on the classical Gs GTP-binding protein but requires a specific G protein subunit heterotrimer containing Gαolf/β2/γ7 in particular association with adenylyl cyclase type 5. This assembly forms an authentic functional signaling unit since loss of one of its members leads to defects of cAMP pathway activation in response to D1 or A2A receptor stimulation, inducing dramatic impairments of behavioral responses dependent on these receptors. Interestingly, D1 receptor (D1R)-dependent cAMP signaling is modulated by the neuronal levels of Gαolf, indicating that Gαolf represents the rate-limiting step in this signaling cascade and could constitute a critical element for regulation of D1R responses. In both Parkinsonian patients and several animal models of Parkinson’s disease, the lesion of dopamine neurons produces a prolonged elevation of Gαolf levels. This observation gives an explanation for the cAMP pathway hypersensitivity to D1R stimulation, occurring despite an unaltered D1R density. In conclusion, alterations in the highly specialized assembly of Gαolf/β2/γ7 subunits can happen in pathological conditions, such as Parkinson’s disease, and it could have important functional consequences in relation to changes in D1R signaling in the striatum.
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Kurokawa K, Mizuno K, Kiyokage E, Shibasaki M, Toida K, Ohkuma S. Dopamine D1 receptor signaling system regulates ryanodine receptor expression after intermittent exposure to methamphetamine in primary cultures of midbrain and cerebral cortical neurons. J Neurochem 2011; 118:773-83. [DOI: 10.1111/j.1471-4159.2011.07366.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Chu HY, Yang Z, Zhao B, Jin GZ, Hu GY, Zhen X. Activation of phosphatidylinositol-linked D1-like receptors increases spontaneous glutamate release in rat somatosensory cortical neurons in vitro. Brain Res 2010; 1343:20-7. [DOI: 10.1016/j.brainres.2010.04.043] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2010] [Revised: 04/15/2010] [Accepted: 04/18/2010] [Indexed: 11/29/2022]
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Undieh AS. Pharmacology of signaling induced by dopamine D(1)-like receptor activation. Pharmacol Ther 2010; 128:37-60. [PMID: 20547182 DOI: 10.1016/j.pharmthera.2010.05.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Accepted: 05/19/2010] [Indexed: 12/30/2022]
Abstract
Dopamine D(1)-like receptors consisting of D(1) and D(5) subtypes are intimately implicated in dopaminergic regulation of fundamental neurophysiologic processes such as mood, motivation, cognitive function, and motor activity. Upon stimulation, D(1)-like receptors initiate signal transduction cascades that are mediated through adenylyl cyclase or phosphoinositide metabolism, with subsequent enhancement of multiple downstream kinase cascades. The latter actions propagate and further amplify the receptor signals, thus predisposing D(1)-like receptors to multifaceted interactions with various other mediators and receptor systems. The adenylyl cyclase response to dopamine or selective D(1)-like receptor agonists is reliably associated with the D(1) subtype, while emerging evidence indicates that the phosphoinositide responses in native brain tissues may be preferentially mediated through stimulation of the D(5) receptor. Besides classic coupling of each receptor subtype to specific G proteins, additional biophysical models are advanced in attempts to account for differential subcellular distribution, heteromolecular oligomerization, and activity-dependent selectivity of the receptors. It is expected that significant advances in understanding of dopamine neurobiology will emerge from current and anticipated studies directed at uncovering the molecular mechanisms of D(5) coupling to phosphoinositide signaling, the structural features that might enhance pharmacological selectivity for D(5) versus D(1) subtypes, the mechanism by which dopamine may modulate phosphoinositide synthesis, the contributions of the various responsive signal mediators to D(1) or D(5) interactions with D(2)-like receptors, and the spectrum of dopaminergic functions that may be attributed to each receptor subtype and signaling pathway.
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Affiliation(s)
- Ashiwel S Undieh
- Laboratory of Integrative Neuropharmacology, Department of Pharmaceutical Sciences, Thomas Jefferson University School of Pharmacy, 130 South 9th Street, Suite 1510, Philadelphia, PA 19107, USA.
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Ukhanov K, Corey EA, Brunert D, Klasen K, Ache BW. Inhibitory odorant signaling in Mammalian olfactory receptor neurons. J Neurophysiol 2009; 103:1114-22. [PMID: 20032232 DOI: 10.1152/jn.00980.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Odorants inhibit as well as excite olfactory receptor neurons (ORNs) in many species of animals. Cyclic nucleotide-dependent activation of canonical mammalian ORNs is well established but it is still unclear how odorants inhibit these cells. Here we further implicate phosphoinositide-3-kinase (PI3K), an indispensable element of PI signaling in many cellular processes, in olfactory transduction in rodent ORNs. We show that odorants rapidly and transiently activate PI3K in the olfactory cilia and in the olfactory epithelium in vitro. We implicate known G-protein-coupled isoforms of PI3K and show that they modulate not only the magnitude but also the onset kinetics of the electrophysiological response of ORNs to complex odorants. Finally, we show that the ability of a single odorant to inhibit another can be PI3K dependent. Our collective results provide compelling support for the idea that PI3K-dependent signaling mediates inhibitory odorant input to mammalian ORNs and at least in part contributes to the mixture suppression typically seen in the response of ORNs to complex natural odorants.
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Affiliation(s)
- Kirill Ukhanov
- Whitney Laboratory, Center for Smell and Taste, University of Florida, Gainesville, FL 32610-0127, USA.
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Arylbenzazepines are potent modulators for the delayed rectifier K+ channel: a potential mechanism for their neuroprotective effects. PLoS One 2009; 4:e5811. [PMID: 19503734 PMCID: PMC2690691 DOI: 10.1371/journal.pone.0005811] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 05/06/2009] [Indexed: 11/19/2022] Open
Abstract
(+/-) SKF83959, like many other arylbenzazepines, elicits powerful neuroprotection in vitro and in vivo. The neuroprotective action of the compound was found to partially depend on its D(1)-like dopamine receptor agonistic activity. The precise mechanism for the (+/-) SKF83959-mediated neuroprotection remains elusive. We report here that (+/-) SKF83959 is a potent blocker for delayed rectifier K(+) channel. (+/-) SKF83959 inhibited the delayed rectifier K(+) current (I(K)) dose-dependently in rat hippocampal neurons. The IC(50) value for inhibition of I(K) was 41.9+/-2.3 microM (Hill coefficient = 1.81+/-0.13, n = 6), whereas that for inhibition of I(A) was 307.9+/-38.5 microM (Hill coefficient = 1.37+/-0.08, n = 6). Thus, (+/-) SKF83959 is 7.3-fold more potent in suppressing I(K) than I(A). Moreover, the inhibition of I(K) by (+/-) SKF83959 was voltage-dependent and not related to dopamine receptors. The rapidly onset of inhibition and recovery suggests that the inhibition resulted from a direct interaction of (+/-) SKF83959 with the K(+) channel. The intracellular application of (+/-) SKF83959 had no effects of on I(K), indicating that the compound most likely acts at the outer mouth of the pore of K(+) channel. We also tested the enantiomers of (+/-) SKF83959, R-(+) SKF83959 (MCL-201), and S-(-) SKF83959 (MCL-202), as well as SKF38393; all these compounds inhibited I(K). However, (+/-) SKF83959, at either 0.1 or 1 mM, exhibited the strongest inhibition on the currents among all tested drug. The present findings not only revealed a new potent blocker of I(K) , but also provided a novel mechanism for the neuroprotective action of arylbenzazepines such as (+/-) SKF83959.
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Mannoury La Cour C, Chaput C, Touzard M, Millan MJ. An immunocapture/scintillation proximity analysis of G alpha q/11 activation by native serotonin (5-HT)2A receptors in rat cortex: blockade by clozapine and mirtazapine. Synapse 2009; 63:95-105. [PMID: 19016481 DOI: 10.1002/syn.20587] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Though transduction mechanisms recruited by heterologously expressed 5-HT(2A) receptors have been extensively studied, their interaction with specific subtypes of G-protein remains to be directly evaluated in cerebral tissue. Herein, as shown by an immunocapture/scintillation proximity analysis, 5-HT, the prototypical 5-HT(2A) agonist, DOI, and Ro60,0175 all enhanced [(35)S]GTPgammaS binding to G alpha q/11 in rat cortex with pEC(50) values of 6.22, 7.24 and 6.35, respectively. No activation of G o or G s/olf was seen at equivalent concentrations of DOI. Stimulation of G alpha q/11 by 5-HT (30 microM) and DOI (30 microM) was abolished by the selective 5-HT(2A) vs. 5-HT(2C)/5-HT(2B) antagonists, ketanserin (pK(B) values of 9.11 and 8.88, respectively) and MDL100,907 (9.82 and 9.68). By contrast, 5-HT-induced [(35)S]GTPgammaS binding to G alpha q/11 was only weakly inhibited by the preferential 5-HT(2C) receptor antagonists, RS102,221 (6.94) and SB242,084 (7.39), and the preferential 5-HT(2B) receptor antagonist, LY266,097 (6.66). The antipsychotic, clozapine, which had marked affinity for 5-HT(2A) receptors, blocked the recruitment of G alpha q/11 by 5-HT and DOI with pK(B) values of 8.54 and 8.14, respectively. Its actions were mimicked by the "atypical" antidepressant and 5-HT(2A) receptor antagonist, mirtazapine, which likewise blocked 5-HT and DOI-induced G alpha q/11 protein activation with pK(B) values of 7.90 and 7.76, respectively. In conclusion, by use of an immunocapture/scintillation proximity strategy, this study shows that native 5-HT(2A) receptors in rat frontal cortex specifically recruit G alpha q/11 and that this action is blocked by clozapine and mirtazapine. Quantification of 5-HT(2A) receptor-mediated G alpha q/11 activation in frontal cortex should prove instructive in characterizing the actions of diverse classes of psychotropic agent.
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Affiliation(s)
- C Mannoury La Cour
- Institut de Recherche Servier, Psychopharmacology Department, 125 Chemin de Ronde, 78290 Croissy sur Seine, France.
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Loiseau F, Millan MJ. Blockade of dopamine D(3) receptors in frontal cortex, but not in sub-cortical structures, enhances social recognition in rats: similar actions of D(1) receptor agonists, but not of D(2) antagonists. Eur Neuropsychopharmacol 2009; 19:23-33. [PMID: 18793829 DOI: 10.1016/j.euroneuro.2008.07.012] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Revised: 07/25/2008] [Accepted: 07/29/2008] [Indexed: 10/21/2022]
Abstract
Though D(3) receptor antagonists can enhance cognitive function, their sites of action remain unexplored. This issue was addressed employing a model of social recognition in rats, and the actions of D(3) antagonists were compared to D(1) agonists that likewise possess pro-cognitive properties. Infusion of the highly selective D(3) antagonists, S33084 and SB277,011 (0.04-2.5 microg/side), into the frontal cortex (FCX) dose-dependently reversed the deficit in recognition induced by a delay. By contrast, the preferential D(2) antagonist, L741,626 (0.63-5.0) had no effect. The action of S33084 was regionally specific inasmuch as its injection into the nucleus accumbens or striatum was ineffective. A similar increase of recognition was obtained upon injection of the D(1) agonist, SKF81297 (0.04-0.63), into the FCX though it was also active (0.63) in the nucleus accumbens. These data suggest that D(3) receptors modulating social recognition are localized in FCX, and underpin their pertinence as targets for antipsychotic agents.
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Affiliation(s)
- Florence Loiseau
- Institut de Recherches Servier, Department of Psychopharmacology, 125 Chemin de ronde, 78290 Croissy-sur-Seine, Paris, France.
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Vonk A, Reinart R, Rinken A. Modulation of adenylyl cyclase activity in rat striatal homogenate by dopaminergic receptors. J Pharmacol Sci 2008; 108:63-70. [PMID: 18818481 DOI: 10.1254/jphs.08019fp] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
We have characterized the modulation of adenylyl cyclase (AC) activity by ligands of dopaminergic receptors in rat striatal homogenate and compared the results with receptor-ligand binding affinities. Despite the fact that rat striatum contains high level of both dopamine D(1) and D(2) receptors, only the D(1)-specific AC activation by agonists could be determined. All D(1)-receptor agonists (dopamine, dihydrexidine, and A 77636) used were able to increase cAMP accumulation in a concentration-dependent manner, while D(1)-receptor antagonists (SCH23390, SKF83566, and butaclamol) blocked the effects induced by the aforementioned agonists. At the same time, the D(2)-receptor agonist quinpirole and antagonist sulpiride had no effect on cAMP accumulation in striatal homogenate neither on the basal level nor on the activated level of AC, while inhibited [(3)H]raclopride binding to these membranes. Comparing the ligands of the D(1) receptor in modulating the activity of AC and displacing D(1)-receptor-specific radioligand [(3)H]SCH23390 binding revealed that the ligands modulate both of these processes with similar affinities. It indicates that under given experimental conditions, only dopamine D(1)-receptor-mediated stimulation of AC activity can be measured in membrane homogenate of rat striatum, while dopamine D(2)-receptor effects remain fully hidden.
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Affiliation(s)
- Argo Vonk
- Institute of Chemistry, University of Tartu, Jakobi 2, Tartu, Estonia
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Ma ZZ, Xu W, Jensen NH, Roth BL, Liu-Chen LY, Lee DYW. Isoquinoline alkaloids isolated from Corydalis yanhusuo and their binding affinities at the dopamine D1 receptor. Molecules 2008; 13:2303-12. [PMID: 18830156 PMCID: PMC6245449 DOI: 10.3390/molecules13092303] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 09/15/2008] [Accepted: 09/16/2008] [Indexed: 11/17/2022] Open
Abstract
Bioactivity-guided fractionation of Corydalis yanhusuo has resulted in the isolation of eight known isoquinoline alkaloids - tetrahydropalmatine, isocorypalmine, stylopine, corydaline, columbamine, coptisin, 13-methylpalmatine, and dehydrocorybulbine. The tertiary alkaloids were further analyzed by chiral HPLC to determine the ratios of d-and l-isomers. The isolated compounds were screened for their binding affinities at the dopamine D(1) receptor. Isocorypalmine had the highest affinity (K(i) = 83 nM). The structure-affinity relationships of these alkaloids are discussed.
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Affiliation(s)
- Zhong-Ze Ma
- Bio-Organic and Natural Products Laboratory, McLean Hospital, Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA
| | - Wei Xu
- Department of Pharmacology and Center for Substance Abuse Research, School of Medicine, Temple University, 3420 N. Broad St, Philadelphia, PA 19140, USA; E-mail: (W. X.), (L-Y. L-C.)
| | - Niels H. Jensen
- Department of Pharmacology, University of North Carolina Medical School, Chapel Hill, NC 27599, USA; E-mail: (N-H. J.)
- Center for Neurobiology Division of Medicinal Chemistry and Natural Products, and NIMH Psychoactive Drug Screening Program, University of North Carolina Medical School, Chapel Hill, NC 27599, USA; E-mail: (B-L. R.)
| | - Bryan L. Roth
- Department of Pharmacology, University of North Carolina Medical School, Chapel Hill, NC 27599, USA; E-mail: (N-H. J.)
- Center for Neurobiology Division of Medicinal Chemistry and Natural Products, and NIMH Psychoactive Drug Screening Program, University of North Carolina Medical School, Chapel Hill, NC 27599, USA; E-mail: (B-L. R.)
| | - Lee-Yuan Liu-Chen
- Department of Pharmacology and Center for Substance Abuse Research, School of Medicine, Temple University, 3420 N. Broad St, Philadelphia, PA 19140, USA; E-mail: (W. X.), (L-Y. L-C.)
| | - David Y. W. Lee
- Bio-Organic and Natural Products Laboratory, McLean Hospital, Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA
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Actions of novel agonists, antagonists and antipsychotic agents at recombinant rat 5-HT6 receptors: a comparative study of coupling to G alpha s. Eur J Pharmacol 2008; 588:170-7. [PMID: 18511034 DOI: 10.1016/j.ejphar.2008.04.039] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Revised: 03/21/2008] [Accepted: 04/11/2008] [Indexed: 01/27/2023]
Abstract
Though 5-HT6 receptors are targets for the treatment of schizophrenia and other psychiatric disorders, the influence of drugs upon signal transduction has not been extensively characterized. Herein, we employed a Scintillation Proximity Assay (SPA)/antibody-immunocapture procedure of coupling to G alpha s to evaluate the interaction of a broad range of novel agonists, antagonists and antipsychotics at rat 5-HT(6) receptors stably expressed in HEK293 cells. Serotonin (pEC(50), 7.7) increased [35S]GTP gamma S binding to G alpha s by ca 2-fold without affecting binding to Gi/o or Gq. LSD (9.2), 5-MeODMT (7.9), 5-CT (7.0) and tryptamine (6.1) were likewise full agonists. In contrast, the novel sulfonyl derivatives, WAY181,187 (9.1) and WAY208,466 (7.8), behaved as partial agonists and attenuated the actions of 5-HT. SB271,046 and SB258,585 abolished activation of G alpha s by 5-HT with pKb values of 10.2 and 9.9, respectively, actions mimicked by the novel antagonist, SB399,885 (10.9). SB271,046 likewise blocked partial agonist properties of WAY181,187 and WAY208,466 with pKb values of 9.8 and 9.0, respectively. 5-HT-stimulated [35S]GTP gamma S binding to G alpha s was antagonised by various antipsychotics including olanzapine (7.8), asenapine (9.1) and SB737,050 (7.8), whereas aripiprazole and bifeprunox were inactive. Further, antagonist properties of clozapine (8.0) were mimicked by its major metabolite, N-desmethylclozapine (7.9). In conclusion, the novel ligands, WAY208,466 and WAY181,187, behaved as partial agonists at 5-HT6 receptors coupled to G alpha s, while SB399,885 was a potent antagonist. Though 5-HT6 receptor blockade is not indispensable for therapeutic efficacy, it may well play a role in the functional actions of certain antipsychotic agents.
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Shilling PD, Saint Marie RL, Shoemaker JM, Swerdlow NR. Strain differences in the gating-disruptive effects of apomorphine: relationship to gene expression in nucleus accumbens signaling pathways. Biol Psychiatry 2008; 63:748-58. [PMID: 18083141 PMCID: PMC2771724 DOI: 10.1016/j.biopsych.2007.10.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 10/09/2007] [Accepted: 10/17/2007] [Indexed: 01/01/2023]
Abstract
BACKGROUND Prepulse inhibition (PPI) of startle is a measure of sensorimotor gating that is deficient in certain psychiatric disorders, including schizophrenia. Sprague Dawley (SD) rats are more sensitive to PPI-disruptive effects of apomorphine (APO) at long interstimulus intervals (ISIs) (60-120 msec) and less sensitive to PPI-enhancing effects of APO at short ISIs (10-30 msec) compared with Long Evans (LE) rats. METHODS Prepulse inhibition was tested in SD and LE rats after APO (.5 mg/kg) or vehicle in a within- subject design and sacrificed 14 days later. Total RNA was extracted from the nucleus accumbens (NAC). Approximately 700 dopamine-relevant transcripts on the Affymetrix 230 2.0 microarray were analyzed. RESULTS As previously reported, SD rats exhibited greater APO-induced PPI deficits at long intervals and less APO-induced PPI enhancement at short intervals compared with LE rats. One hundred four genes exhibited significantly different NAC expression levels in these two strains. Pathway analysis revealed that many of these genes contribute to dopamine receptor signaling, synaptic long-term potentiation, or inositol phosphate metabolism. The expression of some genes significantly correlated with measures of APO-induced PPI sensitivity in either SD or LE rats. The expression of select genes was validated by real-time reverse transcription polymerase chain reaction (RT-PCR). CONCLUSIONS Differences in PPI APO sensitivity in SD versus LE rats are robust and reproducible and may be related to strain differences in the expression of genes that regulate signal transduction in the NAC. These genes could facilitate the identification of targets for ameliorating heritable gating deficits in brain disorders such as schizophrenia.
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Mannoury la Cour C, Herbelles C, Pasteau V, de Nanteuil G, Millan MJ. Influence of positive allosteric modulators on GABA(B) receptor coupling in rat brain: a scintillation proximity assay characterisation of G protein subtypes. J Neurochem 2007; 105:308-23. [PMID: 18021295 DOI: 10.1111/j.1471-4159.2007.05131.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Little is known concerning coupling of cerebral GABA(B) receptors to G protein subtypes, and the influence of positive allosteric modulators (PAMs) has not been evaluated. These questions were addressed by an antibody-capture/scintillation proximity assay strategy. GABA concentration-dependently enhanced the magnitude of [(35)S]GTPgammaS binding to Galphao and, less markedly, Galphai(1/3) in cortex, whereas Gq and Gs/olf were unaffected. (R)-baclofen and SKF97581 likewise activated Galphao and Galphai(1/3), expressing their actions more potently than GABA. Similar findings were acquired in hippocampus and cerebellum, and the GABA(B) antagonist, CGP55845A, abolished agonist-induced activation of Galphao and Galphai(1/3) in all structures. The PAMs, GS39783, CGP7930 and CGP13501, inactive alone, enhanced efficacy and potency of agonist-induced [(35)S]GTPgammaS binding to Galphao in all regions, actions abolished by CGP55845A. In contrast, they did not modify efficacies at Galphai(1/3). Similarly, in human embryonic kidney cells expressing GABA(B(1a+2)) or GABA(B(1b+2)) receptors, allosteric modulators did not detectably enhance efficacy of GABA at Galphai(1/3), though they increased its potency. To summarise, GABA(B) receptors coupled both to Galphao and to Galphai, but not Gq and Gs/olf, in rat brain. PAMs more markedly enhanced efficacy of coupling to Go versus Gi(1/3). It will be of interest to confirm these observations employing complementary techniques and to evaluate their potential therapeutic significance.
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