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Dysfunctional Heteroreceptor Complexes as Novel Targets for the Treatment of Major Depressive and Anxiety Disorders. Cells 2022; 11:cells11111826. [PMID: 35681521 PMCID: PMC9180493 DOI: 10.3390/cells11111826] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/10/2022] [Accepted: 05/20/2022] [Indexed: 02/01/2023] Open
Abstract
Among mental diseases, major depressive disorder (MDD) and anxiety deserve a special place due to their high prevalence and their negative impact both on society and patients suffering from these disorders. Consequently, the development of novel strategies designed to treat them quickly and efficiently, without or at least having limited side effects, is considered a highly important goal. Growing evidence indicates that emerging properties are developed on recognition, trafficking, and signaling of G-protein coupled receptors (GPCRs) upon their heteromerization with other types of GPCRs, receptor tyrosine kinases, and ionotropic receptors such as N-methyl-D-aspartate (NMDA) receptors. Therefore, to develop new treatments for MDD and anxiety, it will be important to identify the most vulnerable heteroreceptor complexes involved in MDD and anxiety. This review focuses on how GPCRs, especially serotonin, dopamine, galanin, and opioid heteroreceptor complexes, modulate synaptic and volume transmission in the limbic networks of the brain. We attempt to provide information showing how these emerging concepts can contribute to finding new ways to treat both MDD and anxiety disorders.
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Guidolin D, Marcoli M, Tortorella C, Maura G, Agnati LF. Adenosine A 2A-dopamine D 2 receptor-receptor interaction in neurons and astrocytes: Evidence and perspectives. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2019; 169:247-277. [PMID: 31952688 DOI: 10.1016/bs.pmbts.2019.11.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The discovery of receptor-receptor interactions in the early 1980s, together with a more accurate focusing of allosteric mechanisms in proteins, expanded the knowledge on the G protein-coupled receptor (GPCR)-mediated signaling processes. GPCRs were seen to operate not only as monomers, but also as quaternary structures shaped by allosteric interactions. These integrative mechanisms can change the function of the GPCRs involved, leading to a sophisticated dynamic of the receptor assembly in terms of modulation of recognition and signaling. In this context, the heterodimeric complex formed by the adenosine A2A and the dopamine D2 receptors likely represents a prototypical example. The pharmacological evidence obtained, together with the tissue distribution of the A2A-D2 heteromeric complexes, suggested they could represent a target for new therapeutic strategies addressing significant disorders of the central nervous system. The research findings and the perspectives they offer from the therapeutic standpoint are the focus of the here presented discussion.
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Affiliation(s)
- Diego Guidolin
- Department of Neuroscience, Section of Anatomy, University of Padova, Padova, Italy.
| | - Manuela Marcoli
- Department of Pharmacy and Center of Excellence for Biomedical Research, University of Genova, Genova, Italy
| | - Cinzia Tortorella
- Department of Neuroscience, Section of Anatomy, University of Padova, Padova, Italy
| | - Guido Maura
- Department of Pharmacy and Center of Excellence for Biomedical Research, University of Genova, Genova, Italy
| | - Luigi F Agnati
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Modena, Italy; Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Borroto-Escuela DO, Fuxe K. Adenosine heteroreceptor complexes in the basal ganglia are implicated in Parkinson's disease and its treatment. J Neural Transm (Vienna) 2019; 126:455-471. [PMID: 30637481 PMCID: PMC6456481 DOI: 10.1007/s00702-019-01969-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 01/06/2019] [Indexed: 02/08/2023]
Abstract
The adenosine homo, iso and heteroreceptor complexes in the basal ganglia play a highly significant role in modulating the indirect and direct pathways and the striosomal projections to the nigro-striatal DA system. The major adenosine receptor complexes in the striato-pallidal GABA neurons can be the A2AR-D2R and A2AR-D2R-mGluR5 receptor complexes, in which A2AR protomers and mGluR5 protomers can allosterically interact to inhibit D2R protomer signaling. Through a reorganization of these heteroreceptor complexes upon chronic dopaminergic treatment a pathological and prolonged inhibition of D2R receptor protomer signaling can develop with motor inhibition and wearing off of the therapeutic effects of levodopa and dopamine receptor agonists. The direct pathway is enriched in D1R in and around glutamate synapses enhancing the ability of these GABA neurons to be activated and increase motor initiation. The brake on these GABA neurons is in this case exerted by A1R forming A1R-D1R heteroreceptor complexes in which they allosterically inhibit D1R signaling and thereby reduce motor initiation. Upon chronic levodopa treatment a reorganization of the D1R heteroreceptor complexes develops with the formation of putative A1R-D1R-D3 in addition to D1R-D3R complexes in which D3R enhances D1R protomer signaling and may make the A1R protomer brake less effective. Alpha-synuclein monomers-dimers are postulated to form complexes with A2AR homo and heteroprotomers in the plasma membrane enhancing alpha-synuclein aggregation and toxicity. The alpha-synuclein fibrils formed in the A2AR enriched dendritic spines of the striato-pallidal GABA neurons may reach the surrounding DA terminals via extracellular-vesicle-mediated volume transmission involving internalization of the vesicles and their cargo (alpha-synuclein fibrils) into the vulnerable DA terminals, enhancing their degeneration followed by retrograde flow of these fibrils in the DA axons to the vulnerable nigral DA nerve cells.
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Affiliation(s)
- Dasiel O. Borroto-Escuela
- Department of Neuroscience, Karolinska Institutet, Biomedicum, B0851, Solnavägen 9, 17177 Stockholm, Sweden
- Observatorio Cubano de Neurociencias, Grupo Bohío-Estudio, Zayas 50, 62100 Yaguajay, Cuba
| | - Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet, Biomedicum, B0851, Solnavägen 9, 17177 Stockholm, Sweden
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Borroto-Escuela DO, Perez De La Mora M, Manger P, Narváez M, Beggiato S, Crespo-Ramírez M, Navarro G, Wydra K, Díaz-Cabiale Z, Rivera A, Ferraro L, Tanganelli S, Filip M, Franco R, Fuxe K. Brain Dopamine Transmission in Health and Parkinson's Disease: Modulation of Synaptic Transmission and Plasticity Through Volume Transmission and Dopamine Heteroreceptors. Front Synaptic Neurosci 2018; 10:20. [PMID: 30042672 PMCID: PMC6048293 DOI: 10.3389/fnsyn.2018.00020] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 06/19/2018] [Indexed: 01/04/2023] Open
Abstract
This perspective article provides observations supporting the view that nigro-striatal dopamine neurons and meso-limbic dopamine neurons mainly communicate through short distance volume transmission in the um range with dopamine diffusing into extrasynaptic and synaptic regions of glutamate and GABA synapses. Based on this communication it is discussed how volume transmission modulates synaptic glutamate transmission onto the D1R modulated direct and D2R modulated indirect GABA pathways of the dorsal striatum. Each nigro-striatal dopamine neuron was first calculated to form large numbers of neostriatal DA nerve terminals and then found to give rise to dense axonal arborizations spread over the neostriatum, from which dopamine is released. These neurons can through DA volume transmission directly influence not only the striatal GABA projection neurons but all the striatal cell types in parallel. It includes the GABA nerve cells forming the island-/striosome GABA pathway to the nigral dopamine cells, the striatal cholinergic interneurons and the striatal GABA interneurons. The dopamine modulation of the different striatal nerve cell types involves the five dopamine receptor subtypes, D1R to D5R receptors, and their formation of multiple extrasynaptic and synaptic dopamine homo and heteroreceptor complexes. These features of the nigro-striatal dopamine neuron to modulate in parallel the activity of practically all the striatal nerve cell types in the dorsal striatum, through the dopamine receptor complexes allows us to understand its unique and crucial fine-tuning of movements, which is lost in Parkinson's disease. Integration of striatal dopamine signals with other transmitter systems in the striatum mainly takes place via the receptor-receptor interactions in dopamine heteroreceptor complexes. Such molecular events also participate in the integration of volume transmission and synaptic transmission. Dopamine modulation of the glutamate synapses on the dorsal striato-pallidal GABA pathway involves D2R heteroreceptor complexes such as D2R-NMDAR, A2AR-D2R, and NTSR1-D2R heteroreceptor complexes. The dopamine modulation of glutamate synapses on the striato-entopeduncular/nigral pathway takes place mainly via D1R heteroreceptor complexes such as D1R-NMDAR, A2R-D1R, and D1R-D3R heteroreceptor complexes. Dopamine modulation of the island/striosome compartment of the dorsal striatum projecting to the nigral dopamine cells involve D4R-MOR heteroreceptor complexes. All these receptor-receptor interactions have relevance for Parkinson's disease and its treatment.
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Affiliation(s)
- Dasiel O. Borroto-Escuela
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Section of Physiology, Department of Biomolecular Science, University of Urbino, Urbino, Italy
- Observatorio Cubano de Neurociencias, Grupo Bohío-Estudio, Yaguajay, Cuba
| | - Miguel Perez De La Mora
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Paul Manger
- Faculty of Health Sciences, School of Anatomical Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Manuel Narváez
- Facultad de Medicina, Instituto de Investigación Biomédica de Málaga, Málaga, Spain
| | - Sarah Beggiato
- Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Minerva Crespo-Ramírez
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Gemma Navarro
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biomedicine, University of Barcelona, Barcelona, Spain
| | - Karolina Wydra
- Laboratory of Drug Addiction Pharmacology, Department of Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland
| | - Zaida Díaz-Cabiale
- Facultad de Medicina, Instituto de Investigación Biomédica de Málaga, Málaga, Spain
| | - Alicia Rivera
- Department of Cell Biology, Faculty of Sciences, University of Málaga, Málaga, Spain
| | - Luca Ferraro
- Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Sergio Tanganelli
- Department of Life Sciences and Biotechnology (SVEB), University of Ferrara, Ferrara, Italy
| | - Małgorzata Filip
- Laboratory of Drug Addiction Pharmacology, Department of Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland
| | - Rafael Franco
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biomedicine, University of Barcelona, Barcelona, Spain
- CiberNed: Centro de Investigación en Red Enfermedades Neurodegenerativas, Instituto de Salud Carlos III, Madrid, Spain
| | - Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Sanjari Moghaddam H, Zare-Shahabadi A, Rahmani F, Rezaei N. Neurotransmission systems in Parkinson’s disease. Rev Neurosci 2017; 28:509-536. [DOI: 10.1515/revneuro-2016-0068] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Accepted: 01/10/2017] [Indexed: 12/17/2022]
Abstract
AbstractParkinson’s disease (PD) is histologically characterized by the accumulation of α-synuclein particles, known as Lewy bodies. The second most common neurodegenerative disorder, PD is widely known because of the typical motor manifestations of active tremor, rigidity, and postural instability, while several prodromal non-motor symptoms including REM sleep behavior disorders, depression, autonomic disturbances, and cognitive decline are being more extensively recognized. Motor symptoms most commonly arise from synucleinopathy of nigrostriatal pathway. Glutamatergic, γ-aminobutyric acid (GABA)ergic, cholinergic, serotoninergic, and endocannabinoid neurotransmission systems are not spared from the global cerebral neurodegenerative assault. Wide intrabasal and extrabasal of the basal ganglia provide enough justification to evaluate network circuits disturbance of these neurotransmission systems in PD. In this comprehensive review, English literature in PubMed, Science direct, EMBASE, and Web of Science databases were perused. Characteristics of dopaminergic and non-dopaminergic systems, disturbance of these neurotransmitter systems in the pathophysiology of PD, and their treatment applications are discussed.
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Affiliation(s)
- Hossein Sanjari Moghaddam
- Research Center for Immunodeficiencies, Children’s Medical Center Hospital, Tehran University of Medical Sciences, Dr Qarib St, Keshavarz Blvd, Tehran 14194, Iran
- NeuroImmunology Research Association (NIRA), Universal Scientific Education and Research Network (USERN), Tehran 1419783151, Iran
- Student Scientific Research Center (SSRC), Tehran University of Medical Sciences, Tehran, Iran
| | - Ameneh Zare-Shahabadi
- Research Center for Immunodeficiencies, Children’s Medical Center Hospital, Tehran University of Medical Sciences, Dr Qarib St, Keshavarz Blvd, Tehran 14194, Iran
- NeuroImmunology Research Association (NIRA), Universal Scientific Education and Research Network (USERN), Tehran 1419783151, Iran
- Psychiatry and Psychology Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Farzaneh Rahmani
- Research Center for Immunodeficiencies, Children’s Medical Center Hospital, Tehran University of Medical Sciences, Dr Qarib St, Keshavarz Blvd, Tehran 14194, Iran
- NeuroImaging Network (NIN), Universal Scientific Education and Research Network (USERN), Tehran, Iran
| | - Nima Rezaei
- Research Center for Immunodeficiencies, Children’s Medical Center Hospital, Tehran University of Medical Sciences, Dr Qarib St, Keshavarz Blvd, Tehran 14194, Iran
- Department of Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran 1419783151, Iran
- Network of Immunity in Infection, Malignancy and Autoimmunity (NIIMA), Universal Scientific Education and Research Network (USERN), Boston, MA, USA
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In search of novel ligands using a structure-based approach: a case study on the adenosine A 2A receptor. J Comput Aided Mol Des 2016; 30:863-874. [PMID: 27629350 PMCID: PMC5083784 DOI: 10.1007/s10822-016-9963-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 09/02/2016] [Indexed: 12/03/2022]
Abstract
In this work, we present a case study to explore the challenges associated with finding novel molecules for a receptor that has been studied in depth and has a wealth of chemical information available. Specifically, we apply a previously described protocol that incorporates explicit water molecules in the ligand binding site to prospectively screen over 2.5 million drug-like and lead-like compounds from the commercially available eMolecules database in search of novel binders to the adenosine A2A receptor (A2AAR). A total of seventy-one compounds were selected for purchase and biochemical assaying based on high ligand efficiency and high novelty (Tanimoto coefficient ≤0.25 to any A2AAR tested compound). These molecules were then tested for their affinity to the adenosine A2A receptor in a radioligand binding assay. We identified two hits that fulfilled the criterion of ~50 % radioligand displacement at a concentration of 10 μM. Next we selected an additional eight novel molecules that were predicted to make a bidentate interaction with Asn2536.55, a key interacting residue in the binding pocket of the A2AAR. None of these eight molecules were found to be active. Based on these results we discuss the advantages of structure-based methods and the challenges associated with finding chemically novel molecules for well-explored targets.
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Navarro G, Borroto-Escuela DO, Fuxe K, Franco R. Purinergic signaling in Parkinson's disease. Relevance for treatment. Neuropharmacology 2015. [PMID: 26211977 DOI: 10.1016/j.neuropharm.2015.07.024] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Purinergic signaling modulates dopaminergic neurotransmission in health and disease. Classically adenosine A1 and A2A receptors have been considered key for the fine tune control of dopamine actions in the striatum, the main CNS motor control center. The main adenosine signaling mechanism is via the cAMP pathway but the future will tell whether calcium signaling is relevant in adenosinergic control of striatal function. Very relevant is the recent approval in Japan of the adenosine A2A receptor antagonist, istradefylline, for use in Parkinson's disease patients. Purine nucleotides are also regulators of striatal dopamine neurotransmission via P2 purinergic receptors. In parallel to the alpha-synuclein hypothesis of Parkinson's disease etiology, purinergic P2X1 receptors have been identified as mediators of accumulation of the Lewy-body enriched protein alpha-synuclein. Of note is the expression in striatum of purinergic-receptor-containing heteromers that are potential targets of anti-Parkinson's disease therapies and should be taken into account in drug discovery programs. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.
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Affiliation(s)
- Gemma Navarro
- Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain; Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain.
| | - Dasiel O Borroto-Escuela
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; Department of Earth, Life and Environmental Sciences, Section of Physiology, Campus Scientifico Enrico Mattei, University of Urbino, Urbino, Italy.
| | - Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | - Rafael Franco
- Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain; Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain.
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Fuxe K, Guidolin D, Agnati LF, Borroto-Escuela DO. Dopamine heteroreceptor complexes as therapeutic targets in Parkinson's disease. Expert Opin Ther Targets 2014; 19:377-98. [PMID: 25486101 DOI: 10.1517/14728222.2014.981529] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Several types of D2R and D1R heteroreceptor complexes were discovered in the indirect and direct pathways of the striatum, respectively. The hypothesis is given that changes in the function of the dopamine heteroreceptor complexes may help us understand the molecular mechanisms underlying the motor complications of long-term therapy in Parkinson's disease (PD) with l-DOPA and dopamine receptor agonists. AREAS COVERED In the indirect pathway, the potential role of the A2AR-D2R, A2AR-D2R-mGluR5 and D2R-NMDAR heteroreceptor complexes in PD are covered and in the direct pathway, the D1R-D3R, A1R-D1R, D1R-NMDAR and putative A1R-D1R-D3R heteroreceptor complexes. EXPERT OPINION One explanation for the more powerful ability of l-DOPA treatment versus treatment with the partial dopamine receptor agonist/antagonist activity to induce dyskinesias, may be that dopamine formed from l-DOPA acts as a full agonist. The field of D1R and D2R heteroreceptor complexes in the CNS opens up a new understanding of the wearing off of the antiparkinson actions of l-DOPA and dopamine receptor agonists and the production of l-DOPA-induced dyskinesias. It can involve a reorganization of the D1R and D2R heteroreceptor complexes and a disbalance of the D1R and D2R homomers versus non-dopamine receptor homomers in the direct and indirect pathways.
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Affiliation(s)
- Kjell Fuxe
- Karolinska Institutet, Department of Neuroscience , Retzius väg 8, 17177 Stockholm , Sweden +46 852 487 077 ; +46 8 315 721 ;
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Fuxe K, Borroto-Escuela DO, Romero-Fernandez W, Palkovits M, Tarakanov AO, Ciruela F, Agnati LF. Moonlighting proteins and protein-protein interactions as neurotherapeutic targets in the G protein-coupled receptor field. Neuropsychopharmacology 2014; 39:131-55. [PMID: 24105074 PMCID: PMC3857668 DOI: 10.1038/npp.2013.242] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 07/04/2013] [Accepted: 07/05/2013] [Indexed: 12/28/2022]
Abstract
There is serious interest in understanding the dynamics of the receptor-receptor and receptor-protein interactions in space and time and their integration in GPCR heteroreceptor complexes of the CNS. Moonlighting proteins are special multifunctional proteins because they perform multiple autonomous, often unrelated, functions without partitioning into different protein domains. Moonlighting through receptor oligomerization can be operationally defined as an allosteric receptor-receptor interaction, which leads to novel functions of at least one receptor protomer. GPCR-mediated signaling is a more complicated process than previously described as every GPCR and GPCR heteroreceptor complex requires a set of G protein interacting proteins, which interacts with the receptor in an orchestrated spatio-temporal fashion. GPCR heteroreceptor complexes with allosteric receptor-receptor interactions operating through the receptor interface have become major integrative centers at the molecular level and their receptor protomers act as moonlighting proteins. The GPCR heteroreceptor complexes in the CNS have become exciting new targets for neurotherapeutics in Parkinson's disease, schizophrenia, drug addiction, and anxiety and depression opening a new field in neuropsychopharmacology.
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Affiliation(s)
- Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet,, Stockholm, Sweden
| | | | | | - Miklós Palkovits
- Department of Anatomy, Histology and Embryology, Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary
| | - Alexander O Tarakanov
- Russian Academy of Sciences, St. Petersburg Institute for Informatics and Automation, Saint Petersburg, Russia
| | - Francisco Ciruela
- Facultat de Medicina, Departament de Patologia i Terapèutica Experimental IDIBELL-Universitat de Barcelona, L'Hospitalet de Llobregat, Unitat de Farmacologia, Barcelona, Spain
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Adenosine-dopamine interactions in the pathophysiology and treatment of CNS disorders. CNS Neurosci Ther 2010; 16:e18-42. [PMID: 20345970 DOI: 10.1111/j.1755-5949.2009.00126.x] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Adenosine-dopamine interactions in the central nervous system (CNS) have been studied for many years in view of their relevance for disorders of the CNS and their treatments. The discovery of adenosine and dopamine receptor containing receptor mosaics (RM, higher-order receptor heteromers) in the striatum opened up a new understanding of these interactions. Initial findings indicated the existence of A(2A)R-D(2)R heterodimers and A(1)R-D(1)R heterodimers in the striatum that were followed by indications for the existence of striatal A(2A)R-D(3)R and A(2A)R-D(4)R heterodimers. Of particular interest was the demonstration that antagonistic allosteric A(2A)-D(2) and A(1)-D(1) receptor-receptor interactions take place in striatal A(2A)R-D(2)R and A(1)R-D(1)R heteromers. As a consequence, additional characterization of these heterodimers led to new aspects on the pathophysiology of Parkinson's disease (PD), schizophrenia, drug addiction, and l-DOPA-induced dyskinesias relevant for their treatments. In fact, A(2A)R antagonists were introduced in the symptomatic treatment of PD in view of the discovery of the antagonistic A(2A)R-D(2)R interaction in the dorsal striatum that leads to reduced D(2)R recognition and G(i/o) coupling in striato-pallidal GABAergic neurons. In recent years, indications have been obtained that A(2A)R-D(2)R and A(1)R-D(1)R heteromers do not exist as heterodimers, rather as RM. In fact, A(2A)-CB(1)-D(2) RM and A(2A)-D(2)-mGlu(5) RM have been discovered using a sequential BRET-FRET technique and by using the BRET technique in combination with bimolecular fluorescence complementation. Thus, other pathogenic mechanisms beside the well-known alterations in the release and/or decoding of dopamine in the basal ganglia and limbic system are involved in PD, schizophrenia and drug addiction. In fact, alterations in the stoichiometry and/or topology of A(2A)-CB(1)-D(2) and A(2A)-D(2)-mGlu5 RM may play a role. Thus, the integrative receptor-receptor interactions in these RM give novel aspects on the pathophysiology and treatment strategies, based on combined treatments, for PD, schizophrenia, and drug addiction.
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Borroto-Escuela DO, Marcellino D, Narvaez M, Flajolet M, Heintz N, Agnati L, Ciruela F, Fuxe K. A serine point mutation in the adenosine A2AR C-terminal tail reduces receptor heteromerization and allosteric modulation of the dopamine D2R. Biochem Biophys Res Commun 2010; 394:222-7. [PMID: 20197060 DOI: 10.1016/j.bbrc.2010.02.168] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Accepted: 02/26/2010] [Indexed: 11/30/2022]
Abstract
Evidence exists that the adenosine receptor A(2A)R and the dopamine receptor D(2)R form constitutive heteromers in living cells. Mass spectrometry and pull-down data showed that an arginine-rich domain of the D(2)R third intracellular loop binds via electrostatic interactions to a specific motif of the A(2A)R C-terminal tail. It has been indicated that the phosphorylated serine 374 might represent an important residue in this motif. In the present study, it was found that a point mutation of serine 374 to alanine reduced the A(2A)R ability to interact with D(2)R. Also, this point mutation abolished the A(2A)R-mediated inhibition of both the D(2)R high affinity agonist binding and signaling. These results point to a key role of serine 374 in the A(2A)R-D(2)R interface. All together these results indicate that by targeting A(2A)R serine 374 it will be possible to allosterically modulate A(2A)R-D(2)R function, thus representing a new approach for therapeutically modulate D(2)R function.
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Fuxe K, Marcellino D, Woods AS, Giuseppina L, Antonelli T, Ferraro L, Tanganelli S, Agnati LF. Integrated signaling in heterodimers and receptor mosaics of different types of GPCRs of the forebrain: relevance for schizophrenia. J Neural Transm (Vienna) 2009; 116:923-39. [PMID: 19156349 PMCID: PMC2953764 DOI: 10.1007/s00702-008-0174-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 12/11/2008] [Indexed: 11/26/2022]
Abstract
Receptor-receptor interactions within receptor heterodimers and receptor mosaics formed by different types of GPCRs represent an important integrative mechanism for signaling in brain networks at the level of the plasma membrane. The malfunction of special heterodimers and receptor mosaics in the ventral striatum containing D(2) receptors and 5-HT(2A) receptors in cortical networks may contribute to disturbances of key pathways involving ventral striato-pallidal GABA neurons and mediodorsal thalamic prefrontal glutamate neurons that may lead to the development of schizophrenia. The ventral striatum transmits emotional information to the cerebral cortex through a D(2) regulated accumbal-ventral pallidal-mediodorsal-prefrontal circuit which is of special interest to schizophrenia in view of the reduced number of glutamate mediodorsal-prefrontal projections associated with this disease. This circuit is especially vulnerable to D(2) receptor activity in the nucleus accumbens, since it produces a reduction in the prefrontal glutamate drive from the mediodorsal nucleus. The following D(2) receptor containing heterodimers/receptor mosaics are of special interest to schizophrenia: A(2A)-D(2), mGluR5-D(2), CB(1)-D(2), NTS(1)-D(2) and D(2)-D(3) and are discussed in this review. They may have a differential distribution pattern in the local circuits of the ventral striato-pallidal GABA pathway, predominantly located extrasynaptically. Specifically, trimeric receptor mosaics consisting of A(2A)-D(2)-mGluR5 and CB(1)-D(2)-A(2A) may also exist in these local circuits and are discussed. The integration of receptor signaling within assembled heterodimers/receptor mosaics is brought about by agonists and allosteric modulators. These cause the intramembrane receptor-receptor interactions, via allosteric mechanisms, to produce conformational changes that pass over the receptor interfaces. Exogenous and endogenous cooperativity is discussed as well as the role of the cortical mGluR2-5-HT(2A) heterodimer/receptor mosaic in schizophrenia (Gonzalez-Maeso et al. 2008). Receptor-receptor interactions within receptor heterodimer/receptor mosaics of different receptors in the ventral striatum and cerebral cortex give novel strategies for treatment of schizophrenia involving, e.g., monotherapy with either A(2A), mGluR5, CB(1) or NTS(1) agonists or combined therapies with some of these agonists combined with D(2)-like antagonists that specifically target the ventral striatum. In addition, a combined targeting of receptor mosaics in the ventral striatum and in the cerebral cortex should also be considered.
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Affiliation(s)
- Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 17177 Stockholm, Sweden.
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Abstract
Advances in radiotracer chemistry have resulted in the development of novel molecular imaging probes for adenosine receptors (ARs). With the availability of these molecules, the function of ARs in human pathophysiology as well as the safety and efficacy of approaches to the different AR targets can now be determined. Molecular imaging is a rapidly growing field of research that allows the identification of molecular targets and functional processes in vivo. It is therefore gaining increasing interest as a tool in drug development because it permits the process of evaluating promising therapeutic targets to be stratified. Further, molecular imaging has the potential to evolve into a useful diagnostic tool, particularly for neurological and psychiatric disorders. This chapter focuses on currently available AR ligands that are suitable for molecular neuroimaging and describes first applications in healthy subjects and patients using positron emission tomography (PET).
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Affiliation(s)
- Andreas Bauer
- Institute of Neuroscience and Biophysics (INB-3), Research Center Jülich, 52425 Jülich, Germany.
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Fuxe K, Marcellino D, Rivera A, Diaz-Cabiale Z, Filip M, Gago B, Roberts D, Langel U, Genedani S, Ferraro L, de la Calle A, Narvaez J, Tanganelli S, Woods A, Agnati L. Receptor–receptor interactions within receptor mosaics. Impact on neuropsychopharmacology. ACTA ACUST UNITED AC 2008; 58:415-52. [DOI: 10.1016/j.brainresrev.2007.11.007] [Citation(s) in RCA: 167] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 11/26/2007] [Accepted: 11/29/2007] [Indexed: 01/01/2023]
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Fuxe K, Marcellino D, Genedani S, Agnati L. Adenosine A(2A) receptors, dopamine D(2) receptors and their interactions in Parkinson's disease. Mov Disord 2008; 22:1990-2017. [PMID: 17618524 DOI: 10.1002/mds.21440] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Future therapies in Parkinson's disease may substantially build on the existence of intra-membrane receptor-receptor interactions in DA receptor containing heteromeric receptor complexes. The A(2A)/D(2) heteromer is of substantial interest in view of its specific location in cortico-striatal glutamate terminals and in striato-pallidal GABA neurons. Antagonistic A(2A)/D(2) receptor interactions in this heteromer demonstrated at the cellular level, and at the level of the striato-pallidal GABA neuron and at the network level made it possible to suggest A(2A) antagonists as anti-parkinsonian drugs. The major mechanism is an enhancement of D(2) signaling leading to attenuation of hypokinesia, tremor, and rigidity in models of Parkinson's disease with inspiring results in two clinical trials. Other interactions are antagonism at the level of the adenylyl cyclase; heterologous sensitization at the A(2A) activated adenylyl cyclase by persistent D(2) activation and a compensatory up-regulation of A(2A) receptors in response to intermittent Levodopa treatment. An increased dominance of A(2A) homomers over D(2) homomers and A(2A)/D(2) heteromers after intermittent Levodopa treatment may therefore contribute to development of Levodopa induced dyskinesias and to the wearing off of the therapeutic actions of Levodopa giving additional therapeutic roles of A(2A) antagonists. Their neuroprotective actions may involve an increase in the retrograde trophic signaling in the nigro-striatal DA system.
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Affiliation(s)
- Kjell Fuxe
- Division of Cellular and Molecular Neurochemistry, Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden.
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Schwarzschild MA, Agnati L, Fuxe K, Chen JF, Morelli M. Targeting adenosine A2A receptors in Parkinson's disease. Trends Neurosci 2006; 29:647-54. [PMID: 17030429 DOI: 10.1016/j.tins.2006.09.004] [Citation(s) in RCA: 333] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2006] [Revised: 07/25/2006] [Accepted: 09/22/2006] [Indexed: 10/24/2022]
Abstract
The adenosine A2A receptor has emerged as an attractive non-dopaminergic target in the pursuit of improved therapy for Parkinson's disease (PD), based in part on its unique CNS distribution. It is highly enriched in striatopallidal neurons and can form functional heteromeric complexes with other G-protein-coupled receptors, including dopamine D2, metabotropic glutamate mGlu5 and adenosine A1 receptors. Blockade of the adenosine A2A receptor in striatopallidal neurons reduces postsynaptic effects of dopamine depletion, and in turn lessens the motor deficits of PD. A2A antagonists might partially improve not only the symptoms of PD but also its course, by slowing the underlying neurodegeneration and reducing the maladaptive neuroplasticity that complicates standard 'dopamine replacement' treatments. Thus, we review here a prime example of translational neuroscience, through which antagonism of A2A receptors has now entered the arena of clinical trials with realistic prospects for advancing PD therapeutics.
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Affiliation(s)
- Michael A Schwarzschild
- MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Boston, MA 02129, USA.
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18
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Tanganelli S, Sandager Nielsen K, Ferraro L, Antonelli T, Kehr J, Franco R, Ferré S, Agnati LF, Fuxe K, Scheel-Krüger J. Striatal plasticity at the network level. Focus on adenosine A2A and D2 interactions in models of Parkinson's Disease. Parkinsonism Relat Disord 2004; 10:273-80. [PMID: 15196505 DOI: 10.1016/j.parkreldis.2004.02.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2004] [Accepted: 02/23/2004] [Indexed: 10/26/2022]
Abstract
Behavioral and microdialysis studies have been performed on antagonistic A(2A)/D(2) interactions in animal models of Parkinson's Disease. The behavioral analysis involved studies on locomotor activity in reserpinized mice, haloperidol-induced catalepsy in rats and rotational behavior in rats with unilateral 6-OHDA lesions of the ascending DA pathways (Ungerstedt model). Dual probe microdialysis studies were indirectly performed on the striatopallidal GABA neurons by studying extracellular glutamate levels in the striatum and globus pallidus of the awake freely moving rat. The striatum was perfused with A(2A) and/or D(2) agonists via reverse microdialysis. The results show that the A(2A) antagonists SCH58261 and KF17837 can increase locomotor activity in reserpinized mice and produce contralateral rotational behavior only after administration of subthreshold doses of l-DOPA or the D(2) like agonist quinpirole. Furthermore, antagonizing the A(2A) receptor (R) reduced haloperidol induced catalepsy. The behavioral results underline the view that A(2A) antagonists act by blocking A(2A) R in A(2A)/D(2) heterodimers where A(2A) R inhibits the D(2) R transduction and D(2) inhibits the adenylate cyclase (AC) activated by A(2A) R. The microdialysis studies show that the A(2A) agonist CGS21680 striatally coperfused with the D(2) agonist quinpirole more potently counteract the D(2) agonist (quinpirole) induced reduction of pallidal glutamate levels in the DA denervated vs the control striatum indicating an enhancement of the inhibitory A(2A)/D(2) interaction. In the DA denervated but not in the control striatum the A(2A) agonist CGS21680 could strongly increase striatal glutamate levels, indicating an increased receptor signaling in the A(2A) R located on the striatal glutamate terminals, where also D(2) like R exist, here probably as D(4). Thus, the signaling of this A(2A) R may be set free by the loss of D(4) tone on the AC activated by A(2A) in this postulated A(2A)/D(4) heteromer on the glutamate terminals. Taken together, the results indicate that the antiparkinsonian actions of A(2A) antagonists probably are produced by blockade of A(2A) R in the A(2A)/D(2) heterodimers mainly located in the striatopallidal GABA neurons.
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Affiliation(s)
- S Tanganelli
- Department of Clinical and Experimental Medicine, Section of Pharmacology, University of Ferrara, Ferrara, Italy
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Agnati LF, Ferré S, Lluis C, Franco R, Fuxe K. Molecular mechanisms and therapeutical implications of intramembrane receptor/receptor interactions among heptahelical receptors with examples from the striatopallidal GABA neurons. Pharmacol Rev 2003; 55:509-50. [PMID: 12869660 DOI: 10.1124/pr.55.3.2] [Citation(s) in RCA: 244] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The molecular basis for the known intramembrane receptor/receptor interactions among G protein-coupled receptors was postulated to be heteromerization based on receptor subtype-specific interactions between different types of receptor homomers. The discovery of GABAB heterodimers started this field rapidly followed by the discovery of heteromerization among isoreceptors of several G protein-coupled receptors such as delta/kappa opioid receptors. Heteromerization was also discovered among distinct types of G protein-coupled receptors with the initial demonstration of somatostatin SSTR5/dopamine D2 and adenosine A1/dopamine D1 heteromeric receptor complexes. The functional meaning of these heteromeric complexes is to achieve direct or indirect (via adapter proteins) intramembrane receptor/receptor interactions in the complex. G protein-coupled receptors also form heteromeric complexes involving direct interactions with ion channel receptors, the best example being the GABAA/dopamine D5 receptor heteromerization, as well as with receptor tyrosine kinases and with receptor activity modulating proteins. As an example, adenosine, dopamine, and glutamate metabotropic receptor/receptor interactions in the striatopallidal GABA neurons are discussed as well as their relevance for Parkinson's disease, schizophrenia, and drug dependence. The heterodimer is only one type of heteromeric complex, and the evidence is equally compatible with the existence of higher order heteromeric complexes, where also adapter proteins such as homer proteins and scaffolding proteins can exist. These complexes may assist in the process of linking G protein-coupled receptors and ion channel receptors together in a receptor mosaic that may have special integrative value and may constitute the molecular basis for some forms of learning and memory.
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Affiliation(s)
- Luigi F Agnati
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden.
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20
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Kulisevsky J, Barbanoj M, Gironell A, Antonijoan R, Casas M, Pascual-Sedano B. A double-blind crossover, placebo-controlled study of the adenosine A2A antagonist theophylline in Parkinson's disease. Clin Neuropharmacol 2002; 25:25-31. [PMID: 11852293 DOI: 10.1097/00002826-200201000-00005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Blockade of the adenosine A2A receptor potentiates the effects of levodopa in experimental animals and may offer a novel nondopaminergic target for drug therapy in Parkinson's disease (PD). Open-label trials suggest that the nonspecific adenosine antagonist theophylline improves parkinsonian symptoms and increases ON time in advanced patients with PD. In a double-blind, crossover, placebo-controlled trial, the authors investigated the ability of stable plasma levels of theophylline (between 10-20 microg/mL after 15 days of treatment) to modulate the long-duration response and the short-duration response of levodopa in 10 patients with PD. Although theophylline induced a longer duration of the effect of levodopa in all Unified Parkinson's Disease Rating Scale variables considered, including dyskinesias, maximal levodopa-induced improvement and the duration of the effect of levodopa did not differ significantly from placebo. Only the secondary variable "akinesia" showed a statistical tendency to a more prolonged beneficial response with theophylline during an acute levodopa test (short-duration response), and tremor worsened with theophylline during levodopa withdrawal (long-duration response). No differences were observed during the subacute course of study medication added to levodopa. During this exploratory study, the effects of theophylline were not strong enough to potentiate clearly the antiparkinsonian action of levodopa or to increase ON time in patients with advanced PD.
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Affiliation(s)
- Jaime Kulisevsky
- Movement Disorders Unit, Department of Neurology, Sant Pau Hospital, Autonomous University of Barcelona, Spain
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21
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Casas M, Prat G, Robledo P, Barbanoj M, Kulisevsky J, Jané F. Repeated co-administration of caffeine and bromocriptine prevents tolerance to the effects of caffeine in the turning behavior animal model. Eur Neuropsychopharmacol 1999; 9:515-21. [PMID: 10625120 DOI: 10.1016/s0924-977x(99)00037-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The present study examined the effects of repeated co-administrations of caffeine and bromocriptine for 9 consecutive days on contralateral turning in unilateral nigrostriatal 6-hydroxydopamine denervated rats. In agreement with previous data, our results showed that on the first administration, both caffeine and bromocriptine injected plus saline produced a significant increase in contralateral rotational behavior as compared to saline-saline injections. However, with repeated administrations, tolerance was observed to caffeine, but not to bromocriptine. The combination of different doses of bromocriptine (0.1, 0.2, 0.4 and 0.8 mg/kg) with caffeine (40 mg/kg) significantly enhanced the effects of either drug injected with saline on rotational behavior, and no tolerance was observed with repeated treatment. The continuous co-administration of both substances was necessary to maintain elevated levels of rotational behavior, since withdrawing one or the other drug led to decreased contralateral turning. These results demonstrate that when caffeine is administered repeatedly in combination with bromocriptine, tolerance to its psychostimulant effects is not observed, suggesting that caffeine could be used as an adjunctive therapeutic agent with dopamine agonists for the treatment of Parkinson's disease.
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Affiliation(s)
- M Casas
- Departament de Psiquiatria, Institut de Recerca Sant Pau, Programa Sant Pau-CITRAN y FISP, Universitat Autònoma de Barcelona, Unitat de Toxicomanies, Hospital de la Sta. Creu i St. Pau, Barcelona, Spain.
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22
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Demet EM, Chicz-Demet A, Fallon JH, Sokolski KN. Sleep deprivation therapy in depressive illness and Parkinson's disease. Prog Neuropsychopharmacol Biol Psychiatry 1999; 23:753-84. [PMID: 10509373 DOI: 10.1016/s0278-5846(99)00039-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
1. Sleep deprivation is commonly associated with feelings of fatigue and cognitive impairment. 2. Patients with depressive illness, however, often experience mood improvements under these same conditions. 3. Other studies now show that tremor and rigidity, in patients with Parkinson's disease, are also improved by sleep depression therapy. 4. The neural substrates which underlie these effects are unclear. Some recent evidence, however, suggests that sleep deprivation may activate mechanisms which are otherwise typical of conditions of metabolic stress. 5. A common feature of these mechanisms is the suppression of cholinergic activity which is thought to be excessive, in relation to monoamine transmission, in both depression and Parkinson's disease.
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Affiliation(s)
- E M Demet
- Mental Health Care Group, VA Medical Center, Long Beach, CA, USA
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23
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Casas M, Prat G, Robledo P, Barbanoj M, Kulisevsky J, Jané F. Scopolamine prevents tolerance to the effects of caffeine on rotational behavior in 6-hydroxydopamine-denervated rats. Eur J Pharmacol 1999; 366:1-11. [PMID: 10064145 DOI: 10.1016/s0014-2999(98)00911-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Continuous administration of caffeine has been shown to induce tolerance to its psychostimulant effects. In this study, using unilateral 6-hydroxydopamine nigrostriatal denervated rats, we tested the hypothesis that the muscarinic receptor antagonist, scopolamine, would prevent the tolerance to caffeine-induced contralateral rotational behavior. For that purpose we administered either caffeine (40 mg/kg) plus saline or scopolamine (5, 10 and 20 mg/kg) plus saline, as well as caffeine in combination with the various doses of scopolamine for 7 consecutive days, and measured ipsilateral and contralateral rotational behavior. The results showed that acute injections of scopolamine plus saline produced similar levels of both ipsilateral and contralateral turning, while caffeine produced more contralateral than ipsilateral turning. Tolerance to caffeine-induced contralateral turning was observed as of the second administration, while scopolamine plus saline injections did not produce significant changes in rotational behavior with repeated treatment. Scopolamine co-administered with caffeine significantly attenuated the increased contralateral turning produced by acute injections of caffeine plus saline, but significantly prevented the tolerance effects with repeated administration. These findings strongly suggest that muscarinic cholinergic processes may be involved in tolerance to caffeine-induced contralateral turning. The results are interpreted in terms of the possible interactions between dopamine, adenosine and acetylcholine neurotransmitter systems within the basal ganglia circuitry involved in motor behavior.
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Affiliation(s)
- M Casas
- Institut de Recerca Sant Pau, Departament de Psiquiatria, Universitat Autònoma de Barcelona, Hospital de la Santa Creu i Sant Pau, Spain.
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24
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Fuxe K, Ferré S, Zoli M, Agnati LF. Integrated events in central dopamine transmission as analyzed at multiple levels. Evidence for intramembrane adenosine A2A/dopamine D2 and adenosine A1/dopamine D1 receptor interactions in the basal ganglia. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1998; 26:258-73. [PMID: 9651540 DOI: 10.1016/s0165-0173(97)00049-0] [Citation(s) in RCA: 226] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
An analysis at the network and membrane level has provided evidence that antagonistic interactions between adenosine A2A/dopamine D2 and adenosine A1/dopamine D1 receptors in the ventral and dorsal striatum are at least in part responsible for the motor stimulant effects of adenosine receptor antagonists like caffeine and for the motor depressant actions of adenosine receptor agonists. The results obtained in stably cotransfected cells also underline the hypothesis that the intramembrane A2A/D2 and A1/D1 receptor interactions represent functionally important mechanisms that may be the major mechanism for the demonstrated antagonistic A2A/D2 and A1/D1 receptor interactions found in vivo in behavioural studies and in studies on in vivo microdialysis of the striopallidal and strioentopeduncular GABAergic pathways. A major mechanism for the direct intramembrane A2A/D2 and A1/D1 receptor interactions may involve formation of A2A/D2 and A1/D1 heterodimers leading to allosteric changes that will alter the affinity as well as the G protein coupling and thus the efficacy to control the target proteins in the membranes. This is the first molecular network to cellular integration in the nerve cell membrane and may be well suited for a number of integrated tasks and can be performed in a short-time scale, in comparison with the very long-time scale observed when receptor heteroregulation involves phosphorylation or receptor resynthesis. Multiple receptor-receptor interactions within the membranes through formation of receptor clusters may lead to the storage of information within the membranes. Such molecular circuits can represent hidden layers within the membranes that substantially increase the computational potential of neuronal networks. These molecular circuits are biased and may therefore represent part of the molecular mechanism for the storage of memory traces (engrams) in the membranes.
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Affiliation(s)
- K Fuxe
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden.
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Abstract
The adenosine A2A receptor subtype is one of the four adenosine receptors that have been identified in the mammalian organism. In addition to being found in blood vessels, platelets and polymorphonuclear leukocytes, the A2A receptors are abundant in the central nervous system, especially in the striatum. The recent development of selective A2A receptor ligands, in particular of receptor antagonists, makes it possible to elucidate the function of A2A receptors in normal and altered conditions. Pharmacological studies have shown that A2A receptor antagonists are potentially effective for treatment of neurodegenerative processes such as Parkinson's disease. Their activity is attributed to the close anatomical and functional links between A2A receptors and dopaminergic pathways in the basal ganglia. More recently, A2A receptor antagonists have proved to be active in models of cerebral ischemia. While the mechanisms underlying the role of A2A receptors in the hypoxia/ ischemia processes remains to be clarified, it is recognized that A2A receptor antagonists counteract the effects of excitatory aminoacids, which are massively released after cerebral ischemia. Another function of A2A receptors is related to protection from seizures, but further studies are needed to elucidate their specific interaction, if any, with neuronal excitability. Altogether, the great advance recently made with the discovery of selective A2A receptor ligands provides increasing information on the function of A2A receptors and opens new perspectives for treatment of neurological disorders.
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Affiliation(s)
- E Ongini
- Schering-Plough Research Institute, Milan, Italy.
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Bairam A, De Grandpré P, Dauphin C, Marchal F. Effects of caffeine on carotid sinus nerve chemosensory discharge in kittens and cats. J Appl Physiol (1985) 1997; 82:413-8. [PMID: 9049718 DOI: 10.1152/jappl.1997.82.2.413] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Caffeine (C) decreases apneic episodes in premature infants and is thought to stimulate breathing mainly by a central mechanism. While the methylxanthines theophylline and aminophylline are known to alter the carotid chemoreceptor activity, there are little data on C. The aim of the study was to examine the effects of C on the carotid sinus nerve discharge (CSND) in developing animals. Nine kittens 17-21 days old and six adult cats that were anesthetized and artificially ventilated were studied. They received four consecutive doses of C, each of 10 mg/kg, administered at intervals of 20 min either as intravenous bolus injection (6 kittens, 3 cats) or continuous infusion (3 kittens, 3 cats). Bolus injections of C invariably induced a prompt but transient increase in the CSND from 4.1 +/- 0.6 to 8.1 +/- 1.0 (SE) impulses/s in kittens (P = 0.01) and form 3.9 +/- 0.1 to 7.9 to 1.0 impulses/s in cats (after the first injection). This response was associated with a significant decrease in arterial blood pressure. Continuous infusion of C did not induce any early change in either CSND or blood pressure in kittens or cats. Fifteen minutes after C injection or infusion was begun, CSND values in air, 8% O2-balance N2, or 100% O2 were not significantly different from control. Haloperidol administered at the end of the experiment in four cats and four kittens significantly increased CSND and did not suppress the early response to C injection. It is concluded that caffeine administered by bolus in the kitten induces a transient stimulation of the CSND that is associated with a decrease in the arterial blood pressure and is independent of the dopaminergic mechanisms in the carotid body. The lack of sustained effect implies the main mechanism to the ventilatory stimulation by C must be central.
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Affiliation(s)
- A Bairam
- Unité de Néonatologie, Hôpital Saint-François d'Assise, Université Laval, Quebec, Canada
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Latini S, Pazzagli M, Pepeu G, Pedata F. A2 adenosine receptors: their presence and neuromodulatory role in the central nervous system. GENERAL PHARMACOLOGY 1996; 27:925-33. [PMID: 8909972 DOI: 10.1016/0306-3623(96)00044-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
1. Adenosine is an endogenous neuromodulator that exerts its depressant effect on neurons by acting on the A1 adenosine receptor subtype. Excitatory actions of adenosine, mediated by the activation of the A2 adenosine receptor subtype, have also been shown in the central nervous system. 2. Adenosine A2a receptors are highly localized in the striatum, as demonstrated by the binding assay of the A2a selective agonist, CGS2680, and by analysis of the A2 receptor mRNA localization with in situ hybridization histochemistry. However, adenosine A2a, receptors, albeit at lower levels, are also localized in other brain regions, such as the cortex and the hippocampus. 3. In the striatum, adenosine A2a, receptors are implicated in the control of motor activity. Evidences exists of an antagonistic interaction between adenosine A2a and dopamine D2 receptors. 4. Utilizing selective agonists and antagonists for adenosine A2a receptors, their role in the modulation of the release of several neurotransmitters (acetylcholine, dopamine, glutamate, GABA) has been extensively studied in the brain (striatum, cortex, hippocampus). Controversial results have been obtained and, because the overall effect of endogenous adenosine in the brain is that of an inhibitory tonus, the physiological meaning of the excitatory A2 receptor remains to be clarified.
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Affiliation(s)
- S Latini
- Department of Preclinical and Clinical Pharmacology, University of Florence, Italy
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Varani K, Gessi S, Dalpiaz A, Borea PA. Pharmacological and biochemical characterization of purified A2a adenosine receptors in human platelet membranes by [3H]-CGS 21680 binding. Br J Pharmacol 1996; 117:1693-701. [PMID: 8732278 PMCID: PMC1909568 DOI: 10.1111/j.1476-5381.1996.tb15341.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
1. The binding properties of human platelet A2a adenosine receptors, assayed with the A2a-selective agonist, [3H]-2-[p-(2-carboxyethyl)-phenethylamino]-5'-N-ethylcarboxamidoad enosine ([3H]-CGS 21680), are masked by a non-receptorial component, the adenotin site. In order to separate A2a receptors from adenotin sites, human platelet membranes were solubilized with 1% 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propanesulphonate (CHAPS). The soluble platelet extract was precipitated with polyethylene glycol (PEG) and the fraction enriched in adenosine receptors was isolated from the precipitate by differential centrifugation. 2. The present paper describes the binding characteristics of the selective A2a agonist, [3H]-CGS 21680, to this purified platelet membrane preparation. In addition, receptor affinity and potency of several adenosine agonists and antagonists were determined in binding and adenylyl cyclase studies. 3. Saturation experiments revealed a single class of binding site with Kd and Bmax values of 285 nM and 2.07 pmol mg-1 of protein respectively. Adenosine receptor ligands competed for the binding of 50 nM [3H]-CGS 21680 to purified protein, showing a rank order of potency consistent with that typically found for interactions with the A2a adenosine receptors. In the adenylyl cyclase assay the compounds examined exhibited a rank order of potency very close to that observed in binding experiments. 4. Thermodynamic data indicated that [3H]-CGS 21680 binding to the purified receptor is totally entropy-driven in agreement with results obtained in rat striatal A2a adenosine receptors. 5. It is concluded that in the purified platelet membranes there is a CGS 21680 binding site showing the characteristic properties of the A2a receptor. This makes it possible to use this compound for reliable radioligand binding studies on the A2a adenosine receptor of human platelets.
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Affiliation(s)
- K Varani
- Institute of Pharmacology, University of Ferrara, Italy
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Baraldi PG, Cacciari B, Spalluto G, Pineda de las Infantas y Villatoro MJ, Zocchi C, Dionisotti S, Ongini E. Pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine derivatives: potent and selective A(2A) adenosine antagonists. J Med Chem 1996; 39:1164-71. [PMID: 8676354 DOI: 10.1021/jm950746l] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A series of pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine derivatives (10a-o,q,r), bearing alkyl and aralkyl chains on positions 7 and 8, were synthesized in the attempt to obtain potent and selective antagonists for the A(2A) adenosine receptor subtype. The compounds were tested in binding and functional assays to evaluate their potency for the A(2A) compared with the A1 adenosine receptor subtype. In binding studies in rat brain membranes, most of the compounds showed affinity for A(2A) receptors in the low nanomolar range with a different degree of A(2A) versus A1 selectivity. Comparison of N(7) (10a-d,h-o)- and N(8) (10e-g)-substituted pyrazolo derivatives indicates that N(7) substitution decreases the A1 affinity with the concomitant increase of A(2A) selectivity. Specifically, the introduction of a 3-phenylpropyl group at pyrazolo nitrogen in position 7 (101) increased significantly the A(2A) selectivity, being 210-fold, while the A(2A) receptor affinity remained high (Ki=2.4 nM). With regards to the affinity for A(2A) receptors, also the compound 10n, bearing in the 7-position a beta-morpholin-4-ylethyl group, deserves attention (Ki=5.6 nM) even though the A2A selectivity (84-fold) was not as high as that of 101. Conversely, the compound 10m (N(7)-4-phenylbutyl derivative) showed a remarkable selectivity (A1/a(2A) ratio = 129) associated with lower A(2A) affinity (Ki = 21 nM). In functional studies, most of the compounds examined reversed 5'-(N-ethylcarbamoyl) adenosine-induced inhibition of rabbit platelet aggregation inhibition which is a biological response mediated by the A2A receptor subtype. The compounds are potent and selective A2A antagonists which can be useful to elucidate the pathophysiological role of this adenosine receptor subtype. These compounds deserve to be further developed to assess their potential for treatment of neurodegenerative disorders such as Parkinson's disease.
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Affiliation(s)
- P G Baraldi
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Ferrara, Ferrara, Italy
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31
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Kafka SH, Corbett R. Selective adenosine A2A receptor/dopamine D2 receptor interactions in animal models of schizophrenia. Eur J Pharmacol 1996; 295:147-54. [PMID: 8720578 DOI: 10.1016/0014-2999(95)00668-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In the apomorphine-induced climbing mouse assay, the potencies of the selective adenosine A1 receptor agonist, N6-cyclohexyladenosine (CHA), and the selective A2A adenosine receptor agonist, 2-p-(2-carboxyethyl) phenethylamino 5'-N-ethyl-carboxamidoadenosine (CGS 21680), and various dopamine receptor antagonists were as follows: SCH 23390 = haloperidol > raclopride > CHA = CGS 21680. While in catalepsy, their potencies were SCH 23390 > haloperidol > raclopride > CGS 21680. CHA failed to induce catalepsy due to significant sedation/ataxia. The combined administration of the ED15 dose of CHA failed to potentiate the ED50 value of SCH 23390, raclopride, or haloperidol in the apomorphine-induced climbing mouse assay. However, the combined administration of the ED15 dose of CGS 21680 significantly decreased the ED50 of raclopride by 8.0-fold and haloperidol by 35-fold. The adenosine A2A receptor antagonist, 1,3,7-trimethyl-8-(3-chlorostyryl)xanthine (CSC), significantly decreased catalepsy induced by raclopride and haloperidol, while the adenosine A1 receptor antagonist, 1,3-dimethyl-8-phenylxanthine (8-PT), was ineffective. The present results show that in behavioral assays predictive for antipsychotic activity, adenosine receptor agonists block behaviors in a similar manner to dopamine receptor antagonists.
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Affiliation(s)
- S H Kafka
- Neuroscience PGU, Hoechst-Roussel Pharmaceuticals, Inc., Somerville, NJ 08876, USA
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32
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Chapter 2 Purines. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1569-2582(96)80089-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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33
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Hauber W, Münkle M. Stimulation of adenosine A2a receptors in the rat striatum induces catalepsy that is reversed by antagonists of N-methyl-D-aspartate receptors. Neurosci Lett 1995; 196:205-8. [PMID: 7501284 DOI: 10.1016/0304-3940(95)11871-s] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Bilateral infusion of the selective adenosine A2a agonist CGS 21680C (1 microgram per side) into the anterodorsal striatum of rats produced profound catalepsy. Intraperitoneal coadministration of the non-competitive N-methyl-D-aspartate (NMDA) antagonist dizocilpine (0.16 mg/kg) or the competitive NMDA antagonist CGP 37849 (4 mg/kg) completely reversed CGS 21680C-induced catalepsy, while lower doses of both NMDA antagonists induced no or only weak anticataleptic effects. The adenosine A2a receptor localization to striatopallidal neurons suggests that a selective activation of the striatopallidal efferent pathway is involved in the expression of catalepsy induced by intrastriatal infusion of CGS 21680C. In addition, striatopallidal neurons seem to be an important neuronal substrate of the anticataleptic effects of NMDA antagonists.
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Affiliation(s)
- W Hauber
- Department of Animal Physiology, University of Stuttgart, Germany
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Baraldi PG, Manfredini S, Simoni D, Zappaterra L, Zocchi C, Dionisotti S, Ongini E. Synthesis of new pyrazolo[4,3-e]1,2,4-triazolo[1,5-c] pyrimidine and 1,2,3-triazolo[4,5-e]1,2,4-triazolo[1,5-c] pyrimidine displaying potent and selective activity as A2a adenosine receptor antagonists. Bioorg Med Chem Lett 1994. [DOI: 10.1016/s0960-894x(01)80279-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Ferré S, Schwarcz R, Li XM, Snaprud P, Ogren SO, Fuxe K. Chronic haloperidol treatment leads to an increase in the intramembrane interaction between adenosine A2 and dopamine D2 receptors in the neostriatum. Psychopharmacology (Berl) 1994; 116:279-84. [PMID: 7892417 DOI: 10.1007/bf02245329] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Stimulation of adenosine A2 receptors (with the selective adenosine A2 agonist CGS 21680) in rat striatal membrane preparations, produces a decrease in both the affinity of D2 receptors and the transduction of the signal from the D2 receptor to the G protein. This intramembrane A2-D2 interaction might be responsible for the behavioural depressant effects of adenosine agonists and for the behavioural stimulant effects of adenosine antagonists such as caffeine and theophylline. Dopamine denervation induces an increase in the intramembrane A2-D2 interaction, which may underlie the observed higher sensitivity to the behavioural effects induced by adenosine antagonists found in these animals. The present study was designed to examine if chronic treatment with haloperidol, which also produces dopamine receptor supersensitivity, is also associated with an increase in the intramembrane A2-D2 interaction in the neostriatum and with a higher sensitivity to the behavioural effects induced by adenosine antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S Ferré
- Department of Neurochemistry, C.S.I.C., Barcelona, Spain
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Normile HJ, Gaston S, Johnson G, Barraco RA. Activation of adenosine A1 receptors in the nucleus accumbens impairs inhibitory avoidance memory. BEHAVIORAL AND NEURAL BIOLOGY 1994; 62:163-6. [PMID: 7993306 DOI: 10.1016/s0163-1047(05)80037-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Potent and highly selective adenosine A1 and A2 receptor agonists were bilaterally injected into the nucleus accumbens of mice 10 min prior to inhibitory avoidance training. Retention of the inhibitory avoidance response was assessed 24 h after training. Intra-ACB activation of A1 receptors, but not A2a receptor activation, significantly impaired the performance of mice during the subsequent retention test. Furthermore, the retention deficit produced by activation of A1 receptors was significantly attenuated by pretreating mice with a highly selective A1 receptor antagonist. These findings suggest that endogenous adenosine may modulate information processing in the ventral striatum via adenosine A1 receptors.
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Affiliation(s)
- H J Normile
- Department of Psychiatry, Wayne State University, School of Medicine, Detroit, Michigan 48202
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37
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Garrett BE, Holtzman SG. Caffeine cross-tolerance to selective dopamine D1 and D2 receptor agonists but not to their synergistic interaction. Eur J Pharmacol 1994; 262:65-75. [PMID: 7813580 DOI: 10.1016/0014-2999(94)90029-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This study examined the role of dopamine systems in tolerance to caffeine-induced stimulation of motor activity in the rat. Selective dopamine D1 and D2 receptor agonists were tested alone and combined in rats receiving caffeine chronically by a method of scheduled access to a caffeine solution or in control rats receiving no caffeine. Rats treated chronically with oral caffeine were tolerant to the motor stimulant effects of caffeine (3.0-100 mg/kg, i.p.). The partial dopamine D1 receptor agonist SKF-77434 (1.0-30 mg/kg, s.c.) and the dopamine D2 receptor agonists quinpirole (0.03-10 mg/kg, s.c.) and R(-)-pro-pylnorapomorphine (NPA, 0.03-1.0 mg/kg, s.c.) dose-dependently increased activity in control rats. Caffeine-treated rats were cross-tolerant to the locomotor stimulant effect of these selective dopamine D1 and D2 receptor agonist. The concurrent administration of the partial dopamine D1 receptor agonist SKF-38393 (10 mg/kg, s.c.) with the dopamine D2 receptor agonists quinpirole and R(-)-propylnorapomorphine had a synergistic effect on locomotor activity in both control and caffeine-treated rats. This synergistic effect was also seen when the partial dopamine D1 receptor agonist SKF-77434 (1.0 and 10 mg/kg, s.c.) was given in combination with quinpirole. There was little or no cross-tolerance to the concurrent administration of selective dopamine D1 and D2 receptor agonists. It appears that tolerance to the locomotor stimulant effect of caffeine is mediated by both dopamine D1 and D2 receptor sub-types. Cross-tolerance occurs to drugs that activate a single type of dopamine receptor but not to drug combinations that concurrently activate more than one type of receptor.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/administration & dosage
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/analogs & derivatives
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Administration, Oral
- Analysis of Variance
- Animals
- Apomorphine/administration & dosage
- Apomorphine/analogs & derivatives
- Apomorphine/pharmacology
- Caffeine/administration & dosage
- Caffeine/pharmacology
- Dopamine Agonists/administration & dosage
- Dopamine Agonists/pharmacology
- Dose-Response Relationship, Drug
- Drug Synergism
- Drug Tolerance
- Ergolines/administration & dosage
- Ergolines/pharmacology
- Injections, Intraperitoneal
- Injections, Subcutaneous
- Male
- Motor Activity/drug effects
- Quinpirole
- Rats
- Rats, Sprague-Dawley
- Receptors, Dopamine D1/agonists
- Receptors, Dopamine D2/agonists
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Affiliation(s)
- B E Garrett
- Emory University School of Medicine, Atlanta, GA 30322
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Jackson DM, Westlind-Danielsson A. Dopamine receptors: molecular biology, biochemistry and behavioural aspects. Pharmacol Ther 1994; 64:291-370. [PMID: 7878079 DOI: 10.1016/0163-7258(94)90041-8] [Citation(s) in RCA: 319] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The description of new dopamine (DA) receptor subtypes, D1-(D1 and D5) and D2-like (D2A, D2B, D3, D4), has given an impetus to DA research. While selective agonists and antagonists are not generally available yet, the receptor distribution in the brain suggests that they could be new targets for drug development. Binding characteristics and second messenger coupling has been explored in cell lines expressing the new cloned receptors. The absence of selective ligands has meant that in vivo studies have lagged behind. However, progress has been made in understanding the function of DA-containing discrete brain nuclei and the functional consequence of the DA's interaction with other neurotransmitters. This review explores some of the latest advances in these various areas.
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Affiliation(s)
- D M Jackson
- Department of Behavioural, Pharmacology, Astra Arcus AB, Södertälje, Sweden
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Abstract
The identification and characterization of adenosine receptors and the development of potent, receptor subtype-selective agonists and antagonists has been an active area of research for the past 20 years. Major recent advances in the field have been the cloning of several adenosine receptor subtypes of different species, including the discovery of a new subtype, designated A3, the discovery and development of new agonists and antagonists, particularly those with selectivity for the A2a adenosine receptor, the characterization of signal transduction pathways, and the development of agents which act indirectly on the adenosine receptor system. The present article focusses on aspects of pharmaceutical/medicinal chemistry related to adenosine receptors.
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Affiliation(s)
- C E Müller
- Pharmazeutisches Institut, Pharmazeutische Chemie, Tübingen, Germany
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Schiffmann SN, Halleux P, Menu R, Vanderhaeghen JJ. Adenosine A2a receptor expression in striatal neurons: Implications for basal ganglia pathophysiology. Drug Dev Res 1993. [DOI: 10.1002/ddr.430280335] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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