1
|
Nunes ACL, Carmo M, Behrenswerth A, Canas PM, Agostinho P, Cunha RA. Adenosine A 2A Receptor Blockade Provides More Effective Benefits at the Onset Rather than after Overt Neurodegeneration in a Rat Model of Parkinson's Disease. Int J Mol Sci 2024; 25:4903. [PMID: 38732120 PMCID: PMC11084368 DOI: 10.3390/ijms25094903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 04/24/2024] [Accepted: 04/26/2024] [Indexed: 05/13/2024] Open
Abstract
Adenosine A2A receptor (A2AR) antagonists are the leading nondopaminergic therapy to manage Parkinson's disease (PD) since they afford both motor benefits and neuroprotection. PD begins with a synaptic dysfunction and damage in the striatum evolving to an overt neuronal damage of dopaminergic neurons in the substantia nigra. We tested if A2AR antagonists are equally effective in controlling these two degenerative processes. We used a slow intracerebroventricular infusion of the toxin MPP+ in male rats for 15 days, which caused an initial loss of synaptic markers in the striatum within 10 days, followed by a neuronal loss in the substantia nigra within 30 days. Interestingly, the initial loss of striatal nerve terminals involved a loss of both dopaminergic and glutamatergic synaptic markers, while GABAergic markers were preserved. The daily administration of the A2AR antagonist SCH58261 (0.1 mg/kg, i.p.) in the first 10 days after MPP+ infusion markedly attenuated both the initial loss of striatal synaptic markers and the subsequent loss of nigra dopaminergic neurons. Strikingly, the administration of SCH58261 (0.1 mg/kg, i.p. for 10 days) starting 20 days after MPP+ infusion was less efficacious to attenuate the loss of nigra dopaminergic neurons. This prominent A2AR-mediated control of synaptotoxicity was directly confirmed by showing that the MPTP-induced dysfunction (MTT assay) and damage (lactate dehydrogenase release assay) of striatal synaptosomes were prevented by 50 nM SCH58261. This suggests that A2AR antagonists may be more effective to counteract the onset rather than the evolution of PD pathology.
Collapse
Affiliation(s)
- Ana Carla L. Nunes
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; (A.C.L.N.); (M.C.); (A.B.); (P.M.C.); (P.A.)
| | - Marta Carmo
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; (A.C.L.N.); (M.C.); (A.B.); (P.M.C.); (P.A.)
| | - Andrea Behrenswerth
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; (A.C.L.N.); (M.C.); (A.B.); (P.M.C.); (P.A.)
| | - Paula M. Canas
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; (A.C.L.N.); (M.C.); (A.B.); (P.M.C.); (P.A.)
| | - Paula Agostinho
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; (A.C.L.N.); (M.C.); (A.B.); (P.M.C.); (P.A.)
- Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Rodrigo A. Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; (A.C.L.N.); (M.C.); (A.B.); (P.M.C.); (P.A.)
- Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| |
Collapse
|
2
|
Siddique AHH, Kale PP. Importance of glucose and its metabolism in neurodegenerative disorder, as well as the combination of multiple therapeutic strategies targeting α-synuclein and neuroprotection in the treatment of Parkinson's disease. Rev Neurol (Paris) 2023:S0035-3787(23)01066-4. [PMID: 38040547 DOI: 10.1016/j.neurol.2023.08.011] [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: 01/18/2022] [Revised: 04/04/2023] [Accepted: 08/18/2023] [Indexed: 12/03/2023]
Abstract
According to recent findings, Phosphoglycerate Kinase 1 (pgk-1) enzyme is linked to Parkinson's disease (PD). Mutations in the PGK-1 gene lead to decreases in the pgk-1 enzyme which causes an imbalance in the levels of energy demand and supply. An increase in glycolytic adenosine triphosphate (ATP) production would help alleviate energy deficiency and sustain the acute energetic need of neurons. Neurodegeneration is caused by an imbalance or reduction in ATP levels. Recent data suggest that medications that increase glycolysis and neuroprotection can be used to treat PD. The current study focuses on treatment options for disorders associated with the pgk-1 enzyme, GLP-1, and A2A receptor which can be utilized to treat PD. A combination of metformin and terazosin, exenatide and meclizine, istradefylline and salbutamol treatments may benefit parkinsonism. The review also looked at potential target-specific new techniques that might assist in satisfying unfulfilled requirements in the treatment of PD.
Collapse
Affiliation(s)
- A H H Siddique
- Department of Pharmacology, SVKM's Dr Bhanuben Nanavati College of Pharmacy, V. L. Mehta Road, Vile Parle west, 400056 Mumbai, India.
| | - P P Kale
- Department of Pharmacology, SVKM's Dr Bhanuben Nanavati College of Pharmacy, V. L. Mehta Road, Vile Parle west, 400056 Mumbai, India.
| |
Collapse
|
3
|
Karati D, Mukherjee S, Roy S. Molecular and Structural Insight into Adenosine A 2A Receptor in Neurodegenerative Disorders: A Significant Target for Efficient Treatment Approach. Mol Neurobiol 2023; 60:5987-6000. [PMID: 37391647 DOI: 10.1007/s12035-023-03441-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2022] [Accepted: 06/10/2023] [Indexed: 07/02/2023]
Abstract
All biological tissues and bodily fluids include the autacoid adenosine. The P1 class of purinergic receptors includes adenosine receptors. Four distinct G-protein-coupled receptors on the cellular membrane mediate the effects of adenosine, whose cytoplasmic content is regulated by producing/degrading enzymes and nucleoside transporters. A2A receptor has received a great deal of attention in recent years because it has a wide range of potential therapeutic uses. A2B and, more significantly, A2A receptors regulate numerous physiological mechanisms in the central nervous system (CNS). The inferior targetability of A2B receptors towards adenosine points that they might portray a promising medicinal target since they are triggered only under pharmacological circumstances (when adenosine levels rise up to micromolar concentrations). The accessibility of specific ligands for A2B receptors would permit the exploration of such a theory. A2A receptors mediate both potentially neurotoxic and neuroprotective actions. Hence, it is debatable to what extent they play a role in neurodegenerative illnesses. However, A2A receptor blockers have demonstrated clear antiparkinsonian consequences, and a significant attraction exists in the role of A2A receptors in other neurodegenerative disorders. Amyloid peptide extracellular accumulation and tau hyperphosphorylation are the pathogenic components of AD that lead to neuronal cell death, cognitive impairment, and memory loss. Interestingly, in vitro and in vivo research has shown that A2A adenosine receptor antagonists may block each of these clinical symptoms, offering a crucial new approach to combat a condition for which, regrettably, only symptomatic medications are currently available. At least two requirements must be met to determine whether such receptors are a target for diseases of the CNS: a complete understanding of the mechanisms governing A2A-dependent processes and the availability of ligands that can distinguish between the various receptor populations. This review concisely summarises the biological effects mediated by A2A adenosine receptors in neurodegenerative disorders and discusses the chemical characteristics of A2A adenosine receptor antagonists undergoing clinical trials. Selective A2A receptor blocker against neurodegenerative disorders.
Collapse
Affiliation(s)
- Dipanjan Karati
- Department of Pharmaceutical Technology, School of Pharmacy, Techno India University, Kolkata, 700091, India
| | - Swarupananda Mukherjee
- Department of Pharmaceutical Technology, NSHM Knowledge Campus, Kolkata, 124 B.L. Saha Road, Kolkata, West Bengal, 700053, India
| | - Souvik Roy
- Department of Pharmaceutical Technology, NSHM Knowledge Campus, Kolkata, 124 B.L. Saha Road, Kolkata, West Bengal, 700053, India.
| |
Collapse
|
4
|
Dopamine Release in Nucleus Accumbens Is under Tonic Inhibition by Adenosine A 1 Receptors Regulated by Astrocytic ENT1 and Dysregulated by Ethanol. J Neurosci 2022; 42:1738-1751. [PMID: 35042768 PMCID: PMC8896549 DOI: 10.1523/jneurosci.1548-21.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 11/20/2021] [Accepted: 11/23/2021] [Indexed: 11/21/2022] Open
Abstract
Striatal adenosine A1 receptor (A1R) activation can inhibit dopamine release. A1Rs on other striatal neurons are activated by an adenosine tone that is limited by equilibrative nucleoside transporter 1 (ENT1) that is enriched on astrocytes and is ethanol sensitive. We explored whether dopamine release in nucleus accumbens core is under tonic inhibition by A1Rs, and is regulated by astrocytic ENT1 and ethanol. In ex vivo striatal slices from male and female mice, A1R agonists inhibited dopamine release evoked electrically or optogenetically and detected using fast-scan cyclic voltammetry, most strongly for lower stimulation frequencies and pulse numbers, thereby enhancing the activity-dependent contrast of dopamine release. Conversely, A1R antagonists reduced activity-dependent contrast but enhanced evoked dopamine release levels, even for single optogenetic pulses indicating an underlying tonic inhibition. The ENT1 inhibitor nitrobenzylthioinosine reduced dopamine release and promoted A1R-mediated inhibition, and, conversely, virally mediated astrocytic overexpression of ENT1 enhanced dopamine release and relieved A1R-mediated inhibition. By imaging the genetically encoded fluorescent adenosine sensor [GPCR-activation based (GRAB)-Ado], we identified a striatal extracellular adenosine tone that was elevated by the ENT1 inhibitor and sensitive to gliotoxin fluorocitrate. Finally, we identified that ethanol (50 mm) promoted A1R-mediated inhibition of dopamine release, through diminishing adenosine uptake via ENT1. Together, these data reveal that dopamine output dynamics are gated by a striatal adenosine tone, limiting amplitude but promoting contrast, regulated by ENT1, and promoted by ethanol. These data add to the diverse mechanisms through which ethanol modulates striatal dopamine, and to emerging datasets supporting astrocytic transporters as important regulators of striatal function.SIGNIFICANCE STATEMENT Dopamine axons in the mammalian striatum are emerging as strategic sites where neuromodulators can powerfully influence dopamine output in health and disease. We found that ambient levels of the neuromodulator adenosine tonically inhibit dopamine release in nucleus accumbens core via adenosine A1 receptors (A1Rs), to a variable level that promotes the contrast in dopamine signals released by different frequencies of activity. We reveal that the equilibrative nucleoside transporter 1 (ENT1) on astrocytes limits this tonic inhibition, and that ethanol promotes it by diminishing adenosine uptake via ENT1. These findings support the hypotheses that A1Rs on dopamine axons inhibit dopamine release and, furthermore, that astrocytes perform important roles in setting the level of striatal dopamine output, in health and disease.
Collapse
|
5
|
D’Angelo V, Giorgi M, Paldino E, Cardarelli S, Fusco FR, Saverioni I, Sorge R, Martella G, Biagioni S, Mercuri NB, Pisani A, Sancesario G. A2A Receptor Dysregulation in Dystonia DYT1 Knock-Out Mice. Int J Mol Sci 2021; 22:2691. [PMID: 33799994 PMCID: PMC7962104 DOI: 10.3390/ijms22052691] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 03/01/2021] [Indexed: 01/28/2023] Open
Abstract
We aimed to investigate A2A receptors in the basal ganglia of a DYT1 mouse model of dystonia. A2A was studied in control Tor1a+/+ and Tor1a+/- knock-out mice. A2A expression was assessed by anti-A2A antibody immunofluorescence and Western blotting. The co-localization of A2A was studied in striatal cholinergic interneurons identified by anti-choline-acetyltransferase (ChAT) antibody. A2A mRNA and cyclic adenosine monophosphate (cAMP) contents were also assessed. In Tor1a+/+, Western blotting detected an A2A 45 kDa band, which was stronger in the striatum and the globus pallidus than in the entopeduncular nucleus. Moreover, in Tor1a+/+, immunofluorescence showed A2A roundish aggregates, 0.3-0.4 μm in diameter, denser in the neuropil of the striatum and the globus pallidus than in the entopeduncular nucleus. In Tor1a+/-, A2A Western blotting expression and immunofluorescence aggregates appeared either increased in the striatum and the globus pallidus, or reduced in the entopeduncular nucleus. Moreover, in Tor1a+/-, A2A aggregates appeared increased in number on ChAT positive interneurons compared to Tor1a+/+. Finally, in Tor1a+/-, an increased content of cAMP signal was detected in the striatum, while significant levels of A2A mRNA were neo-expressed in the globus pallidus. In Tor1a+/-, opposite changes of A2A receptors' expression in the striatal-pallidal complex and the entopeduncular nucleus suggest that the pathophysiology of dystonia is critically dependent on a composite functional imbalance of the indirect over the direct pathway in basal ganglia.
Collapse
Affiliation(s)
- Vincenza D’Angelo
- Department of Systems Medicine, Tor Vergata University of Rome, 00133 Rome, Italy; (V.D.); (R.S.); (G.M.); (N.B.M.)
| | - Mauro Giorgi
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University of Rome, 00185 Rome, Italy; (M.G.); (S.C.); (I.S.); (S.B.)
| | - Emanuela Paldino
- IRCCS Santa Lucia Foundation, 00179 Rome, Italy; (E.P.); (F.R.F.)
| | - Silvia Cardarelli
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University of Rome, 00185 Rome, Italy; (M.G.); (S.C.); (I.S.); (S.B.)
| | | | - Ilaria Saverioni
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University of Rome, 00185 Rome, Italy; (M.G.); (S.C.); (I.S.); (S.B.)
| | - Roberto Sorge
- Department of Systems Medicine, Tor Vergata University of Rome, 00133 Rome, Italy; (V.D.); (R.S.); (G.M.); (N.B.M.)
| | - Giuseppina Martella
- Department of Systems Medicine, Tor Vergata University of Rome, 00133 Rome, Italy; (V.D.); (R.S.); (G.M.); (N.B.M.)
- IRCCS Santa Lucia Foundation, 00179 Rome, Italy; (E.P.); (F.R.F.)
| | - Stefano Biagioni
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University of Rome, 00185 Rome, Italy; (M.G.); (S.C.); (I.S.); (S.B.)
| | - Nicola B. Mercuri
- Department of Systems Medicine, Tor Vergata University of Rome, 00133 Rome, Italy; (V.D.); (R.S.); (G.M.); (N.B.M.)
| | - Antonio Pisani
- IRCCS Mondino Foundation, 27100 Pavia, Italy;
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy
| | - Giuseppe Sancesario
- Department of Systems Medicine, Tor Vergata University of Rome, 00133 Rome, Italy; (V.D.); (R.S.); (G.M.); (N.B.M.)
| |
Collapse
|
6
|
Jenner P, Mori A, Aradi SD, Hauser RA. Istradefylline - a first generation adenosine A 2A antagonist for the treatment of Parkinson's disease. Expert Rev Neurother 2021; 21:317-333. [PMID: 33507105 DOI: 10.1080/14737175.2021.1880896] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Introduction It is now accepted that Parkinson's disease (PD) is not simply due to dopaminergic dysfunction, and there is interest in developing non-dopaminergic approaches to disease management. Adenosine A2A receptor antagonists represent a new way forward in the symptomatic treatment of PD.Areas covered In this narrative review, we summarize the literature supporting the utility of adenosine A2A antagonists in PD with a specific focus on istradefylline, the most studied and only adenosine A2A antagonist currently in clinical use.Expert opinion: At this time, the use of istradefylline in the treatment of PD is limited to the management of motor fluctuations as supported by the results of randomized clinical trials and evaluation by Japanese and USA regulatory authorities. The relatively complicated clinical development of istradefylline was based on classically designed studies conducted in PD patients with motor fluctuations on an optimized regimen of levodopa plus adjunctive dopaminergic medications. In animal models, there is consensus that a more robust effect of istradefylline in improving motor function is produced when combined with low or threshold doses of levodopa rather than with high doses that produce maximal dopaminergic improvement. Exploration of istradefylline as a 'levodopa sparing' strategy in earlier PD would seem warranted.
Collapse
Affiliation(s)
- Peter Jenner
- Institute of Pharmaceutical Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Akihisa Mori
- Medical Affairs Department, Kyowa Kirin Co Ltd, Otemachi, Chiyoda-ku, Tokyo, Japan
| | - Stephen D Aradi
- Department of Neurology, University of South Florida, Tampa, Florida, USA
| | - Robert A Hauser
- Department of Neurology, University of South Florida, Tampa, Florida, USA
| |
Collapse
|
7
|
Mori A. How do adenosine A 2A receptors regulate motor function? Parkinsonism Relat Disord 2020; 80 Suppl 1:S13-S20. [PMID: 33349575 DOI: 10.1016/j.parkreldis.2020.09.025] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 01/17/2023]
Abstract
Adenosine A2A receptor antagonism is a new therapeutic strategy in the symptomatic treatment of Parkinson's disease (PD). This review addresses how adenosine A2A receptors are involved with the control of motor function via the basal ganglia-thalamocortical circuit, and considers the anatomical localization and physiological function of the receptor, along with its ultrastructural localization in critical areas/neurons of the circuit. Based on this understanding of the functional significance of the adenosine A2A receptor in the basal ganglia, the mode of action of A2A receptor antagonists is explored in terms of the dynamic functioning of the basal ganglia and the activity of the internal circuits of the striatum in PD. Finally, the pathophysiological differences between the normal and PD states are examined to emphasize the importance of the adenosine A2A receptor.
Collapse
|
8
|
The neurobiological basis for novel experimental therapeutics in dystonia. Neurobiol Dis 2019; 130:104526. [PMID: 31279827 DOI: 10.1016/j.nbd.2019.104526] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 06/13/2019] [Accepted: 07/03/2019] [Indexed: 12/17/2022] Open
Abstract
Dystonia is a movement disorder characterized by involuntary muscle contractions, twisting movements, and abnormal postures that may affect one or multiple body regions. Dystonia is the third most common movement disorder after Parkinson's disease and essential tremor. Despite its relative frequency, small molecule therapeutics for dystonia are limited. Development of new therapeutics is further hampered by the heterogeneity of both clinical symptoms and etiologies in dystonia. Recent advances in both animal and cell-based models have helped clarify divergent etiologies in dystonia and have facilitated the identification of new therapeutic targets. Advances in medicinal chemistry have also made available novel compounds for testing in biochemical, physiological, and behavioral models of dystonia. Here, we briefly review motor circuit anatomy and the anatomical and functional abnormalities in dystonia. We then discuss recently identified therapeutic targets in dystonia based on recent preclinical animal studies and clinical trials investigating novel therapeutics.
Collapse
|
9
|
Balance between dopamine and adenosine signals regulates the PKA/Rap1 pathway in striatal medium spiny neurons. Neurochem Int 2019; 122:8-18. [DOI: 10.1016/j.neuint.2018.10.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 10/02/2018] [Accepted: 10/03/2018] [Indexed: 12/19/2022]
|
10
|
Abudukeyoumu N, Hernandez-Flores T, Garcia-Munoz M, Arbuthnott GW. Cholinergic modulation of striatal microcircuits. Eur J Neurosci 2018; 49:604-622. [PMID: 29797362 PMCID: PMC6587740 DOI: 10.1111/ejn.13949] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 03/30/2018] [Accepted: 04/04/2018] [Indexed: 12/15/2022]
Abstract
The purpose of this review is to bridge the gap between earlier literature on striatal cholinergic interneurons and mechanisms of microcircuit interaction demonstrated with the use of newly available tools. It is well known that the main source of the high level of acetylcholine in the striatum, compared to other brain regions, is the cholinergic interneurons. These interneurons provide an extensive local innervation that suggests they may be a key modulator of striatal microcircuits. Supporting this idea requires the consideration of functional properties of these interneurons, their influence on medium spiny neurons, other interneurons, and interactions with other synaptic regulators. Here, we underline the effects of intrastriatal and extrastriatal afferents onto cholinergic interneurons and discuss the activation of pre‐ and postsynaptic muscarinic and nicotinic receptors that participate in the modulation of intrastriatal neuronal interactions. We further address recent findings about corelease of other transmitters in cholinergic interneurons and actions of these interneurons in striosome and matrix compartments. In addition, we summarize recent evidence on acetylcholine‐mediated striatal synaptic plasticity and propose roles for cholinergic interneurons in normal striatal physiology. A short examination of their role in neurological disorders such as Parkinson's, Huntington's, and Tourette's pathologies and dystonia is also included.
Collapse
Affiliation(s)
| | | | | | - Gordon W Arbuthnott
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| |
Collapse
|
11
|
Johnson JA, Montgomery AP, Starr ER, Ludwig J, Trevitt J. Dose-dependent effects of adenosine antagonists on tacrine-induced tremulous jaw movements. Eur J Pharmacol 2018; 833:364-369. [PMID: 29883670 DOI: 10.1016/j.ejphar.2018.06.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 06/04/2018] [Accepted: 06/05/2018] [Indexed: 10/14/2022]
Abstract
The present study examines the effect of three adenosine receptor antagonists on tremulous jaw movements (TJMs), an animal model of tremor. Forty-five rats were pre-treated with one adenosine antagonist: caffeine (0.0, 5.0, or 10.0 mg/kg; non-selective adenosine receptor antagonist), 8-cyclopentyltheophylline (CPT; 0.0, 5.0, or 10.0 mg/kg; selective adenosine A1 receptor antagonist), or SCH 58261 (0.0 or 8.0 mg/kg; selective adenosine A2A receptor antagonist) followed by TJM induction with tacrine (0.0, 0.75, or 2.5 mg/kg; acetylcholinesterase inhibitor). CPT and SCH 58261 both significantly reduced TJMs while caffeine did not. Unexpectedly, both SCH 58261 and CPT reduced TJMs even in the absence of tacrine. Also, CPT showed a robust reduction of TJMs, achieved at both (5.0 mg/kg) and (10.0 mg/kg) doses and regardless of tacrine dose. In conclusion, this study shows adenosine receptor antagonism to generally suppress low-dose tacrine-induced TJMs. In concert with two prior studies, these results are suggestive of behavioral evidence for a biphasic effect of adenosine A2A receptor antagonists (caffeine and SCH 58261) that is modulated by tacrine, and a model of this effect is proposed.
Collapse
Affiliation(s)
- Joel A Johnson
- California State University, Fullerton Department of Psychology, 800 N. State College Blvd., Fullerton, CA 92831, United States.
| | - Aaron P Montgomery
- California State University, Fullerton Department of Psychology, 800 N. State College Blvd., Fullerton, CA 92831, United States.
| | - Eric R Starr
- California State University, Fullerton Department of Psychology, 800 N. State College Blvd., Fullerton, CA 92831, United States.
| | - Justin Ludwig
- California State University, Fullerton Department of Psychology, 800 N. State College Blvd., Fullerton, CA 92831, United States.
| | - Jennifer Trevitt
- California State University, Fullerton Department of Psychology, 800 N. State College Blvd., Fullerton, CA 92831, United States.
| |
Collapse
|
12
|
Silkis IG. The reasons for the preferable use of A2A receptor antagonists for improvement of locomotor activity and learning. NEUROCHEM J+ 2014. [DOI: 10.1134/s1819712414040072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
13
|
Mode of Action of Adenosine A2A Receptor Antagonists as Symptomatic Treatment for Parkinson's Disease. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 119:87-116. [DOI: 10.1016/b978-0-12-801022-8.00004-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
|
14
|
Metaxas A, Al-Hasani R, Farshim P, Tubby K, Berwick A, Ledent C, Hourani S, Kitchen I, Bailey A. Genetic deletion of the adenosine A(2A) receptor prevents nicotine-induced upregulation of α7, but not α4β2* nicotinic acetylcholine receptor binding in the brain. Neuropharmacology 2013; 71:228-36. [PMID: 23583933 DOI: 10.1016/j.neuropharm.2013.03.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Revised: 03/11/2013] [Accepted: 03/22/2013] [Indexed: 10/27/2022]
Abstract
Considerable evidence indicates that adenosine A(2A) receptors (A(2A)Rs) modulate cholinergic neurotransmission, nicotinic acetylcholine receptor (nAChR) function, and nicotine-induced behavioural effects. To explore the interaction between A(2A) and nAChRs, we examined if the complete genetic deletion of adenosine A(2A)Rs in mice induces compensatory alterations in the binding of different nAChR subtypes, and whether the long-term effects of nicotine on nAChR regulation are altered in the absence of the A(2A)R gene. Quantitative autoradiography was used to measure cytisine-sensitive [¹²⁵I]epibatidine and [¹²⁵I]α-bungarotoxin binding to α4β2* and α7 nAChRs, respectively, in brain sections of drug-naïve (n = 6) or nicotine treated (n = 5-7), wild-type and adenosine A(2A)R knockout mice. Saline or nicotine (7.8 mg/kg/day; free-base weight) were administered to male CD1 mice via subcutaneous osmotic minipumps for a period of 14 days. Blood plasma levels of nicotine and cotinine were measured at the end of treatment. There were no compensatory developmental alterations in nAChR subtype distribution or density in drug-naïve A(2A)R knockout mice. In nicotine treated wild-type mice, both α4β2* and α7 nAChR binding sites were increased compared with saline treated controls. The genetic ablation of adenosine A(2A)Rs prevented nicotine-induced upregulation of α7 nAChRs, without affecting α4β2* receptor upregulation. This selective effect was observed at plasma levels of nicotine that were within the range reported for smokers (10-50 ng ml⁻¹). Our data highlight the involvement of adenosine A(2A)Rs in the mechanisms of nicotine-induced α7 nAChR upregulation, and identify A(2A)Rs as novel pharmacological targets for modulating the long-term effects of nicotine on α7 receptors.
Collapse
Affiliation(s)
- Athanasios Metaxas
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, Institute of Health & Medical Sciences, University of Surrey, UK.
| | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Baba Y, Higuchi MA, Abe H, Fukuyama K, Onozawa R, Uehara Y, Inoue T, Yamada T. Anti-cholinergics for axial symptoms in Parkinson's disease after subthalamic stimulation. Clin Neurol Neurosurg 2012; 114:1308-11. [PMID: 22516415 DOI: 10.1016/j.clineuro.2012.03.046] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 01/28/2012] [Accepted: 03/24/2012] [Indexed: 11/19/2022]
Abstract
OBJECTIVE We studied the effect of anti-cholinergic therapy on axial symptoms that show a tendency to worsen over time after deep brain stimulation of the subthalamic nucleus (STN-DBS) in patients with Parkinson's disease (PD). PATIENTS AND METHODS We conducted a prospective study of 20 consecutive patients treated with the anti-cholinergic agent trihexyphenidyl after bilateral STN-DBS and assessed the effect of anti-cholinergic therapy on parkinsonism 1 month after its initiation using the Unified Parkinson's Disease Rating Scale (UPDRS). RESULTS After a mean post-operative follow-up period of 22.3 months, the scores of axial symptoms on UPDRS part II (ADL score) and part III (motor score) deteriorated by 87% and 54% (baseline), respectively, compared with the pre-operative scores (P < 0.001 for both comparisons). After adding trihexyphenidyl to dopaminergic medication with stimulation, the scores of axial symptoms on UPDRS part II and part III improved from baseline by 33% and 39%, respectively (P < 0.001 for both comparisons). CONCLUSIONS Our findings demonstrated that the anti-cholinergic agent trihexyphenidyl shows positive effect for a patient population developing deterioration of axial symptoms after STN-DBS. The results in the present study may provide insights into the mechanism of emergence or progression of axial symptoms in patients with PD after STN-DBS.
Collapse
Affiliation(s)
- Yasuhiko Baba
- Department of Speech and Hearing Sciences, International University of Health and Welfare School of Rehabilitation, Fukuoka, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Peterson JD, Goldberg JA, Surmeier DJ. Adenosine A2a receptor antagonists attenuate striatal adaptations following dopamine depletion. Neurobiol Dis 2011; 45:409-16. [PMID: 21964253 DOI: 10.1016/j.nbd.2011.08.030] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Revised: 08/11/2011] [Accepted: 08/31/2011] [Indexed: 11/24/2022] Open
Abstract
The motor symptoms of Parkinson's disease (PD) are widely thought to arise from an imbalance in the activity of the two major striatal efferent pathways following the loss of dopamine (DA) signaling. In striatopallidal, indirect pathway spiny projection neurons (iSPNs), intrinsic excitability rises following the loss of inhibitory D2 receptor signaling. Because these receptors are normally counterbalanced by adenosine A2a adenosine receptors, antagonists of these receptors are being examined as an adjunct to conventional pharmacological therapies. However, little is known about the effects of sustained A2a receptor antagonism on striatal adaptations in PD models. To address this issue, the A2a receptor antagonist SCH58261 was systemically administered to DA-depleted mice. After 5 days of treatment, the effects of SCH58261 on iSPNs were examined in brain slices using electrophysiological and optical approaches. SCH58261 treatment did not prevent spine loss in iSPNs following depletion, but did significantly attenuate alterations in synaptic currents, spine morphology and dendritic excitability. In part, these effects were attributable to the ability of SCH58261 to blunt the effects of DA depletion on cholinergic interneurons, another striatal cell type that co-expresses A2a and D(2) receptors. Collectively, these results suggest that A2a receptor antagonism improves striatal function in PD models by attenuating iSPN adaptations to DA depletion.
Collapse
Affiliation(s)
- Jayms D Peterson
- Department of Physiology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave, Chicago, IL 60611, USA.
| | | | | |
Collapse
|
17
|
Ferré S, Quiroz C, Orru M, Guitart X, Navarro G, Cortés A, Casadó V, Canela EI, Lluis C, Franco R. Adenosine A(2A) Receptors and A(2A) Receptor Heteromers as Key Players in Striatal Function. Front Neuroanat 2011; 5:36. [PMID: 21731559 PMCID: PMC3118889 DOI: 10.3389/fnana.2011.00036] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 06/08/2011] [Indexed: 11/24/2022] Open
Abstract
A very significant density of adenosine A2A receptors (A2ARs) is present in the striatum, where they are preferentially localized postsynaptically in striatopallidal medium spiny neurons (MSNs). In this localization A2ARs establish reciprocal antagonistic interactions with dopamine D2 receptors (D2Rs). In one type of interaction, A2AR and D2R are forming heteromers and, by means of an allosteric interaction, A2AR counteracts D2R-mediated inhibitory modulation of the effects of NMDA receptor stimulation in the striatopallidal neuron. This interaction is probably mostly responsible for the locomotor depressant and activating effects of A2AR agonist and antagonists, respectively. The second type of interaction involves A2AR and D2R that do not form heteromers and takes place at the level of adenylyl cyclase (AC). Due to a strong tonic effect of endogenous dopamine on striatal D2R, this interaction keeps A2AR from signaling through AC. However, under conditions of dopamine depletion or with blockade of D2R, A2AR-mediated AC activation is unleashed with an increased gene expression and activity of the striatopallidal neuron and with a consequent motor depression. This interaction is probably the main mechanism responsible for the locomotor depression induced by D2R antagonists. Finally, striatal A2ARs are also localized presynaptically, in cortico-striatal glutamatergic terminals that contact the striato-nigral MSN. These presynaptic A2ARs heteromerize with A1 receptors (A1Rs) and their activation facilitates glutamate release. These three different types of A2ARs can be pharmacologically dissected by their ability to bind ligands with different affinity and can therefore provide selective targets for drug development in different basal ganglia disorders.
Collapse
Affiliation(s)
- Sergi Ferré
- National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, U.S. Department of Health and Human Services Baltimore, MD, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Oswald MJ, Oorschot DE, Schulz JM, Lipski J, Reynolds JNJ. IH current generates the afterhyperpolarisation following activation of subthreshold cortical synaptic inputs to striatal cholinergic interneurons. J Physiol 2010; 587:5879-97. [PMID: 19884321 DOI: 10.1113/jphysiol.2009.177600] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Pauses in the tonic firing of striatal cholinergic interneurons emerge during reward-related learning and are triggered by neutral cues which develop behavioural significance. In a previous in vivo study we have proposed that these pauses in firing may be due to intrinsically generated afterhyperpolarisations (AHPs) evoked by excitatory synaptic inputs, including those below the threshold for action potential firing. The aim of this study was to investigate the mechanism of the AHPs using a brain slice preparation which preserved both cerebral hemispheres. Augmenting cortically evoked postsynaptic potentials (PSPs) by repetitive stimulation of cortical afferents evoked AHPs that were unaffected by blocking either GABA(A) receptors with bicuculline, or GABA(B) receptors with saclofen or CGP55845. Apamin (a blocker of small conductance Ca(2+)-activated K(+) channels) had minimal effects, while chelation of intracellular Ca(2+) with BAPTA reduced the AHP by about 30%. In contrast, blocking hyperpolarisation and cyclic nucleotide activated (HCN) cation current (I(H)) with ZD7288 or Cs(+) diminished the size of the AHPs by 60% and reduced the proportion of episodes that contained this hyperpolarisation. The reversal potential (20 mV) and voltage dependence of the AHPs were consistent with the hypothesis that a transient deactivation of I(H) caused most of the AHP at hyperpolarised potentials, while the slow AHP-type Ca(2+)-activated K(+) channels increasingly contributed at more depolarised membrane potentials. Subthreshold somatic current injections yielded similar AHPs with a median duration of approximately 700 ms that were not affected by firing of a single action potential. These results indicate that transient deactivation of HCN channels evokes pauses in tonic firing of cholinergic interneurons, an event likely to be elicited by augmentation of afferent synaptic inputs during learning.
Collapse
Affiliation(s)
- Manfred J Oswald
- Department of Anatomy and Structural Biology, Otago School of Medical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand
| | | | | | | | | |
Collapse
|
19
|
Cieślak M, Komoszyński M, Wojtczak A. Adenosine A(2A) receptors in Parkinson's disease treatment. Purinergic Signal 2008; 4:305-12. [PMID: 18438720 PMCID: PMC2583202 DOI: 10.1007/s11302-008-9100-8] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Accepted: 03/17/2008] [Indexed: 02/07/2023] Open
Abstract
Latest results on the action of adenosine A(2A) receptor antagonists indicate their potential therapeutic usefulness in the treatment of Parkinson's disease. Basal ganglia possess high levels of adenosine A(2A) receptors, mainly on the external surfaces of neurons located at the indirect tracts between the striatum, globus pallidus, and substantia nigra. Experiments with animal models of Parkinson's disease indicate that adenosine A(2A) receptors are strongly involved in the regulation of the central nervous system. Co-localization of adenosine A(2A) and dopaminergic D2 receptors in striatum creates a milieu for antagonistic interaction between adenosine and dopamine. The experimental data prove that the best improvement of mobility in patients with Parkinson's disease could be achieved with simultaneous activation of dopaminergic D2 receptors and inhibition of adenosine A(2A) receptors. In animal models of Parkinson's disease, the use of selective antagonists of adenosine A(2A) receptors, such as istradefylline, led to the reversibility of movement dysfunction. These compounds might improve mobility during both monotherapy and co-administration with L-DOPA and dopamine receptor agonists. The use of adenosine A(2A) receptor antagonists in combination therapy enables the reduction of the L-DOPA doses, as well as a reduction of side effects. In combination therapy, the adenosine A(2A) receptor antagonists might be used in both moderate and advanced stages of Parkinson's disease. The long-lasting administration of adenosine A(2A) receptor antagonists does not decrease the patient response and does not cause side effects typical of L-DOPA therapy. It was demonstrated in various animal models that inhibition of adenosine A(2A) receptors not only decreases the movement disturbance, but also reveals a neuroprotective activity, which might impede or stop the progression of the disease. Recently, clinical trials were completed on the use of istradefylline (KW-6002), an inhibitor of adenosine A(2A) receptors, as an anti-Parkinson drug.
Collapse
Affiliation(s)
- Marek Cieślak
- Neurological Department, WSZ Hospital, Toruń, Poland
| | | | | |
Collapse
|
20
|
|
21
|
Simola N, Fenu S, Baraldi PG, Tabrizi MA, Morelli M. Dopamine and adenosine receptor interaction as basis for the treatment of Parkinson's disease. J Neurol Sci 2006; 248:48-52. [PMID: 16780890 DOI: 10.1016/j.jns.2006.05.038] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Preclinical evidence strongly indicate that adenosine A(2A) receptor antagonists represent a promising class of drugs for the treatment of motor deficits associated to Parkinson's disease. The effects of adenosine A(2A) receptor antagonists were here assessed in a rat model of parkinsonian tremor induced by cholinomimetic drugs by evaluating the counteraction of tremulous jaw movements. Systemic administration of the A(2A) antagonist SCH 58261 dose-dependently reduced the magnitude of perioral tremor induced by the acetylcholinesterase inhibitor tacrine (2.5 mg/kg). Furthermore, intrastriatal infusion of SCH BT2 (5 microg/microl), a water-soluble analogue of SCH 58261, antagonized tacrine-induced jaw movements with a maximal effect in the ventrolateral striatum. On the other hand, SCH 58261 (5 mg/kg) was ineffective in blocking tremulous jaw movements stimulated by the direct muscarinic agonist pilocarpine (1 mg/kg). Taken together, these results indicate that A(2A) antagonists reduce parkinsonian tremor stimulated in rats by tacrine and that the striatum is deeply involved in the observed effect. Moreover, the ineffectiveness of SCH 58261 in blocking pilocarpine-stimulated perioral tremor suggests that the antitremorigenic effects of A(2A) antagonists described here are not related to a direct action on muscarinic receptor. The prospective of providing additional antitremor benefits considerably enhances the therapeutic potential of A(2A) antagonists.
Collapse
Affiliation(s)
- Nicola Simola
- Department of Toxicology and Centre of Excellence for Neurobiology of Dependence, University of Cagliari, 09124 Cagliari, Italy
| | | | | | | | | |
Collapse
|
22
|
O’Connor J, Muly EC, Hemby SE. Molecular mapping of striatal subdivisions in juvenile Macaca Mulata. Exp Neurol 2006; 198:326-37. [PMID: 16455077 PMCID: PMC5076375 DOI: 10.1016/j.expneurol.2005.11.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 11/23/2005] [Accepted: 11/23/2005] [Indexed: 11/21/2022]
Abstract
The striatum of the primate brain can be subdivided into three distinct anatomical subregions: caudate (CAU), putamen (PUT), and ventral striatum (VS). Although these subregions share several anatomical connections, cell morphological, and histochemical features, they differ considerably in their vulnerability to different neurological and psychiatric diseases, and these brain regions have significantly different functions in health and disease. In order to better understand the molecular underpinnings of the different disease and functional vulnerabilities, transcriptional profiles were generated from the CAU, PUT, and VS of five juvenile rhesus macaques (Macaca mulatta) using human cDNA neuromicroarrays containing triplicate spots of 1227 cDNAs. Differences in microarray gene expression were assessed using z score analysis and 1.5-fold change between paired subregions. Clustering of genes based on dissimilarity of expression patterns between regions revealed subregion specific expression profiles encoding G-protein-coupled receptor signaling transcripts, transcription factors, kinases and phosphatases, and cell signaling and signal transduction transcripts. Twelve transcripts were examined using quantitative real-time PCR (qPCR), and 81% demonstrated alterations similar to those seen with microarray analysis, some of which were statistically significant. Subregion specific transcription profiles support the anatomical differentiation and potential disease vulnerabilities of the respective subregions.
Collapse
Affiliation(s)
- Joann O’Connor
- Molecular and Systems Pharmacology Program, Graduate Division of Biological and Behavioral Sciences, Emory University, Atlanta, GA 30322, USA
| | - Emil C. Muly
- Department of Psychiatry and Behavioral Sciences, Emory University, Atlanta, GA 30322, USA
- Yerkes National Primate Research Center, Division of Neuroscience, Emory University, Atlanta, GA 30329, USA
| | - Scott E. Hemby
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
- Corresponding author. Fax: +1 336 716 8501. (S.E. Hemby)
| |
Collapse
|
23
|
Xu K, Bastia E, Schwarzschild M. Therapeutic potential of adenosine A2A receptor antagonists in Parkinson's disease. Pharmacol Ther 2005; 105:267-310. [PMID: 15737407 DOI: 10.1016/j.pharmthera.2004.10.007] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Accepted: 10/14/2004] [Indexed: 10/26/2022]
Abstract
In the pursuit of improved treatments for Parkinson's disease (PD), the adenosine A(2A) receptor has emerged as an attractive nondopaminergic target. Based on the compelling behavioral pharmacology and selective basal ganglia expression of this G-protein-coupled receptor, its antagonists are now crossing the threshold of clinical development as adjunctive symptomatic treatment for relatively advanced PD. The antiparkinsonian potential of A(2A) antagonism has been boosted further by recent preclinical evidence that A(2A) antagonists might favorably alter the course as well as the symptoms of the disease. Convergent epidemiological and laboratory data have suggested that A(2A) blockade may confer neuroprotection against the underlying dopaminergic neuron degeneration. In addition, rodent and nonhuman primate studies have raised the possibility that A(2A) receptor activation contributes to the pathophysiology of dyskinesias-problematic motor complications of standard PD therapy--and that A(2A) antagonism might help prevent them. Realistically, despite being targeted to basal ganglia pathophysiology, A(2A) antagonists may be expected to have other beneficial and adverse effects elsewhere in the central nervous system (e.g., on mood and sleep) and in the periphery (e.g., on immune and inflammatory processes). The thoughtful design of new clinical trials of A(2A) antagonists should take into consideration these counterbalancing hopes and concerns and may do well to shift toward a broader set of disease-modifying as well as symptomatic indications in early PD.
Collapse
Affiliation(s)
- Kui Xu
- MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Charlestown, MA 02129, USA
| | | | | |
Collapse
|
24
|
Uustare A, Vonk A, Terasmaa A, Fuxe K, Rinken A. Kinetic and functional properties of [3H]ZM241385, a high affinity antagonist for adenosine A2A receptors. Life Sci 2004; 76:1513-26. [PMID: 15680315 DOI: 10.1016/j.lfs.2004.10.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Accepted: 10/02/2004] [Indexed: 12/01/2022]
Abstract
We have characterized the binding of [2-(3)H]-4-(2-[7-Amino-2-(2-furyl)-[1,2,4]-triazolo-[2,3-a]-[1,3,5]-triazin-5-ylamino]ethyl)phenol ([(3)H]ZM241385) to adenosine A(2A) receptors in membranes of rat striatum and transfected CHO cells. Saturation experiments showed that [(3)H]ZM241385 binds to a single class of binding sites with high affinity (K(d) = 0.23 nM and 0.14 nM in CHO cell and striatal membranes, respectively). The membranes of CHO cells required pretreatment with adenosine deaminase (ADA) to achieve high-affinity binding, while ADA had no influence on the ligand binding properties in striatal membranes. The binding of [(3)H]ZM241385 was fast and reversible, achieving equilibrium within 20 minutes at all radioligand concentrations. The kinetic analysis of the [(3)H]ZM241385 interaction with A(2A) receptors indicated that the reaction had at least two subsequent steps. The first step corresponds to a fast equilibrium, which also determines the antagonist potency to competitively inhibit CGS21680-induced accumulation of cAMP (first equilibrium constant K(A) = 6.6 nM). The second step corresponds to a slow process of conformational isomerization (equilibrium constant K(i) = 0.03). The combination of the two steps gives the dissociation constant K(d) = 0.20 nM based on the kinetic data, which is in good agreement with the directly measured value. The data obtained shed light on the mechanism of the [(3)H]ZM241385 interaction with adenosine A(2A) receptors from different sources in vitro. The isomerization step of the A(2A) antagonist radioligand binding has to be taken into account for the interpretation of the binding parameters obtained from the various competition assays and explain the discrepancy between antagonist affinity in saturation experiments versus its potency in functional assays.
Collapse
Affiliation(s)
- Ain Uustare
- Institute of Organic and Bioorganic Chemistry, University of Tartu, Jakobi Str. 2, EE-51014 Tartu, Estonia
| | | | | | | | | |
Collapse
|
25
|
Núñez-Taltavull JF, Prat G, Rubio A, Robledo P, Casas M. Biphasic effects of oxotremorine-M on turning behavior induced by caffeine in 6-OHDA-lesioned rats. Eur J Pharmacol 2004; 506:71-4. [PMID: 15588626 DOI: 10.1016/j.ejphar.2004.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Accepted: 10/06/2004] [Indexed: 11/29/2022]
Abstract
This work studied the interactions between cholinergic and adenosine systems in the denervated striatum. For that purpose, we evaluated the effects of an intrastriatal administration of the muscarincic receptor agonist, oxotremorine-M on turning behavior induced by systemic caffeine in unilaterally 6-hydroxydopamine-lesioned rats. Low doses of oxotremorine-M (0.1 ng/microl) enhanced, whereas high doses (100 ng/microl) attenuated contralateral turning induced by caffeine. These results support a functional link between muscarinic and adenosinergic systems in the denervated striatum and suggest opposite actions of muscarinic M2 and M1 receptors on caffeine-induced turning behavior.
Collapse
Affiliation(s)
- Juan Francisco Núñez-Taltavull
- Laboratori de Neuropsicofarmacologia, Institut de Recerca de l'Hospital de la Santa Creu i Sant Pau, Departaments de Psiquiatria i de Farmacología, Universitat Autónoma de Barcelona, Barcelona, Spain
| | | | | | | | | |
Collapse
|
26
|
Cunha GMA, Farias PAM, Viana GSB. Evidence for the involvement of the muscarinic cholinergic system in the central actions of pentoxifylline. Behav Pharmacol 2002; 13:149-56. [PMID: 11981227 DOI: 10.1097/00008877-200203000-00006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study shows that pentoxifylline (ptx), a xanthine derivative, significantly attenuates scopolamine-induced memory impairment in rats, as demonstrated in a passive avoidance task (50 mg/kg intraperitoneally [i.p.]) and in an elevated T-maze (10 and 50 mg/kg i.p.). Ptx (25, 50 and 100 mg/kg i.p.) also potentiates oxotremorine-induced tremors in mice, in a dose-dependent manner, and this effect was completely prevented by atropine. In addition, ptx (50 and 100 mg/kg i.p.) increased the number of animals developing pilocarpine-induced seizures, and potentiated the latency to the first pilocarpine-induced convulsion. Hippocampus homogenates from rats treated with ptx (100 mg/kg) for 1 week and sacrificed 15 min after the last injection showed a significant decrease in the muscarinic receptor numbers, indicative of a downregulation phenomenon. Similar effects were observed when assays were performed 24 h after the last ptx injection (10 and 50 mg/kg i.p.), but not after 72 h. Additionally, in vitro assays showed that ptx inhibits acetylcholinesterase activity in a dose-dependent manner when incubated with homogenates from rat hippocampus. Our data suggest that the muscarinic agonist effect of ptx could possibly depend on factors such as endogenous cholinergic activity.
Collapse
Affiliation(s)
- G M A Cunha
- Department of Physiology and Pharmacology, Faculty of Medicine, Federal University of Ceará, Rua Coronel Nunes de Melo, 1127 Fortaleza, Brazil, CEP 60430-270.
| | | | | |
Collapse
|
27
|
Hettinger BD, Lee A, Linden J, Rosin DL. Ultrastructural localization of adenosine A2A receptors suggests multiple cellular sites for modulation of GABAergic neurons in rat striatum. J Comp Neurol 2001; 431:331-46. [PMID: 11170009 DOI: 10.1002/1096-9861(20010312)431:3<331::aid-cne1074>3.0.co;2-w] [Citation(s) in RCA: 192] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Activation of adenosine A2A receptors (A2AR) has been shown to antagonize the function of D2 dopaminergic regulation of striatal gamma-aminobutyric acid (GABA)-ergic output and, thus, locomotor activity. Adenosine A2A receptor immunoreactivity (A2A-LI) has been localized to rat striatum by light microscopy by using a previously characterized human A2AR monoclonal antibody. In this study, we evaluated the localization of A2A-LI and its colocalization with GABA immunoreactivity (GABA-LI) in dorsolateral rat striatum by immunoelectron microscopy to further characterize the potential mechanism of purinergic control of striatal output. Ultrastructural analysis demonstrated A2A-LI associated with the plasma membrane and cytoplasmic membranous structures of striatal neurons. A2A-LI was prevalent in dendrites and dendritic spines ( approximately 70% of total A2A-profiles counted) and less prevalent in axons and axon terminals (23%), soma (3%), and glia (3%). Cellular elements exhibiting both A2A-LI and GABA-LI comprised 23% of the total profiles counted; colabeling was most common in dendrites. A2A-LI was observed primarily at asymmetric synapses (n = 70) (both pre- and postsynaptically but predominantly in the postsynaptic element) and less frequently at symmetric synapses (n = 17). Of the 714 A2A-immunoreactive profiles examined, 37% were apposed to GABA-labeled profiles. The most common appositions were A2A-labeled dendrites apposed to GABA-immunoreactive dendrites (n = 132), axon terminals (n = 28), and somata (n = 22) and A2A-labeled axons apposed to GABA-labeled dendrites (n = 58), axon terminals (n = 14), and somata (n = 9). Our findings suggest that adenosine may play an important role in modulating excitatory input to striatal neurons and that A2AR may modulate GABAergic signaling at several cellular sites within the rat striatum.
Collapse
Affiliation(s)
- B D Hettinger
- Department of Cardiovascular Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA
| | | | | | | |
Collapse
|