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Szopa A, Bogatko K, Herbet M, Serefko A, Ostrowska M, Wośko S, Świąder K, Szewczyk B, Wlaź A, Skałecki P, Wróbel A, Mandziuk S, Pochodyła A, Kudela A, Dudka J, Radziwoń-Zaleska M, Wlaź P, Poleszak E. The Interaction of Selective A1 and A2A Adenosine Receptor Antagonists with Magnesium and Zinc Ions in Mice: Behavioural, Biochemical and Molecular Studies. Int J Mol Sci 2021; 22:ijms22041840. [PMID: 33673282 PMCID: PMC7918707 DOI: 10.3390/ijms22041840] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/08/2021] [Accepted: 02/10/2021] [Indexed: 02/06/2023] Open
Abstract
The purpose of the study was to investigate whether the co-administration of Mg2+ and Zn2+ with selective A1 and A2A receptor antagonists might be an interesting antidepressant strategy. Forced swim, tail suspension, and spontaneous locomotor motility tests in mice were performed. Further, biochemical and molecular studies were conducted. The obtained results indicate the interaction of DPCPX and istradefylline with Mg2+ and Zn2+ manifested in an antidepressant-like effect. The reduction of the BDNF serum level after co-administration of DPCPX and istradefylline with Mg2+ and Zn2+ was noted. Additionally, Mg2+ or Zn2+, both alone and in combination with DPCPX or istradefylline, causes changes in Adora1 expression, DPCPX or istradefylline co-administered with Zn2+ increases Slc6a15 expression as compared to a single-drug treatment, co-administration of tested agents does not have a more favourable effect on Comt expression. Moreover, the changes obtained in Ogg1, MsrA, Nrf2 expression show that DPCPX-Mg2+, DPCPX-Zn2+, istradefylline-Mg2+ and istradefylline-Zn2+ co-treatment may have greater antioxidant capacity benefits than administration of DPCPX and istradefylline alone. It seems plausible that a combination of selective A1 as well as an A2A receptor antagonist and magnesium or zinc may be a new antidepressant therapeutic strategy.
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Affiliation(s)
- Aleksandra Szopa
- Chair and Department of Applied and Social Pharmacy, Laboratory of Preclinical Testing, Medical University of Lublin, 1 Chodźki Street, PL 20–093 Lublin, Poland; (K.B.); (A.S.); (S.W.)
- Correspondence: (A.S.); (E.P.)
| | - Karolina Bogatko
- Chair and Department of Applied and Social Pharmacy, Laboratory of Preclinical Testing, Medical University of Lublin, 1 Chodźki Street, PL 20–093 Lublin, Poland; (K.B.); (A.S.); (S.W.)
| | - Mariola Herbet
- Chair and Department of Toxicology, Medical University of Lublin, 8 Chodźki Street, PL 20–093 Lublin, Poland; (M.H.); (M.O.); (A.K.) (J.D.)
| | - Anna Serefko
- Chair and Department of Applied and Social Pharmacy, Laboratory of Preclinical Testing, Medical University of Lublin, 1 Chodźki Street, PL 20–093 Lublin, Poland; (K.B.); (A.S.); (S.W.)
| | - Marta Ostrowska
- Chair and Department of Toxicology, Medical University of Lublin, 8 Chodźki Street, PL 20–093 Lublin, Poland; (M.H.); (M.O.); (A.K.) (J.D.)
| | - Sylwia Wośko
- Chair and Department of Applied and Social Pharmacy, Laboratory of Preclinical Testing, Medical University of Lublin, 1 Chodźki Street, PL 20–093 Lublin, Poland; (K.B.); (A.S.); (S.W.)
| | - Katarzyna Świąder
- Chair and Department of Applied and Social Pharmacy, Medical University of Lublin, 1 Chodźki Street, PL 20–093 Lublin, Poland; (K.Ś.); (A.P.)
| | - Bernadeta Szewczyk
- Department of Neurobiology, Polish Academy of Sciences, Maj Institute of Pharmacology, 12 Smętna Street, PL 31–343 Kraków, Poland;
| | - Aleksandra Wlaź
- Department of Pathophysiology, Medical University of Lublin, 8 Jaczewskiego Street, PL 20–090 Lublin, Poland;
| | - Piotr Skałecki
- Department of Commodity Science and Processing of Raw Animal Materials, University of Life Sciences, 13 Akademicka Street, PL 20–950 Lublin, Poland;
| | - Andrzej Wróbel
- Second Department of Gynecology, 8 Jaczewskiego Street, PL 20–090 Lublin, Poland;
| | - Sławomir Mandziuk
- Department of Pneumology, Oncology and Allergology, Medical University of Lublin, 8 Jaczewskiego Street, PL 20–090 Lublin, Poland;
| | - Aleksandra Pochodyła
- Chair and Department of Applied and Social Pharmacy, Medical University of Lublin, 1 Chodźki Street, PL 20–093 Lublin, Poland; (K.Ś.); (A.P.)
| | - Anna Kudela
- Chair and Department of Toxicology, Medical University of Lublin, 8 Chodźki Street, PL 20–093 Lublin, Poland; (M.H.); (M.O.); (A.K.) (J.D.)
| | - Jarosław Dudka
- Chair and Department of Toxicology, Medical University of Lublin, 8 Chodźki Street, PL 20–093 Lublin, Poland; (M.H.); (M.O.); (A.K.) (J.D.)
| | - Maria Radziwoń-Zaleska
- Department of Psychiatry, Medical University of Warsaw, 27 Nowowiejska Street, PL 00–665 Warsaw, Poland;
| | - Piotr Wlaź
- Department of Animal Physiology and Pharmacology, Institute of Biological Sciences, Maria Curie–Skłodowska University, Akademicka 19, PL 20–033 Lublin, Poland;
| | - Ewa Poleszak
- Chair and Department of Applied and Social Pharmacy, Laboratory of Preclinical Testing, Medical University of Lublin, 1 Chodźki Street, PL 20–093 Lublin, Poland; (K.B.); (A.S.); (S.W.)
- Correspondence: (A.S.); (E.P.)
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Adenosine and NMDA Receptors Modulate Neuroprotection-Induced NMDA Preconditioning in Mice. J Mol Neurosci 2019; 70:590-599. [DOI: 10.1007/s12031-019-01463-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 12/05/2019] [Indexed: 12/20/2022]
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Mayhew J, Graham BA, Biber K, Nilsson M, Walker FR. Purinergic modulation of glutamate transmission: An expanding role in stress-linked neuropathology. Neurosci Biobehav Rev 2018; 93:26-37. [PMID: 29959963 DOI: 10.1016/j.neubiorev.2018.06.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 06/18/2018] [Accepted: 06/24/2018] [Indexed: 02/04/2023]
Abstract
Chronic stress has been extensively linked to disturbances in glutamatergic signalling. Emerging from this field of research is a considerable number of studies identifying the ability of purines at the pre-, post-, and peri-synaptic levels to tune glutamatergic neurotransmission. While the evidence describing purinergic control of glutamate has continued to grow, there has been relatively little attention given to how chronic stress modulates purinergic functions. The available research on this topic has demonstrated that chronic stress can not only disturb purinergic receptors involved in the regulation of glutamate neurotransmission, but also perturb glial-dependent purinergic signalling. This review will provide a detailed examining of the complex literature relating to glutamatergic-purinergic interactions with a focus on both neuronal and glial contributions. Once these detailed interactions have been described and contextualised, we will integrate recent findings from the field of stress research.
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Affiliation(s)
- J Mayhew
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Centre for Translational Neuroscience and Mental Health Research, University of Newcastle, Callaghan, NSW, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW, Australia.
| | - B A Graham
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Centre for Translational Neuroscience and Mental Health Research, University of Newcastle, Callaghan, NSW, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - K Biber
- Department of Psychiatry and Psychotherapy, University Hospital Freiburg, 79104 Freiburg, Germany; Department of Neuroscience, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - M Nilsson
- Centre for Translational Neuroscience and Mental Health Research, University of Newcastle, Callaghan, NSW, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - F R Walker
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia; Centre for Translational Neuroscience and Mental Health Research, University of Newcastle, Callaghan, NSW, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
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Synergistic antidepressant-like effect of the joint administration of caffeine and NMDA receptor ligands in the forced swim test in mice. J Neural Transm (Vienna) 2015; 123:463-72. [PMID: 26510772 PMCID: PMC4805709 DOI: 10.1007/s00702-015-1467-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 09/25/2015] [Indexed: 11/29/2022]
Abstract
The optimal treatment of depressed patients remains one of the most important challenges concerning depression. The identification of the best treatment strategies and development of new, safer, and more effective agents are crucial. The glutamatergic system seems to be a promising drug target, and consequently the use of the NMDA receptor ligands, particularly in co-administration with other substances exerting the antidepressant activity, has emerged among the new ideas. The objective of this study was to examine the effect of caffeine on the performance of mice treated with various NMDA modulators in the forced swim test. We demonstrated a significant interaction between caffeine (5 mg/kg) and the following NMDA receptor ligands: MK-801 (an antagonist binding in the ion channel, 0.05 mg/kg), CGP 37849 (an antagonist of the glutamate site, 0.312 mg/kg), L-701,324 (an antagonist of the glycine site, 1 mg/kg), and d-cycloserine (a high-efficacy partial agonist of the glycine site, 2.5 mg/kg), while the interaction between caffeine and the inorganic modulators, i.e., Zn2+ (2.5 mg/kg) and Mg2+ (10 mg/kg), was not considered as significant. Based on the obtained results, the simultaneous blockage of the adenosine and NMDA receptors may be a promising target in the development of new antidepressants.
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Eguchi R, Akao S, Otsuguro KI, Yamaguchi S, Ito S. Different mechanisms of extracellular adenosine accumulation by reduction of the external Ca(2+) concentration and inhibition of adenosine metabolism in spinal astrocytes. J Pharmacol Sci 2015; 128:47-53. [PMID: 26003082 DOI: 10.1016/j.jphs.2015.04.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 03/26/2015] [Accepted: 04/21/2015] [Indexed: 12/11/2022] Open
Abstract
Extracellular adenosine is a neuromodulator in the central nervous system. Astrocytes mainly participate in adenosine production, and extracellular adenosine accumulates under physiological and pathophysiological conditions. Inhibition of intracellular adenosine metabolism and reduction of the external Ca(2+) concentration ([Ca(2+)]e) participate in adenosine accumulation, but the precise mechanisms remain unclear. This study investigated the mechanisms underlying extracellular adenosine accumulation in cultured rat spinal astrocytes. The combination of adenosine kinase and deaminase (ADK/ADA) inhibition and a reduced [Ca(2+)]e increased the extracellular adenosine level. ADK/ADA inhibitors increased the level of extracellular adenosine but not of adenine nucleotides, which was suppressed by inhibition of equilibrative nucleoside transporter (ENT) 2. Unlike ADK/ADA inhibition, a reduced [Ca(2+)]e increased the extracellular level not only of adenosine but also of ATP. This adenosine increase was enhanced by ENT2 inhibition, and suppressed by sodium polyoxotungstate (ecto-nucleoside triphosphate diphosphohydrolase inhibitor). Gap junction inhibitors suppressed the increases in adenosine and adenine nucleotide levels by reduction of [Ca(2+)]e. These results indicate that extracellular adenosine accumulation by ADK/ADA inhibition is due to the adenosine release via ENT2, while that by reduction of [Ca(2+)]e is due to breakdown of ATP released via gap junction hemichannels, after which ENT2 incorporates adenosine into the cells.
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Affiliation(s)
- Ryota Eguchi
- Laboratory of Pharmacology, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan
| | - Sanae Akao
- Laboratory of Pharmacology, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan
| | - Ken-ichi Otsuguro
- Laboratory of Pharmacology, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan.
| | - Soichiro Yamaguchi
- Laboratory of Pharmacology, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan
| | - Shigeo Ito
- Laboratory of Pharmacology, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan
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Constantino LC, Pamplona FA, Matheus FC, Ludka FK, Gomez-Soler M, Ciruela F, Boeck CR, Prediger RD, Tasca CI. Adenosine A1 receptor activation modulates N-methyl-d-aspartate (NMDA) preconditioning phenotype in the brain. Behav Brain Res 2015; 282:103-10. [DOI: 10.1016/j.bbr.2014.12.056] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 12/22/2014] [Accepted: 12/25/2014] [Indexed: 12/20/2022]
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Wall MJ, Dale N. Neuronal transporter and astrocytic ATP exocytosis underlie activity-dependent adenosine release in the hippocampus. J Physiol 2013; 591:3853-71. [PMID: 23713028 DOI: 10.1113/jphysiol.2013.253450] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The neuromodulator adenosine plays an important role in many physiological and pathological processes within the mammalian CNS. However, the precise mechanisms of how the concentration of extracellular adenosine increases following neural activity remain contentious. Here we have used microelectrode biosensors to directly measure adenosine release induced by focal stimulation in stratum radiatum of area CA1 in mouse hippocampal slices. Adenosine release was both action potential and Ca²⁺ dependent and could be evoked with low stimulation frequencies and small numbers of stimuli. Adenosine release required the activation of ionotropic glutamate receptors and could be evoked by local application of glutamate receptor agonists. Approximately 40% of stimulated-adenosine release occurred by translocation of adenosine via equilibrative nucleoside transporters (ENTs). This component of release persisted in the presence of the gliotoxin fluoroacetate and thus results from the direct release of adenosine from neurons. A reduction of adenosine release in the presence of NTPDase blockers, in slices from CD73(-/-) and dn-SNARE mice, provides evidence that a component of adenosine release arises from the extracellular metabolism of ATP released from astrocytes. This component of release appeared to have slower kinetics than the direct ENT-mediated release of adenosine. These data suggest that activity-dependent adenosine release is surprisingly complex and, in the hippocampus, arises from at least two distinct mechanisms with different cellular sources.
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Affiliation(s)
- Mark J Wall
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK.
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Gniel HM, Martin RL. Cortical spreading depression-induced preconditioning in mouse neocortex is lamina specific. J Neurophysiol 2013; 109:2923-36. [PMID: 23515796 DOI: 10.1152/jn.00855.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cortical spreading depression (CSD) is able to confer neuroprotection when delivered at least 1 day in advance of an ischemic event. However, its ability to confer neuroprotection in a more immediate time frame has not previously been investigated. Here we have used mouse neocortical brain slices to study the effects of repeated episodes of CSD in layer V and layer II/III pyramidal neurons. In layer V, CSD evoked at 15-min intervals caused successively smaller membrane depolarizations and increases in intracellular calcium compared with the response to the first CSD. With an inter-CSD interval of 30 min this preconditioning effect was much less marked, indicating that preconditioning lasts between 15 and 30 min. A single episode of CSD also provided a degree of protection in oxygen-glucose deprivation (OGD) by significantly lengthening the time a cell could withstand OGD before anoxic depolarization occurred. In layer II/III pyramidal neurons no preconditioning by CSD on subsequent episodes of CSD was observed, demonstrating that the response of pyramidal neurons to repeated CSD is lamina specific. The A1 receptor antagonist 8-cyclopentyl theophylline (8-CPT) reduced the layer V preconditioning in a concentration-related manner. Inhibition of extracellular formation of adenosine by blocking ecto-5'-nucleotidase with α,β-methyleneadenosine 5'-diphosphate prevented preconditioning in most but not all cells. Block of equilibrative nucleoside transporters 1 and 2 with dipyramidole alone or in combination with 6-[(4-nitrobenzyl)thio]-9-β-d-ribofuranosylpurine also prevented preconditioning in some but not all cells. These data provide evidence that rapid preconditioning of one CSD by another is primarily mediated by adenosine.
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Affiliation(s)
- Helen M Gniel
- Research School of Biology, The Australian National Univ. Bldg. 134, Linnaeus Way, Acton, ACT, 0200, Australia.
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Heinrich A, Andó RD, Túri G, Rózsa B, Sperlágh B. K+ depolarization evokes ATP, adenosine and glutamate release from glia in rat hippocampus: a microelectrode biosensor study. Br J Pharmacol 2013; 167:1003-20. [PMID: 22394324 DOI: 10.1111/j.1476-5381.2012.01932.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE This study was undertaken to characterize the ATP, adenosine and glutamate outflow evoked by depolarization with high K(+) concentrations, in slices of rat hippocampus. EXPERIMENTAL APPROACH We utilized the microelectrode biosensor technique and extracellular electrophysiological recording for the real-time monitoring of the efflux of ATP, adenosine and glutamate. KEY RESULTS ATP, adenosine and glutamate sensors exhibited transient and reversible current during depolarization with 25 mM K(+) , with distinct kinetics. The ecto-ATPase inhibitor ARL67156 enhanced the extracellular level of ATP and inhibited the prolonged adenosine efflux, suggesting that generation of adenosine may derive from the extracellular breakdown of ATP. Stimulation-evoked ATP, adenosine and glutamate efflux was inhibited by tetrodotoxin, while exposure to Ca(2+) -free medium abolished ATP and adenosine efflux from hippocampal slices. Extracellular elevation of ATP and adenosine were decreased in the presence of NMDA receptor antagonists, D-AP-5 and ifenprodil, whereas non-NMDA receptor blockade by CNQX inhibited glutamate but not ATP and adenosine efflux. The gliotoxin fluoroacetate and P2X7 receptor antagonists inhibited the K(+) -evoked ATP, adenosine and glutamate efflux, while carbenoxolone in low concentration and probenecid decreased only the adenosine efflux. CONCLUSIONS AND IMPLICATIONS Our results demonstrated activity-dependent gliotransmitter release in the hippocampus in response to ongoing neuronal activity. ATP and glutamate were released by P2X7 receptor activation into extracellular space. Although the increased extracellular levels of adenosine did derive from released ATP, adenosine might also be released directly via pannexin hemichannels.
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Affiliation(s)
- A Heinrich
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary Femtonics Ltd, Budapest, Hungary
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Role of the ecto-nucleotidases in the cooperative effect of adenosine and neuropeptide-S on locomotor activity in mice. Pharmacol Biochem Behav 2011; 99:726-30. [PMID: 21741987 DOI: 10.1016/j.pbb.2011.06.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2010] [Revised: 06/17/2011] [Accepted: 06/24/2011] [Indexed: 02/08/2023]
Abstract
Activation of adenosine receptors modifies the action of classic neurotransmitters (i.e. dopamine, glutamate and acetylcholine) and other neuromodulators, like vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP) and neuropeptide S (NPS). Similarly to adenosine, NPS is involved in the regulation of stimulus and response to fear and arousal. Thus, the present study investigates the effects of NPS on locomotor activity in mice treated with or without α,β-methylene adenosine 5'-diphosphate (AOPCP), the inhibitor of ecto-5'-nucleotidase. Additionally, we evaluate the activity of ecto-5'-nucleotidase in brain slices of mice treated with or without NPS. Male adult CF-1 mice received i.c.v. NPS as 0.1 nmol injection with or without pre-treatment with 1 nmol α,β-methylene adenosine 5'-diphosphate (AOPCP), the selective inhibitor of ecto-5'-nucleotidase, to evaluate locomotor activity. In another set of experiments, mice received i.c.v. infusion of 0.1 nmol NPS to assay enzymatic activity in brain slices. The results demonstrated that the pre-treatment with AOPCP, which was inactive per se, prevented NPS-induced hyperlocomotion in mice. The dose of 0.1 nmol NPS was efficient to induce hyperlocomotion in animals during the observation period in the activity cage. Regarding enzymatic activity, i.c.v. NPS injection did not induce any significant alterations in ATP and AMP hydrolysis in striatum and hippocampus brain slices of mice. The present study shows that the hyperlocomotor effect of NPS depends on the ecto-5'-nucleotidase activity.
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Klyuch BP, Richardson MJE, Dale N, Wall MJ. The dynamics of single spike-evoked adenosine release in the cerebellum. J Physiol 2010; 589:283-95. [PMID: 21078589 DOI: 10.1113/jphysiol.2010.198986] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The purine adenosine is a potent neuromodulator in the brain, with roles in a number of diverse physiological and pathological processes. Modulators such as adenosine are difficult to study as once released they have a diffuse action (which can affect many neurones) and, unlike classical neurotransmitters, have no inotropic receptors. Thus rapid postsynaptic currents (PSCs) mediated by adenosine (equivalent to mPSCs) are not available for study. As a result the mechanisms and properties of adenosine release still remain relatively unclear. We have studied adenosine release evoked by stimulating the parallel fibres in the cerebellum. Using adenosine biosensors combined with deconvolution analysis and mathematical modelling, we have characterised the release dynamics and diffusion of adenosine in unprecedented detail. By partially blocking K+ channels, we were able to release adenosine in response to a single stimulus rather than a train of stimuli. This allowed reliable sub-second release of reproducible quantities of adenosine with stereotypic concentration waveforms that agreed well with predictions of a mathematical model of purine diffusion. We found no evidence for ATP release and thus suggest that adenosine is directly released in response to parallel fibre firing and does not arise from extracellular ATP metabolism. Adenosine release events showed novel short-term dynamics, including facilitated release with paired stimuli at millisecond stimulation intervals but depletion-recovery dynamics with paired stimuli delivered over minute time scales. These results demonstrate rich dynamics for adenosine release that are placed, for the first time, on a quantitative footing and show strong similarity with vesicular exocytosis.
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Affiliation(s)
- Boris P Klyuch
- Department of Biological Sciences, University of Warwick, Coventry, UK
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Wall M, Dale N. Activity-dependent release of adenosine: a critical re-evaluation of mechanism. Curr Neuropharmacol 2010; 6:329-37. [PMID: 19587854 PMCID: PMC2701281 DOI: 10.2174/157015908787386087] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 07/18/2008] [Accepted: 07/31/2008] [Indexed: 12/13/2022] Open
Abstract
Adenosine is perhaps the most important and universal modulator in the brain. The current consensus is that it is primarily produced in the extracellular space from the breakdown of previously released ATP. It is also accepted that it can be released directly, as adenosine, during pathological events primarily by equilibrative transport. Nevertheless, there is a growing realization that adenosine can be rapidly released from the nervous system in a manner that is dependent upon the activity of neurons. We consider three competing classes of mechanism that could explain neuronal activity dependent adenosine release (exocytosis of ATP followed by extracellular conversion to adenosine; exocytotic release of an unspecified transmitter followed by direct non-exocytotic adenosine release from an interposed cell; and direct exocytotic release of adenosine) and outline discriminatory experimental tests to decide between them. We review several examples of activity dependent adenosine release and explore their underlying mechanisms where these are known. We discuss the limits of current experimental techniques in definitively discriminating between the competing models of release, and identify key areas where technologies need to advance to enable definitive discriminatory tests. Nevertheless, within the current limits, we conclude that there is evidence for a mechanism that strongly resembles direct exocytosis of adenosine underlying at least some examples of neuronal activity dependent adenosine release.
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Affiliation(s)
- Mark Wall
- The Neuroscience Research Group, Department of Biological Sciences, University of Warwick, Coventry, CV4 7AL, UK
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Wall M, Eason R, Dale N. Biosensor measurement of purine release from cerebellar cultures and slices. Purinergic Signal 2010; 6:339-48. [PMID: 21103217 PMCID: PMC2947654 DOI: 10.1007/s11302-010-9185-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 05/05/2010] [Indexed: 02/08/2023] Open
Abstract
We have previously described an action-potential and Ca2+-dependent form of adenosine release in the molecular layer of cerebellar slices. The most likely source of the adenosine is the parallel fibres, the axons of granule cells. Using microelectrode biosensors, we have therefore investigated whether cultured granule cells (from postnatal day 7–8 rats) can release adenosine. Although no purine release could be detected in response to focal electrical stimulation, purine (adenosine, inosine or hypoxanthine) release occurred in response to an increase in extracellular K+ concentration from 3 to 25 mM coupled with addition of 1 mM glutamate. The mechanism of purine release was transport from the cytoplasm via an ENT transporter. This process did not require action-potential firing but was Ca2+dependent. The major purine released was not adenosine, but was either inosine or hypoxanthine. In order for inosine/hypoxanthine release to occur, cultures had to contain both granule cells and glial cells; neither cellular component was sufficient alone. Using the same stimulus in cerebellar slices (postnatal day 7–25), it was possible to release purines. The release however was not blocked by ENT blockers and there was a shift in the Ca2+ dependence during development. This data from cultures and slices further illustrates the complexities of purine release, which is dependent on cellular composition and developmental stage.
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Affiliation(s)
- Mark Wall
- Neuroscience Group, Department of Biological Sciences, University of Warwick, Coventry, CV4 7AL UK
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Zamzow CR, Bose R, Parkinson FE. N-methyl-D-aspartate-evoked adenosine and inosine release from neurons requires extracellular calcium. Can J Physiol Pharmacol 2010; 87:850-8. [PMID: 20052011 DOI: 10.1139/y09-075] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The nucleoside adenosine (ADO) is a neuromodulator in brain. ADO and its metabolite inosine (INO) have been shown to increase cell viability in stroke models. During ischemia, extracellular levels of both ADO and INO are increased. In this study, we treated rat cortical neurons with N-methyl-D-aspartate (NMDA) to initiate excitotoxicity and then investigated the mechanisms of ADO and INO release. NMDA induced a significant increase in ADO and INO production. The effect of NMDA receptor antagonists on NMDA-evoked ADO and INO release was examined. MK-801 (1 micromol/L), a potent antagonist that lacks receptor subunit selectivity, completely blocked evoked release of both ADO and INO. Memantine (10 micromol/L), a lower affinity antagonist that also lacks subunit selectivity, blocked INO, but not ADO, release. Ifenprodil (10 micromol/L), an inhibitor selective for NMDA receptors containing the NR2B subunit, completely blocked evoked ADO and INO release. NVP-AAM077 (NVP, 0.4 micromol/L), an inhibitor selective for NMDA receptors containing the NR2A subunit, did not significantly block evoked release of either ADO or INO. Removal of extracellular Ca2+ abolished NMDA-evoked release of both ADO and INO. BAPTA (25 micromol/L), which chelates intracellular Ca2+, had no significant effect on either ADO or INO release unless extracellular Ca2+ was also removed. Inhibitors of Ca2+/calmodulin-dependent protein kinase II (CaMKII) prevented NMDA-evoked ADO and INO release and decreased nucleoside transporter function. These data indicate that NMDA-evoked ADO and INO release is dependent on subunit composition of NMDA receptors. As well, NMDA-evoked ADO and INO release requires nucleoside transporters and extracellular Ca2+ and is enhanced by activation of CaMKII.
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Affiliation(s)
- Christina R Zamzow
- Department of Pharmacology and Therapeutics, A402-753 McDermot Avenue, University of Manitoba, Winnipeg, MB R3E 0T6, Canada
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Atterbury A, Wall MJ. Adenosine signalling at immature parallel fibre-Purkinje cell synapses in rat cerebellum. J Physiol 2009; 587:4497-508. [PMID: 19651764 DOI: 10.1113/jphysiol.2009.176420] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The purine adenosine is an extracellular signalling molecule involved in a large number of physiological and pathological conditions throughout the mammalian brain. However little is known about how adenosine release and its subsequent clearance change during brain development. We have combined electrophysiology and microelectrode biosensor measurements to investigate the properties of adenosine signalling at early stages of cerebellar development, when parallel fibre-Purkinje cell synapses have recently been formed (postnatal days 9-12). At this stage of development, we could detect little or no inhibitory A(1) receptor tone in basal conditions and during trains of stimuli. Addition of pharmacological agents, to inhibit adenosine clearance, had only minor effects on synaptic transmission suggesting that under basal conditions, the concentration of adenosine moving in and out of the extracellular space is small. Active adenosine release was stimulated with hypoxia and trains of electrical stimuli. Although hypoxia released significant concentrations of adenosine, the release was delayed and slow. No adenosine release could be detected following electrical stimulation in the molecular layer. In conclusion, at this stage of development, although adenosine receptors and the mechanisms of adenosine clearance are present there is very little adenosine release.
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Affiliation(s)
- Alison Atterbury
- Neuroscience Group, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
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16
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Zamzow CR, Xiong W, Parkinson FE. Astrocytes affect the profile of purines released from cultured cortical neurons. J Neurosci Res 2009; 86:2641-9. [PMID: 18478552 DOI: 10.1002/jnr.21718] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Adenosine (ADO) is produced by cultured neurons and astrocytes, albeit by different pathways, during in vitro stroke models (Parkinson and Xiong [2004] J. Neurochem. 88:1305-1312). Expression of ecto-5' nucleotidase (e-N), the enzyme responsible for extracellular dephosphorylation of AMP to ADO, is more abundant in astrocytes than neurons. Therefore, we tested the hypothesis that N-methyl-D-aspartate (NMDA) evokes ADO release per se from neurons, whereas dephosphorylation of extracellular adenine nucleotides contributes to NMDA-evoked ADO production in the presence of astrocytes. We used four different cell preparations-cortical rat neurons, cortical rat astrocytes, cocultures of neurons and astrocytes, and transient cocultures of neurons with astrocytes on transwell filters-to show that astrocytes contribute to NMDA-evoked increases in extracellular ADO. NMDA significantly increased ADO and inosine (INO) production from cultured cortical neurons but only increased extracellular INO production from cocultures. In neurons, the equilibrative nucleoside transport (ENT) inhibitor dipyridamole (DPR) prevented NMDA-evoked ADO and INO production, whereas the e-N inhibitor alpha,beta-methylene ADP (AOPCP) had no effect. Conversely, from both cocultures and transient cocultures DPR significantly decreased NMDA-evoked INO but not ADO generation. AOPCP inhibited NMDA-evoked production of both ADO and INO from transient cocultures. In the absence of astrocytes, NMDA evoked release of intracellular ADO and INO from cultured cortical neurons through ENT. However, in the presence of astrocytes, extracellular conversion of adenine nucleotides to ADO contributed significantly to NMDA-evoked production of this purine.
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Affiliation(s)
- Christina R Zamzow
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba, Canada
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17
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Cunha RA, Ferré S, Vaugeois JM, Chen JF. Potential therapeutic interest of adenosine A2A receptors in psychiatric disorders. Curr Pharm Des 2008; 14:1512-24. [PMID: 18537674 DOI: 10.2174/138161208784480090] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The interest on targeting adenosine A(2A) receptors in the realm of psychiatric diseases first arose based on their tight physical and functional interaction with dopamine D(2) receptors. However, the role of central A(2A) receptors is now viewed as much broader than just controlling D(2) receptor function. Thus, there is currently a major interest in the ability of A(2A) receptors to control synaptic plasticity at glutamatergic synapses. This is due to a combined ability of A(2A) receptors to facilitate the release of glutamate and the activation of NMDA receptors. Therefore, A(2A) receptors are now conceived as a normalizing device promoting adequate adaptive responses in neuronal circuits, a role similar to that fulfilled, in essence, by dopamine. This makes A(2A) receptors particularly attractive targets to manage psychiatric disorders since adenosine may act as go-between glutamate and dopamine, two of the key players in mood processing. Furthermore, A(2A) receptors also control glia function and brain metabolic adaptation, two other emerging mechanisms to understand abnormal processing of mood, and A(2A) receptors are important players in controlling the demise of neurodegeneration, considered an amplificatory loop in psychiatric disorders. Current data only provide an indirect confirmation of this putative role of A(2A) receptors, based on the effects of caffeine (an antagonist of both A(1) and A(2A) receptors) in psychiatric disorders. However, the introduction of A(2A) receptors antagonists in clinics as anti-parkinsonian agents is hoped to bolster our knowledge on the role of A(2A) receptors in mood disorders in the near future.
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Affiliation(s)
- Rodrigo A Cunha
- Center for Neuroscience of Coimbra, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Portugal.
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18
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Abstract
To re-examine how the basal extracellular concentration of adenosine is regulated in acutely isolated cerebellar slices we have combined electrophysiological and microelectrode biosensor measurements. In almost all cases, synaptic transmission was tonically inhibited by adenosine acting via A1 receptors. By contrast, in most slices, the biosensors did not measure an adenosine tone but did record a spatially non-uniform extracellular tone of the downstream metabolites (inosine and hypoxanthine). Most of the extracellular hypoxanthine arose from the metabolism of inosine by ecto-purine nucleoside phosphorylase (PNP). Adenosine kinase was the major determinant of adenosine levels, as its inhibition increased both adenosine concentration and A1 receptor-mediated synaptic inhibition. Breakdown of adenosine by adenosine deaminase was the major source of the inosine/hypoxanthine tone. However adenosine deaminase played a minor role in determining the level of adenosine at synapses, suggesting a distal location. Blockade of adenosine transport (by NBTI/dipyridamole) had inconsistent effects on basal levels of adenosine and synaptic transmission. Unexpectedly, application of NBTI/dipyridamole prevented the efflux of adenosine resulting from block of adenosine kinase at only a subset of synapses. We conclude that there is spatial variation in the functional expression of NBTI/dipyridamole-sensitive transporters. The increased spatial and temporal resolution of the purine biosensor measurements has revealed the complexity of the control of adenosine and purine tone in the cerebellum.
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Affiliation(s)
- Mark J Wall
- Neuroscience Group, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
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Bespalov A, Dravolina O, Belozertseva I, Adamcio B, Zvartau E. Lowered brain stimulation reward thresholds in rats treated with a combination of caffeine and N-methyl-D-aspartate but not alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate or metabotropic glutamate receptor-5 receptor antagonists. Behav Pharmacol 2006; 17:295-302. [PMID: 16914947 DOI: 10.1097/01.fbp.0000205014.67079.be] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previous studies suggested that adenosine A1 and A2A receptor agonists counteract behavioral effects of N-methyl-D-aspartate (NMDA) receptor antagonists while adenosine receptor antagonists may produce opposite effects enhancing the actions of NMDA receptor antagonists. To further evaluate the effects of combined administration of adenosine receptor antagonist caffeine and various NMDA and non-NMDA glutamate receptor antagonists on brain stimulation reward (discrete-trial threshold current intensity titration procedure), rats with electrodes implanted into the ventral tegmental area were tested after pretreatment with NMDA receptor channel blocker MK-801 (0.01-0.3 mg/kg), competitive antagonist D-CPPene (0.3-5.6 mg/kg), glycine site antagonist L-701,324 (1.25-5 mg/kg), alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor antagonist GYKI-53655 (1-10 mg/kg), metabotropic glutamate receptor 5 (mGluR5) antagonist MPEP (1-10 mg/kg) alone and in combination with caffeine (1-30 mg/kg). MK-801 (0.056 and 0.1 mg/kg) was the only tested glutamate antagonist that lowered self-stimulation thresholds, while D-CPPene (5.6 mg/kg) and MPEP (5.6 and 10 mg/kg) had the opposite effects. Threshold-increasing effects of D-CPPene, but not of MPEP, however, were associated with marked impairment of operant performance, reflected by longer latencies to respond and higher rates of responding during the inter-trial intervals. Operant performance was also disrupted by the highest dose of MK-801 (0.3 mg/kg). For subsequent experiments, caffeine (1-30 mg/kg) was combined with the highest doses of NMDA receptor antagonists that did not lower the brain stimulation reward thresholds and did not impair operant performance. Caffeine had no appreciable effects on self-stimulation behavior when given alone. A low dose of caffeine (3 mg/kg) significantly lowered self-stimulation thresholds only when given together with MK-801 (0.03 mg/kg) or D-CPPene (3 mg/kg). Combined with the same antagonist drugs, higher doses of caffeine (10 and 30 mg/kg) facilitated time-out responding. These results indicate that, within a limited dose range, caffeine in combination with an NMDA receptor channel blocker and a competitive antagonist significantly lowers brain stimulation reward thresholds in rats.
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MESH Headings
- Animals
- Benzodiazepines/pharmacology
- Brain/drug effects
- Brain/physiology
- Caffeine/pharmacology
- Central Nervous System Stimulants/pharmacology
- Conditioning, Operant/drug effects
- Conditioning, Operant/physiology
- Dizocilpine Maleate/pharmacology
- Dose-Response Relationship, Drug
- Drug Synergism
- Electric Stimulation
- Excitatory Amino Acid Antagonists/pharmacology
- Male
- N-Methylaspartate/pharmacology
- Piperazines/pharmacology
- Pyridines/pharmacology
- Quinolones/pharmacology
- Rats
- Rats, Wistar
- Receptor, Adenosine A2A/drug effects
- Receptor, Adenosine A2A/physiology
- Receptor, Metabotropic Glutamate 5
- Receptors, AMPA/antagonists & inhibitors
- Receptors, Metabotropic Glutamate/antagonists & inhibitors
- Receptors, N-Methyl-D-Aspartate/antagonists & inhibitors
- Reward
- Self Stimulation
- Ventral Tegmental Area/physiology
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Affiliation(s)
- Anton Bespalov
- Institute of Pharmacology, IP Pavlov Medical University, St Petersburg, Russia.
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20
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Lara DR, Dall'Igna OP, Ghisolfi ES, Brunstein MG. Involvement of adenosine in the neurobiology of schizophrenia and its therapeutic implications. Prog Neuropsychopharmacol Biol Psychiatry 2006; 30:617-29. [PMID: 16580767 DOI: 10.1016/j.pnpbp.2006.02.002] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Based on the neuromodulatory and homeostatic actions of adenosine, adenosine dysfunction may contribute to the neurobiological and clinical features of schizophrenia. The present model of adenosine dysfunction in schizophrenia takes into consideration the dopamine and glutamate hypotheses, since adenosine exerts neuromodulatory roles on these systems, and proposes that adenosine plays a role in the inhibitory deficit found in schizophrenia. Given the role of adenosine activation of adenosine A1 receptor (A1R) in mediating neurotoxicity in early stages of brain development, pre- and peri-natal complications leading to excessive adenosine release could induce primary brain changes (i.e., first hit). These events would lead to an adenosine inhibitory deficit through a partial loss of A1R that may emerge as reduced control of dopamine activity and increased vulnerability to excitotoxic glutamate action in the mature brain (i.e., second hit). Adenosine dysfunction is reasonably compatible with symptoms, gray and white matter abnormalities, progressive brain loss, pre- and peri-natal risk factors, age of onset, response to current treatments, impaired sensory gating and increased smoking in schizophrenia. Pharmacological treatments enhancing adenosine activity could be effective for symptom control and for alleviating deterioration in the course of the illness. Accordingly, allopurinol, which may indirectly increase adenosine, has been effective and well tolerated in the treatment of schizophrenia. Since much of the evidence for the adenosine hypothesis is preliminary and theoretical, further investigation in the field is warranted.
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Affiliation(s)
- Diogo R Lara
- Departamento de Ciências Fisiológicas, Faculdade de Biociências, PUCRS, Porto Alegre, Brazil.
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21
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Schotanus SM, Fredholm BB, Chergui K. NMDA depresses glutamatergic synaptic transmission in the striatum through the activation of adenosine A1 receptors: evidence from knockout mice. Neuropharmacology 2006; 51:272-82. [PMID: 16712880 DOI: 10.1016/j.neuropharm.2006.03.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 03/15/2006] [Accepted: 03/17/2006] [Indexed: 11/20/2022]
Abstract
N-methyl-D-aspartate (NMDA) receptors play several essential roles in the physiology and pathophysiology of the brain. Their activation results in long-term changes in glutamatergic synaptic transmission in several brain areas, but excessive activation of these receptors induces neurotoxicity. Some of NMDA-mediated actions are critically dependent on functional interactions with the neuromodulator adenosine. In the present study, we have examined whether pharmacological activation of NMDA receptors induces long-term changes in synaptic strength in the striatum. We found that NMDA depressed the amplitude of the field excitatory postsynaptic potential/population spike (fEPSP/PS) recorded in corticostriatal mouse brain slices in a concentration-dependent manner. Inhibition of synaptic transmission was more pronounced at room temperature (22 degrees C) than at 32 degrees C and long lasting (> 2 h) depression of the fEPSP/PS was observed only at room temperature. NMDA-induced depression of the fEPSP/PS was reduced or abolished in the presence of an A1 receptor antagonist and in A1 receptor knockout mice. In addition, exogenous application of adenosine depressed fEPSP/PS amplitude in wild-type mice, but not in A1 receptor knockout mice, in a concentration-dependent manner. Our results demonstrate that NMDA depresses synaptic transmission in a concentration- and temperature-dependent manner via release of adenosine and activation of adenosine A1 receptors.
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Affiliation(s)
- Sietske M Schotanus
- The Karolinska Institute, Department of Physiology and Pharmacology, Section of Molecular Neurophysiology, Von Eulers Väg 8, 171 77 Stockholm, Sweden
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22
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Franke H, Krügel U, Illes P. P2 receptors and neuronal injury. Pflugers Arch 2006; 452:622-44. [PMID: 16645849 DOI: 10.1007/s00424-006-0071-8] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Accepted: 03/09/2006] [Indexed: 02/08/2023]
Abstract
Extracellular adenosine 5'-triphosphate (ATP) was proposed to be an activity-dependent signaling molecule that regulates glia-glia and glia-neuron communications. ATP is a neurotransmitter of its own right and, in addition, a cotransmitter of other classical transmitters such as glutamate or GABA. The effects of ATP are mediated by two receptor families belonging either to the P2X (ligand-gated cationic channels) or P2Y (G protein-coupled receptors) types. P2X receptors are responsible for rapid synaptic responses, whereas P2Y receptors mediate slow synaptic responses and other types of purinergic signaling involved in neuronal damage/regeneration. ATP may act at pre- and postsynaptic sites and therefore, it may participate in the phenomena of long-term potentiation and long-term depression of excitatory synaptic transmission. The release of ATP into the extracellular space, e.g., by exocytosis, membrane transporters, and connexin hemichannels, is a widespread physiological process. However, ATP may also leave cells through their plasma membrane damaged by inflammation, ischemia, and mechanical injury. Functional responses to the activation of multiple P2 receptors were found in neurons and glial cells under normal and pathophysiological conditions. P2 receptor-activation could either be a cause or a consequence of neuronal cell death/glial activation and may be related to detrimental and/or beneficial effects. The present review aims at demonstrating that purinergic mechanisms correlate with the etiopathology of brain insults, especially because of the massive extracellular release of ATP, adenosine, and other neurotransmitters after brain injury. We will focus in this review on the most important P2 receptor-mediated neurodegenerative and neuroprotective processes and their beneficial modulation by possible therapeutic manipulations.
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Affiliation(s)
- Heike Franke
- Rudolf-Boehm Institute of Pharmacology and Toxicology, University of Leipzig, Härtelstrasse 16-18, 04107, Leipzig, Germany.
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23
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Ohata H, Cao S, Koehler RC. Contribution of adenosine A2A and A2B receptors and heme oxygenase to AMPA-induced dilation of pial arterioles in rats. Am J Physiol Regul Integr Comp Physiol 2006; 291:R728-35. [PMID: 16601261 PMCID: PMC1764456 DOI: 10.1152/ajpregu.00757.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nitric oxide (NO) has been implicated in mediation of cerebral vasodilation during neuronal activation and, specifically, in pharmacological activation of N-methyl-d-aspartate (NMDA) and kainate receptors. Possible mediators of cerebral vasodilation to alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) have not been well studied in mature brain, although heme oxygenase (HO) activity has been implicated in newborn pigs. In anesthetized rats, 5 min of topical superfusion of 30 and 100 microM AMPA on the cortical surface through a closed cranial window resulted in increases in pial arteriolar diameter. The dilatory response to AMPA was not inhibited by superfusion of an NO synthase inhibitor, a cyclooxygenase-2 inhibitor, or a cytochrome P-450 epoxygenase inhibitor, all of which have been shown to inhibit the cortical blood flow response to sensory activation. However, the 48 +/- 13% dilation to 100 microM AMPA was attenuated 56-71% by superfusion of the adenosine A(2A) receptor antagonist ZM-241385, the A(2B) receptor antagonist alloxazine, and the HO inhibitor chromium mesoporphyrin. Combination of the latter three inhibitors did not attenuate the dilator response more than the individual inhibitors, whereas an AMPA receptor antagonist fully blocked the vasodilation to AMPA. These results indicate that cortical pial arteriolar dilation to AMPA does not require activation of NO synthase, cyclooxygenase-2, or cytochrome P-450 epoxygenase but does depend on activation of adenosine A(2A) and A(2B) receptors. In addition, CO derived from HO appears to play a role in the vascular response to AMPA receptor activation in mature brain by a mechanism that is not additive with that of adenosine receptor activation.
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Affiliation(s)
- Hiroto Ohata
- Dept. of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD 21287-4961, USA
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24
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Bilodeau ML, Ji M, Paris M, Andrisani OM. Adenosine signaling promotes neuronal, catecholaminergic differentiation of primary neural crest cells and CNS-derived CAD cells. Mol Cell Neurosci 2005; 29:394-404. [PMID: 15886017 DOI: 10.1016/j.mcn.2005.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Revised: 03/17/2005] [Accepted: 03/18/2005] [Indexed: 11/22/2022] Open
Abstract
In neural crest (NC) cultures cAMP signaling is an instructive signal in catecholaminergic, sympathoadrenal cell development. However, the extracellular signals activating the cAMP pathway during NC cell development have not been identified. We demonstrate that in avian NC cultures, evidenced by tyrosine hydroxylase expression and catecholamine biosynthesis, adenosine and not adrenergic signaling, together with BMP2, promotes sympathoadrenal cell development. In NC cultures, addition of the adenosine receptor agonist NECA in the presence of BMP2 promotes sympathoadrenal cell development, whereas the antagonist CGS 15943 or the adenosine degrading enzyme adenosine deaminase (ADA) suppresses TH expression. Importantly, NC cells express A2A and A2B receptors which couple with Gsalpha increasing intracellular cAMP. Employing the CNS-derived catecholaminergic CAD cell line, we also demonstrate that neuronal differentiation mediated by serum withdrawal is further enhanced by treatment with IBMX, a cAMP-elevating agent, or the adenosine receptor agonist NECA, acting via cAMP. By contrast, the adenosine receptor antagonist CGS 15943 or the adenosine degrading enzyme ADA inhibits CAD cell neuronal differentiation mediated by serum withdrawal. These results support that adenosine is a physiological signal in neuronal differentiation of the CNS-derived catecholaminergic CAD cell line and suggest that adenosine signaling is involved in NC cell development in vivo.
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Affiliation(s)
- Matthew L Bilodeau
- Department of Basic Medical Sciences, 1246 Lynn Hall, Purdue University, West Lafayette, IN 47907-1246, USA
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25
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Rathbone MP, Middlemiss PJ, Crocker CE, Glasky MS, Juurlink BH, Ramirez JJ, Ciccarelli R, Di Iorio P, Caciagli F. AIT-082 as a potential neuroprotective and regenerative agent in stroke and central nervous system injury. Expert Opin Investig Drugs 2005; 8:1255-62. [PMID: 15992149 DOI: 10.1517/13543784.8.8.1255] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The synthetic purine 4-[[3-(1,6 dihydro-6-oxo-9-purin-9-yl)-1-oxypropyl] amino] benzoic acid (AIT-082, Neotrofin, leteprinim potassium) possesses several biological properties of note: it stimulates outgrowth of neurites from PC12 cells and neurones, stimulates synthesis and/or release of neurotrophic factors from astrocytes, enhances nerve fibre regeneration in vivo and enhances of memory in animals and humans. AIT-082 also protects against glutamate neurotoxicity in vitro and in vivo, which has led to successful tests of AIT-082 in animal models of acute central nervous system injury. In such cases, AIT-082 probably functions by both acutely reducing glutamate excitotoxicity and, over a longer period, by enhancing neuronal sprouting and functional recovery.
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Affiliation(s)
- M P Rathbone
- Department of Medicine, McMaster University Health Sciences Center, Hamilton, ON L8N 2S1, Canada.
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26
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Shepel PN, Ramonet D, Stevens P, Geiger JD. Purine level regulation during energy depletion associated with graded excitatory stimulation in brain. Neurol Res 2005; 27:139-48. [PMID: 15829176 DOI: 10.1179/016164105x21832] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVES The formation and release of adenosine following graded excitatory stimulation of the brain may serve important physiological functions such as sleep regulation, as well as an early resistance mechanism against excitotoxicity. However, adenosine at high levels may reflect merely the results of obstructed energy metabolism. METHODS We examined the extent to which levels of adenosine and adenylate energy charge are affected in vivo by graded excitatory stimulations of brain using unilateral intrastriatal injections of glutamatergic agents and head-focused high energy microwaving for accurate and precise measures of purines. RESULTS Our results confirmed that adenosine levels rise when adenylate energy charge decreases and showed that these increases occurred in three distinct phases with the rate of adenosine formation in each phase increasing as tissue adenylate energy charge was further depleted. In addition, we observed that, in most cases, the effects of focal excitatory stimulation on changes in tissue purine levels were restricted spatially within the immediate vicinity of the injection site; however, when strongly depolarizing stimuli were used, changes in purine levels could be observed in adjacent and, occasionally, even in contralateral brain regions. DISCUSSION These results provide new insight into purine regulation that occurs under physiologically relevant conditions, such as sleep and during the early stages of brain insults that induce excitotoxicity.
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Affiliation(s)
- P Nickolas Shepel
- Department of Pharmacology and Therapeutics, University of Manitoba Faculty of Medicine, Winnipeg, Manitoba, R3E 0W3, Canada
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27
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Parkinson FE, Xiong W, Zamzow CR. Astrocytes and neurons: different roles in regulating adenosine levels. Neurol Res 2005; 27:153-60. [PMID: 15829178 DOI: 10.1179/016164105x21878] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVES Adenosine is an endogenous nucleoside that signals through G-protein coupled receptors. Extracellular adenosine is required for receptor activation and two pathways have been identified for formation and cellular release of adenosine. The CLASSICAL pathway relies on intracellular formation of adenosine from adenine nucleotides and cellular efflux of adenosine via equilibrative nucleoside transporters (ENTs). The ALTERNATE pathway involves cellular release of adenine nucleotides, hydrolysis via ecto-5'-nucleotidases and extracellular formation of adenosine. METHODS A rat model of cerebral ischemia and primary cultures of rat forebrain astrocytes and neurons were used. RESULTS Using a rat model of cerebral ischemia, the ENT1 inhibitor nitrobenzylmercaptopurine ribonucleoside (NBMPR) significantly increased post-ischemic forebrain adenosine levels and significantly decreased hippocampal neuron injury relative to saline-treatment. NBMPR-induced increases in adenosine receptor activation were not detected, suggesting that altering the intracellular:extracellular distribution of adenosine can affect ischemic outcome. Using primary cultures of rat forebrain astrocytes and neurons, adenosine release was evoked by ischemic-like conditions. Dipyridamole, an inhibitor of ENTs, was more effective at inhibiting adenosine release from neurons than from astrocytes. In contrast, alpha , beta-methylene ADP, an inhibitor of ecto-5'-nucleotidase, was effective at inhibiting adenosine release from astrocytes, but not from neurons. Thus, during ischemic-like conditions, neurons released adenosine via the CLASSICAL pathway, while astrocytes released adenosine via the ALTERNATE pathway. DISCUSSION These cell type differences in pathways for adenosine formation during ischemia may allow transport inhibitors to block simultaneously adenosine release from neurons and adenosine uptake into astrocytes. In principle, this could improve neuronal ATP levels without decreasing adenosine receptor activation.
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Affiliation(s)
- Fiona E Parkinson
- Department of Pharmacology and Therapeutics, University of Manitoba, A203-753 McDermot Avenue, Winnipeg MB Canada R3E 0T6.
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28
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Bruno AN, Diniz GP, Ricachenevsky FK, Pochmann D, Bonan CD, Barreto-Chaves MLM, Sarkis JJF. Hypo-and hyperthyroidism affect the ATP, ADP and AMP hydrolysis in rat hippocampal and cortical slices. Neurosci Res 2005; 52:61-8. [PMID: 15811553 DOI: 10.1016/j.neures.2005.01.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2004] [Revised: 01/18/2005] [Accepted: 01/20/2005] [Indexed: 10/25/2022]
Abstract
The presence of severe neurological symptoms in thyroid diseases has highlighted the importance of thyroid hormones in the normal functioning of the mature brain. Since, ATP is an important excitatory neurotransmitter and adenosine acts as a neuromodulatory structure inhibiting neurotransmitters release in the central nervous system (CNS), the ectonucleotidase cascade that hydrolyzes ATP to adenosine, is also involved in the control of brain functions. Thus, we investigated the influence of hyper-and hypothyroidism on the ATP, ADP and AMP hydrolysis in hippocampal and cortical slices from adult rats. Hyperthyroidism was induced by daily injections of l-thyroxine (T4) 25 microg/100 g body weight, for 14 days. Hypothyroidism was induced by thyroidectomy and methimazole (0.05%) added to their drinking water for 14 days. Hypothyroid rats were hormonally replaced by daily injections of T4 (5 microg/100 g body weight, i.p.) for 5 days. Hyperthyroidism significantly inhibited the ATP, ADP and AMP hydrolysis in hippocampal slices. In brain cortical slices, hyperthyroidism inhibited the AMP hydrolysis. In contrast, hypothyroidism increased the ATP, ADP and AMP hydrolysis in both hippocampal and cortical slices and these effects were reverted by T4 replacement. Furthermore, hypothyroidism increased the expression of NTPDase1 and 5'-nucleotidase, whereas hyperthyroidism decreased the expression of 5'-nucleotidase in hippocampus of adult rats. These findings demonstrate that thyroid disorders may influence the enzymes involved in the complete degradation of ATP to adenosine and possibly affects the responses mediated by adenine nucleotides in the CNS of adult rats.
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Affiliation(s)
- Alessandra Nejar Bruno
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Avenida Ramiro Barcellos 2600-ANEXO, 90035-003 Porto Alegre, RS, Brazil
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Brambilla D, Chapman D, Greene R. Adenosine mediation of presynaptic feedback inhibition of glutamate release. Neuron 2005; 46:275-83. [PMID: 15848805 DOI: 10.1016/j.neuron.2005.03.016] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2004] [Revised: 01/11/2005] [Accepted: 03/12/2005] [Indexed: 11/23/2022]
Abstract
Conditions of increased metabolic demand relative to metabolite availability are associated with increased extracellular adenosine in CNS tissue. Synaptic activation of postsynaptic NMDA receptors on neurons of the cholinergic brainstem arousal center can increase sufficient extracellular adenosine to act on presynaptic A1 adenosine receptors (A1ADRs) of glutamate terminals, reducing release from the readily releasable pool. The time course of the adenosine response to an increase in glutamate release is slow (tau > 10 min), consistent with the role of adenosine as a fatigue factor that inhibits the activity of cholinergic arousal centers to reduce arousal.
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Affiliation(s)
- Dario Brambilla
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Malec D, Poleszak E. Adenosine receptor ligands and dizocilpine-induced antinociception in mice. Int J Neurosci 2005; 115:511-22. [PMID: 15809217 DOI: 10.1080/00207450590519139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Interactions between adenosine receptor ligands and dizocilpine (uncompetitive NMDA receptor antagonist) was studied in antinociceptive, writhing test in mice. Minimal effective, antinociceptive doses of adenosine receptor agonists were: 0.1 mg/kg (NECA--A1/A2 agonist). Generally, these agonists did not potentiate the subthreshold dose of dizocilpine (0.05 mg/kg). Of all adenosine receptor antagonists used, only caffeine (A2 and A2 antagonists) reversed dizocilpine-induced (0.1 mg/kg) antinociception dose-dependently. These findings indicate that dizocilpin-induced antinociception in the writhing test is only partly influenced by adenosine receptor ligands.
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Affiliation(s)
- Danuta Malec
- Department of Pharmacodynamics, Skubiszewski Medical University of Lublin, Lublin, Poland.
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31
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Boeck CR, Kroth EH, Bronzatto MJ, Vendite D. Adenosine receptors co-operate with NMDA preconditioning to protect cerebellar granule cells against glutamate neurotoxicity. Neuropharmacology 2005; 49:17-24. [PMID: 15992577 DOI: 10.1016/j.neuropharm.2005.01.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Revised: 01/10/2005] [Accepted: 01/26/2005] [Indexed: 10/25/2022]
Abstract
N-Methyl-D-aspartate (NMDA) preconditioning is evoked by subtoxic concentrations of NMDA (50 microM), which has been shown previously to lead to transient resistance to subsequent lethal dose of glutamate or NMDA in cultured neurons. The purpose of this study was to investigate the participation of adenosine A1 and A2A receptors on NMDA preconditioning against glutamate-induced cellular damage in cerebellar granule cells. NMDA preconditioning prevented the stimulatory effect induced by glutamate on AMP hydrolysis, but not on ADP hydrolysis. The neuroprotection evoked by NMDA preconditioning against glutamate-induced cellular damage was prevented by the presence of adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dimethylxanthine (CPT, 100 nM), but not by the adenosine A2A receptors antagonist, (4-(2[7-amino-2-(2-furyl {1,2,4}-triazolo{2,3-a{1,3,5}triazian-5-yl-aminoethyl)phenol (ZM 241385, 50 nM). Interestingly, a long-term treatment with CPT or ZM 241385 alone protected cells against glutamate-induced neurotoxicity. Moreover, the functionality of adenosine A1 receptor was not affected by NMDA preconditioning, but this treatment promoted adenosine A2A receptor desensitization, measured by cAMP accumulation. Taken together, the results described herein suggest that the neuroprotection evoked by NMDA preconditioning against cellular damage elicited by glutamate occurs through mechanisms involving adenosine A2A receptors desensitization co-operating with adenosine A1 receptors activation in cerebellar granule cells.
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Affiliation(s)
- Carina R Boeck
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600 (anexo), 90035-035, Porto Alegre, RS, Brazil
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32
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de Oliveira RV, Dall'Igna OP, Tort ABL, Schuh JF, Neto PF, Santos Gomes MW, Souza DO, Lara DR. Effect of subchronic caffeine treatment on MK-801-induced changes in locomotion, cognition and ataxia in mice. Behav Pharmacol 2005; 16:79-84. [PMID: 15767842 DOI: 10.1097/00008877-200503000-00002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
N-Methyl-D-aspartate (NMDA) receptor antagonists cause hyperlocomotion and cognitive deficits in rodents, and caffeine-tolerant mice show diminished locomotor response to NMDA receptor antagonists. The aim of this study was to evaluate the effect of subchronic caffeine treatment on MK-801-induced hyperlocomotion, ataxia and cognitive deficits, as well as amphetamine-induced hyperlocomotion in mice. Mice were treated subchronically with caffeine (0, 0.1, 0.3 and 1 mg/ml and 1, 3 and 7 days) and evaluated for locomotor activity, working memory (delayed alternation test), long-term memory (inhibitory avoidance task) and ataxia. Hyperlocomotion induced by MK-801 (0.25 mg/kg i.p.) was diminished after 3 days and almost abolished after 7 days of caffeine treatment at the 1 mg/ml dose, and this effect was also dose-dependent. Ataxia induced by 0.5 mg/kg MK-801 was not affected by caffeine treatment, but a short-lived hyperlocomotor effect was observed. Performance deficit in the inhibitory avoidance task induced by MK-801 (0.01 mg/kg) was prevented in mice treated with caffeine for 7 days at 1 mg/ml, and perseverative errors in the T-maze by MK-801 (0.4 mg/kg) were attenuated. The locomotor effect of amphetamine (5 mg/kg) was unaffected by subchronic caffeine treatment. The findings that hyperlocomotion and cognitive effects induced by MK-801 can be specifically influenced by reduced adenosinergic activity agree with a model of adenosine hypofunction in schizophrenia, since NMDA receptor antagonists are pharmacological models for this disorder.
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Affiliation(s)
- R V de Oliveira
- Departamento de Bioquímica, ICBS, UFRGS, Porto Alegre, Brazil
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Seamans JK, Yang CR. The principal features and mechanisms of dopamine modulation in the prefrontal cortex. Prog Neurobiol 2005; 74:1-58. [PMID: 15381316 DOI: 10.1016/j.pneurobio.2004.05.006] [Citation(s) in RCA: 1101] [Impact Index Per Article: 57.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2003] [Accepted: 05/04/2004] [Indexed: 12/17/2022]
Abstract
Mesocortical [corrected] dopamine (DA) inputs to the prefrontal cortex (PFC) play a critical role in normal cognitive process and neuropsychiatic pathologies. This DA input regulates aspects of working memory function, planning and attention, and its dysfunctions may underlie positive and negative symptoms and cognitive deficits associated with schizophrenia. Despite intense research, there is still a lack of clear understanding of the basic principles of actions of DA in the PFC. In recent years, there has been considerable efforts by many groups to understand the cellular mechanisms of DA modulation of PFC neurons. However, the results of these efforts often lead to contradictions and controversies. One principal feature of DA that is agreed by most researchers is that DA is a neuromodulator and is clearly not an excitatory or inhibitory neurotransmitter. The present article aims to identify certain principles of DA mechanisms by drawing on published, as well as unpublished data from PFC and other CNS sites to shed light on aspects of DA neuromodulation and address some of the existing controversies. Eighteen key features about DA modulation have been identified. These points directly impact on the end result of DA neuromodulation, and in some cases explain why DA does not yield identical effects under all experimental conditions. It will become apparent that DA's actions in PFC are subtle and depend on a variety of factors that can no longer be ignored. Some of these key factors include distinct bell-shaped dose-response profiles of postsynaptic DA effects, different postsynaptic responses that are contingent on the duration of DA receptor stimulation, prolonged duration effects, bidirectional effects following activation of D1 and D2 classes of receptors and membrane potential state and history dependence of subsequent DA actions. It is hoped that these factors will be borne in mind in future research and as a result a more consistent picture of DA neuromodulation in the PFC will emerge. Based on these factors, a theory is proposed for DA's action in PFC. This theory suggests that DA acts to expand or contract the breadth of information held in working memory buffers in PFC networks.
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Affiliation(s)
- Jeremy K Seamans
- Department of Physiology, MUSC, 173 Ashley Avenue, Suite 403, Charleston, SC 29425, USA.
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Lu Y, Li Y, Herin GA, Aizenman E, Epstein PM, Rosenberg PA. Elevation of intracellular cAMP evokes activity-dependent release of adenosine in cultured rat forebrain neurons. Eur J Neurosci 2004; 19:2669-81. [PMID: 15147301 DOI: 10.1111/j.0953-816x.2004.03396.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Adenosine is an important regulator of neuronal excitability. Zaprinast is a cyclic nucleotide phosphodiesterase inhibitor, and has been shown in the hippocampal slice to suppress excitation. This action can be blocked by an adenosine receptor antagonist, and therefore is presumably due to adenosine release stimulated by exposure to zaprinast. To explore the mechanism of this phenomenon further, we examined the effect of zaprinast on adenosine release itself in cultured rat forebrain neurons. Zaprinast significantly stimulated extracellular adenosine accumulation. The effect of zaprinast on adenosine appeared to be mediated by increasing intracellular cyclic adenosine monophosphate (cAMP) and activation of protein kinase A (PKA): (i) zaprinast stimulated intracellular cAMP accumulation; (ii) a cAMP antagonist (Rp-8-Br-cAMP) significantly reduced the zaprinast effect on adenosine; (iii) an inhibitor of phosphodiesterase (PDE)1 (vinpocetine) and an activator of adenylate cyclase (forskolin) mimicked the effect of zaprinast on adenosine. We also found that zaprinast had no effect on adenosine in astrocyte cultures, and tetrodotoxin completely blocked zaprinast-evoked adenosine accumulation in neuronal cultures, suggesting that neuronal activity was likely to be involved. Consistent with a dependence on neuronal activity, NMDA receptor antagonists (MK-801 and D-APV) and removal of extracellular glutamate by glutamate-pyruvate transaminase blocked the effect of zaprinast. In addition, zaprinast was shown to stimulate glutamate release. Thus, our data suggest that zaprinast-evoked adenosine accumulation is likely to be mediated by stimulation of glutamate release by a cAMP- and PKA-dependent mechanism, most likely by inhibition of PDE1 in neurons. Furthermore, regulation of cAMP, either by inhibiting cAMP-PDE activity or by stimulating adenylate cyclase activity, may play an important role in modulating neuronal excitability. These data suggest the existence of a homeostatic negative feedback loop in which increases in neuronal activity are damped by release of adenosine following activation of glutamate receptors.
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Affiliation(s)
- Yin Lu
- Department of Neurology and Program in Neuroscience, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
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Nagel J, Hauber W. Reverse microdialysis of a dopamine D2 receptor antagonist alters extracellular adenosine levels in the rat nucleus accumbens. Neurochem Int 2004; 44:609-15. [PMID: 15016476 DOI: 10.1016/j.neuint.2003.10.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2003] [Accepted: 10/02/2003] [Indexed: 11/16/2022]
Abstract
Recent evidence suggests that modulation of dopaminergic transmission alters striatal levels of extracellular adenosine. The present study used reverse microdialysis of the selective dopamine D(2) receptor antagonist raclopride to investigate whether a blockade of dopamine D(2) receptors modifies extracellular adenosine concentrations in the nucleus accumbens. Results reveal that perfusion of raclopride produced an increase of dialysate adenosine which was significant with a high (10 mM) and intermediate (1 mM) drug concentration, but not with lower drug concentrations (10 and 100 microM). Thus, the present study demonstrates that a selective blockade of dopamine D(2) receptors in the nucleus accumbens produced a pronounced increase of extracellular adenosine. The cellular mechanisms underlying this effect are yet unknown. It is suggested that the increase of extracellular adenosine might be related to a homeostatic modulatory mechanism proposed to be a key function of adenosine in response to neuronal metabolic challenges.
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Affiliation(s)
- J Nagel
- Department of Animal Physiology, Institute of Biology, University of Stuttgart, Pfaffenwaldring 57, Stuttgart D-70550, Germany
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36
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Caffeine withdrawal syndrome in social interaction test in mice: Effects of the NMDA receptor channel blockers, memantine and neramexane. Behav Pharmacol 2004. [DOI: 10.1097/01.fbp.0000129748.60495.85] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Aumeerally N, Allen G, Sawynok J. Glutamate-evoked release of adenosine and regulation of peripheral nociception. Neuroscience 2004; 127:1-11. [PMID: 15219663 DOI: 10.1016/j.neuroscience.2004.04.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/08/2004] [Indexed: 10/26/2022]
Abstract
Glutamate (which facilitates peripheral nociception) releases adenosine (which inhibits peripheral nociception via adenosine A(1) receptors) when injected locally into the rat hindpaw. The present study determined whether this locally released adenosine could modulate spontaneous pain behaviors produced by a local injection of 1.5% formalin, by determining the effect of 8-cyclopentyl-theophylline (CPT; selective adenosine A(1) receptor antagonist) on flinching produced by formalin/glutamate combinations. Experiments were performed following a prior conditioning injection of 2.5% formalin into the contralateral hindpaw 3-4 days earlier. CPT augmented flinching behaviors produced by 1.5% formalin/1 micromol glutamate, but had no effect on behaviors produced by formalin or glutamate alone. CPT also augmented flinches generated by formalin/alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and formalin/kainic acid, but not by formalin/N-methyl-D-aspartate (NMDA) combinations. The conditioning leads to a clearer expression of the peripheral inhibitory effect of adenosine (inhibitory effect of an inhibitor of adenosine kinase on flinching also was observed), rather than an increased release of adenosine (no enhanced release observed by microdialysis). Microglia appear to be involved in the conditioning, as microglia are activated in the dorsal spinal cord 3 days following injection of 2.5% formalin, and augmentation of formalin/glutamate-induced flinching by CPT is inhibited by the glial metabolic inhibitor fluorocitrate. The augmentation of flinching by CPT is also eliminated following a spinal pretreatment with MK-801 (NMDA receptor antagonist), cyclohexyladenosine (adenosine A(1) receptor agonist), N(G)-nitro-L-arginine methyl ester HCl (nitric oxide synthetase inhibitor), and chelerythrine (protein kinase C inhibitor). The conditioning pretreatment with 2.5% formalin does not lead to a generalized chemical or thermal hypersensitivity in the contralateral hindpaw. This study demonstrates that prior exposure to 2.5% formalin in the contralateral hindpaw reveals an inhibitory effect of adenosine on peripheral nociception in the presence of glutamate; this conditioning involves microglia and other mechanisms involved in central sensitization.
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Affiliation(s)
- N Aumeerally
- Department of Pharmacology and Anatomy, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5
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38
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Saransaari P, Oja SS. Enhanced release of adenosine under cell-damaging conditions in the developing and adult mouse hippocampus. Neurochem Res 2003; 28:1409-17. [PMID: 12938864 DOI: 10.1023/a:1024956701683] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The inhibitory neuromodulator adenosine has been thought to act as an endogenous neuroprotectant against cerebral ischemia and neuronal damage. The release of preloaded [3H]adenosine from hippocampal slices from developing (7-day-old) and adult (3-month-old) mice was characterized using a superfusion system under various cell-damaging conditions, including hypoxia, hypoglycemia, ischemia, oxidative stress, and the presence of free radicals and metabolic poisons. The release of adenosine was greatly potentiated under the above conditions at both ages, with free radicals, metabolic poisons, and ischemia generally having the strongest stimulatory effects. Depolarization by K+ ions (50 mM) could then evoke more release of adenosine only in the immature hippocampus. Omission of Ca2+ from the superfusion media had no effect on the ischemia-induced release in the adults, indicating that it occurs by a Ca2+-independent system. In contrast, the release in the immature hippocampus was partially dependent on extracellular Ca2+. Furthermore, the ischemia-induced adenosine release was reduced in Na+-deficient media and enhanced by ouabain at both ages, pointing to the involvement of Na+-dependent transporters. The release was also reduced by Cl- channel blockers, thus indicating that a part of the evoked release occurs through anion channels. Another inhibitory neuromodulator and cell volume regulator, taurine, was seen to enhance adenosine release in ischemia at both ages. The simultaneous release of taurine and adenosine under cell-damaging conditions could constitute an important protective mechanism against excessive amounts of excitatory amino acids, counteracting their harmful effects and preventing excitation from reaching neurotoxic levels.
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Affiliation(s)
- Pirjo Saransaari
- Tampere Brain Research Center, Medical School, FIN-33014 University of Tampere, Finland.
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Deng Q, Watson CJ, Kennedy RT. Aptamer affinity chromatography for rapid assay of adenosine in microdialysis samples collected in vivo. J Chromatogr A 2003; 1005:123-30. [PMID: 12924787 DOI: 10.1016/s0021-9673(03)00812-4] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
An anti-adenosine aptamer was evaluated as a stationary phase in packed capillary liquid chromatography. Using an aqueous mobile phase containing 20 mM Mg2+, adenosine was strongly retained on the column. A gradient of increasing Ni2+ (to 18 mM), which is presumed to complex with nitrogen atoms in adenosine involved in binding to the aptamer, eluted adenosine in a narrow zone. Up to 6 microl of 1.2 microM adenosine could be injected onto the 150-microm I.D. x 7 cm long column without loss of adenosine. With UV absorbance detection, the detection limit was 30 nM or 120 fmol (4 microl injected). Samples could be repetitively injected with 4.6% relative standard deviation in peak area. Columns were stable to at least 200 injections. The adenosine assay, which required no sample preparation, was used on microdialysis samples collected from the somatosensory cortex of chloral hydrate anesthetized rats. Total analysis times were short enough that dialysate samples could be injected every 5 min. Basal dialysate concentrations of adenosine stabilized at 87+/-10 nM (n=5) with the probe operated at 0.6 microl/min.
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Affiliation(s)
- Qing Deng
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI 48109-1055, USA
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Bennett HJ, White TD, Semba K. Activation of cholinergic and adrenergic receptors increases the concentration of extracellular adenosine in the cerebral cortex of unanesthetized rat. Neuroscience 2003; 117:119-27. [PMID: 12605898 DOI: 10.1016/s0306-4522(02)00826-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Adenosine is an inhibitory neuromodulator in the CNS. For extracellular adenosine to play a physiological role in the brain, it must be present at effective concentrations. Acetylcholine and noradrenaline are known to play an important role in modulating the activity of cortical neurons, and they might have a role also in the release of adenosine in the cerebral cortex in vivo. We examined whether activation of cholinergic and adrenergic receptors affects extracellular adenosine levels in the cerebral cortex of unanesthetized rats using in vivo microdialysis. All drugs were administered locally within the cortex by reverse dialysis. Both acetylcholine and the acetylcholinesterase inhibitor neostigmine increased extracellular adenosine levels, and the effect of neostigmine was blocked by the nicotinic receptor antagonist mecamylamine. Both nicotine and the nicotinic receptor agonist epibatidine increased the concentration of extracellular adenosine. Activation of muscarinic receptors using the nonselective agonist oxotremorine and a selective M1 receptor agonist also increased extracellular adenosine levels. Noradrenaline and the noradrenergic reuptake inhibitor desipramine increased extracellular adenosine levels. The alpha(1)-adrenergic receptor agonist phenylephrine and the beta-adrenergic agonist isoproterenol increased extracellular adenosine levels, whereas the alpha(2)-adrenergic receptor agonist clonidine did not have an effect. These findings indicate that activation of specific cholinergic and adrenergic receptors can increase extracellular levels of adenosine in the cortex, and suggest that cholinergic and adrenergic receptor-mediated regulation of adenosine levels may represent a mechanism for controlling the excitability of cortical neurons.
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Affiliation(s)
- H J Bennett
- Department of Anatomy and Neurobiology, Faculty of Medicine, Dalhousie University, Halifax, NS B3H 1X5, Canada
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Iliff JJ, D'Ambrosio R, Ngai AC, Winn HR. Adenosine receptors mediate glutamate-evoked arteriolar dilation in the rat cerebral cortex. Am J Physiol Heart Circ Physiol 2003; 284:H1631-7. [PMID: 12543638 DOI: 10.1152/ajpheart.00909.2002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the hypothesis that adenosine (Ado) mediates glutamate-induced vasodilation in the cerebral cortex by monitoring pial arteriole diameter in chloralose-anesthetized rats equipped with closed cranial windows. Topical application of 100 microM glutamate and 100 microM N-methyl-d-aspartate (NMDA) dilated pial arterioles (baseline diameter 25 +/- 2 microm) by 17 +/- 1% and 18 +/- 4%, respectively. Coapplication of the nonselective Ado receptor antagonist theophylline (Theo; 10 microM) significantly reduced glutamate- and NMDA-induced vasodilation to 4 +/- 2% (P < 0.01) and 6 +/- 2% (P < 0.05), whereas the Ado A(1) receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (0.1 microM) had no effect. Moreover, application of the Ado A(2A) receptor-selective antagonist 4-(2-[7-amino-2-(2-furyl)(1,2,4)triazolo(2,3-a)(1,3,5)triazin-5-ylamino]ethyl)phenol (ZM-241385), either by superfusion (0.1 microM, 1 microM) or intravenously (1 mg/kg), significantly inhibited the pial arteriole dilation response to glutamate. Neither Theo nor ZM-241385 affected vascular reactivity to mild hypercapnia induced by 5% CO(2) inhalation. These results suggest that Ado contributes to the dilation of rat cerebral arterioles induced by exogenous glutamate, and that the Ado A(2A) receptor subtype may be involved in this dilation response.
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Affiliation(s)
- Jeffrey J Iliff
- Department of Neurological Surgery, University of Washington School of Medicine, Harborview Medical Center, 325 Ninth Avenue, Seattle, WA 98104, USA
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Dall'Igna OP, Da Silva AL, Dietrich MO, Hoffmann A, de Oliveira RV, Souza DO, Lara DR. Chronic treatment with caffeine blunts the hyperlocomotor but not cognitive effects of the N-methyl-D-aspartate receptor antagonist MK-801 in mice. Psychopharmacology (Berl) 2003; 166:258-63. [PMID: 12589526 DOI: 10.1007/s00213-002-1362-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2002] [Accepted: 11/21/2002] [Indexed: 11/28/2022]
Abstract
RATIONALE Administration of N-methyl- d-aspartate (NMDA) receptor antagonists produce hyperlocomotion and cognitive deficits in rodents. Activation of NMDA receptors promotes adenosine release, and adenosine agonists prevent central effects of NMDA receptor antagonists. We hypothesized that if NMDA receptor antagonists require adenosine to produce behavioral effects, mice tolerant to the adenosine receptor antagonist caffeine would have a diminished response to NMDA receptor antagonists. OBJECTIVES To evaluate MK-801-induced hyperlocomotion and cognitive deficits after chronic caffeine treatment in mice. METHODS Locomotor activity was analyzed in a computerized system, spontaneous alternation was assessed in the Y-maze and long-term memory was assessed with the inhibitory avoidance task in mice. RESULTS Mice chronically treated with caffeine in drinking solution (1 mg/ml for 7 days) presented normal habituation and substantial tolerance to acute caffeine (30 mg/kg, i.p.) locomotor effects. MK-801 (0.25 mg/kg, i.p.) produced pronounced hyperlocomotion in water-treated mice, but this effect was abolished in caffeine-drinking mice. Chronic caffeine treatment had no influence on either normal or MK-801-induced deficits in spontaneous alternation and inhibitory avoidance tasks. CONCLUSION Hyperlocomotion induced by MK-801 may be mediated by reduced adenosinergic activity. These results also suggest that locomotor and cognitive effects of MK-801 can be dissociated and are distinctly modulated. Finally, these findings agree with the adenosine hypofunction model of schizophrenia, since NMDA receptor antagonists are a pharmacological model for this disorder.
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Lu Y, Chung HJ, Li Y, Rosenberg PA. NMDA receptor-mediated extracellular adenosine accumulation in rat forebrain neurons in culture is associated with inhibition of adenosine kinase. Eur J Neurosci 2003; 17:1213-22. [PMID: 12670309 DOI: 10.1046/j.1460-9568.2003.02554.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effect of N-methyl-d-aspartate (NMDA) on regulation of extracellular adenosine was investigated in rat forebrain neurons in culture. NMDA evoked accumulation of extracellular adenosine with an EC50 value of 4.8 +/- 1.2 microM. The effect of NMDA was blocked by (+)-5-methyl-10,11-dihydro-5H-dibenzo [a, d] cyclohepten-5,10-imine hydrogen maleate indicating that NMDA receptor activation was involved. The NMDA effect was also blocked by chelation of extracellular Ca2+ indicating that influx of calcium was required. The nitric oxide-cyclic GMP signalling pathway was not involved, as nitric oxide synthase inhibitors were unable to block, and cGMP analogs were unable to mimic, the effect of NMDA. The source for extracellular adenosine was likely to be intracellular adenosine as the ecto-5'-nucleotidase inhibitor alpha beta-methylene-ADP was unable to block the effect of NMDA. One possible cause of intracellular adenosine accumulation might be NMDA receptor-mediated inhibition of mitochondrial function and ATP hydrolysis. We found that NMDA caused a concentration dependent depletion of intracellular ATP with an EC50 value of 21 +/- 8 microM. NMDA also caused a significant decrease in adenosine kinase activity, assayed by two different methods. Consistent with the hypothesis that inhibition of adenosine kinase is sufficient to cause an increase in extracellular adenosine, inhibition of adenosine kinase by 5'-iodotubercidin resulted in elevation of extracellular adenosine. However, in the presence of a concentration of 5'-iodotubercidin that inhibited over 90% of adenosine kinase activity, exposure to NMDA still caused adenosine accumulation. These studies suggest that several possible mechanisms are likely to be involved in NMDA-evoked extracellular adenosine accumulation.
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Affiliation(s)
- Yin Lu
- Department of Neurology and Program in Neuroscience, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
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Krügel U, Kittner H, Franke H, Illes P. Purinergic modulation of neuronal activity in the mesolimbic dopaminergic system in vivo. Synapse 2003; 47:134-42. [PMID: 12454951 DOI: 10.1002/syn.10162] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
ATP and its metabolite adenosine activate membrane receptors, termed P2 and P1, respectively. In the present study, the modulation of the mesolimbic neuronal circuit by ATPergic and adenosinergic mechanisms was investigated by microdialysis in the nucleus accumbens (NAc) and by telemetrically recorded EEG from both the NAc and the ventral tegmental area (VTA) of freely moving rats. The basal extracellular dopamine concentration was enhanced after accumbal perfusion with the ATP analog 2-methylthio ATP (2-MeSATP; 100 microM); by contrast, adenosine (100 microM) caused a reduction of extracellular dopamine. When given alone, the P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; 20 microM) decreased the concentration of dopamine, whereas the P1 receptor antagonist 8-(p-sulfophenyl)theophylline (8-SPT; 100 microM) increased it. In the same animals, P2 receptor stimulation by 2-MeSATP caused neuronal activation, indicated by an elevation of the absolute power in the EEG of the NAc mainly by enhancement of the relative power in the alpha band (8-13 Hz) of the EEG spectrum. By contrast, adenosine led to a depression of the absolute power in the VTA accompanied by an elevation of the delta-band power (0.4-6 Hz) in the NAc corresponding to a slowing of neuronal activity. When given alone, PPADS reduced the absolute EEG power in the NAc accompanied by a decrease in the high-frequency power, but had no effects on the VTA. 8-SPT on its own enhanced the total power in both the NAc and the VTA, reflected by an enhancement in the slow and the high-frequency bands. Whereas the 8-SPT-evoked changes of EEG pattern as well as of dopamine concentration in the NAc were abolished by the co-application of PPADS, the 8-SPT-induced EEG changes in the VTA persisted under these conditions. In conclusion, the accumbal neuronal output, reflected by both dopamine release and neuronal electrical activity, is modulated in a functionally antagonistic manner by P2 and P1 receptor stimulation. It is suggested that an inhibitory GABAergic feedback projection to the VTA is stimulated by adenosine, either directly or indirectly via glutamate release.
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Affiliation(s)
- Ute Krügel
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, D-04107 Leipzig, Germany.
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Saransaari P, Oja SS. Mechanisms of adenosine release in the developing and adult mouse hippocampus. Neurochem Res 2002; 27:911-8. [PMID: 12396102 DOI: 10.1023/a:1020343631833] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Adenosine is a neuromodulator known to inhibit the synaptic release of neurotransmitters, e.g., glutamate, and to hyperpolarize postsynaptic neurons. The release of adenosine is markedly enhanced under ischemic conditions. It may then act as an endogenous neuroprotectant against cerebral ischemia and excitotoxic neuronal damage. The mechanisms by which adenosine is released from nervous tissue are not fully known, particularly in the immature brain. We now characterized the release of [3H]adenosine from hippocampal slices from developing (7-day-old) and adult (3-month-old) mice using a superfusion system. The properties of the release differed only partially in the immature and mature hippocampus. The K(+)-evoked release was Ca2+ and Na+ dependent. Anion channels were also involved. Ionotropic glutamate receptor agonists potentiated the release in a receptor-mediated manner. Activation of metabotropic glutamate receptors enhanced the release in developing mice, with group II receptors alone being effective. The evoked adenosine release apparently provides neuroprotective effects against excitotoxicity under cell-damaging conditions. Taurine had no effect on adenosine release in adult mice, but depressed the release concentration dependently in the immature hippocampus.
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Affiliation(s)
- Pirjo Saransaari
- Tampere Brain Research Center, Medical School, University of Tampere, Finland.
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46
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Latini S, Pedata F. Adenosine in the central nervous system: release mechanisms and extracellular concentrations. J Neurochem 2001; 79:463-84. [PMID: 11701750 DOI: 10.1046/j.1471-4159.2001.00607.x] [Citation(s) in RCA: 549] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Adenosine has several functions within the CNS that involve an inhibitory tone of neurotransmission and neuroprotective actions in pathological conditions. The understanding of adenosine production and release in the brain is therefore of fundamental importance and has been extensively studied. Conflicting results are often obtained regarding the cellular source of adenosine, the stimulus that induces release and the mechanism for release, in relation to different experimental approaches used to study adenosine production and release. A neuronal origin of adenosine has been demonstrated through electrophysiological approaches showing that neurones can release significant quantities of adenosine, sufficient to activate adenosine receptors and to modulate synaptic functions. Specific actions of adenosine are mediated by different receptor subtypes (A(1), A(2A), A(2B) and A(3)), which are activated by various ranges of adenosine concentrations. Another important issue is the measurement of adenosine concentrations in the extracellular fluid under different conditions in order to know the degree of receptor stimulation and understand adenosine central actions. For this purpose, several experimental approaches have been used both in vivo and in vitro, which provide an estimation of basal adenosine levels in the range of 50-200 nM. The purpose of this review is to describe pathways of adenosine production and metabolism, and to summarize characteristics of adenosine release in the brain in response to different stimuli. Finally, studies performed to evaluate adenosine concentrations under physiological and hypoxic/ischemic conditions will be described to evaluate the degree of adenosine receptor activation.
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Affiliation(s)
- S Latini
- Department of Preclinical and Clinical Pharmacology, University of Florence, Florence, Italy
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47
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Abstract
Adenosine is a modulator that has a pervasive and generally inhibitory effect on neuronal activity. Tonic activation of adenosine receptors by adenosine that is normally present in the extracellular space in brain tissue leads to inhibitory effects that appear to be mediated by both adenosine A1 and A2A receptors. Relief from this tonic inhibition by receptor antagonists such as caffeine accounts for the excitatory actions of these agents. Characterization of the effects of adenosine receptor agonists and antagonists has led to numerous hypotheses concerning the role of this nucleoside. Previous work has established a role for adenosine in a diverse array of neural phenomena, which include regulation of sleep and the level of arousal, neuroprotection, regulation of seizure susceptibility, locomotor effects, analgesia, mediation of the effects of ethanol, and chronic drug use.
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Affiliation(s)
- T V Dunwiddie
- Department of Pharmacology and Program in Neuroscience, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
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Huang CC, Hsu KS. Progress in understanding the factors regulating reversibility of long-term potentiation. Rev Neurosci 2001; 12:51-68. [PMID: 11236065 DOI: 10.1515/revneuro.2001.12.1.51] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Over the past two decades there has been a progressive understanding of the properties and mechanisms underlying long-term potentiation (LTP) of synaptic efficacy, a putative mechanism for learning and memory storage in the brain. Although LTP is remarkable for its stability, recent work has provided evidence that various manipulations can disrupt LTP if applied shortly after its induction. This kind of reversal of synaptic strength from the potentiated state to pre-LTP levels is termed depotentiation. Depotentiation of LTP is effectively induced by low-frequency afferent stimulation (1-5 Hz), brief periods of hypoxia, application of adenosine receptor agonists and brief cooling shocks. The examples of depotentiation described to date are input specific, and not differently expressed during development. The mechanisms responsible for this phenomenon remain to be fully characterized, although some possibilities are dependent on NMDA receptor activation, the increases in intracellular Ca2+, and altered states of protein kinases or phosphatases. In this review, we summarize the recent data concerning putative depotentiation mechanisms and the implications of this phenomenon in the mechanisms of "forgetting", and discuss the prevention of saturation of the storage capacity of a neuronal network.
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Affiliation(s)
- C C Huang
- Department of Pharmacology, College of Medicine, National Cheng-Kung University, Tainan City, Taiwan
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Ciccarelli R, Ballerini P, Sabatino G, Rathbone MP, D'Onofrio M, Caciagli F, Di Iorio P. Involvement of astrocytes in purine‐mediated reparative processes in the brain. Int J Dev Neurosci 2001; 19:395-414. [PMID: 11378300 DOI: 10.1016/s0736-5748(00)00084-8] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Astrocytes are involved in multiple brain functions in physiological conditions, participating in neuronal development, synaptic activity and homeostatic control of the extracellular environment. They also actively participate in the processes triggered by brain injuries, aimed at limiting and repairing brain damages. Purines may play a significant role in the pathophysiology of numerous acute and chronic disorders of the central nervous system (CNS). Astrocytes are the main source of cerebral purines. They release either adenine-based purines, e.g. adenosine and adenosine triphosphate, or guanine-based purines, e.g. guanosine and guanosine triphosphate, in physiological conditions and release even more of these purines in pathological conditions. Astrocytes express several receptor subtypes of P1 and P2 types for adenine-based purines. Receptors for guanine-based purines are being characterised. Specific ecto-enzymes such as nucleotidases, adenosine deaminase and, likely, purine nucleoside phosphorylase, metabolise both adenine- and guanine-based purines after release from astrocytes. This regulates the effects of nucleotides and nucleosides by reducing their interaction with specific membrane binding sites. Adenine-based nucleotides stimulate astrocyte proliferation by a P2-mediated increase in intracellular [Ca2+] and isoprenylated proteins. Adenosine also, via A2 receptors, may stimulate astrocyte proliferation, but mostly, via A1 and/or A3 receptors, inhibits astrocyte proliferation, thus controlling the excessive reactive astrogliosis triggered by P2 receptors. The activation of A1 receptors also stimulates astrocytes to produce trophic factors, such as nerve growth factor, S100beta protein and transforming growth factor beta, which contribute to protect neurons against injuries. Guanosine stimulates the output of adenine-based purines from astrocytes and in addition it directly triggers these cells to proliferate and to produce large amount of neuroprotective factors. These data indicate that adenine- and guanine-based purines released in large amounts from injured or dying cells of CNS may act as signals to initiate brain repair mechanisms widely involving astrocytes.
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Affiliation(s)
- R Ciccarelli
- Department of Biomedical Sciences, Section of Pharmacology, Via del Vestini Pal. B, 66013, Chieti, Italy.
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Bennett HJ, White TD, Semba K. Activation of metabotropic glutamate receptors increases extracellular adenosine in vivo. Neuroreport 2000; 11:3489-92. [PMID: 11095505 DOI: 10.1097/00001756-200011090-00018] [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: 10/26/2022]
Abstract
In order to identify the mechanisms that would lead to increased levels of the inhibitory neuromodulator adenosine in the brain, we tested metabotropic glutamate receptor agonists for their ability to increase extracellular adenosine in the cortex of unanesthetized rat using in vivo microdialysis. The group I/II metabotropic glutamate receptor agonist trans-(+/-)- 1-amino-(1S,3R)-cyclopenyanedicarboxylic acid (I mM) increased extracellular adenosine as did the specific group I agonist (S)- 3,5-dihydroxyphenylglycine (DHPG; 1 mM). The evoked increase of adenosine by 1 mM DHPG was reduced by the group I antagonist (RS)- 1-aminoindan-1,5,-dicarboxylic acid. Activation of group II or III metabotropic receptors did not affect extracellular adenosine. These results suggest that activation of group I metabotropic receptors contributes to elevated extracellular adenosine levels in vivo.
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Affiliation(s)
- H J Bennett
- Department of Anatomy, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
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