1
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Lopes CR, Gonçalves FQ, Olaio S, Tomé AR, Cunha RA, Lopes JP. Adenosine A 2A Receptors Shut Down Adenosine A 1 Receptor-Mediated Presynaptic Inhibition to Promote Implementation of Hippocampal Long-Term Potentiation. Biomolecules 2023; 13:biom13040715. [PMID: 37189461 DOI: 10.3390/biom13040715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/13/2023] [Accepted: 04/17/2023] [Indexed: 05/17/2023] Open
Abstract
Adenosine operates a modulation system fine-tuning the efficiency of synaptic transmission and plasticity through A1 and A2A receptors (A1R, A2AR), respectively. Supramaximal activation of A1R can block hippocampal synaptic transmission, and the tonic engagement of A1R-mediated inhibition is increased with increased frequency of nerve stimulation. This is compatible with an activity-dependent increase in extracellular adenosine in hippocampal excitatory synapses, which can reach levels sufficient to block synaptic transmission. We now report that A2AR activation decreases A1R-medated inhibition of synaptic transmission, with particular relevance during high-frequency-induced long-term potentiation (LTP). Thus, whereas the A1R antagonist DPCPX (50 nM) was devoid of effects on LTP magnitude, the addition of an A2AR antagonist SCH58261 (50 nM) allowed a facilitatory effect of DPCPX on LTP to be revealed. Additionally, the activation of A2AR with CGS21680 (30 nM) decreased the potency of the A1R agonist CPA (6-60 nM) to inhibit hippocampal synaptic transmission in a manner prevented by SCH58261. These observations show that A2AR play a key role in dampening A1R during high-frequency induction of hippocampal LTP. This provides a new framework for understanding how the powerful adenosine A1R-mediated inhibition of excitatory transmission can be controlled to allow the implementation of hippocampal LTP.
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Affiliation(s)
- Cátia R Lopes
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Francisco Q Gonçalves
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Simão Olaio
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Angelo R Tomé
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
- Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Rodrigo A Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
- Faculty of Medicine, University of Coimbra, 3000-534 Coimbra, Portugal
| | - João Pedro Lopes
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
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2
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Martínez-Gallego I, Pérez-Rodríguez M, Coatl-Cuaya H, Flores G, Rodríguez-Moreno A. Adenosine and Astrocytes Determine the Developmental Dynamics of Spike Timing-Dependent Plasticity in the Somatosensory Cortex. J Neurosci 2022; 42:6038-6052. [PMID: 35768208 PMCID: PMC9351642 DOI: 10.1523/jneurosci.0115-22.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 04/18/2022] [Accepted: 05/18/2022] [Indexed: 02/05/2023] Open
Abstract
During development, critical periods of synaptic plasticity facilitate the reordering and refinement of neural connections, allowing the definitive synaptic circuits responsible for correct adult physiology to be established. The L4-L2/3 synapses in the somatosensory cortex (S1) exhibit a presynaptic form of spike timing-dependent long-term depression (t-LTD) that probably fulfills a role in synaptic refinement. This t-LTD persists until the fourth postnatal week in mice, disappearing thereafter. When we investigated the mechanisms underlying this maturation-related loss of t-LTD in either sex mouse slices, we found that it could be completely recovered by antagonizing adenosine type 1 receptors. By contrast, an agonist of A1R impeded the induction of t-LTD at P13-27. Furthermore, we found that the adenosine that mediated the loss of t-LTD at the end of the fourth week of development is most probably supplied by astrocytes. At more mature stages (P38-60), we found that the protocol used to induce t-LTD provokes t-LTP. We characterized the mechanisms underlying the induction of this form of LTP, and we found it to be expressed presynaptically, as witnessed by paired-pulse and coefficient of variation analysis. In addition, this form of presynaptic t-LTP requires the activation of NMDARs and mGlu1Rs, and the entry of Ca2+ into the postsynaptic neuron through L-type voltage-dependent Ca2+ channels. Nitric oxide is also required for t-LTP as a messenger in the postsynaptic neuron as are the adenosine and glutamate that are released in association with astrocyte signaling. These results provide direct evidence of the mechanisms that close the window of plasticity associated with t-LTD and that drive the switch in synaptic transmission from t-LTD to t-LTP at L4-L2/3 synapses, in which astrocytes play a central role.SIGNIFICANCE STATEMENT During development, critical periods of plasticity facilitate the reordering and refining of neural connections, allowing correct adult physiology to be established. The L4-L2/3 synapses in the somatosensory cortex exhibit a presynaptic form plasticity (LTD) that probably fulfills a role in synaptic refinement. It is present until the fourth postnatal week in mice, disappearing thereafter. The mechanisms that are responsible for this loss of plasticity are not clear. We describe here these mechanisms and those involved in the switch from LTD to LTP observed as the brain matures. Defining these events responsible for closing (and opening) plasticity windows may be important for brain repair, sensorial recovery, the treatment of neurodevelopmental disorders, and for educational policy.
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Affiliation(s)
- Irene Martínez-Gallego
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, ES-41013 Seville, Spain
| | - Mikel Pérez-Rodríguez
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, ES-41013 Seville, Spain
| | - Heriberto Coatl-Cuaya
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, ES-41013 Seville, Spain
| | - Gonzalo Flores
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla CP 72570, México
| | - Antonio Rodríguez-Moreno
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, ES-41013 Seville, Spain
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3
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Wall MJ, Puddefoot K, Yin W, Bingham C, Seifi M, Swinny JD, Ngomba RT. Adenosine is released during thalamic oscillations to provide negative feedback control. Neuropharmacology 2022; 216:109172. [PMID: 35780977 DOI: 10.1016/j.neuropharm.2022.109172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 10/17/2022]
Abstract
Physiological oscillations in the cortico-thalamo-cortical loop occur during processes such as sleep, but these can become dysfunctional in pathological conditions such as absence epilepsy. The purine neuromodulator adenosine can act as an endogenous anticonvulsant: it is released into the extracellular space during convulsive seizures to activate A1 receptors suppressing on-going activity and delaying the occurrence of the next seizure. However, the role of adenosine in thalamic physiological and epileptiform oscillations is less clear. Here we have combined immunohistochemistry, electrophysiology, and fixed potential amperometry (FPA) biosensor measurements to characterise the release and actions of adenosine in thalamic oscillations measured in rodent slices. In the thalamus, A1 receptors are highly expressed particularly in the ventral basal (VB) thalamus and reticular thalamic nucleus (nRT) supporting a role for adenosine signalling in controlling oscillations. In agreement with previous studies, both adenosine and adenosine A1 receptor agonists inhibited thalamic oscillations in control (spindle-like) and in epileptic conditions. Here we have shown for the first time that both control and epileptiform oscillations are enhanced (i.e., increased number of oscillatory cycles) by blocking A1 receptors consistent with adenosine release occurring during oscillations. Although increases in extracellular adenosine could not be directly detected during control oscillations, clear increases in adenosine concentration could be detected with a biosensor during epileptiform oscillation activity. Thus, adenosine is released during thalamic oscillations and acts via A1 receptors to feedback and reduce thalamic oscillatory activity.
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Affiliation(s)
- Mark J Wall
- School of Life Sciences, University of Warwick, Coventry, UK.
| | - Katie Puddefoot
- School of Life Sciences, University of Warwick, Coventry, UK
| | | | | | - Mohsen Seifi
- Leicester School of Pharmacy, De Montfort University, Leicester, LE1 9BH, UK
| | - Jerome D Swinny
- School of Pharmacy & Biomedical Sciences, University of Portsmouth, St Michael's Building, White Swan Road, Portsmouth, PO12DT, UK
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4
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Gomez-Castro F, Zappettini S, Pressey JC, Silva CG, Russeau M, Gervasi N, Figueiredo M, Montmasson C, Renner M, Canas PM, Gonçalves FQ, Alçada-Morais S, Szabó E, Rodrigues RJ, Agostinho P, Tomé AR, Caillol G, Thoumine O, Nicol X, Leterrier C, Lujan R, Tyagarajan SK, Cunha RA, Esclapez M, Bernard C, Lévi S. Convergence of adenosine and GABA signaling for synapse stabilization during development. Science 2021; 374:eabk2055. [PMID: 34735259 DOI: 10.1126/science.abk2055] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Ferran Gomez-Castro
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France
| | - Stefania Zappettini
- Aix Marseille Université, INSERM, INS, Institut de Neurosciences des Systèmes, Marseille, France
| | - Jessica C Pressey
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France.,Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Carla G Silva
- Aix Marseille Université, INSERM, INS, Institut de Neurosciences des Systèmes, Marseille, France.,CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Marion Russeau
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France
| | - Nicolas Gervasi
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France.,Center for Interdisciplinary Research in Biology, College de France, INSERM U1050, CNRS UMR7241, Labex Memolife, Paris, France
| | - Marta Figueiredo
- Institute of Pharmacology and Toxicology, University of Zürich, 8057 Zürich, Switzerland
| | - Claire Montmasson
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France
| | - Marianne Renner
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France
| | - Paula M Canas
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Francisco Q Gonçalves
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Sofia Alçada-Morais
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Eszter Szabó
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Ricardo J Rodrigues
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Paula Agostinho
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Angelo R Tomé
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
| | - Ghislaine Caillol
- Aix Marseille Université, CNRS, INP UMR7051, NeuroCyto, Marseille, France
| | - Olivier Thoumine
- Université Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, Bordeaux, France
| | - Xavier Nicol
- Sorbonne Université, Inserm, CNRS, Institut de la Vision, Paris, France
| | | | - Rafael Lujan
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, 02008 Albacete, Spain
| | - Shiva K Tyagarajan
- Institute of Pharmacology and Toxicology, University of Zürich, 8057 Zürich, Switzerland
| | - Rodrigo A Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Monique Esclapez
- Aix Marseille Université, INSERM, INS, Institut de Neurosciences des Systèmes, Marseille, France
| | - Christophe Bernard
- Aix Marseille Université, INSERM, INS, Institut de Neurosciences des Systèmes, Marseille, France
| | - Sabine Lévi
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France
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5
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How Are Adenosine and Adenosine A 2A Receptors Involved in the Pathophysiology of Amyotrophic Lateral Sclerosis? Biomedicines 2021; 9:biomedicines9081027. [PMID: 34440231 PMCID: PMC8392384 DOI: 10.3390/biomedicines9081027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 08/03/2021] [Accepted: 08/12/2021] [Indexed: 12/19/2022] Open
Abstract
Adenosine is extensively distributed in the central and peripheral nervous systems, where it plays a key role as a neuromodulator. It has long been implicated in the pathogenesis of progressive neurogenerative disorders such as Parkinson’s disease, and there is now growing interest in its role in amyotrophic lateral sclerosis (ALS). The motor neurons affected in ALS are responsive to adenosine receptor function, and there is accumulating evidence for beneficial effects of adenosine A2A receptor antagonism. In this article, we focus on recent evidence from ALS clinical pathology and animal models that support dynamism of the adenosinergic system (including changes in adenosine levels and receptor changes) in ALS. We review the possible mechanisms of chronic neurodegeneration via the adenosinergic system, potential biomarkers and the acute symptomatic pharmacology, including respiratory motor neuron control, of A2A receptor antagonism to explore the potential of the A2A receptor as target for ALS therapy.
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6
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Beamer E, Kuchukulla M, Boison D, Engel T. ATP and adenosine-Two players in the control of seizures and epilepsy development. Prog Neurobiol 2021; 204:102105. [PMID: 34144123 DOI: 10.1016/j.pneurobio.2021.102105] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 04/07/2021] [Accepted: 06/09/2021] [Indexed: 02/08/2023]
Abstract
Despite continuous advances in understanding the underlying pathogenesis of hyperexcitable networks and lowered seizure thresholds, the treatment of epilepsy remains a clinical challenge. Over one third of patients remain resistant to current pharmacological interventions. Moreover, even when effective in suppressing seizures, current medications are merely symptomatic without significantly altering the course of the disease. Much effort is therefore invested in identifying new treatments with novel mechanisms of action, effective in drug-refractory epilepsy patients, and with the potential to modify disease progression. Compelling evidence has demonstrated that the purines, ATP and adenosine, are key mediators of the epileptogenic process. Extracellular ATP concentrations increase dramatically under pathological conditions, where it functions as a ligand at a host of purinergic receptors. ATP, however, also forms a substrate pool for the production of adenosine, via the action of an array of extracellular ATP degrading enzymes. ATP and adenosine have assumed largely opposite roles in coupling neuronal excitability to energy homeostasis in the brain. This review integrates and critically discusses novel findings regarding how ATP and adenosine control seizures and the development of epilepsy. This includes purine receptor P1 and P2-dependent mechanisms, release and reuptake mechanisms, extracellular and intracellular purine metabolism, and emerging receptor-independent effects of purines. Finally, possible purine-based therapeutic strategies for seizure suppression and disease modification are discussed.
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Affiliation(s)
- Edward Beamer
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin D02 YN77, Ireland; Centre for Bioscience, Manchester Metropolitan University, John Dalton Building, All Saints Campus, Manchester M15 6BH, UK
| | - Manvitha Kuchukulla
- Department of Neurosurgery, Robert Wood Johnson & New Jersey Medical Schools, Rutgers University, Piscataway, NJ 08854, USA
| | - Detlev Boison
- Department of Neurosurgery, Robert Wood Johnson & New Jersey Medical Schools, Rutgers University, Piscataway, NJ 08854, USA.
| | - Tobias Engel
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin D02 YN77, Ireland; FutureNeuro, Science Foundation Ireland Research Centre for Chronic and Rare Neurological Diseases, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin D02 YN77, Ireland.
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7
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Dale N. Biological insights from the direct measurement of purine release. Biochem Pharmacol 2021; 187:114416. [PMID: 33444569 DOI: 10.1016/j.bcp.2021.114416] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/05/2021] [Accepted: 01/07/2021] [Indexed: 12/23/2022]
Abstract
Although purinergic signalling has been a well-established and accepted mechanism of chemical communication for many years, it remains important to measure the extracellular concentration of ATP and adenosine in real time. In this review I summarize the reasons why such measurements are still needed, how they provide additional mechanistic insight and give an overview of the techniques currently available to make spatially localised measurements of ATP and adenosine in real time. To illustrate the impact of direct real-time measurements, I explore CO2 and nutrient sensing in the medulla oblongata and hypothalamus. In both of these examples, the sensing involves hemichannel mediated ATP release from glial cells. For CO2 the hemichannels involved, connexin26, are directly CO2-sensitive. This mechanism contributes to the chemosensory control of breathing. In the hypothamalus, specialised glial cells, tanycytes, directly contact the cerebrospinal fluid in the 3rd ventricle and sense nutrients via sweet and umami taste receptors. Nutrient sensing by tanycytes is likely to contribute to the control of body weight as their selective stimulation alters food intake. To illustrate the importance of direct adenosine measurements, I consider the complex and multiple mechanisms of activity-dependent adenosine release in different brain regions. This activity dependent release of adenosine is likely to mediate important feedback regulation and may also be involved in controlling the sleep-wake state. I finish by briefly considering the potential of whole blood purine measurements in clinical practice.
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Affiliation(s)
- Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK.
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8
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Lopes CR, Lourenço VS, Tomé ÂR, Cunha RA, Canas PM. Use of knockout mice to explore CNS effects of adenosine. Biochem Pharmacol 2020; 187:114367. [PMID: 33333075 DOI: 10.1016/j.bcp.2020.114367] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 12/09/2020] [Accepted: 12/09/2020] [Indexed: 12/11/2022]
Abstract
The initial exploration using pharmacological tools of the role of adenosine receptors in the brain, concluded that adenosine released as such acted on A1R to inhibit excitability and glutamate release from principal neurons throughout the brain and that adenosine A2A receptors (A2AR) were striatal-'specific' receptors controlling dopamine D2R. This indicted A1R as potential controllers of neurodegeneration and A2AR of psychiatric conditions. Global knockout of these two receptors questioned the key role of A1R and instead identified extra-striatal A2AR as robust controllers of neurodegeneration. Furthermore, transgenic lines with altered metabolic sources of adenosine revealed a coupling of ATP-derived adenosine to activate A2AR and a role of A1R as a hurdle to initiate neurodegeneration. Additionally, cell-selective knockout of A2AR unveiled the different roles of A2AR in different cell types (neurons/astrocytes) in different portions of the striatal circuits (dorsal versus lateral) and in different brain areas (hippocampus/striatum). Finally, a new transgenic mouse line with deletion of all adenosine receptors seems to indicate a major allostatic rather than homeostatic role of adenosine and may allow isolating P2R-mediated responses to unravel their role in the brain, a goal close to heart of Geoffrey Burnstock, to whom we affectionately dedicate this review.
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Affiliation(s)
- Cátia R Lopes
- CNC- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
| | - Vanessa S Lourenço
- CNC- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
| | - Ângelo R Tomé
- CNC- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal; Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, 3000-456 Coimbra, Portugal
| | - Rodrigo A Cunha
- CNC- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal; Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal.
| | - Paula M Canas
- CNC- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
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9
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Astrocyte-mediated switch in spike timing-dependent plasticity during hippocampal development. Nat Commun 2020; 11:4388. [PMID: 32873805 PMCID: PMC7463247 DOI: 10.1038/s41467-020-18024-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 07/31/2020] [Indexed: 01/31/2023] Open
Abstract
Presynaptic spike timing-dependent long-term depression (t-LTD) at hippocampal CA3-CA1 synapses is evident until the 3rd postnatal week in mice, disappearing during the 4th week. At more mature stages, we found that the protocol that induced t-LTD induced t-LTP. We characterized this form of t-LTP and the mechanisms involved in its induction, as well as that driving this switch from t-LTD to t-LTP. We found that this t-LTP is expressed presynaptically at CA3-CA1 synapses, as witnessed by coefficient of variation, number of failures, paired-pulse ratio and miniature responses analysis. Additionally, this form of presynaptic t-LTP does not require NMDARs but the activation of mGluRs and the entry of Ca2+ into the postsynaptic neuron through L-type voltage-dependent Ca2+ channels and the release of Ca2+ from intracellular stores. Nitric oxide is also required as a messenger from the postsynaptic neuron. Crucially, the release of adenosine and glutamate by astrocytes is required for t-LTP induction and for the switch from t-LTD to t-LTP. Thus, we have discovered a developmental switch of synaptic transmission from t-LTD to t-LTP at hippocampal CA3-CA1 synapses in which astrocytes play a central role and revealed a form of presynaptic LTP and the rules for its induction. Presynaptic spike timing-dependent long-term depression at hippocampal CA3-CA1 synapses is evident until the third postnatal week in mice. The authors show that maturation beyond four weeks is associated with a switch to long-term potentiation in which astrocytes play a central role.
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10
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Pérez-Rodríguez M, Arroyo-García LE, Prius-Mengual J, Andrade-Talavera Y, Armengol JA, Pérez-Villegas EM, Duque-Feria P, Flores G, Rodríguez-Moreno A. Adenosine Receptor-Mediated Developmental Loss of Spike Timing-Dependent Depression in the Hippocampus. Cereb Cortex 2020; 29:3266-3281. [PMID: 30169759 PMCID: PMC6644873 DOI: 10.1093/cercor/bhy194] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 06/18/2018] [Accepted: 07/20/2018] [Indexed: 02/04/2023] Open
Abstract
Critical periods of synaptic plasticity facilitate the reordering and refining of neural connections during development, allowing the definitive synaptic circuits responsible for correct adult physiology to be established. Presynaptic spike timing-dependent long-term depression (t-LTD) exists in the hippocampus, which depends on the activation of NMDARs and that probably fulfills a role in synaptic refinement. This t-LTD is present until the third postnatal week in mice, disappearing in the fourth week of postnatal development. We were interested in the mechanisms underlying this maturation related loss of t-LTD and we found that at CA3–CA1 synapses, presynaptic NMDA receptors (pre-NMDARs) are tonically active between P13 and P21, mediating an increase in glutamate release during this critical period of plasticity. Conversely, at the end of this critical period (P22–P30) and coinciding with the loss of t-LTD, these pre-NMDARs are no longer tonically active. Using immunogold electron microscopy, we demonstrated the existence of pre-NMDARs at Schaffer collateral synaptic boutons, where a decrease in the number of pre-NMDARs during development coincides with the loss of both tonic pre-NMDAR activation and t-LTD. Interestingly, this t-LTD can be completely recovered by antagonizing adenosine type 1 receptors (A1R), which also recovers the tonic activation of pre-NMDARs at P22–P30. By contrast, the induction of t-LTD was prevented at P13–P21 by an agonist of A1R, as was tonic pre-NMDAR activation. Furthermore, we found that the adenosine that mediated the loss of t-LTD during the fourth week of development is supplied by astrocytes. These results provide direct evidence for the mechanism that closes the window of plasticity associated with t-LTD, revealing novel events probably involved in synaptic remodeling during development.
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Affiliation(s)
- Mikel Pérez-Rodríguez
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Luis E Arroyo-García
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain.,Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, 72570 Puebla, Mexico
| | - José Prius-Mengual
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Yuniesky Andrade-Talavera
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - José A Armengol
- Human Anatomy and Embryology Unit, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Eva M Pérez-Villegas
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Paloma Duque-Feria
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Gonzalo Flores
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, 72570 Puebla, Mexico
| | - Antonio Rodríguez-Moreno
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
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11
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Wang Y, Copeland J, Shin M, Chang Y, Venton BJ. CD73 or CD39 Deletion Reveals Different Mechanisms of Formation for Spontaneous and Mechanically Stimulated Adenosine and Sex Specific Compensations in ATP Degradation. ACS Chem Neurosci 2020; 11:919-928. [PMID: 32083837 DOI: 10.1021/acschemneuro.9b00620] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Adenosine is important for local neuromodulation, and rapid adenosine signaling can occur spontaneously or after mechanical stimulation, but little is known about how adenosine is formed in the extracellular space for those stimulations. Here, we studied mechanically stimulated and spontaneous adenosine to determine if rapid adenosine is formed by extracellular breakdown of adenosine triphosphate (ATP) using mice globally deficient in extracellular breakdown enzymes, either CD39 (nucleoside triphosphate diphosphohydrolase 1, NTPDase1) or CD73 (ecto-5'-nucleotidase). CD39 knockout (KO) mice have a lower frequency of spontaneous adenosine events than wild-type (WT, C57BL/6). Surprisingly, CD73KO mice demonstrate sex differences in spontaneous adenosine; males maintain similar event frequencies as WT, but females have significantly fewer events and lower concentrations. Examining the mRNA expression of other enzymes that metabolize ATP revealed tissue nonspecific alkaline phosphatase (TNAP) was upregulated in male CD73KO mice, but not secreted prostatic acid phosphatase (PAP) or transmembrane PAP. Thus, TNAP upregulation compensates for CD73 loss in males but not in females. These sex differences highlight that spontaneous adenosine is formed by metabolism of extracellular ATP by many enzymes. For mechanically stimulated adenosine, CD39KO or CD73KO did not change stimulation frequency, concentration, or t1/2. Thus, the mechanism of formation for mechanically stimulated adenosine is likely direct release of adenosine, different than spontaneous adenosine. Understanding these different mechanisms of rapid adenosine formation will help to develop pharmacological treatments that differentially target modes of rapid adenosine signaling, and all treatments should be studied in both sexes, given possible differences in extracellular ATP degradation.
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Affiliation(s)
- Ying Wang
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Jeffrey Copeland
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
- Department of Biology, Eastern Mennonite University, Harrisonburg, Virginia 22802, United States
| | - Mimi Shin
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Yuanyu Chang
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - B. Jill Venton
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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12
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Hill E, Hickman C, Diez R, Wall M. Role of A 1 receptor-activated GIRK channels in the suppression of hippocampal seizure activity. Neuropharmacology 2019; 164:107904. [PMID: 31812775 DOI: 10.1016/j.neuropharm.2019.107904] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 11/12/2019] [Accepted: 12/03/2019] [Indexed: 12/19/2022]
Abstract
The neuromodulator adenosine is released during seizure activity to provide negative feedback suppression of ongoing activity and to delay the occurrence of the next burst of activity. Adenosine acts via multiple G-protein-coupled receptors including the A1 receptor (A1R) which inhibits neurotransmitter release and hyperpolarises neuronal membrane potential. The hyperpolarisation is produced, at least in part, by the activation of G-protein-activated inwardly rectifying K+ (GIRK) channels. We have used tertiapin-Q (TQ), a potent and selective inhibitor of GIRK channels, to assess the role of GIRK channels in controlling seizure activity in areas CA1 and CA2 of mouse hippocampal slices. TQ (100-300 nM) blocked ~50% of the adenosine-mediated membrane potential hyperpolarisation of hippocampal CA1 and CA2 neurons. TQ (100 nM) had no significant effect on synaptic transmission in area CA1 of the hippocampus but enhanced transmission in CA2, an effect prevented by blocking A1Rs. TQ (100 nM) increased the frequency of spontaneous activity (induced by removing Mg2+ and increasing K+) and blunted the effects of exogenous adenosine on the suppression of activity. TQ had a significantly greater effect on electrically-stimulated seizure activity induced in CA2 versus that in CA1, producing a greater increase in both the duration and amplitude of the stimulated bursts. This is consistent with the greater A1R density and A1R activation tone in CA2. Thus GIRK channels play a role in the supressing effects of adenosine on seizure activity.
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Affiliation(s)
- Emily Hill
- School of Life Sciences, University of Warwick, Gibbet Hill, Coventry, CV4 7AL, UK
| | - Charlotte Hickman
- School of Life Sciences, University of Warwick, Gibbet Hill, Coventry, CV4 7AL, UK
| | - Rebecca Diez
- School of Life Sciences, University of Warwick, Gibbet Hill, Coventry, CV4 7AL, UK
| | - Mark Wall
- School of Life Sciences, University of Warwick, Gibbet Hill, Coventry, CV4 7AL, UK.
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13
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Mild hypothermia protects synaptic transmission from experimental ischemia through reduction in the function of nucleoside transporters in the mouse hippocampus. Neuropharmacology 2019; 163:107853. [PMID: 31734385 DOI: 10.1016/j.neuropharm.2019.107853] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 10/28/2019] [Accepted: 11/12/2019] [Indexed: 12/24/2022]
Abstract
Ischemia, a severe metabolic stress, increases adenosine levels and causes the suppression of synaptic transmission through adenosine A1 receptors. Although temperature also regulates extracellular adenosine levels, the effect of temperature on ischemia-induced activation of adenosine receptors is not yet fully understood. Here we examined the role of adenosine A1 receptors in mild hypothermia-mediated neuroprotection during the acute phase of ischemia. Severe ischemia-induced neurosynaptic impairment was reproduced by oxygen-glucose deprivation at normothermia (36 °C) and assessed with extracellular recordings or whole-cell patch clamp recordings in acute hippocampal slices in mice. Mild hypothermia (32 °C) induced the protection of synaptic transmission by activating adenosine A1 receptors. Stricter hypothermia (28 °C) caused additional neuroprotective effects by extending the onset time to anoxic depolarization; however, this effect was not associated with adenosine A1 receptors. The response of exogenous adenosine-induced inhibition of hippocampal synaptic transmission was increased by lowering the temperature to 32 °C or 28 °C. Hypothermia also reduced the function of dipryidamole-sensitive nucleoside transporters. These findings suggest that an increased response of adenosine A1 receptors, caused by a reduction in the function of nucleoside transporters, is one mechanism by which therapeutic hypothermia (usually used within the mild range) mediates neurosynaptic protection in the acute phase of stroke.
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14
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Beamer E, Conte G, Engel T. ATP release during seizures - A critical evaluation of the evidence. Brain Res Bull 2019; 151:65-73. [PMID: 30660718 DOI: 10.1016/j.brainresbull.2018.12.021] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 12/06/2018] [Accepted: 12/20/2018] [Indexed: 01/17/2023]
Abstract
That adenosine 5' triphosphate (ATP) functions as an extracellular signaling molecule has been established since the 1970s. Ubiquitous throughout the body as the principal molecular store of intracellular energy, ATP has a short extracellular half-life and is difficult to measure directly. Extracellular ATP concentrations are dependent both on the rate of cellular release and of enzymatic degradation. Some findings from in vitro studies suggest that extracellular ATP concentrations increase during high levels of neuronal activity and seizure-like events in hippocampal slices. Pharmacological studies suggest that antagonism of ATP-sensitive purinergic receptors can suppress the severity of seizures and block epileptogenesis. Directly measuring extracellular ATP concentrations in the brain, however, has a number of specific challenges, notably, the rapid hydrolysis of ATP and huge gradient between intracellular and extracellular compartments. Two studies using microdialysis found no change in extracellular ATP in the hippocampus of rats during experimentally-induced status epilepticus. One of which demonstrated that ATP increased measurably, only in the presence of ectoATPase inhibitors, with the other study demonstrating increases only during later spontaneous seizures. Current evidence is mixed and seems highly dependent on the model used and method of detection. More sensitive methods of detection with higher spatial resolution, which induce less tissue disruption will be necessary to provide evidence for or against the hypothesis of seizure-induced elevations in extracellular ATP. Here we describe the current hypothesis for ATP release during seizures and its role in epileptogenesis, describe the technical challenges involved and critically examine the current evidence.
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Affiliation(s)
- Edward Beamer
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, D02YN77, Dublin, Ireland.
| | - Giorgia Conte
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, D02YN77, Dublin, Ireland
| | - Tobias Engel
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, D02YN77, Dublin, Ireland
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15
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Hackett TA. Adenosine A 1 Receptor mRNA Expression by Neurons and Glia in the Auditory Forebrain. Anat Rec (Hoboken) 2018; 301:1882-1905. [PMID: 30315630 PMCID: PMC6282551 DOI: 10.1002/ar.23907] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 12/05/2017] [Accepted: 01/10/2018] [Indexed: 12/30/2022]
Abstract
In the brain, purines such as ATP and adenosine can function as neurotransmitters and co‐transmitters, or serve as signals in neuron–glial interactions. In thalamocortical (TC) projections to sensory cortex, adenosine functions as a negative regulator of glutamate release via activation of the presynaptic adenosine A1 receptor (A1R). In the auditory forebrain, restriction of A1R‐adenosine signaling in medial geniculate (MG) neurons is sufficient to extend LTP, LTD, and tonotopic map plasticity in adult mice for months beyond the critical period. Interfering with adenosine signaling in primary auditory cortex (A1) does not contribute to these forms of plasticity, suggesting regional differences in the roles of A1R‐mediated adenosine signaling in the forebrain. To advance understanding of the circuitry, in situ hybridization was used to localize neuronal and glial cell types in the auditory forebrain that express A1R transcripts (Adora1), based on co‐expression with cell‐specific markers for neuronal and glial subtypes. In A1, Adora1 transcripts were concentrated in L3/4 and L6 of glutamatergic neurons. Subpopulations of GABAergic neurons, astrocytes, oligodendrocytes, and microglia expressed lower levels of Adora1. In MG, Adora1 was expressed by glutamatergic neurons in all divisions, and subpopulations of all glial classes. The collective findings imply that A1R‐mediated signaling broadly extends to all subdivisions of auditory cortex and MG. Selective expression by neuronal and glial subpopulations suggests that experimental manipulations of A1R‐adenosine signaling could impact several cell types, depending on their location. Strategies to target Adora1 in specific cell types can be developed from the data generated here. Anat Rec, 301:1882–1905, 2018. © 2018 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.
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Affiliation(s)
- Troy A Hackett
- Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA.,Department of Psychology, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee, USA
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16
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Cell-subtype-specific changes in adenosine pathways in schizophrenia. Neuropsychopharmacology 2018; 43:1667-1674. [PMID: 29483661 PMCID: PMC6006250 DOI: 10.1038/s41386-018-0028-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 02/01/2018] [Accepted: 02/05/2018] [Indexed: 12/22/2022]
Abstract
Prior work in animal models implicates abnormalities of adenosine metabolism in astrocytes as a possible pathophysiological mechanism underlying the symptoms of schizophrenia. In the present study, we sought to reverse-translate these findings back to the human brain in schizophrenia, focusing on the following questions: (1) Which components of the adenosine system are dysregulated in schizophrenia, and (2) are these changes limited to astrocytes? To address these questions, we captured enriched populations of DLPFC pyramidal neurons and astrocytes from schizophrenia and control subjects using laser capture microdissection and assessed expression of adenosine system components using qPCR. Interestingly, we found changes in enriched populations of astrocytes and neurons spanning metabolic and catabolic pathways. Ectonucleoside triphosphate diphosphohydrolase-1 (ENTPD1) and ENTPD2 mRNA levels were significantly decreased (p < 0.05, n = 16 per group) in enriched populations of astrocytes; in pyramidal neurons equilibrative nucleoside transporter 1 (ENT1) and adenosine A1 receptor mRNA levels were significantly decreased, with an increase in adenosine deaminase (ADA) (p < 0.05, n = 16 per group). Rodent studies suggest that some of our findings (A1R and ENTPD2) may be due to treatment with antipsychotics. Our findings suggest changes in expression of genes involved in regulating metabolism of ATP in enriched populations of astrocytes, leading to lower availability of substrates needed to generate adenosine. In pyramidal neurons, changes in ENT1 and ADA mRNA may suggest increased catabolism of adenosine. These results offer new insights into the cell-subtype-specific pathophysiology of the adenosine system in this illness.
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17
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Lee ST, Venton BJ. Regional Variations of Spontaneous, Transient Adenosine Release in Brain Slices. ACS Chem Neurosci 2018; 9:505-513. [PMID: 29135225 DOI: 10.1021/acschemneuro.7b00280] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Transient adenosine signaling has been recently discovered in vivo, where the concentration is on average 180 nM and the duration only 3-4 s. In order to rapidly screen different brain regions and mechanisms of formation and regulation, here we develop a rat brain slice model to study adenosine transients. The frequency, concentration, and duration of transient adenosine events were compared in the prefrontal cortex (PFC), hippocampus (CA1), and thalamus. Adenosine transients in the PFC were similar to those in vivo, with a concentration of 160 ± 10 nM, and occurred frequently, averaging one every 50 ± 5 s. In the thalamus, transients were infrequent, occurring every 280 ± 40 s, and lower concentration (110 ± 10 nM), but lasted twice as long as in the PFC. In the hippocampus, adenosine transients were less frequent than those in the PFC, occurring every 79 ± 7 s, but the average concentration (240 ± 20 nM) was significantly higher. Adenosine transients are largely maintained after applying 200 nM tetrodotoxin, implying they are not activity dependent. The response to adenosine A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) differed by region; DPCPX had no significant effects in the PFC, but increased the average transient concentration in the thalamus and both the transient frequency and concentration in the hippocampus. Thus, the amount of adenosine available to activate receptors, and the ability to upregulate adenosine signaling with DPCPX, varies by brain region. This is an important consideration for designing treatments that modulate adenosine in order to cause neuroprotective effects.
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Affiliation(s)
- Scott T. Lee
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22901, United States
| | - B. Jill Venton
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22901, United States
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18
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Interplay between global and pathway-specific synaptic plasticity in CA1 pyramidal cells. Sci Rep 2017; 7:17040. [PMID: 29213058 PMCID: PMC5719010 DOI: 10.1038/s41598-017-17161-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 11/22/2017] [Indexed: 12/22/2022] Open
Abstract
Mechanisms underlying information storage have been depicted for global cell-wide and pathway-specific synaptic plasticity. Yet, little is known how these forms of plasticity interact to enhance synaptic competition and network stability. We examined synaptic interactions between apical and basal dendrites of CA1 pyramidal neurons in mouse hippocampal slices. Bursts (50 Hz) of three action potentials (AP-bursts) paired with preceding presynaptic stimulation in stratum radiatum specifically led to LTP of the paired pathway in adult mice (P75). At adolescence (P28), an increase in burst frequency (>50 Hz) was required to gain timing-dependent LTP. Surprisingly, paired radiatum and unpaired oriens pathway potentiated, unless the pre-post delay was shortened from 10 to 5 ms, which selectively potentiated paired radiatum pathway, since unpaired oriens pathway decreased back to baseline. Conversely, the exact same 5 ms pairing in stratum oriens potentiated both pathways, as did AP-bursts alone, which potentiated synaptic efficacy as well as current-evoked postsynaptic spiking. L-type voltage-gated Ca2+ channels were involved in mediating synaptic potentiation in oriens, whereas NMDA and adenosine receptors counteracted unpaired stratum oriens potentiation following pairing in stratum radiatum. This asymmetric plasticity uncovers important insights into alterations of synaptic efficacy and intrinsic neuronal excitability for pathways that convey hippocampal and extra-hippocampal information.
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19
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Diez R, Richardson MJE, Wall MJ. Reducing Extracellular Ca 2+ Induces Adenosine Release via Equilibrative Nucleoside Transporters to Provide Negative Feedback Control of Activity in the Hippocampus. Front Neural Circuits 2017; 11:75. [PMID: 29066955 PMCID: PMC5641293 DOI: 10.3389/fncir.2017.00075] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 09/27/2017] [Indexed: 12/04/2022] Open
Abstract
Neural circuit activity increases the release of the purine neuromodulator adenosine into the extracellular space leading to A1 receptor activation and negative feedback via membrane hyperpolarization and inhibition of transmitter release. Adenosine can be released by a number of different mechanisms that include Ca2+ dependent processes such as the exocytosis of ATP. During sustained pathological network activity, ischemia and hypoxia the extracellular concentration of calcium ions (Ca2+) markedly falls, inhibiting exocytosis and potentially reducing adenosine release. However it has been observed that reducing extracellular Ca2+ can induce paradoxical neural activity and can also increase adenosine release. Here we have investigated adenosine signaling and release mechanisms that occur when extracellular Ca2+ is removed. Using electrophysiology and microelectrode biosensor measurements we have found that adenosine is directly released into the extracellular space by the removal of extracellular Ca2+ and controls the induced neural activity via A1 receptor-mediated membrane potential hyperpolarization. Following Ca2+ removal, adenosine is released via equilibrative nucleoside transporters (ENTs), which when blocked leads to hyper-excitation. We propose that sustained action potential firing following Ca2+ removal leads to hydrolysis of ATP and a build-up of intracellular adenosine which then effluxes into the extracellular space via ENTs.
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Affiliation(s)
- Rebecca Diez
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | | | - Mark J Wall
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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20
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Acton D, Miles GB. Gliotransmission and adenosinergic modulation: insights from mammalian spinal motor networks. J Neurophysiol 2017; 118:3311-3327. [PMID: 28954893 DOI: 10.1152/jn.00230.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Astrocytes are proposed to converse with neurons at tripartite synapses, detecting neurotransmitter release and responding with release of gliotransmitters, which in turn modulate synaptic strength and neuronal excitability. However, a paucity of evidence from behavioral studies calls into question the importance of gliotransmission for the operation of the nervous system in healthy animals. Central pattern generator (CPG) networks in the spinal cord and brain stem coordinate the activation of muscles during stereotyped activities such as locomotion, inspiration, and mastication and may therefore provide tractable models in which to assess the contribution of gliotransmission to behaviorally relevant neural activity. We review evidence for gliotransmission within spinal locomotor networks, including studies indicating that adenosine derived from astrocytes regulates the speed of locomotor activity via metamodulation of dopamine signaling.
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Affiliation(s)
- David Acton
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife , United Kingdom
| | - Gareth B Miles
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife , United Kingdom
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21
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Newton AJH, Wall MJ, Richardson MJE. Modeling microelectrode biosensors: free-flow calibration can substantially underestimate tissue concentrations. J Neurophysiol 2016; 117:937-949. [PMID: 27927788 PMCID: PMC5338626 DOI: 10.1152/jn.00788.2016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 12/05/2016] [Indexed: 12/11/2022] Open
Abstract
Microelectrode biosensors are typically calibrated in a free-flow environment where the concentrations at the biosensor surface are constant. However, when in tissue, the analyte reaches the biosensor via diffusion and so analyte breakdown by the biosensor results in a concentration gradient and consequently a lower concentration around the biosensor. This effect means that naive free-flow calibration will underestimate tissue concentration. We develop mathematical models to better quantify the discrepancy between the calibration and tissue environment and experimentally verify our key predictions. Microelectrode amperometric biosensors are widely used to measure concentrations of analytes in solution and tissue including acetylcholine, adenosine, glucose, and glutamate. A great deal of experimental and modeling effort has been directed at quantifying the response of the biosensors themselves; however, the influence that the macroscopic tissue environment has on biosensor response has not been subjected to the same level of scrutiny. Here we identify an important issue in the way microelectrode biosensors are calibrated that is likely to have led to underestimations of analyte tissue concentrations. Concentration in tissue is typically determined by comparing the biosensor signal to that measured in free-flow calibration conditions. In a free-flow environment the concentration of the analyte at the outer surface of the biosensor can be considered constant. However, in tissue the analyte reaches the biosensor surface by diffusion through the extracellular space. Because the enzymes in the biosensor break down the analyte, a density gradient is set up resulting in a significantly lower concentration of analyte near the biosensor surface. This effect is compounded by the diminished volume fraction (porosity) and reduction in the diffusion coefficient due to obstructions (tortuosity) in tissue. We demonstrate this effect through modeling and experimentally verify our predictions in diffusive environments. NEW & NOTEWORTHY Microelectrode biosensors are typically calibrated in a free-flow environment where the concentrations at the biosensor surface are constant. However, when in tissue, the analyte reaches the biosensor via diffusion and so analyte breakdown by the biosensor results in a concentration gradient and consequently a lower concentration around the biosensor. This effect means that naive free-flow calibration will underestimate tissue concentration. We develop mathematical models to better quantify the discrepancy between the calibration and tissue environment and experimentally verify our key predictions.
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Affiliation(s)
- Adam J H Newton
- Warwick Mathematics Institute, University of Warwick, Coventry, United Kingdom; and
| | - Mark J Wall
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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22
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Yamashiro K, Fujii Y, Maekawa S, Morita M. Multiple pathways for elevating extracellular adenosine in the rat hippocampal CA1 region characterized by adenosine sensor cells. J Neurochem 2016; 140:24-36. [PMID: 27896810 DOI: 10.1111/jnc.13888] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 10/03/2016] [Accepted: 10/19/2016] [Indexed: 12/17/2022]
Abstract
Extracellular adenosine in the brain, which modulates various physiological and pathological processes, fluctuates in a complicated manner that reflects the circadian cycle, neuronal activity, metabolism, and disease states. The dynamics of extracellular adenosine in the brain are not fully understood, largely because of the lack of simple and reliable methods of measuring time-dependent changes in tissue adenosine distribution. This study describes the development of a biosensor, designated an adenosine sensor cell, expressing adenosine A1 receptor, and a genetically modified G protein. This biosensor was used to characterize extracellular adenosine elevation in brain tissue by measuring intracellular calcium elevation in response to adenosine. Placement of adenosine sensor cells below hippocampal slices successfully detected adenosine releases from these slices in response to neuronal activity and astrocyte swelling by conventional calcium imaging. Pharmacological analyses indicated that high-frequency electrical stimulation-induced post-synaptic adenosine release in a manner dependent on L-type calcium channels and calcium-induced calcium release. Adenosine release following treatments that cause astrocyte swelling is independent of calcium channels, but dependent on aquaporin 4, an astrocyte-specific water channel subtype. The ability of ectonucleotidase inhibitors to inhibit adenosine release following astrocyte swelling, but not electrical stimulation, suggests that the former reflects astrocytic ATP release and subsequent enzymatic breakdown, whereas the latter reflects direct adenosine release from neurons. These results suggest that distinct mechanisms are responsible for extracellular adenosine elevations by neurons and astrocytes, allowing exquisite regulation of extracellular adenosine in the brain.
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Affiliation(s)
- Kunihiko Yamashiro
- Department of Biology, Kobe University Graduate School of Science, Kobe, Japan
| | - Yuki Fujii
- Department of Biology, Kobe University Graduate School of Science, Kobe, Japan
| | - Shohei Maekawa
- Department of Biology, Kobe University Graduate School of Science, Kobe, Japan
| | - Mitsuhiro Morita
- Department of Biology, Kobe University Graduate School of Science, Kobe, Japan
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23
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Cunha RA. How does adenosine control neuronal dysfunction and neurodegeneration? J Neurochem 2016; 139:1019-1055. [PMID: 27365148 DOI: 10.1111/jnc.13724] [Citation(s) in RCA: 312] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 05/23/2016] [Accepted: 06/23/2016] [Indexed: 12/11/2022]
Abstract
The adenosine modulation system mostly operates through inhibitory A1 (A1 R) and facilitatory A2A receptors (A2A R) in the brain. The activity-dependent release of adenosine acts as a brake of excitatory transmission through A1 R, which are enriched in glutamatergic terminals. Adenosine sharpens salience of information encoding in neuronal circuits: high-frequency stimulation triggers ATP release in the 'activated' synapse, which is locally converted by ecto-nucleotidases into adenosine to selectively activate A2A R; A2A R switch off A1 R and CB1 receptors, bolster glutamate release and NMDA receptors to assist increasing synaptic plasticity in the 'activated' synapse; the parallel engagement of the astrocytic syncytium releases adenosine further inhibiting neighboring synapses, thus sharpening the encoded plastic change. Brain insults trigger a large outflow of adenosine and ATP, as a danger signal. A1 R are a hurdle for damage initiation, but they desensitize upon prolonged activation. However, if the insult is near-threshold and/or of short-duration, A1 R trigger preconditioning, which may limit the spread of damage. Brain insults also up-regulate A2A R, probably to bolster adaptive changes, but this heightens brain damage since A2A R blockade affords neuroprotection in models of epilepsy, depression, Alzheimer's, or Parkinson's disease. This initially involves a control of synaptotoxicity by neuronal A2A R, whereas astrocytic and microglia A2A R might control the spread of damage. The A2A R signaling mechanisms are largely unknown since A2A R are pleiotropic, coupling to different G proteins and non-canonical pathways to control the viability of glutamatergic synapses, neuroinflammation, mitochondria function, and cytoskeleton dynamics. Thus, simultaneously bolstering A1 R preconditioning and preventing excessive A2A R function might afford maximal neuroprotection. The main physiological role of the adenosine modulation system is to sharp the salience of information encoding through a combined action of adenosine A2A receptors (A2A R) in the synapse undergoing an alteration of synaptic efficiency with an increased inhibitory action of A1 R in all surrounding synapses. Brain insults trigger an up-regulation of A2A R in an attempt to bolster adaptive plasticity together with adenosine release and A1 R desensitization; this favors synaptotocity (increased A2A R) and decreases the hurdle to undergo degeneration (decreased A1 R). Maximal neuroprotection is expected to result from a combined A2A R blockade and increased A1 R activation. This article is part of a mini review series: "Synaptic Function and Dysfunction in Brain Diseases".
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Affiliation(s)
- Rodrigo A Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,FMUC-Faculty of Medicine, University of Coimbra, Coimbra, Portugal
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24
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al-Rashida M, Batool G, Sattar A, Ejaz SA, Khan S, Lecka J, Sévigny J, Hameed A, Iqbal J. 2-Alkoxy-3-(sulfonylarylaminomethylene)-chroman-4-ones as potent and selective inhibitors of ectonucleotidases. Eur J Med Chem 2016; 115:484-94. [DOI: 10.1016/j.ejmech.2016.02.073] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Revised: 02/26/2016] [Accepted: 02/28/2016] [Indexed: 10/22/2022]
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25
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Vindeirinho J, Santiago AR, Cavadas C, Ambrósio AF, Santos PF. The Adenosinergic System in Diabetic Retinopathy. J Diabetes Res 2016; 2016:4270301. [PMID: 27034960 PMCID: PMC4789509 DOI: 10.1155/2016/4270301] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 12/29/2015] [Indexed: 11/18/2022] Open
Abstract
The neurodegenerative and inflammatory environment that is prevalent in the diabetic eye is a key player in the development and progression of diabetic retinopathy. The adenosinergic system is widely regarded as a significant modulator of neurotransmission and the inflammatory response, through the actions of the four types of adenosine receptors (A1R, A2AR, A2BR, and A3R), and thus could be revealed as a potential player in the events unfolding in the early stages of diabetic retinopathy. Herein, we review the studies that explore the impact of diabetic conditions on the retinal adenosinergic system, as well as the role of the said system in ameliorating or exacerbating those conditions. The experimental results described suggest that this system is heavily affected by diabetic conditions and that the modulation of its components could reveal potential therapeutic targets for the treatment of diabetic retinopathy, particularly in the early stages of the disease.
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Affiliation(s)
- J. Vindeirinho
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, 3004-504 Coimbra, Portugal
- Institute for Interdisciplinary Research (III), University of Coimbra, 3030-789 Coimbra, Portugal
- CNC.IBILI, University of Coimbra, 3004-504 Coimbra, Portugal
- *J. Vindeirinho:
| | - A. R. Santiago
- CNC.IBILI, University of Coimbra, 3004-504 Coimbra, Portugal
- Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
- Association for Innovation and Biomedical Research on Light and Image (AIBILI), 3000-548 Coimbra, Portugal
| | - C. Cavadas
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, 3004-504 Coimbra, Portugal
- CNC.IBILI, University of Coimbra, 3004-504 Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - A. F. Ambrósio
- CNC.IBILI, University of Coimbra, 3004-504 Coimbra, Portugal
- Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
- Association for Innovation and Biomedical Research on Light and Image (AIBILI), 3000-548 Coimbra, Portugal
| | - P. F. Santos
- CNC.IBILI, University of Coimbra, 3004-504 Coimbra, Portugal
- Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, 3000-456 Coimbra, Portugal
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Frenguelli BG, Wall MJ. Combined electrophysiological and biosensor approaches to study purinergic regulation of epileptiform activity in cortical tissue. J Neurosci Methods 2015; 260:202-14. [PMID: 26381061 DOI: 10.1016/j.jneumeth.2015.09.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 09/05/2015] [Accepted: 09/07/2015] [Indexed: 12/16/2022]
Abstract
BACKGROUND Cortical brain slices offer a readily accessible experimental model of a region of the brain commonly affected by epilepsy. The diversity of recording techniques, seizure-promoting protocols and mutant mouse models provides a rich diversity of avenues of investigation, which is facilitated by the regular arrangement of distinct neuronal populations and afferent fibre pathways, particularly in the hippocampus. NEW METHOD AND RESULTS We have been interested in the regulation of seizure activity in hippocampal and neocortical slices by the purines, adenosine and ATP. Via the use of microelectrode biosensors we have been able to measure the release of these important neuroactive compounds simultaneously with on-going epileptiform activity, even of brief durations. In addition, detailed numerical analysis and computational modelling has produced new insights into the kinetics and spatial distribution of elevations in purine concentration that occur during seizure activity. COMPARISON AND CONCLUSIONS Such an approach allows the spatio-temporal characteristics of neurotransmitter/neuromodulator release to be directly correlated with electrophysiological measures of synaptic and seizure activity, and can provide greater insight into the role of purines in epilepsy.
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Affiliation(s)
| | - Mark J Wall
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
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Acton D, Miles GB. Stimulation of Glia Reveals Modulation of Mammalian Spinal Motor Networks by Adenosine. PLoS One 2015; 10:e0134488. [PMID: 26252389 PMCID: PMC4529192 DOI: 10.1371/journal.pone.0134488] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Accepted: 07/09/2015] [Indexed: 01/05/2023] Open
Abstract
Despite considerable evidence that glia can release modulators to influence the excitability of neighbouring neurons, the importance of gliotransmission for the operation of neural networks and in shaping behaviour remains controversial. Here we characterise the contribution of glia to the modulation of the mammalian spinal central pattern generator for locomotion, the output of which is directly relatable to a defined behaviour. Glia were stimulated by specific activation of protease-activated receptor-1 (PAR1), an endogenous G-protein coupled receptor preferentially expressed by spinal glia during ongoing activity of the spinal central pattern generator for locomotion. Selective activation of PAR1 by the agonist TFLLR resulted in a reversible reduction in the frequency of locomotor-related bursting recorded from ventral roots of spinal cord preparations isolated from neonatal mice. In the presence of the gliotoxins methionine sulfoximine or fluoroacetate, TFLLR had no effect, confirming the specificity of PAR1 activation to glia. The modulation of burst frequency upon PAR1 activation was blocked by the non-selective adenosine-receptor antagonist theophylline and by the A1-receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine, but not by the A2A-receptor antagonist SCH5826, indicating production of extracellular adenosine upon glial stimulation, followed by A1-receptor mediated inhibition of neuronal activity. Modulation of network output following glial stimulation was also blocked by the ectonucleotidase inhibitor ARL67156, indicating glial release of ATP and its subsequent degradation to adenosine rather than direct release of adenosine. Glial stimulation had no effect on rhythmic activity recorded following blockade of inhibitory transmission, suggesting that glial cell-derived adenosine acts via inhibitory circuit components to modulate locomotor-related output. Finally, the modulation of network output by endogenous adenosine was found to scale with the frequency of network activity, implying activity-dependent release of adenosine. Together, these data indicate that glia play an active role in the modulation of mammalian locomotor networks, providing negative feedback control that may stabilise network activity.
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Affiliation(s)
- David Acton
- School of Psychology and Neuroscience, University of St Andrews, Fife, United Kingdom
| | - Gareth B. Miles
- School of Psychology and Neuroscience, University of St Andrews, Fife, United Kingdom
- * E-mail:
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Navarro G, Borroto-Escuela DO, Fuxe K, Franco R. Purinergic signaling in Parkinson's disease. Relevance for treatment. Neuropharmacology 2015. [PMID: 26211977 DOI: 10.1016/j.neuropharm.2015.07.024] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Purinergic signaling modulates dopaminergic neurotransmission in health and disease. Classically adenosine A1 and A2A receptors have been considered key for the fine tune control of dopamine actions in the striatum, the main CNS motor control center. The main adenosine signaling mechanism is via the cAMP pathway but the future will tell whether calcium signaling is relevant in adenosinergic control of striatal function. Very relevant is the recent approval in Japan of the adenosine A2A receptor antagonist, istradefylline, for use in Parkinson's disease patients. Purine nucleotides are also regulators of striatal dopamine neurotransmission via P2 purinergic receptors. In parallel to the alpha-synuclein hypothesis of Parkinson's disease etiology, purinergic P2X1 receptors have been identified as mediators of accumulation of the Lewy-body enriched protein alpha-synuclein. Of note is the expression in striatum of purinergic-receptor-containing heteromers that are potential targets of anti-Parkinson's disease therapies and should be taken into account in drug discovery programs. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.
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Affiliation(s)
- Gemma Navarro
- Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain; Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain.
| | - Dasiel O Borroto-Escuela
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; Department of Earth, Life and Environmental Sciences, Section of Physiology, Campus Scientifico Enrico Mattei, University of Urbino, Urbino, Italy.
| | - Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | - Rafael Franco
- Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain; Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain.
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Siebel AM, Menezes FP, Capiotti KM, Kist LW, da Costa Schaefer I, Frantz JZ, Bogo MR, Da Silva RS, Bonan CD. Role of adenosine signaling on pentylenetetrazole-induced seizures in zebrafish. Zebrafish 2015; 12:127-36. [PMID: 25560904 DOI: 10.1089/zeb.2014.1004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Adenosine is a well-known endogenous modulator of neuronal excitability with anticonvulsant properties. Thus, the modulation exerted by adenosine might be an effective tool to control seizures. In this study, we investigated the effects of drugs that are able to modulate adenosinergic signaling on pentylenetetrazole (PTZ)-induced seizures in adult zebrafish. The adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) decreased the latency to the onset of the tonic-clonic seizure stage. The adenosine A1 receptor agonist cyclopentyladenosine (CPA) increased the latency to reach the tonic-clonic seizure stage. Both the adenosine A2A receptor agonist and antagonist, CGS 21680 and ZM 241385, respectively, did not promote changes in seizure parameters. Pretreatment with the ecto-5'nucleotidase inhibitor adenosine 5'-(α,β-methylene) diphosphate (AMPCP) decreased the latency to the onset of the tonic-clonic seizure stage. However, when pretreated with the adenosine deaminase (ADA) inhibitor, erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA), or with the nucleoside transporter (NT) inhibitors, dipyridamole and S-(4-Nitrobenzyl)-6-thioinosine (NBTI), animals showed longer latency to reach the tonic-clonic seizure status. Finally, our molecular analysis of the c-fos gene expression corroborates these behavioral results. Our findings indicate that the activation of adenosine A1 receptors is an important mechanism to control the development of seizures in zebrafish. Furthermore, the actions of ecto-5'-nucleotidase, ADA, and NTs are directly involved in the control of extracellular adenosine levels and have an important role in the development of seizure episodes in zebrafish.
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Affiliation(s)
- Anna Maria Siebel
- 1 Laboratório de Neuroquímica e Psicofarmacologia, Departamento de Biologia Celular e Molecular, Programa de Pós-Graduação em Biologia Celular e Molecular, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul , Porto Alegre, Brazil
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Nguyen MD, Venton BJ. Fast-scan Cyclic Voltammetry for the Characterization of Rapid Adenosine Release. Comput Struct Biotechnol J 2014; 13:47-54. [PMID: 26900429 PMCID: PMC4720017 DOI: 10.1016/j.csbj.2014.12.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 12/19/2014] [Accepted: 12/23/2014] [Indexed: 12/20/2022] Open
Abstract
Adenosine is a signaling molecule and downstream product of ATP that acts as a neuromodulator. Adenosine regulates physiological processes, such as neurotransmission and blood flow, on a time scale of minutes to hours. Recent developments in electrochemical techniques, including fast-scan cyclic voltammetry (FSCV), have allowed direct detection of adenosine with sub-second temporal resolution. FSCV studies have revealed a novel mode of rapid signaling that lasts only a few seconds. This rapid release of adenosine can be evoked by electrical or mechanical stimulations or it can be observed spontaneously without stimulation. Adenosine signaling on this time scale is activity dependent; however, the mode of release is not fully understood. Rapid adenosine release modulates oxygen levels and evoked dopamine release, indicating that adenosine may have a rapid modulatory role. In this review, we outline how FSCV can be used to detect adenosine release, compare FSCV with other techniques used to measure adenosine, and present an overview of adenosine signaling that has been characterized using FSCV. These studies point to a rapid mode of adenosine modulation, whose mechanism and function will continue to be characterized in the future.
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Affiliation(s)
- Michael D Nguyen
- Department of Chemistry, University of Virginia, McCormick Road, PO BOX 400319, Charlottesville, VA 22904, United States
| | - B Jill Venton
- Department of Chemistry, University of Virginia, McCormick Road, PO BOX 400319, Charlottesville, VA 22904, United States
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Ross AE, Venton BJ. Adenosine transiently modulates stimulated dopamine release in the caudate-putamen via A1 receptors. J Neurochem 2014; 132:51-60. [PMID: 25219576 DOI: 10.1111/jnc.12946] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 08/26/2014] [Accepted: 09/10/2014] [Indexed: 01/20/2023]
Abstract
Adenosine modulates dopamine in the brain via A1 and A2A receptors, but that modulation has only been characterized on a slow time scale. Recent studies have characterized a rapid signaling mode of adenosine that suggests a possible rapid modulatory role. Here, fast-scan cyclic voltammetry was used to characterize the extent to which transient adenosine changes modulate stimulated dopamine release (5 pulses at 60 Hz) in rat caudate-putamen brain slices. Exogenous adenosine was applied and dopamine concentration monitored. Adenosine only modulated dopamine when it was applied 2 or 5 s before stimulation. Longer time intervals and bath application of 5 μM adenosine did not decrease dopamine release. Mechanical stimulation of endogenous adenosine 2 s before dopamine stimulation also decreased stimulated dopamine release by 41 ± 7%, similar to the 54 ± 6% decrease in dopamine after exogenous adenosine application. Dopamine inhibition by transient adenosine was recovered within 10 min. The A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine blocked the dopamine modulation, whereas dopamine modulation was unaffected by the A2A receptor antagonist SCH 442416. Thus, transient adenosine changes can transiently modulate phasic dopamine release via A1 receptors. These data demonstrate that adenosine has a rapid, but transient, modulatory role in the brain. Here, transient adenosine was shown to modulate phasic dopamine release on the order of seconds by acting at the A1 receptor. However, sustained increases in adenosine did not regulate phasic dopamine release. This study demonstrates for the first time a transient, neuromodulatory function of rapid adenosine to regulate rapid neurotransmitter release.
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Affiliation(s)
- Ashley E Ross
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
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Ross AE, Nguyen MD, Privman E, Venton BJ. Mechanical stimulation evokes rapid increases in extracellular adenosine concentration in the prefrontal cortex. J Neurochem 2014; 130:50-60. [PMID: 24606335 PMCID: PMC4065624 DOI: 10.1111/jnc.12711] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 02/28/2014] [Accepted: 03/05/2014] [Indexed: 12/22/2022]
Abstract
Mechanical perturbations can release ATP, which is broken down to adenosine. In this work, we used carbon-fiber microelectrodes and fast-scan cyclic voltammetry to measure mechanically stimulated adenosine in the brain by lowering the electrode 50 μm. Mechanical stimulation evoked adenosine in vivo (average: 3.3 ± 0.6 μM) and in brain slices (average: 0.8 ± 0.1 μM) in the prefrontal cortex. The release was transient, lasting 18 ± 2 s. Lowering a 15-μm-diameter glass pipette near the carbon-fiber microelectrode produced similar results as lowering the actual microelectrode. However, applying a small puff of artificial cerebral spinal fluid was not sufficient to evoke adenosine. Multiple stimulations within a 50-μm region of a slice did not significantly change over time or damage cells. Chelating calcium with EDTA or blocking sodium channels with tetrodotoxin significantly decreased mechanically evoked adenosine, signifying that the release is activity dependent. An alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, did not affect mechanically stimulated adenosine; however, the nucleoside triphosphate diphosphohydrolase 1,2 and 3 (NTDPase) inhibitor POM-1 significantly reduced adenosine so a portion of adenosine is dependent on extracellular ATP metabolism. Thus, mechanical perturbations from inserting a probe in the brain cause rapid, transient adenosine signaling which might be neuroprotective. We have discovered immediate changes in adenosine concentration in the prefrontal cortex following mechanical stimulation. The adenosine increase lasts only about 20 s. Mechanically stimulated adenosine was activity dependent and mostly because of extracellular ATP metabolism. This rapid, transient increase in adenosine may help protect tissue and would occur during implantation of any electrode, such as during deep brain stimulation.
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Affiliation(s)
| | | | | | - B. Jill Venton
- corresponding author Dept. of Chemistry University of Virginia Charlottesville, VA 22904 (434) 243-2132
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Abstract
Evidences in the central nervous system are in favor that adenosine under basal conditions is released by a direct excitation-secretion modality. However, till now, there is no direct evidence that adenosine is contained in synaptic vesicles. Eight synaptic vesicle fractions were recovered on a discontinuous sucrose gradient after ultracentrifugation of the crude synaptosomal fraction (pellet P2) of rat brain. The adenosine content in each fraction was measured by high-performance liquid chromatography coupled to a fluorescence detector (minimum sensitivity 10 femtomoles). The immunoblot analysis, to detect synaptophysin, a molecular marker for the vesicle membrane, showed that fractions from 3 to 8 were rich in synaptophysin. The sum of adenosine found in fractions 3-8 was (mean ± SEM, n = 4) 3325.6 ± 94.6 pmol/mg of tissue protein. We proved that adenosine measured in synaptic vesicle fractions was not contaminated by cytosolic adenosine, as adenosine exogenously added to the P2 preferentially distributed in fractions 1 and 2 that are synaptophysin-free and did not contaminate the vesicle pellet P3. Data provide direct demonstration that adenosine is present in rat brain synaptic vesicle fractions. This information is consistent with the notion that adenosine is stored in synaptic vesicles and is released under normoxic physiological conditions by an excitation-secretion mechanism typical of neuronal cells.
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35
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Lynch G, Cox CD, Gall CM. Pharmacological enhancement of memory or cognition in normal subjects. Front Syst Neurosci 2014; 8:90. [PMID: 24904313 PMCID: PMC4033242 DOI: 10.3389/fnsys.2014.00090] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 04/30/2014] [Indexed: 12/14/2022] Open
Abstract
The possibility of expanding memory or cognitive capabilities above the levels in high functioning individuals is a topic of intense discussion among scientists and in society at large. The majority of animal studies use behavioral endpoint measures; this has produced valuable information but limited predictability for human outcomes. Accordingly, several groups are pursuing a complementary strategy with treatments targeting synaptic events associated with memory encoding or forebrain network operations. Transcription and translation figure prominently in substrate work directed at enhancement. Notably, the question of why new proteins would be needed for a now-forming memory given that learning-driven synthesis presumably occurred throughout the immediate past has been largely ignored. Despite this conceptual problem, and some controversy, recent studies have reinvigorated the idea that selective gene manipulation is a plausible route to enhancement. Efforts to improve memory by facilitating synaptic encoding of information have also progressed, in part due of breakthroughs on mechanisms that stabilize learning-related, long-term potentiation (LTP). These advances point to a reductionistic hypothesis for a diversity of experimental results on enhancement, and identify under-explored possibilities. Cognitive enhancement remains an elusive goal, in part due to the difficulty of defining the target. The popular view of cognition as a collection of definable computations seems to miss the fluid, integrative process experienced by high functioning individuals. The neurobiological approach obviates these psychological issues to directly test the consequences of improving throughput in networks underlying higher order behaviors. The few relevant studies testing drugs that selectively promote excitatory transmission indicate that it is possible to expand cortical networks engaged by complex tasks and that this is accompanied by capabilities not found in normal animals.
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Affiliation(s)
- Gary Lynch
- Department of Psychiatry and Human Behavior, University of California Irvine, CA, USA ; Department of Anatomy and Neurobiology, University of California Irvine, CA, USA
| | - Conor D Cox
- Department of Anatomy and Neurobiology, University of California Irvine, CA, USA
| | - Christine M Gall
- Department of Anatomy and Neurobiology, University of California Irvine, CA, USA
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36
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Purinergic neuron-glia interactions in sensory systems. Pflugers Arch 2014; 466:1859-72. [DOI: 10.1007/s00424-014-1510-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 03/26/2014] [Accepted: 03/26/2014] [Indexed: 02/06/2023]
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Sims RE, Dale N. Activity-dependent adenosine release may be linked to activation of Na(+)-K(+) ATPase: an in vitro rat study. PLoS One 2014; 9:e87481. [PMID: 24489921 PMCID: PMC3906196 DOI: 10.1371/journal.pone.0087481] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 12/23/2013] [Indexed: 01/06/2023] Open
Abstract
In the brain, extracellular adenosine increases as a result of neuronal activity. The mechanisms by which this occurs are only incompletely understood. Here we investigate the hypothesis that the Na+ influxes associated with neuronal signalling activate the Na+-K+ ATPase which, by consuming ATP, generates intracellular adenosine that is then released via transporters. By measuring adenosine release directly with microelectrode biosensors, we have demonstrated that AMPA-receptor evoked adenosine release in basal forebrain and cortex depends on extracellular Na+. We have simultaneously imaged intracellular Na+ and measured adenosine release. The accumulation of intracellular Na+ during AMPA receptor activation preceded adenosine release by some 90 s. By removing extracellular Ca2+, and thus preventing indiscriminate neuronal activation, we used ouabain to test the role of the Na+-K+ ATPase in the release of adenosine. Under conditions which caused a Na+ influx, brief applications of ouabain increased the accumulation of intracellular Na+ but conversely rapidly reduced extracellular adenosine levels. In addition, ouabain greatly reduced the amount of adenosine released during application of AMPA. Our data therefore suggest that activity of the Na+-K+ ATPase is directly linked to the efflux of adenosine and could provide a universal mechanism that couples adenosine release to neuronal activity. The Na+-K+ ATPase-dependent adenosine efflux is likely to provide adenosine-mediated activity-dependent negative feedback that will be important in many diverse functional contexts including the regulation of sleep.
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Affiliation(s)
- Robert Edward Sims
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
- * E-mail:
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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Nguyen MD, Lee ST, Ross AE, Ryals M, Choudhry VI, Venton BJ. Characterization of spontaneous, transient adenosine release in the caudate-putamen and prefrontal cortex. PLoS One 2014; 9:e87165. [PMID: 24494035 PMCID: PMC3907895 DOI: 10.1371/journal.pone.0087165] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 12/19/2013] [Indexed: 12/20/2022] Open
Abstract
Adenosine is a neuroprotective agent that inhibits neuronal activity and modulates neurotransmission. Previous research has shown adenosine gradually accumulates during pathologies such as stroke and regulates neurotransmission on the minute-to-hour time scale. Our lab developed a method using carbon-fiber microelectrodes to directly measure adenosine changes on a sub-second time scale with fast-scan cyclic voltammetry (FSCV). Recently, adenosine release lasting a couple of seconds has been found in murine spinal cord slices. In this study, we characterized spontaneous, transient adenosine release in vivo, in the caudate-putamen and prefrontal cortex of anesthetized rats. The average concentration of adenosine release was 0.17±0.01 µM in the caudate and 0.19±0.01 µM in the prefrontal cortex, although the range was large, from 0.04 to 3.2 µM. The average duration of spontaneous adenosine release was 2.9±0.1 seconds and 2.8±0.1 seconds in the caudate and prefrontal cortex, respectively. The concentration and number of transients detected do not change over a four hour period, suggesting spontaneous events are not caused by electrode implantation. The frequency of adenosine transients was higher in the prefrontal cortex than the caudate-putamen and was modulated by A1 receptors. The A1 antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine, 6 mg/kg i.p.) increased the frequency of spontaneous adenosine release, while the A1 agonist CPA (N(6)-cyclopentyladenosine, 1 mg/kg i.p.) decreased the frequency. These findings are a paradigm shift for understanding the time course of adenosine signaling, demonstrating that there is a rapid mode of adenosine signaling that could cause transient, local neuromodulation.
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Affiliation(s)
- Michael D. Nguyen
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Scott T. Lee
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Ashley E. Ross
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Matthew Ryals
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Vishesh I. Choudhry
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - B. Jill Venton
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail:
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Rodrigues TM, Jerónimo-Santos A, Sebastião AM, Diógenes MJ. Adenosine A(2A) Receptors as novel upstream regulators of BDNF-mediated attenuation of hippocampal Long-Term Depression (LTD). Neuropharmacology 2013; 79:389-98. [PMID: 24361450 DOI: 10.1016/j.neuropharm.2013.12.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 11/08/2013] [Accepted: 12/08/2013] [Indexed: 01/05/2023]
Abstract
Hippocampal Long-Term Potentiation (LTP) is facilitated by BDNF, through the activation of tropomyosin-related kinase B (TrkB) receptors. However, an influence of BDNF upon Long-Term Depression (LTD) was also shown. The present work aimed to further evaluate the effect of BDNF and TrkB receptors upon CA1 hippocampal LTD and to elucidate whether this effect is under the upstream control of other signalling processes, such as the adenosine A(2A)Receptors (A(2A)Rs). LTD, induced by a Low-Frequency Stimulation (LFS, 900 pulses, 1 Hz) in the CA1 area of rat hippocampal slices, was significantly attenuated when these slices were exposed to BDNF (60-100 ng/mL). A lower BDNF concentration (20 ng/ml) was only effective to inhibit LTD if A(2A)Rs were activated by a selective agonist, CGS 21680 (10 nM), or if the extracellular adenosine level was increased by 5-iodotubercidin (100 nM). BDNF (100 ng/ml) effect upon LTD was prevented by K252a (200 nM), which is known to prevent TrkB transphosphorylation, hence suggesting that this action requires TrkB receptor activation. BDNF (100 ng/ml) lacked effect on an adenosine-depleted background (adenosine deaminase, 2 U/ml) or under selective A(2A)R blockade (SCH 58261, 100 nM), indicating that it relies on tonic A(2A)R activation. Forskolin (10 μM), a cell-permeable activator of adenylate cyclase, rescued BDNF (100 ng/ml) effect in slices where A(2A)Rs were blocked with SCH 58261 (100 nM), whereas a PKA inhibitor, H-89 (1 μM), prevented LTD attenuation by BDNF (100 ng/ml). We conclude that the influence of BDNF TrkB receptors upon LTD is under the strict control of A(2A)Rs activation, through a mechanism that requires the cAMP/PKA transducing system.
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Affiliation(s)
- Tiago M Rodrigues
- Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal; Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, Lisbon, Portugal
| | - André Jerónimo-Santos
- Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal; Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, Lisbon, Portugal
| | - Ana M Sebastião
- Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal; Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, Lisbon, Portugal
| | - Maria José Diógenes
- Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal; Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, Lisbon, Portugal.
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40
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Abstract
The neuromodulator adenosine is widely considered to be a key regulator of sleep homeostasis and an indicator of sleep need. Although the effect of adenosine on subcortical areas has been previously described, the effects on cortical neurons have not been addressed systematically to date. To that purpose, we performed in vitro whole-cell patch-clamp recordings and biocytin staining of pyramidal neurons and interneurons throughout all layers of rat prefrontal and somatosensory cortex, followed by morphological analysis. We found that adenosine, via the A1 receptor, exerts differential effects depending on neuronal cell type and laminar location. Interneurons and pyramidal neurons in layer 2 and a subpopulation of layer 3 pyramidal neurons that displayed regular spiking were insensitive to adenosine application, whereas other pyramidal cells in layers 3-6 were hyperpolarized (range 1.2-10.8 mV). Broad tufted pyramidal neurons with little spike adaptation showed a small adenosine response, whereas slender tufted pyramidal neurons with substantial adaptation showed a bigger response. These studies of the action of adenosine at the postsynaptic level may contribute to the understanding of the changes in cortical circuit functioning that take place between sleep and awakening.
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Affiliation(s)
- Karlijn I van Aerde
- Forschungszentrum Jülich, Institute of Neuroscience and Medicine, INM-2, D-52425 Jülich, Germany Current address: Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Science, 1105 BA Amsterdam, The Netherlands
| | - Guanxiao Qi
- Forschungszentrum Jülich, Institute of Neuroscience and Medicine, INM-2, D-52425 Jülich, Germany Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Medical School, D-52074 Aachen, Germany
| | - Dirk Feldmeyer
- Forschungszentrum Jülich, Institute of Neuroscience and Medicine, INM-2, D-52425 Jülich, Germany Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Medical School, D-52074 Aachen, Germany JARA-Translational Brain Medicine, Aachen, Germany
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41
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Tissue-nonspecific alkaline phosphatase acts redundantly with PAP and NT5E to generate adenosine in the dorsal spinal cord. J Neurosci 2013; 33:11314-22. [PMID: 23825434 DOI: 10.1523/jneurosci.0133-13.2013] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Prostatic acid phosphatase (PAP) and ecto-5'-nucleotidase (NT5E) hydrolyze extracellular AMP to adenosine in dorsal root ganglia (DRG) neurons and in the dorsal spinal cord. Previously, we found that adenosine production was reduced, but not eliminated, in Pap⁻/⁻/Nt5e⁻/⁻ double knock-out (dKO) mice, suggesting that a third AMP ectonucleotidase was present in these tissues. Here, we found that tissue-nonspecific alkaline phosphatase (TNAP, encoded by the Alpl gene) is expressed and functional in DRG neurons and spinal neurons. Using a cell-based assay, we found that TNAP rapidly hydrolyzed extracellular AMP and activated adenosine receptors. This activity was eliminated by MLS-0038949, a selective pharmacological inhibitor of TNAP. In addition, MLS-0038949 eliminated AMP hydrolysis in DRG and spinal lamina II of dKO mice. Using fast-scan-cyclic voltammetry, we found that adenosine was rapidly produced from AMP in spinal cord slices from dKO mice, but virtually no adenosine was produced in spinal cord slices from dKO mice treated with MLS-0038949. Last, we found that AMP inhibited excitatory neurotransmission via adenosine A1 receptor activation in spinal cord slices from wild-type, Pap⁻/⁻, Nt5e⁻/⁻, and dKO mice, but failed to inhibit neurotransmission in slices from dKO mice treated with MLS-0038949. These data suggest that triple elimination of TNAP, PAP, and NT5E is required to block AMP hydrolysis to adenosine in DRG neurons and dorsal spinal cord. Moreover, our data reveal that TNAP, PAP, and NT5E are the main AMP ectonucleotidases in primary somatosensory neurons and regulate physiology by metabolizing extracellular purine nucleotides.
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Ecto-5'-nucleotidase (CD73)-mediated formation of adenosine is critical for the striatal adenosine A2A receptor functions. J Neurosci 2013; 33:11390-9. [PMID: 23843511 DOI: 10.1523/jneurosci.5817-12.2013] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Adenosine is a neuromodulator acting through inhibitory A1 receptors (A1Rs) and facilitatory A2ARs, which have similar affinities for adenosine. It has been shown that the activity of intracellular adenosine kinase preferentially controls the activation of A1Rs, but the source of the adenosine activating A2ARs is unknown. We now show that ecto-5'-nucleotidase (CD73), the major enzyme able to convert extracellular AMP into adenosine, colocalizes with A2ARs in the basal ganglia. In addition to astrocytes, striatal CD73 is prominently localized to postsynaptic sites. Notably, CD73 coimmunoprecipitated with A2ARs and proximity ligation assays confirmed the close proximity of CD73 and A2ARs in the striatum. Accordingly, the cAMP formation in synaptosomes as well as the hypolocomotion induced by a novel A2AR prodrug that requires CD73 metabolization to activate A2ARs were observed in wild-type mice, but not in CD73 knock-out (KO) mice or A2AR KO mice. Moreover, CD73 KO mice displayed increased working memory performance and a blunted amphetamine-induced sensitization, mimicking the phenotype of global or forebrain-A2AR KO mice, as well as upon pharmacological A2AR blockade. These results show that CD73-mediated formation of extracellular adenosine is responsible for the activation of striatal A2AR function. This study points to CD73 as a new target that can fine-tune A2AR activity, and a novel therapeutic target to manipulate A2AR-mediated control of striatal function and neurodegeneration.
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Muzzi M, Coppi E, Pugliese AM, Chiarugi A. Anticonvulsant effect of AMP by direct activation of adenosine A1 receptor. Exp Neurol 2013; 250:189-93. [PMID: 24056265 DOI: 10.1016/j.expneurol.2013.09.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 08/26/2013] [Accepted: 09/11/2013] [Indexed: 12/19/2022]
Abstract
Purinergic neurotransmission mediated by adenosine (Ado) type 1 receptors (A1Rs) plays pivotal roles in negative modulation of epileptic seizures, and Ado is thought to be a key endogenous anticonvulsant. Recent evidence, however, indicates that AMP, the metabolic precursor of Ado, also activate A1Rs. Here, we evaluated the antiepileptic effects of AMP adopting in vitro and in vivo models of epilepsy. We report that AMP reversed the increase in population spike (PS) amplitude and the decrease in PS latency induced by a Mg(2+)-free extracellular solution in CA1 neurons of mouse hippocampal slices. The AMP effects were inhibited by the A1R antagonist DPCPX, but not prevented by inhibiting conversion of AMP into Ado, indicating that AMP inhibited per se sustained hippocampal excitatory neurotransmission by directly activating A1Rs. AMP also reduced seizure severity and mortality in a model of audiogenic convulsion. Of note, the anticonvulsant effects of AMP were potentiated by preventing its conversion into Ado and inhibited by DPCPX. When tested in a model of kainate-induced seizure, AMP prolonged latency of convulsions but had no effects on seizure severity and mortality. Data provide the first evidence that AMP is an endogenous anticonvulsant acting at A1Rs.
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Affiliation(s)
- Mirko Muzzi
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Italy.
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FACS array profiling identifies Ecto-5' nucleotidase as a striatopallidal neuron-specific gene involved in striatal-dependent learning. J Neurosci 2013; 33:8794-809. [PMID: 23678122 DOI: 10.1523/jneurosci.2989-12.2013] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The striatopallidal (STP) and striatonigral (STN) neurons constitute the main neuronal populations of the striatum. Despite the increasing knowledge concerning their involvement in multiple tasks associated with the striatum, it is still challenging to understand the precise differential functions of these two neuronal populations and to identify and study new genes involved in these functions. Here, we describe a reliable approach, applied on adult mouse brain, to generate specific STP and STN neuron gene profiles. STP and STN neurons were identified in the same animal using the transgenic Adora2A-Cre × Z/EG mouse model combined with retrograde labeling, respectively. Gene profiling was generated from FACS-purified neurons leading to the identification of new STP and STN neuron-specific genes. Knock-down models based on Cre-dependent lentiviral vector were developed to investigate their function either in striatal or in STP neurons. Thereby, we demonstrate that ecto-5'-nucleotidase (NT5e) is specifically expressed in STP neurons and is at the origin of most of the extracellular adenosine produced in the striatum. Behavioral analysis of striatal and STP neuron knock-down mouse models as well as NT5e knock-out mice demonstrates the implication of this STP neuron enzyme in motor learning.
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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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Dias RB, Rombo DM, Ribeiro JA, Henley JM, Sebastião AM. Adenosine: setting the stage for plasticity. Trends Neurosci 2013; 36:248-57. [PMID: 23332692 DOI: 10.1016/j.tins.2012.12.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 10/09/2012] [Accepted: 12/14/2012] [Indexed: 12/19/2022]
Abstract
It is widely accepted that Hebbian forms of plasticity mediate selective modifications in synaptic strength underlying information encoding in response to experience and circuit formation or refinement throughout development. Several complementary forms of homeostatic plasticity coordinate to keep Hebbian plasticity in check, frequently through the actions of conserved regulatory molecules. Recent evidence suggests that this may be the case for adenosine, which is ubiquitous in the brain and is released by both neurons and glial cells via constitutive and activity-dependent mechanisms. Through A1 and A2A receptor activation, adenosine modulates neuronal homeostasis and tunes the ability of synapses to undergo and/or sustain plasticity. Here, we review how adenosine equilibrates neuronal activity and sets the stage for synaptic plasticity.
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Affiliation(s)
- Raquel B Dias
- Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal
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47
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Sims RE, Wu HHT, Dale N. Sleep-wake sensitive mechanisms of adenosine release in the basal forebrain of rodents: an in vitro study. PLoS One 2013; 8:e53814. [PMID: 23326515 PMCID: PMC3543262 DOI: 10.1371/journal.pone.0053814] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 12/05/2012] [Indexed: 12/24/2022] Open
Abstract
Adenosine acting in the basal forebrain is a key mediator of sleep homeostasis. Extracellular adenosine concentrations increase during wakefulness, especially during prolonged wakefulness and lead to increased sleep pressure and subsequent rebound sleep. The release of endogenous adenosine during the sleep-wake cycle has mainly been studied in vivo with microdialysis techniques. The biochemical changes that accompany sleep-wake status may be preserved in vitro. We have therefore used adenosine-sensitive biosensors in slices of the basal forebrain (BFB) to study both depolarization-evoked adenosine release and the steady state adenosine tone in rats, mice and hamsters. Adenosine release was evoked by high K+, AMPA, NMDA and mGlu receptor agonists, but not by other transmitters associated with wakefulness such as orexin, histamine or neurotensin. Evoked and basal adenosine release in the BFB in vitro exhibited three key features: the magnitude of each varied systematically with the diurnal time at which the animal was sacrificed; sleep deprivation prior to sacrifice greatly increased both evoked adenosine release and the basal tone; and the enhancement of evoked adenosine release and basal tone resulting from sleep deprivation was reversed by the inducible nitric oxide synthase (iNOS) inhibitor, 1400 W. These data indicate that characteristics of adenosine release recorded in the BFB in vitro reflect those that have been linked in vivo to the homeostatic control of sleep. Our results provide methodologically independent support for a key role for induction of iNOS as a trigger for enhanced adenosine release following sleep deprivation and suggest that this induction may constitute a biochemical memory of this state.
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Affiliation(s)
- Robert Edward Sims
- School of Life Sciences, University of Warwick, Coventry, West Midlands, United Kingdom.
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Superior working memory and behavioural habituation but diminished psychomotor coordination in mice lacking the ecto-5'-nucleotidase (CD73) gene. Purinergic Signal 2012; 9:175-82. [PMID: 23274765 DOI: 10.1007/s11302-012-9344-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 11/19/2012] [Indexed: 12/22/2022] Open
Abstract
Adenosine is an important neuromodulator in the central nervous system involved in the regulation of wakefulness, sleep, learning and memory, fear and anxiety as well as motor functions. Extracellular adenosine is synthesized by the cell-surface ectoenzyme ecto-5'-nucleotidase (CD73) from 5'-adenosine monophosphate. While CD73 is widely expressed throughout the mammalian brain, its specific role for behaviour is poorly understood. We examined spatial working memory, emotional responses, motor coordination and motor learning as well as behavioural habituation in mice with a targeted deletion of CD73. CD73 knockout (CD73-/-) mice exhibit enhanced spatial working memory in the Y-maze and enhanced long-term behavioural habituation in the open field. Furthermore, impaired psychomotor coordination on the accelerating rotarod was found in CD73-/- mice. No changes in motor learning and/or anxiety-like behaviour were evident in CD73-/- mice. Our data provide evidence for a role of CD73 in the regulation of learning and memory and psychomotor coordination. Our results might be important for the evaluation of adenosine neuromodulators as possible treatments to ameliorate cognitive and motor deficits associated with neurodegenerative diseases.
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Pajski ML, Venton BJ. The mechanism of electrically stimulated adenosine release varies by brain region. Purinergic Signal 2012. [PMID: 23192278 DOI: 10.1007/s11302-012-9343-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Adenosine plays an important role in neuromodulation and neuroprotection. Recent identification of transient changes in adenosine concentration suggests adenosine may have a rapid modulatory role; however, the extent of these changes throughout the brain is not well understood. In this report, transient changes in adenosine evoked by one second, 60 Hz electrical stimulation trains were compared in the caudate-putamen, nucleus accumbens, hippocampus, and cortex. The concentration of evoked adenosine varies between brain regions, but there is less variation in the duration of signaling. The highest concentration of adenosine was evoked in the dorsal caudate-putamen (0.34 ± 0.08 μM), while the lowest concentration was in the secondary motor cortex (0.06 ± 0.02 μM). In all brain regions, adenosine release was activity-dependent. In the nucleus accumbens, hippocampus, and prefrontal cortex, this release was partly due to extracellular ATP breakdown. However, in the caudate-putamen, release was not due to ATP metabolism but was ionotropic glutamate receptor-dependent. The results demonstrate that transient, activity-dependent adenosine can be evoked in many brain regions but that the mechanism of formation and release varies by region.
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Affiliation(s)
- Megan L Pajski
- Chemistry Department, University of Virginia, Charlottesville, VA 22904, USA
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50
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Varshavsky A. Augmented generation of protein fragments during wakefulness as the molecular cause of sleep: a hypothesis. Protein Sci 2012; 21:1634-61. [PMID: 22930402 PMCID: PMC3527701 DOI: 10.1002/pro.2148] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 08/21/2012] [Indexed: 02/05/2023]
Abstract
Despite extensive understanding of sleep regulation, the molecular-level cause and function of sleep are unknown. I suggest that they originate in individual neurons and stem from increased production of protein fragments during wakefulness. These fragments are transient parts of protein complexes in which the fragments were generated. Neuronal Ca²⁺ fluxes are higher during wakefulness than during sleep. Subunits of transmembrane channels and other proteins are cleaved by Ca²⁺-activated calpains and by other nonprocessive proteases, including caspases and secretases. In the proposed concept, termed the fragment generation (FG) hypothesis, sleep is a state during which the production of fragments is decreased (owing to lower Ca²⁺ transients) while fragment-destroying pathways are upregulated. These changes facilitate the elimination of fragments and the remodeling of protein complexes in which the fragments resided. The FG hypothesis posits that a proteolytic cleavage, which produces two fragments, can have both deleterious effects and fitness-increasing functions. This (previously not considered) dichotomy can explain both the conservation of cleavage sites in proteins and the evolutionary persistence of sleep, because sleep would counteract deleterious aspects of protein fragments. The FG hypothesis leads to new explanations of sleep phenomena, including a longer sleep after sleep deprivation. Studies in the 1970s showed that ethanol-induced sleep in mice can be strikingly prolonged by intracerebroventricular injections of either Ca²⁺ alone or Ca²⁺ and its ionophore (Erickson et al., Science 1978;199:1219-1221; Harris, Pharmacol Biochem Behav 1979;10:527-534; Erickson et al., Pharmacol Biochem Behav 1980;12:651-656). These results, which were never interpreted in connection to protein fragments or the function of sleep, may be accounted for by the FG hypothesis about molecular causation of sleep.
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Affiliation(s)
- Alexander Varshavsky
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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