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Chen YH, Lin S, Jin SY, Gao TM. Extracellular ATP Is a Homeostatic Messenger That Mediates Cell-Cell Communication in Physiological Processes and Psychiatric Diseases. Biol Psychiatry 2024:S0006-3223(24)01261-7. [PMID: 38679359 DOI: 10.1016/j.biopsych.2024.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 03/14/2024] [Accepted: 04/15/2024] [Indexed: 05/01/2024]
Abstract
Neuronal activity is the basis of information encoding and processing in the brain. During neuronal activation, intracellular ATP (adenosine triphosphate) is generated to meet the high-energy demands. Simultaneously, ATP is secreted, increasing the extracellular ATP concentration and acting as a homeostatic messenger that mediates cell-cell communication to prevent aberrant hyperexcitability of the nervous system. In addition to the confined release and fast synaptic signaling of classic neurotransmitters within synaptic clefts, ATP can be released by all brain cells, diffuses widely, and targets different types of purinergic receptors on neurons and glial cells, making it possible to orchestrate brain neuronal activity and participate in various physiological processes, such as sleep and wakefulness, learning and memory, and feeding. Dysregulation of extracellular ATP leads to a destabilizing effect on the neural network, as found in the etiopathology of many psychiatric diseases, including depression, anxiety, schizophrenia, and autism spectrum disorder. In this review, we summarize advances in the understanding of the mechanisms by which extracellular ATP serves as an intercellular signaling molecule to regulate neural activity, with a focus on how it maintains the homeostasis of neural networks. In particular, we also focus on neural activity issues that result from dysregulation of extracellular ATP and propose that aberrant levels of extracellular ATP may play a role in the etiopathology of some psychiatric diseases, highlighting the potential therapeutic targets of ATP signaling in the treatment of these psychiatric diseases. Finally, we suggest potential avenues to further elucidate the role of extracellular ATP in intercellular communication and psychiatric diseases.
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Affiliation(s)
- Yi-Hua Chen
- State Key Laboratory of Organ Failure Research, Key Laboratory of Mental Health of the Ministry of Education, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangdong-Hong Kong Joint Laboratory for Psychiatric Disorders, Guangdong Province Key Laboratory of Psychiatric Disorders, Guangdong Basic Research Center of Excellence for Integrated Traditional and Western Medicine for Qingzhi Diseases, Department of Neurobiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Song Lin
- Department of Physiology, School of Medicine, Jinan University, Guangzhou, China
| | - Shi-Yang Jin
- State Key Laboratory of Organ Failure Research, Key Laboratory of Mental Health of the Ministry of Education, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangdong-Hong Kong Joint Laboratory for Psychiatric Disorders, Guangdong Province Key Laboratory of Psychiatric Disorders, Guangdong Basic Research Center of Excellence for Integrated Traditional and Western Medicine for Qingzhi Diseases, Department of Neurobiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Tian-Ming Gao
- State Key Laboratory of Organ Failure Research, Key Laboratory of Mental Health of the Ministry of Education, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangdong-Hong Kong Joint Laboratory for Psychiatric Disorders, Guangdong Province Key Laboratory of Psychiatric Disorders, Guangdong Basic Research Center of Excellence for Integrated Traditional and Western Medicine for Qingzhi Diseases, Department of Neurobiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China.
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Caruso V, Zuccarini M, Di Iorio P, Muhammad I, Ronci M. Metabolic Changes Induced by Purinergic Signaling: Role in Food Intake. Front Pharmacol 2021; 12:655989. [PMID: 33995077 PMCID: PMC8117016 DOI: 10.3389/fphar.2021.655989] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 04/09/2021] [Indexed: 01/30/2023] Open
Abstract
The purinergic signalling has a well-established role in the regulation of energy homeostasis, but there is growing evidence of its implication in the control of food intake. In this review, we provide an integrative view of the molecular mechanisms leading to changes in feeding behaviour within hypothalamic neurons following purinergic receptor activation. We also highlight the importance of purinergic signalling in metabolic homeostasis and the possibility of targeting its receptors for therapeutic purposes.
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Affiliation(s)
- Vanni Caruso
- School of Pharmacy and Pharmacology, University of Tasmania, Hobart, TAS, Australia.,Institute for Research on Pain, ISAL-Foundation, Rimini, Italy
| | - Mariachiara Zuccarini
- Department of Medical, Oral and Biotechnological Sciences, University of Chieti-Pescara, Chieti, Italy.,Center for Advanced Studies and Technologies (CAST), University of Chieti-Pescara, Chieti, Italy
| | - Patrizia Di Iorio
- Department of Medical, Oral and Biotechnological Sciences, University of Chieti-Pescara, Chieti, Italy.,Center for Advanced Studies and Technologies (CAST), University of Chieti-Pescara, Chieti, Italy
| | - Ishaq Muhammad
- School of Pharmacy and Pharmacology, University of Tasmania, Hobart, TAS, Australia
| | - Maurizio Ronci
- Center for Advanced Studies and Technologies (CAST), University of Chieti-Pescara, Chieti, Italy.,Department of Pharmacy, University of Chieti-Pescara, Chieti, Italy
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Stofkova A, Murakami M. Neural activity regulates autoimmune diseases through the gateway reflex. Bioelectron Med 2019; 5:14. [PMID: 32232103 PMCID: PMC7098223 DOI: 10.1186/s42234-019-0030-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 07/18/2019] [Indexed: 12/15/2022] Open
Abstract
The brain, spinal cord and retina are protected from blood-borne compounds by the blood-brain barrier (BBB), blood-spinal cord barrier (BSCB) and blood-retina barrier (BRB) respectively, which create a physical interface that tightly controls molecular and cellular transport. The mechanical and functional integrity of these unique structures between blood vessels and nervous tissues is critical for maintaining organ homeostasis. To preserve the stability of these barriers, interplay between constituent barrier cells, such as vascular endothelial cells, pericytes, glial cells and neurons, is required. When any of these cells are defective, the barrier can fail, allowing blood-borne compounds to encroach neural tissues and cause neuropathologies. Autoimmune diseases of the central nervous system (CNS) and retina are characterized by barrier disruption and the infiltration of activated immune cells. Here we review our recent findings on the role of neural activity in the regulation of these barriers at the vascular endothelial cell level in the promotion of or protection against the development of autoimmune diseases. We suggest nervous system reflexes, which we named gateway reflexes, are fundamentally involved in these diseases. Although their reflex arcs are not completely understood, we identified the activation of specific sensory neurons or receptor cells to which barrier endothelial cells respond as effectors that regulate gateways for immune cells to enter the nervous tissue. We explain this novel mechanism and describe its role in neuroinflammatory conditions, including models of multiple sclerosis and posterior autoimmune uveitis.
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Affiliation(s)
- Andrea Stofkova
- 1Department of Physiology, Third Faculty of Medicine, Charles University, Prague, Czech Republic
- 2Division of Molecular Psychoimmunology, Institute for Genetic Medicine, Hokkaido University, Kita-15, Nishi-7, Kita-ku, Sapporo, 060-0815 Japan
| | - Masaaki Murakami
- 2Division of Molecular Psychoimmunology, Institute for Genetic Medicine, Hokkaido University, Kita-15, Nishi-7, Kita-ku, Sapporo, 060-0815 Japan
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4
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Pollatzek E, Hitzel N, Ott D, Raisl K, Reuter B, Gerstberger R. Functional expression of P2 purinoceptors in a primary neuroglial cell culture of the rat arcuate nucleus. Neuroscience 2016; 327:95-114. [PMID: 27072848 DOI: 10.1016/j.neuroscience.2016.04.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 04/06/2016] [Accepted: 04/06/2016] [Indexed: 12/22/2022]
Abstract
The arcuate nucleus (ARC) plays an important role in the hypothalamic control of energy homeostasis. Expression of various purinoceptor subtypes in the rat ARC and physiological studies suggest a modulatory function of P2 receptors within the neuroglial ARC circuitry. A differentiated mixed neuronal and glial microculture was therefore established from postnatal rat ARC, revealing neuronal expression of ARC-specific transmitters involved in food intake regulation (neuropeptide Y (NPY), proopiomelanocortin (POMC), tyrosine hydroxylase (TH)). Some NPYergic neurons cosynthesized TH, while POMC and TH expression proved to be mutually exclusive. Stimulation with the general purinoceptor agonists 2-methylthioadenosine-5'triphosphate (2-MeSATP) and ATP but not the P2X1/P2X3 receptor subtype agonist α,β-methyleneadenosine-5'triphosphate (α,β-meATP) induced intracellular calcium signals in ARC neurons and astrocytes. Some 5-10% each of 2-MeSATP responsive neurons expressed POMC, NYP or TH. Supporting the calcium imaging data, radioligand binding studies to hypothalamic membranes showed high affinity for 2-MeSATP, ATP but not α,β-meATP to displace [α-(35)S]deoxyadenosine-5'thiotriphosphate ([(35)S]dATPαS) from P2 receptors. Repetitive superfusion with equimolar 2-MeSATP allowed categorization of ARC cells into groups with a high or low (LDD) degree of purinoceptor desensitization, the latter allowing further receptor characterization. Calcium imaging experiments performed at 37°C vs. room temperature showed further reduction of desensitization. Agonist-mediated intracellular calcium signals were suppressed in all LDD neurons but only 25% of astrocytes in the absence of extracellular calcium, suggestive of metabotropic P2Y receptor expression in the majority of ARC astrocytes. The highly P2Y1-selective receptor agonists MRS2365 and 2-methylthioadenosine-5'diphosphate (2-MeSADP) activated 75-85% of all 2-MeSATP-responsive ARC astrocytes. Taking into consideration the high potency to dose-dependently stimulate ARC cells of the LDD group, the high affinity for rat P2X(1-3) and low affinity for rat P2X4, P2X7 and P2Y receptor subtypes except P2Y1 and P2Y13, the agonist 2-MeSATP primarily acted upon P2X2 and P2Y1 purinoceptors to trigger intracellular calcium signaling in ARC neurons and astrocytes.
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Affiliation(s)
- Eric Pollatzek
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Norma Hitzel
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Daniela Ott
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Katrin Raisl
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Bärbel Reuter
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Rüdiger Gerstberger
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
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Salgado M, Tarifeño-Saldivia E, Ordenes P, Millán C, Yañez MJ, Llanos P, Villagra M, Elizondo-Vega R, Martínez F, Nualart F, Uribe E, de los Angeles García-Robles M. Dynamic localization of glucokinase and its regulatory protein in hypothalamic tanycytes. PLoS One 2014; 9:e94035. [PMID: 24739934 PMCID: PMC3989220 DOI: 10.1371/journal.pone.0094035] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 03/11/2014] [Indexed: 11/28/2022] Open
Abstract
Glucokinase (GK), the hexokinase involved in glucose sensing in pancreatic β cells, is also expressed in hypothalamic tanycytes, which cover the ventricular walls of the basal hypothalamus and are implicated in an indirect control of neuronal activity by glucose. Previously, we demonstrated that GK was preferentially localized in tanycyte nuclei in euglycemic rats, which has been reported in hepatocytes and is suggestive of the presence of the GK regulatory protein, GKRP. In the present study, GK intracellular localization in hypothalamic and hepatic tissues of the same rats under several glycemic conditions was compared using confocal microscopy and Western blot analysis. In the hypothalamus, increased GK nuclear localization was observed in hyperglycemic conditions; however, it was primarily localized in the cytoplasm in hepatic tissue under the same conditions. Both GK and GKRP were next cloned from primary cultures of tanycytes. Expression of GK by Escherichia coli revealed a functional cooperative protein with a S0.5 of 10 mM. GKRP, expressed in Saccharomyces cerevisiae, inhibited GK activity in vitro with a Ki 0.2 µM. We also demonstrated increased nuclear reactivity of both GK and GKRP in response to high glucose concentrations in tanycyte cultures. These data were confirmed using Western blot analysis of nuclear extracts. Results indicate that GK undergoes short-term regulation by nuclear compartmentalization. Thus, in tanycytes, GK can act as a molecular switch to arrest cellular responses to increased glucose.
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Affiliation(s)
- Magdiel Salgado
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Estefanía Tarifeño-Saldivia
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Patricio Ordenes
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Carola Millán
- Facultad de Artes Liberales, Universidad Adolfo Ibañez, Viña del Mar, Chile
| | - María José Yañez
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Paula Llanos
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Marcos Villagra
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Roberto Elizondo-Vega
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Fernando Martínez
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Francisco Nualart
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Elena Uribe
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
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6
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Orellana JA, Sáez PJ, Cortés-Campos C, Elizondo RJ, Shoji KF, Contreras-Duarte S, Figueroa V, Velarde V, Jiang JX, Nualart F, Sáez JC, García MA. Glucose increases intracellular free Ca(2+) in tanycytes via ATP released through connexin 43 hemichannels. Glia 2011; 60:53-68. [PMID: 21987367 DOI: 10.1002/glia.21246] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 08/26/2011] [Accepted: 08/31/2011] [Indexed: 11/10/2022]
Abstract
The ventromedial hypothalamus is involved in regulating feeding and satiety behavior, and its neurons interact with specialized ependymal-glial cells, termed tanycytes. The latter express glucose-sensing proteins, including glucose transporter 2, glucokinase, and ATP-sensitive K(+) (K(ATP) ) channels, suggesting their involvement in hypothalamic glucosensing. Here, the transduction mechanism involved in the glucose-induced rise of intracellular free Ca(2+) concentration ([Ca(2+) ](i) ) in cultured β-tanycytes was examined. Fura-2AM time-lapse fluorescence images revealed that glucose increases the intracellular Ca(2+) signal in a concentration-dependent manner. Glucose transportation, primarily via glucose transporters, and metabolism via anaerobic glycolysis increased connexin 43 (Cx43) hemichannel activity, evaluated by ethidium uptake and whole cell patch clamp recordings, through a K(ATP) channel-dependent pathway. Consequently, ATP export to the extracellular milieu was enhanced, resulting in activation of purinergic P2Y(1) receptors followed by inositol trisphosphate receptor activation and Ca(2+) release from intracellular stores. The present study identifies the mechanism by which glucose increases [Ca(2+) ](i) in tanycytes. It also establishes that Cx43 hemichannels can be rapidly activated under physiological conditions by the sequential activation of glucosensing proteins in normal tanycytes.
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Affiliation(s)
- Juan A Orellana
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile.
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7
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Colldén G, Mangano C, Meister B. P2X2 purinoreceptor protein in hypothalamic neurons associated with the regulation of food intake. Neuroscience 2010; 171:62-78. [DOI: 10.1016/j.neuroscience.2010.08.036] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Revised: 08/06/2010] [Accepted: 08/18/2010] [Indexed: 10/19/2022]
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8
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Rozlosnik N. New directions in medical biosensors employing poly(3,4-ethylenedioxy thiophene) derivative-based electrodes. Anal Bioanal Chem 2009; 395:637-45. [PMID: 19644677 DOI: 10.1007/s00216-009-2981-8] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2009] [Revised: 07/14/2009] [Accepted: 07/15/2009] [Indexed: 01/27/2023]
Abstract
Demand is growing in the field of medical diagnostics for simple, disposable devices that also demonstrate fast response times, are easy to handle, are cost-efficient, and are suitable for mass production. Polymer-based microfluidic devices meet the requirements of cost efficiency and mass production and they are suitable for biosensor applications. Conducting polymer-based electrochemical sensors have shown numerous advantages in a number of areas related to human health, such as the diagnosis of infectious diseases, genetic mutations, drug discovery, forensics and food technology, due to their simplicity and high sensitivity. One of the most promising group of conductive polymers is poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives due to their attractive properties: high stability, high conductivity (up to 400-600 S/cm) and high transparency. This review paper summarizes newly developed methods associated with the application of PEDOT to diagnostic sensing.
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Affiliation(s)
- Noemi Rozlosnik
- Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads, Bygning 345e, DK-2800, Kgs. Lyngby, Denmark.
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Adenosine 5′-triphosphate incorporated poly(3,4-ethylenedioxythiophene) modified electrode: a bioactive platform with electroactivity, stability and biocompatibility. J APPL ELECTROCHEM 2008. [DOI: 10.1007/s10800-008-9623-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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10
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Kodama N, Funahashi M, Mitoh Y, Minagi S, Matsuo R. Purinergic modulation of area postrema neuronal excitability in rat brain slices. Brain Res 2007; 1165:50-9. [PMID: 17658494 DOI: 10.1016/j.brainres.2007.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Revised: 05/31/2007] [Accepted: 06/02/2007] [Indexed: 10/23/2022]
Abstract
ATP has been shown to excite neurons in various regions of the central nervous system. Whereas immunohistochemical studies show P2X receptors in the area postrema, the responsiveness of area postrema neurons to extracellular ATP has not been studied. To investigate the effects of purinoceptor activation on area postrema neuronal excitability, we performed whole-cell recordings from area postrema neurons in rat brain slices. Most area postrema neurons responded to ATP application, and most responses were excitatory. Voltage-clamp recordings showed three different types of response: (1) a postsynaptic or extrasynaptic excitatory response (inward currents; n=26/51 cells), (2) a presynaptic excitatory response (increased frequency of miniature excitatory postsynaptic currents with only a small direct postsynaptic current; n=24/51 cells, or (3) a postsynaptic inhibitory response (outward current; n=1/51). The excitatory responses were found in both of the two major electrophysiological cell classes, i.e. cells displaying I(h) and cells not displaying I(h), while the inhibitory responses were found in only cells not displaying I(h). Current-clamp recordings showed ATP-induced depolarization (n=13/15) or hyperpolarization (n=2/15) of membrane potential that modulated the frequency of action potentials. In the presence of CNQX, mEPSCs were abolished and bath-applied ATP did not generate mEPSCs, indicating that glutamate release was facilitated by the activation of presynaptically located ATP receptors. Our pharmacological results from studies with ATP, alphabetame-ATP, betame-ATP and PPADS indicate that the post- and/or extrasynaptic responses are most likely mediated by P2X(7) receptors and/or receptors composed of P2X(2) and P2X(5) subunits. We conclude that half of the presynaptic responses are most likely mediated by P2X(7) receptors and/or receptors composed of P2X(2) and P2X(5) subunits while the others also contain P2X(1) subunits. It is well known that P2X(7) subunit forms only homomultimeric P2X receptors. Finally, the present study suggests that purinoceptor activation may contribute to the control of several autonomic functions by area postrema neurons.
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Affiliation(s)
- Naoki Kodama
- Department of Occlusal and Oral Functional Rehabilitation, Okayama University Graduate School of Medicine, Dentistry & Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8525, Japan.
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Kim DS, Kwak SE, Kim JE, Won MH, Kang TC. The co-treatments of vigabatrin and P2X receptor antagonists protect ischemic neuronal cell death in the gerbil hippocampus. Brain Res 2006; 1120:151-60. [PMID: 16979598 DOI: 10.1016/j.brainres.2006.08.057] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 08/12/2006] [Accepted: 08/15/2006] [Indexed: 10/24/2022]
Abstract
During transient global ischemia, the excessive accumulation of intracellular Ca2+ induced by several episodes triggers delayed neuronal death within the vulnerable CA1 region of the hippocampus after ischemia-reperfusion insults. Although P2X receptors provide an additional source of Ca2+ entry, little data are available that these receptors could modulate the performance of the ischemic neuronal death. Therefore, we investigated the roles of the P2X receptor in the ischemic neuronal damage associated with various sequelae of transient ischemia, and the effects of their antagonist on the ischemic insults. As the results, ischemic insults increased P2X receptor expression in the gerbil hippocampus. Neither vigabatrin (VGB) nor P2X receptor antagonists (suramin, pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid) protected against the delayed neuronal death in the CA1 region of the hippocampus after ischemia. However, the co-treatments of VGB and P2X receptor antagonists effectively prevent ischemia-induced neurodegeneration. Therefore, these findings suggest that blockade of the P2X receptor accompanied by activation of GABAergic inhibition may play an important role in the neuroprotection against ischemic insults.
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Affiliation(s)
- Duk-Soo Kim
- Department of Anatomy, College of Medicine, Hallym University, Chunchon, Kangwon-Do 200-702, South Korea
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12
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Florenzano F, Viscomi MT, Mercaldo V, Longone P, Bernardi G, Bagni C, Molinari M, Carrive P. P2X2R purinergic receptor subunit mRNA and protein are expressed by all hypothalamic hypocretin/orexin neurons. J Comp Neurol 2006; 498:58-67. [PMID: 16856176 DOI: 10.1002/cne.21013] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Neurophysiologic data suggest that orexin neurons are directly excited by ATP through purinergic receptors (P2XR). Anatomical studies, though reporting P2XR in the hypothalamus, did not describe it in the perifornical hypothalamic area, where orexinergic neurons are located. Here we report the presence of the P2X(2)R subunit in the rat perifornical hypothalamus and demonstrate that hypothalamic orexin neurons express the P2X(2)R. Double immunohistochemistry showed that virtually all orexin-immunoreactive neurons are also P2X(2)R immunoreactive, whereas 80% of P2X(2)R-immunoreactive neurons are also orexin positive. Triple-labeling experiments, combining fluorescence in situ hybridization for P2X(2)R mRNA and P2X(2)R/orexin double immunofluorescence, confirmed these findings. In addition, in situ hybridization demonstrated that P2X(2)R mRNA is localized in cellular processes of orexinergic neurons. The present data support neurophysiologic findings on ATP modulation of orexinergic function and provide direct evidence that the entire population of orexin neurons expresses a P2XR subtype, namely, P2X(2)R. Thus, purinergic transmission might intervene in modulating key functions known to be controlled by the orexinergic system, such as feeding behavior and arousal.
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Abstract
The concept of a purinergic signaling system, using purine nucleotides and nucleosides as extracellular messengers, was first proposed over 30 years ago. After a brief introduction and update of purinoceptor subtypes, this article focuses on the diverse pathophysiological roles of purines and pyrimidines as signaling molecules. These molecules mediate short-term (acute) signaling functions in neurotransmission, mechanosensory transduction, secretion and vasodilatation, and long-term (chronic) signaling functions in cell proliferation, differentiation, and death involved in development and regeneration. Plasticity of purinoceptor expression in pathological conditions is frequently observed, including an increase in the purinergic component of autonomic cotransmission. Recent advances in therapies using purinergic-related drugs in a wide range of pathological conditions will be addressed with speculation on future developments in the field.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, Royal Free and University College Medical School, London NW3 2PF, UK.
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14
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Wollmann G, Acuna-Goycolea C, van den Pol AN. Direct Excitation of Hypocretin/Orexin Cells by Extracellular ATP at P2X Receptors. J Neurophysiol 2005; 94:2195-206. [PMID: 15958604 DOI: 10.1152/jn.00035.2005] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypocretin/orexin (hcrt) neurons play an important role in hypothalamic arousal and energy homeostasis. ATP may be released by neurons or glia or by pathological conditions. Here we studied the effect of extracellular ATP on hypocretin cells using whole cell patch-clamp recording in hypothalamic slices of transgenic mice expressing green fluorescent protein (GFP) exclusively in hcrt-producing cells. Local application of ATP induced a dose-dependent increase in spike frequency. In the presence of TTX, ATP (100 μM) depolarized the cells by 7.8 ± 1.2 mV. In voltage clamp under blockade of synaptic activity with the GABAA receptor antagonist bicuculline, and ionotropic glutamate receptor antagonists dl-2-amino-5-phosphonopentanoic acid (AP-5) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), ATP (100 μM) evoked an 18 pA inward current. The inward current was blocked by extracellular choline substitution for Na+, had a reversal potential of −27 mV, and was not affected by nominally Ca2+-free external buffer, suggesting that ATP activated a nonselective cation current. All excitatory effects of ATP showed rapid attenuation. ATP-induced excitatory actions were mimicked by nonhydrolyzable ATP-γ-S but not by α,β-MeATP and inhibited by the purinoceptor antagonists suramin and pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) tetrasodium salt (PPADS). The current was potentiated by a decrease in bath pH, suggesting P2X2 subunit involvement. Frequency and amplitude of spontaneous and miniature synaptic events were not altered by ATP. Suramin, but not PPADS, caused a small suppression of evoked excitatory synaptic potentials. Together, these results show a depolarizing response to extracellular ATP that would lead to an increased activity of the hypocretin arousal system.
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Affiliation(s)
- Guido Wollmann
- Department of Neurosurgery, Yale University School of Medicine, 333 Cedar St., New Haven, Connecticut 06520, USA
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