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Missaghi K, Le Gal JP, Mercier J, Grover M, Beauséjour PA, Chartré S, Messihad O, Auclair F, Dubuc R. Revisiting the two rhythm generators for respiration in lampreys. Front Neuroanat 2024; 17:1270535. [PMID: 38250023 PMCID: PMC10796688 DOI: 10.3389/fnana.2023.1270535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 11/17/2023] [Indexed: 01/23/2024] Open
Abstract
In lampreys, respiration consists of a fast and a slow rhythm. This study was aimed at characterizing both anatomically and physiologically the brainstem regions involved in generating the two rhythms. The fast rhythm generator has been located by us and others in the rostral hindbrain, rostro-lateral to the trigeminal motor nucleus. More recently, this was challenged by researchers reporting that the fast rhythm generator was located more rostrally and dorsomedially, in a region corresponding to the mesencephalic locomotor region. These contradictory observations made us re-examine the location of the fast rhythm generator using anatomical lesions and physiological recordings. We now confirm that the fast respiratory rhythm generator is in the rostro-lateral hindbrain as originally described. The slow rhythm generator has received less attention. Previous studies suggested that it was composed of bilateral, interconnected rhythm generating regions located in the caudal hindbrain, with ascending projections to the fast rhythm generator. We used anatomical and physiological approaches to locate neurons that could be part of this slow rhythm generator. Combinations of unilateral injections of anatomical tracers, one in the fast rhythm generator area and another in the lateral tegmentum of the caudal hindbrain, were performed to label candidate neurons on the non-injected side of the lateral tegmentum. We found a population of neurons extending from the facial to the caudal vagal motor nuclei, with no clear clustering in the cell distribution. We examined the effects of stimulating different portions of the labeled population on the respiratory activity. The rostro-caudal extent of the population was arbitrarily divided in three portions that were each stimulated electrically or chemically. Stimulation of either of the three sites triggered bursts of discharge characteristic of the slow rhythm, whereas inactivating any of them stopped the slow rhythm. Substance P injected locally in the lateral tegmentum accelerated the slow respiratory rhythm in a caudal hindbrain preparation. Our results show that the fast respiratory rhythm generator consists mostly of a population of neurons rostro-lateral to the trigeminal motor nucleus, whereas the slow rhythm generator is distributed in the lateral tegmentum of the caudal hindbrain.
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Affiliation(s)
- Kianoush Missaghi
- Département de Neurosciences, Université de Montréal, Montréal, QC, Canada
| | | | - Julien Mercier
- Département de Neurosciences, Université de Montréal, Montréal, QC, Canada
- Groupe de Recherche en Activité Physique Adaptée (GRAPA), Département des Sciences de l’Activité Physique, Université du Québec à Montréal, Montréal, QC, Canada
| | - Martin Grover
- Groupe de Recherche en Activité Physique Adaptée (GRAPA), Département des Sciences de l’Activité Physique, Université du Québec à Montréal, Montréal, QC, Canada
| | | | - Shannon Chartré
- Groupe de Recherche en Activité Physique Adaptée (GRAPA), Département des Sciences de l’Activité Physique, Université du Québec à Montréal, Montréal, QC, Canada
| | - Omima Messihad
- Département de Neurosciences, Université de Montréal, Montréal, QC, Canada
| | - François Auclair
- Département de Neurosciences, Université de Montréal, Montréal, QC, Canada
| | - Réjean Dubuc
- Département de Neurosciences, Université de Montréal, Montréal, QC, Canada
- Groupe de Recherche en Activité Physique Adaptée (GRAPA), Département des Sciences de l’Activité Physique, Université du Québec à Montréal, Montréal, QC, Canada
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2
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Turk AZ, Millwater M, SheikhBahaei S. Whole-brain analysis of CO 2 chemosensitive regions and identification of the retrotrapezoid and medullary raphé nuclei in the common marmoset ( Callithrix jacchus). BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.26.558361. [PMID: 37986845 PMCID: PMC10659419 DOI: 10.1101/2023.09.26.558361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Respiratory chemosensitivity is an important mechanism by which the brain senses changes in blood partial pressure of CO2 (PCO2). It is proposed that special neurons (and astrocytes) in various brainstem regions play key roles as CO2 central respiratory chemosensors in rodents. Although common marmosets (Callithrix jacchus), New-World non-human primates, show similar respiratory responses to elevated inspired CO2 as rodents, the chemosensitive regions in marmoset brain have not been defined yet. Here, we used c-fos immunostainings to identify brain-wide CO2-activated brain regions in common marmosets. In addition, we mapped the location of the retrotrapezoid nucleus (RTN) and raphé nuclei in the marmoset brainstem based on colocalization of CO2-induced c-fos immunoreactivity with Phox2b, and TPH immunostaining, respectively. Our data also indicated that, similar to rodents, marmoset RTN astrocytes express Phox2b and have complex processes that create a meshwork structure at the ventral surface of medulla. Our data highlight some cellular and structural regional similarities in brainstem of the common marmosets and rodents.
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Affiliation(s)
- Ariana Z. Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Marissa Millwater
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
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3
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Gonye EC, Bayliss DA. Criteria for central respiratory chemoreceptors: experimental evidence supporting current candidate cell groups. Front Physiol 2023; 14:1241662. [PMID: 37719465 PMCID: PMC10502317 DOI: 10.3389/fphys.2023.1241662] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 08/16/2023] [Indexed: 09/19/2023] Open
Abstract
An interoceptive homeostatic system monitors levels of CO2/H+ and provides a proportionate drive to respiratory control networks that adjust lung ventilation to maintain physiologically appropriate levels of CO2 and rapidly regulate tissue acid-base balance. It has long been suspected that the sensory cells responsible for the major CNS contribution to this so-called respiratory CO2/H+ chemoreception are located in the brainstem-but there is still substantial debate in the field as to which specific cells subserve the sensory function. Indeed, at the present time, several cell types have been championed as potential respiratory chemoreceptors, including neurons and astrocytes. In this review, we advance a set of criteria that are necessary and sufficient for definitive acceptance of any cell type as a respiratory chemoreceptor. We examine the extant evidence supporting consideration of the different putative chemoreceptor candidate cell types in the context of these criteria and also note for each where the criteria have not yet been fulfilled. By enumerating these specific criteria we hope to provide a useful heuristic that can be employed both to evaluate the various existing respiratory chemoreceptor candidates, and also to focus effort on specific experimental tests that can satisfy the remaining requirements for definitive acceptance.
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Affiliation(s)
- Elizabeth C. Gonye
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States
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4
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Lavezzi AM, Pusiol T, Paradiso B. Harmful Effect of Intrauterine Smoke Exposure on Neuronal Control of "Fetal Breathing System" in Stillbirths. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19074164. [PMID: 35409845 PMCID: PMC8999022 DOI: 10.3390/ijerph19074164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 03/29/2022] [Accepted: 03/30/2022] [Indexed: 02/04/2023]
Abstract
This article is aimed to contribute to the current knowledge on the role of toxic substances such as nicotine on sudden intrauterine unexplained deaths’ (SIUDS’) pathogenetic mechanisms. The in-depth histopathological examination of the autonomic nervous system in wide groups of victims of SIUDS (47 cases) and controls (20 cases), with both smoking and no-smoking mothers, highlighted the frequent presence of the hypodevelopment of brainstem structures checking the vital functions. In particular, the hypoplasia of the pontine parafacial nucleus together with hypoplastic lungs for gestational age were observed in SIUDS cases with mothers who smoked cigarettes, including electronic ones. The results allow us to assume that the products of cigarette smoke during pregnancy can easily cross the placental barrier, thus entering the fetal circulation and damaging the most sensitive organs, such as lungs and brain. In a non-negligible percentage of SIUDS, the mothers did not smoke. Furthermore, based on previous and ongoing studies conducted through analytical procedures and the use of scanning electron microscopy, the authors envisage the involvement of toxic nanoparticles (such as agricultural pesticides and nanomaterials increasingly used in biomedicine, bioscience and biotechnology) in the death pathogenesis, with similar mechanisms to those of nicotine.
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Affiliation(s)
- Anna M. Lavezzi
- “Lino Rossi” Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20121 Milan, Italy;
- Correspondence:
| | - Teresa Pusiol
- Institute of Anatomic Pathology, APSS, 38122 Trento, Italy;
| | - Beatrice Paradiso
- “Lino Rossi” Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20121 Milan, Italy;
- General Pathology Unit, Dolo Hospital, 30031 Dolo, Italy
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5
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Smith JC. Respiratory rhythm and pattern generation: Brainstem cellular and circuit mechanisms. HANDBOOK OF CLINICAL NEUROLOGY 2022; 188:1-35. [PMID: 35965022 DOI: 10.1016/b978-0-323-91534-2.00004-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Breathing movements in mammals are driven by rhythmic neural activity automatically generated within spatially and functionally organized brainstem neural circuits comprising the respiratory central pattern generator (CPG). This chapter reviews up-to-date experimental information and theoretical studies of the cellular and circuit mechanisms of respiratory rhythm and pattern generation operating within critical components of this CPG in the lower brainstem. Over the past several decades, there have been substantial advances in delineating the spatial architecture of essential medullary regions and their regional cellular and circuit properties required to understand rhythm and pattern generation mechanisms. A fundamental concept is that the circuits in these regions have rhythm-generating capabilities at multiple cellular and circuit organization levels. The regional cellular properties, circuit organization, and control mechanisms allow flexible expression of neural activity patterns for a repertoire of respiratory behaviors under various physiologic conditions that are dictated by requirements for homeostatic regulation and behavioral integration. Many mechanistic insights have been provided by computational modeling studies driven by experimental results and have advanced understanding in the field. These conceptual and theoretical developments are discussed.
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Affiliation(s)
- Jeffrey C Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States.
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6
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Astrocytic contribution to glutamate-related central respiratory chemoreception in vertebrates. Respir Physiol Neurobiol 2021; 294:103744. [PMID: 34302992 DOI: 10.1016/j.resp.2021.103744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/01/2021] [Accepted: 07/18/2021] [Indexed: 12/24/2022]
Abstract
Central respiratory chemoreceptors play a key role in the respiratory homeostasis by sensing CO2 and H+ in brain and activating the respiratory neural network. This ability of specific brain regions to respond to acidosis and hypercapnia is based on neuronal and glial mechanisms. Several decades ago, glutamatergic transmission was proposed to be involved as a main mechanism in central chemoreception. However, a complete identification of mechanism has been elusive. At the rostral medulla, chemosensitive neurons of the retrotrapezoid nucleus (RTN) are glutamatergic and they are stimulated by ATP released by RTN astrocytes in response to hypercapnia. In addition, recent findings show that caudal medullary astrocytes in brainstem can also contribute as CO2 and H+ sensors that release D-serine and glutamate, both gliotransmitters able to activate the respiratory neural network. In this review, we describe the mammalian astrocytic glutamatergic contribution to the central respiratory chemoreception trying to trace in vertebrates the emergence of several components involved in this process.
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7
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Katsuki S, Ikeda K, Onimaru H, Dohi K, Izumizaki M. Effects of acetylcholine on hypoglossal and C4 nerve activity in brainstem-spinal cord preparations from newborn rat. Respir Physiol Neurobiol 2021; 293:103737. [PMID: 34229065 DOI: 10.1016/j.resp.2021.103737] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 06/17/2021] [Accepted: 07/01/2021] [Indexed: 11/17/2022]
Abstract
Effects of acetylcholine (ACh) on respiratory activity have been an intriguing theme especially in relation to central chemoreception and the control of hypoglossal nerve activity. We studied the effects of ACh on hypoglossal and phrenic (C4) nerve activities and inspiratory and pre-inspiratory neurons in the rostral ventrolateral medulla in brainstem-spinal cord preparations from newborn rats. ACh application increased respiratory rhythm, decreased inspiratory hypoglossal and C4 nerve burst amplitude, and enhanced pre-inspiratory hypoglossal activity. ACh induced membrane depolarization of pre-inspiratory neurons that might be involved in facilitation of respiratory rhythm by ACh. Effects of ACh on hypoglossal and C4 nerve activity were partially reversed by a nicotinic receptor blocker, mecamylamine. Further application of a muscarinic receptor antagonist, oxybutynin, resulted in slight increase of hypoglossal (but not C4) burst amplitude. Thus, ACh induced different effects on hypoglossal and C4 nerve activity in the brainstem-spinal cord preparation.
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Affiliation(s)
- Shino Katsuki
- Department of Physiology, Showa University School of Medicine, Tokyo 142-8555, Japan; Department of Emergency, Disaster and Critical Care Medicine, Showa University, Tokyo 142-8555, Japan
| | - Keiko Ikeda
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, Tokyo 142-8555, Japan.
| | - Kenji Dohi
- Department of Emergency, Disaster and Critical Care Medicine, Showa University, Tokyo 142-8555, Japan
| | - Masahiko Izumizaki
- Department of Physiology, Showa University School of Medicine, Tokyo 142-8555, Japan
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8
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Onimaru H, Yazawa I, Takeda K, Fukushi I, Okada Y. Calcium Imaging Analysis of Cellular Responses to Hypercapnia and Hypoxia in the NTS of Newborn Rat Brainstem Preparation. Front Physiol 2021; 12:645904. [PMID: 33841182 PMCID: PMC8027497 DOI: 10.3389/fphys.2021.645904] [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: 12/24/2020] [Accepted: 03/08/2021] [Indexed: 01/13/2023] Open
Abstract
It is supposed that the nucleus of the solitary tract (NTS) in the dorsal medulla includes gas sensor cells responsive to hypercapnia or hypoxia in the central nervous system. In the present study, we analyzed cellular responses to hypercapnia and hypoxia in the NTS region of newborn rat in vitro preparation. The brainstem and spinal cord were isolated from newborn rat (P0-P4) and were transversely cut at the level of the rostral area postrema. To detect cellular responses, calcium indicator Oregon Green was pressure-injected into the NTS just beneath the cut surface of either the caudal or rostral block of the medulla, and the preparation was superfused with artificial cerebrospinal fluid (25–26°C). We examined cellular responses initially to hypercapnic stimulation (to 8% CO2 from 2% CO2) and then to hypoxic stimulation (to 0% O2 from 95% O2 at 5% CO2). We tested these responses in standard solution and in two different synapse blockade solutions: (1) cocktail blockers solution including bicuculline, strychnine, NBQX and MK-801 or (2) TTX solution. At the end of the experiments, the superfusate potassium concentration was lowered to 0.2 from 3 mM to classify recorded cells into neurons and astrocytes. Excitation of cells was detected as changes of fluorescence intensity with a confocal calcium imaging system. In the synaptic blockade solutions (cocktail or TTX solution), 7.6 and 8% of the NTS cells responded to hypercapnic and hypoxic stimulation, respectively, and approximately 2% of them responded to both stimulations. Some of these cells responded to low K+, and they were classified into astrocytes comprising 43% hypercapnia-sensitive cells, 56% hypoxia-sensitive cells and 54% of both stimulation-sensitive cells. Of note, 49% of the putative astrocytes identified by low K+ stimulation were sensitive to hypercapnia, hypoxia or both. In the presence of a glia preferential blocker, 5 mM fluoroacetate (plus 0.5 μM TTX), the percentage of hypoxia-sensitive cells was significantly reduced compared to those of all other conditions. This is the first study to reveal that the NTS includes hypercapnia and hypoxia dual-sensitive cells. These results suggest that astrocytes in the NTS region could act as a central gas sensor.
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Affiliation(s)
- Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, Tokyo, Japan
| | - Itaru Yazawa
- Global Research Center for Innovative Life Science, Hoshi University School of Pharmacy and Pharmaceutical Sciences, Tokyo, Japan
| | - Kotaro Takeda
- Faculty of Rehabilitation, School of Healthcare, Fujita Health University, Toyoake, Japan
| | - Isato Fukushi
- Faculty of Health Sciences, Uekusa Gakuen University, Chiba, Japan.,Clinical Research Center, Murayama Medical Center, Musashimurayama, Japan
| | - Yasumasa Okada
- Clinical Research Center, Murayama Medical Center, Musashimurayama, Japan
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9
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Lei F, Wang W, Fu Y, Wang J, Zheng Y. Oxidative stress in retrotrapezoid nucleus/parafacial respiratory group and impairment of central chemoreception in rat offspring exposed to maternal cigarette smoke. Reprod Toxicol 2021; 100:35-41. [PMID: 33383163 DOI: 10.1016/j.reprotox.2020.12.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 12/16/2020] [Accepted: 12/19/2020] [Indexed: 02/05/2023]
Abstract
We have reported that smoking during pregnancy is associated with deficit in neonatal central chemoreception. However, the underlying mechanism is not well clarified. In this study, we developed a rat model of maternal cigarette smoke (CS) exposure. Pregnant rats were exposed to CS during gestational day 1-20. Offspring were studied on postnatal day 2. Reactive oxygen species (ROS) content and expressions of antioxidant proteins in retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG) were examined by fluorogenic dye MitoSOX™ Red and Western blotting, respectively. The response of hypoglossal rootlets discharge to acidification was also detected with micro-injection of H2O2 into RTN/pFRG of offspring brainstem slices in vitro. Results showed that maternal CS exposure led to an increase in ROS production, and brought about decreases in mitochondrial superoxide dismutase and Kelch-like ECH-associated protein-1, and an increase in NF-E2-related factor 2 in offspring RTN/pFRG. Catalase and glutathione reductase expressions were not significantly changed. Moreover, oxidative stress induced by micro-injection of H2O2 into RTN/pFRG in vitro inhibited the discharge response of hypoglossal rootlets to acidification. These findings suggest that maternal CS exposure results in oxidative stress in RTN/pFRG of rat offspring, which might play a role in the impairment of central chemoreception.
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Affiliation(s)
- Fang Lei
- West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, PR China; Department of Physiology, West China School of Basic Medical Sciences and Forensic Medicine, Sichuan University, Chengdu, 610041, Sichuan, PR China
| | - Wen Wang
- Department of Physiology, West China School of Basic Medical Sciences and Forensic Medicine, Sichuan University, Chengdu, 610041, Sichuan, PR China
| | - Yating Fu
- Department of Physiology, West China School of Basic Medical Sciences and Forensic Medicine, Sichuan University, Chengdu, 610041, Sichuan, PR China
| | - Ji Wang
- Department of Physiology, West China School of Basic Medical Sciences and Forensic Medicine, Sichuan University, Chengdu, 610041, Sichuan, PR China
| | - Yu Zheng
- Department of Physiology, West China School of Basic Medical Sciences and Forensic Medicine, Sichuan University, Chengdu, 610041, Sichuan, PR China.
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10
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Patterson KC, Kahanovitch U, Gonçalves CM, Hablitz JJ, Staruschenko A, Mulkey DK, Olsen ML. K ir 5.1-dependent CO 2 /H + -sensitive currents contribute to astrocyte heterogeneity across brain regions. Glia 2021; 69:310-325. [PMID: 32865323 PMCID: PMC8665280 DOI: 10.1002/glia.23898] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 07/24/2020] [Accepted: 07/26/2020] [Indexed: 09/19/2023]
Abstract
Astrocyte heterogeneity is an emerging concept in which astrocytes within or between brain regions show variable morphological and/or gene expression profiles that presumably reflect different functional roles. Recent evidence indicates that retrotrapezoid nucleus (RTN) astrocytes sense changes in tissue CO2/ H+ to regulate respiratory activity; however, mechanism(s) by which they do so remain unclear. Alterations in inward K+ currents represent a potential mechanism by which CO2 /H+ signals may be conveyed to neurons. Here, we use slice electrophysiology in rats of either sex to show that RTN astrocytes intrinsically respond to CO2 /H+ by inhibition of an inward rectifying potassium (Kir ) conductance and depolarization of the membrane, while cortical astrocytes do not exhibit such CO2 /H+ -sensitive properties. Application of Ba2+ mimics the effect of CO2 /H+ on RTN astrocytes as measured by reductions in astrocyte Kir -like currents and increased RTN neuronal firing. These CO2 /H+ -sensitive currents increase developmentally, in parallel to an increased expression in Kir 4.1 and Kir 5.1 in the brainstem. Finally, the involvement of Kir 5.1 in the CO2 /H+ -sensitive current was verified using a Kir5.1 KO rat. These data suggest that Kir inhibition by CO2 /H+ may govern the degree to which astrocytes mediate downstream chemoreceptive signaling events through cell-autonomous mechanisms. These results identify Kir channels as potentially important regional CO2 /H+ sensors early in development, thus expanding our understanding of how astrocyte heterogeneity may uniquely support specific neural circuits and behaviors.
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Affiliation(s)
- Kelsey C Patterson
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
| | - Uri Kahanovitch
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | | | - John J Hablitz
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
| | - Alexander Staruschenko
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT 06269, USA
| | - Michelle L Olsen
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
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11
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Zhang M, Du S, Ou H, Cui R, Jiang N, Lin Y, Ge R, Ma D, Zhang J. Ablation of Zfhx4 results in early postnatal lethality by disrupting the respiratory center in mice. J Mol Cell Biol 2021; 13:210-224. [PMID: 33475140 PMCID: PMC8260053 DOI: 10.1093/jmcb/mjaa081] [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: 03/10/2020] [Revised: 11/19/2020] [Accepted: 12/07/2020] [Indexed: 01/29/2023] Open
Abstract
Breathing is an integrated motor behavior that is driven and controlled by a network of brainstem neurons. Zfhx4 is a zinc finger transcription factor and our results showed that it was specifically expressed in several regions of the mouse brainstem. Mice lacking Zfhx4 died shortly after birth from an apparent inability to initiate respiration. We also found that the electrical rhythm of brainstem‒spinal cord preparations was significantly depressed in Zfhx4-null mice compared to wild-type mice. Immunofluorescence staining revealed that Zfhx4 was coexpressed with Phox2b and Math1 in the brainstem and that Zfhx4 ablation greatly decreased the expression of these proteins, especially in the retrotrapezoid nucleus. Combined ChIP‒seq and mRNA expression microarray analysis identified Phox2b as the direct downstream target gene of Zfhx4, and this finding was validated by ChIP‒qPCR. Previous studies have reported that both Phox2b and Math1 play key roles in the development of the respiratory center, and Phox2b and Math1 knockout mice are neonatal lethal due to severe central apnea. On top of this, our study revealed that Zfhx4 is a critical regulator of Phox2b expression and essential for perinatal breathing.
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Affiliation(s)
- Meiqin Zhang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences & Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Sichen Du
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences & Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Huayuan Ou
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences & Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Renjie Cui
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences & Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Nan Jiang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences & Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Yifeng Lin
- Children's Hospital, Fudan University, Shanghai 201102, China
| | - Runsheng Ge
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences & Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Duan Ma
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences & Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China.,Children's Hospital, Fudan University, Shanghai 201102, China
| | - Jin Zhang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences & Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
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12
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Maternal cigarette smoke exposure disturbs glutamate/GABA balance in pFRG of neonatal rats. Respir Physiol Neurobiol 2020; 274:103383. [PMID: 31923590 DOI: 10.1016/j.resp.2020.103383] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 12/21/2019] [Accepted: 01/06/2020] [Indexed: 01/14/2023]
Abstract
We previously found that maternal cigarette smoke (CS) exposure resulted in impairment of central chemoreception and oxidative stress and mitochondrial dysfunction of parafacial respiratory group (pFRG, a critical site for mammalian central chemoreception) in neonatal rats. The present work was carried out to identify if maternal CS exposure could disturb the glutamate (GLU)-ergic and γ-aminobutyric acid (GABA)-ergic balance in pFRG of neonatal rats. We found that maternal CS exposure induced a decrease in GLU content and consequently in GLU/GABA ratio in pFRG of neonatal rats. Maternal CS exposure also decreased glutamine content and glutaminase and glutamine synthetase activity in offspring pFRG. In addition, expression of vesicular glutamate transporter 2 was depressed, and those of glutamate transporter 1 and GABA transporter 3 were elevated by maternal CS exposure. These results indicate that maternal CS exposure leads to a disturbance of GLU/GABA balance in pFRG of the neonatal rats, which might contribute to the suppression of central chemoreception in maternal CS-exposed offspring.
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13
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Optogenetic analysis of respiratory neuronal networks in the ventral medulla of neonatal rats producing channelrhodopsin in Phox2b-positive cells. Pflugers Arch 2019; 471:1419-1439. [DOI: 10.1007/s00424-019-02317-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 09/06/2019] [Accepted: 10/04/2019] [Indexed: 12/19/2022]
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14
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Amygdala rapid kindling impairs breathing in response to chemoreflex activation. Brain Res 2019; 1718:159-168. [DOI: 10.1016/j.brainres.2019.05.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 03/16/2019] [Accepted: 05/12/2019] [Indexed: 01/10/2023]
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15
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Levy J, Facchinetti P, Jan C, Achour M, Bouvier C, Brunet JF, Delzescaux T, Giuliano F. Tridimensional mapping of Phox2b expressing neurons in the brainstem of adult Macaca fascicularis and identification of the retrotrapezoid nucleus. J Comp Neurol 2019; 527:2875-2884. [PMID: 31071232 DOI: 10.1002/cne.24713] [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: 01/23/2019] [Revised: 04/29/2019] [Accepted: 04/29/2019] [Indexed: 11/08/2022]
Abstract
Chemosensitivity is a key mechanism for the regulation of breathing in vertebrates. The retrotrapezoid nucleus is a crucial hub for respiratory chemoreception within the brainstem. It integrates chemosensory information that are both peripheral from the carotid bodies (via the nucleus of the solitary tract) and central through the direct sensing of extracellular protons. To date, the location of a genetically defined RTN has only been ascertained in rodents. We first demonstrated that Phox2b, a key determinant for the development of the visceral nervous system and branchiomotor nuclei in the brainstem including the RTN, had a similar distribution in the brainstem of adult macaques compared to adult rats. Second, based on previous description of a specific molecular signature for the RTN in rats, and on an innovative technique for duplex in situ hybridization, we identified parafacial neurons which coexpressed Phox2b and ppGal mRNAs. They were located ventrally to the nucleus of the facial nerve and extended from the caudal part of the nucleus of the superior olive to the rostral tip of the inferior olive. Using the previously described blockface technique, deformations were corrected to allow the proper alignment and stacking of digitized sections, hence providing for the first time a 3D reconstruction of the macaque brainstem, Phox2b distribution and the primate retrotrapezoid nucleus. This description should help bridging the gap between rodents and humans for the description of key respiratory structures in the brainstem.
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Affiliation(s)
- Jonathan Levy
- INSERM UMR1179-Handicap Neuromusculaire, Université de Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France.,Service de Médecine Physique et de Réadaptation-APHP, Hôpital Raymond Poincaré, Garches, France.,Fondation Garches-APHP, Hôpital Raymond Poincaré, Garches, France
| | - Patricia Facchinetti
- INSERM UMR1179-Handicap Neuromusculaire, Université de Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France
| | - Caroline Jan
- Molecular Imaging Research Center (MIRCen)-Commissariat à l'Énergie Atomique (CEA), Fontenay-aux-Roses, France.,CNRS-CEA UMR9199-Neurodegenerative Diseases Laboratory, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - Mélyna Achour
- INSERM UMR1179-Handicap Neuromusculaire, Université de Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France
| | - Clément Bouvier
- Molecular Imaging Research Center (MIRCen)-Commissariat à l'Énergie Atomique (CEA), Fontenay-aux-Roses, France.,NEOXIA, Paris, France
| | - Jean-François Brunet
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole normale supérieure, CNRS, INSERM, PSL Université, Paris, France
| | - Thierry Delzescaux
- Molecular Imaging Research Center (MIRCen)-Commissariat à l'Énergie Atomique (CEA), Fontenay-aux-Roses, France.,CNRS-CEA UMR9199-Neurodegenerative Diseases Laboratory, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - François Giuliano
- INSERM UMR1179-Handicap Neuromusculaire, Université de Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France.,Service de Médecine Physique et de Réadaptation-APHP, Hôpital Raymond Poincaré, Garches, France
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16
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Wu Y, Proch KL, Teran FA, Lechtenberg RJ, Kothari H, Richerson GB. Chemosensitivity of Phox2b-expressing retrotrapezoid neurons is mediated in part by input from 5-HT neurons. J Physiol 2019; 597:2741-2766. [PMID: 30866045 PMCID: PMC6826216 DOI: 10.1113/jp277052] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 03/07/2019] [Indexed: 01/18/2023] Open
Abstract
KEY POINTS Neurons of the retrotrapezoid nucleus (RTN) and medullary serotonin (5-HT) neurons are both candidates for central CO2 /pH chemoreceptors, but it is not known how interactions between them influence their responses to pH. We found that RTN neurons in brain slices were stimulated by exogenous 5-HT and by heteroexchange release of endogenous 5-HT, and these responses were blocked by antagonists of 5-HT7 receptors. The pH response of RTN neurons in brain slices was markedly reduced by the same antagonists of 5-HT7 receptors. Similar results were obtained in dissociated, primary cell cultures prepared from the ventral medulla, where it was also found that the pH response of RTN neurons was blocked by preventing 5-HT synthesis and enhanced by blocking 5-HT reuptake. Exogenous 5-HT did not enable latent intrinsic RTN chemosensitivity. RTN neurons may play more of a role as relays from other central and peripheral chemoreceptors than as CO2 sensors. ABSTRACT Phox2b-expressing neurons in the retrotrapezoid nucleus (RTN) and serotonin (5-HT) neurons in the medullary raphe have both been proposed to be central respiratory chemoreceptors. How interactions between these two sets of neurons influence their responses to acidosis is not known. Here we recorded from mouse Phox2b+ RTN neurons in brain slices, and found that their response to moderate hypercapnic acidosis (pH 7.4 to ∼7.2) was markedly reduced by antagonists of 5-HT7 receptors. RTN neurons were stimulated in response to heteroexchange release of 5-HT, indicating that RTN neurons are sensitive to endogenous 5-HT. This electrophysiological behaviour was replicated in primary, dissociated cell cultures containing 5-HT and RTN neurons grown together. In addition, pharmacological inhibition of 5-HT synthesis in culture reduced RTN neuron chemosensitivity, and blocking 5-HT reuptake enhanced chemosensitivity. The effect of 5-HT on RTN neuron chemosensitivity was not explained by a mechanism whereby activation of 5-HT7 receptors enables or potentiates intrinsic chemosensitivity of RTN neurons, as exogenous 5-HT did not enhance the pH response. The ventilatory response to inhaled CO2 of mice was markedly decreased in vivo after systemic treatment with ketanserin, an antagonist of 5-HT2 and 5-HT7 receptors. These data indicate that 5-HT and RTN neurons may interact synergistically in a way that enhances the respiratory chemoreceptor response. The primary role of RTN neurons may be as relays and amplifiers of the pH response from 5-HT neurons and other chemoreceptors rather than as pH sensors themselves.
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Affiliation(s)
- Yuanming Wu
- Department of NeurologyUniversity of IowaIowa CityIA52242USA
| | - Katherine L. Proch
- Department of NeurologyUniversity of IowaIowa CityIA52242USA
- Graduate Program in NeuroscienceUniversity of IowaIowa CityIA52242USA
| | - Frida A. Teran
- Department of NeurologyUniversity of IowaIowa CityIA52242USA
- Graduate Program in NeuroscienceUniversity of IowaIowa CityIA52242USA
- Iowa Neuroscience InstituteUniversity of IowaIowa CityIA52242USA
| | | | - Harsh Kothari
- Department of PediatricsUniversity of IowaIowa CityIA52242USA
| | - George B. Richerson
- Department of NeurologyUniversity of IowaIowa CityIA52242USA
- Graduate Program in NeuroscienceUniversity of IowaIowa CityIA52242USA
- Department of Molecular Physiology & BiophysicsUniversity of IowaIowa CityIA52242USA
- Neurology ServiceVeterans Affairs Medical CenterIowa CityIA52242USA
- Iowa Neuroscience InstituteUniversity of IowaIowa CityIA52242USA
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17
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Lavezzi AM, Poloniato A, Rovelli R, Lorioli L, Iasi GA, Pusiol T, Barera G, Ferrero S. Massive Amniotic Fluid Aspiration in a Case of Sudden Neonatal Death With Severe Hypoplasia of the Retrotrapezoid/Parafacial Respiratory Group. Front Pediatr 2019; 7:116. [PMID: 31019904 PMCID: PMC6458245 DOI: 10.3389/fped.2019.00116] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 03/11/2019] [Indexed: 11/24/2022] Open
Abstract
We report a case of a baby, who, after pregnancy complicated by maternal Addison's disease and Hashimoto's thyroiditis and natural delivery, unexpectedly presented a cardiorespiratory collapse and died 1 hour after birth without responding to prolonged neonatal resuscitation maneuvers. The cause of death was reliably established by carrying out a forensic postmortem examination. More specifically, the histological examination of the lungs showed the presence of abundant endoalveolar and endobronchial cornea scales caused by absorption of amniotic fluid. The neuropathological examination of the brainstem highlighted severe hypodevelopment of the retrotrapezoid/parafacial respiratory group, which is a complex of neurons located in the caudal pons that is involved in respiratory rhythm coordination, especially expiration, in conditions of enhanced respiratory drive, as well as in chemoreception. This neuropathological finding shed new light on the mechanisms underlying the massive amniotic fluid aspiration which led to this early death.
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Affiliation(s)
- Anna M Lavezzi
- Department of Biomedical, Surgical and Dental Sciences, Lino Rossi Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, University of Milan, Milan, Italy
| | | | | | - Laura Lorioli
- Neonatal Unit, IRCCS Ospedale San Raffaele, Milan, Italy
| | | | - Teresa Pusiol
- Institute of Pathology, Hospital of Rovereto, Rovereto, Italy
| | | | - Stefano Ferrero
- Department of Biomedical, Surgical and Dental Sciences, Lino Rossi Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, University of Milan, Milan, Italy.,Division of Pathology, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
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18
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Ikeda K, Kaneko R, Yanagawa Y, Ogawa M, Kobayashi K, Arata S, Kawakami K, Onimaru H. Analysis of the neuronal network of the medullary respiratory center in transgenic rats expressing archaerhodopsin-3 in Phox2b-expressing cells. Brain Res Bull 2018; 144:39-45. [PMID: 30448454 DOI: 10.1016/j.brainresbull.2018.11.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 10/30/2018] [Accepted: 11/13/2018] [Indexed: 11/18/2022]
Abstract
Preinspiratory (Pre-I) neurons in the parafacial respiratory group (pFRG) comprise one of the respiratory rhythm generators in the medulla of the neonatal rat. A subgroup of pFRG/Pre-I neurons expresses the transcription factor Phox2b. To further analyze detailed neuronal mechanisms of respiratory rhythm generation in the neonatal rat, we developed a transgenic (Tg) rat line in which Phox2b-positive cells expressed archaerhodopsin-3 (Arch). Brainstem-spinal cord preparations were isolated from 0-2-day-old Tg newborn rats and were superfused with artificial cerebrospinal fluid equilibrated with 95% O2 and 5% CO2, pH 7.4, at 25-26 °C. Inspiratory fourth cervical ventral root (C4) activity was monitored, and membrane potentials of neurons in the pFRG including Pre-I and inspiratory neurons were recorded. Phox2b-positive cells in the Tg rats were essentially positive for enhanced green fluorescent protein (EGFP) signals (reporter for Arch) in the pFRG. Continuous photo-stimulation of the rostral ventral medulla for up to 90 s by covering the pFRG with green laser light (532 nm) induced a decrease of respiratory rate measured at C4 accompanied by membrane hyperpolarization of Phox2b-positive pFRG/Pre-I neurons. In contrast, Phox2b-negative inspiratory neurons were not hyperpolarized during the photo-stimulation. Our findings showed that Phox2b-expressing pFRG/Pre-I neurons are involved in the maintenance of the basic respiratory rhythm in neonatal rat.
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Affiliation(s)
- Keiko Ikeda
- Department of Physiology, International University of Health and Welfare (IUHW), 4-3 Kozunomori, Narita City, Chiba 286-8686, Japan
| | - Ryosuke Kaneko
- Bioresource Center, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma 371-8511, Japan
| | - Yuchio Yanagawa
- Department of Genetics and Behavioral Neuroscience, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma 371-8511, Japan
| | - Masaaki Ogawa
- Medical Innovation Center, Graduate School of Medicine, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
| | - Kazuto Kobayashi
- Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Satoru Arata
- Center for Biotechnology, Showa University, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Kiyoshi Kawakami
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, Tokyo 142-8555, Japan.
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19
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The Expression of Galanin in the Parafacial Respiratory Group and its Effects on Respiration in Neonatal Rats. Neuroscience 2018; 384:1-13. [PMID: 29772344 DOI: 10.1016/j.neuroscience.2018.05.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 05/02/2018] [Accepted: 05/04/2018] [Indexed: 11/23/2022]
Abstract
The inhibitory peptide galanin is expressed within the retrotrapezoidal nucleus (RTN) - a key central chemoreceptor site that also contains the active expiratory oscillator. It was previously reported that microinjection of galanin into pre-Bötzinger complex - containing the inspiratory oscillator - exerts inhibitory effects on inspiratory motor output and respiratory rhythm. In neonatal rats, the present study aimed to investigate: (1) expression of galanin within the parafacial respiratory group (pFRG), which overlaps anatomically and functionally with the adult RTN, and; (2) effects of galanin on respiratory rhythm using the in vitro brainstem-spinal cord preparation. We showed that 14 ± 2% of Phox2b-immunoreactive (ir) neurons in the parafacial region were also galanin-ir. Galanin peptide expression was confirmed within 3/9 CO2-sensitive, Phox2b-ir Pre-Inspiratory neurons (Pre-I) recorded in parafacial region. Bath application of galanin (0.1-0.2 µM): (1) decreased the duration of membrane depolarization in both Pre-I and inspiratory pFRG neurons, and; (2) decreased the number of C4 bursts that were associated with each burst in Pre-I neurons within the pFRG. In preparations showing episodic breathing at baseline, the respiratory patterning reverted to the 'normal' pattern of single, uniformly rhythmic C4 bursts (n = 10). In preparations with normal respiratory patterning at baseline, slowing of C4 rhythm (n = 7) resulted although rhythmic bursting in recorded Pre-I neurons remained unperturbed (n = 6). This study therefore demonstrates that galanin is expressed within the pFRG of neonatal rats, including neurons that are intrinsically chemosensitive. Overall the peptide has an inhibitory effect on inspiratory motor output, as previously shown in adults.
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20
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Inhibition of the hypercapnic ventilatory response by adenosine in the retrotrapezoid nucleus in awake rats. Neuropharmacology 2018; 138:47-56. [PMID: 29857188 DOI: 10.1016/j.neuropharm.2018.05.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 05/14/2018] [Accepted: 05/22/2018] [Indexed: 01/13/2023]
Abstract
The brain regulates breathing in response to changes in tissue CO2/H+ via a process called central chemoreception. Neurons and astrocytes in the retrotrapezoid nucleus (RTN) function as respiratory chemoreceptors. The role of astrocytes in this process appears to involve CO2/H+-dependent release of ATP to enhance activity of chemosensitive RTN neurons. Considering that in most brain regions extracellular ATP is rapidly broken down to adenosine by ectonucleotidase activity and since adenosine is a potent neuromodulator, we wondered whether adenosine signaling contributes to RTN chemoreceptor function. To explore this possibility, we pharmacologically manipulated activity of adenosine receptors in the RTN under control conditions and during inhalation of 7-10% CO2 (hypercapnia). In urethane-anesthetized or unrestrained conscious rats, bilateral injections of adenosine into the RTN blunted the hypercapnia ventilatory response. The inhibitory effect of adenosine on breathing was blunted by prior RTN injection of a broad spectrum adenosine receptor blocker (8-PT) or a selective A1-receptor blocker (DPCPX). Although RTN injections of 8PT, DPCPX or the ectonucleotidase inhibitor ARL67156 did not affected baseline breathing in either anesthetized or awake rats. We did find that RTN application of DPCPX or ARL67156 potentiated the respiratory frequency response to CO2, suggesting a portion of ATP released in the RTN during high CO2/H+ is converted to adenosine and serves to limit chemoreceptor function. These results identify adenosine as a novel purinergic regulator of RTN chemoreceptor function during hypercapnia.
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21
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Onimaru H, Nakamura S, Ikeda K, Kawakami K, Inoue T. Confocal calcium imaging analysis of respiratory-related burst activity in the parafacial region. Brain Res Bull 2018; 139:16-20. [PMID: 29374604 DOI: 10.1016/j.brainresbull.2018.01.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 01/18/2018] [Indexed: 11/25/2022]
Abstract
The parafacial respiratory group (pFRG) surrounding the ventrolateral part of the facial motor nucleus is one of respiratory rhythm generators that consists of pre-inspiratory (Pre-I) neurons. Previous studies showed that most of the Pre-I neurons locating in the Phox2b cluster of the rostral ventral medulla were also Phox2b positive and intrinsically CO2 sensitive. However, it is not clear what percentage of Phox2b-expressing cells in the pFRG of the ventral medulla are Pre-I neurons. To address this issue, we analyzed the activity of Phox2b-positive cells by calcium imaging using a confocal laser microscope in transgenic rats in which Phox2b-positive cells expressed EYFP. We found that more than 60% of the EYFP/Phox2b-positive cells showed Pre-I neuron-like rhythmic burst activity in the parafacial region of newborn rat.
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Affiliation(s)
- Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
| | - Shiro Nakamura
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Keiko Ikeda
- Department of Physiology, International University of Health and Welfare (IUHW), 4-3 Kozunomori, Narita City, Chiba 286-8686, Japan
| | - Kiyoshi Kawakami
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - Tomio Inoue
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
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22
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Nagoya K, Nakamura S, Ikeda K, Onimaru H, Yoshida A, Nakayama K, Mochizuki A, Kiyomoto M, Sato F, Kawakami K, Takahashi K, Inoue T. Distinctive features of Phox2b-expressing neurons in the rat reticular formation dorsal to the trigeminal motor nucleus. Neuroscience 2017; 358:211-226. [PMID: 28673717 DOI: 10.1016/j.neuroscience.2017.06.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 06/03/2017] [Accepted: 06/21/2017] [Indexed: 10/19/2022]
Abstract
Phox2b encodes a paired-like homeodomain-containing transcription factor essential for development of the autonomic nervous system. Phox2b-expressing (Phox2b+) neurons are present in the reticular formation dorsal to the trigeminal motor nucleus (RdV) as well as the nucleus of the solitary tract and parafacial respiratory group. However, the nature of Phox2b+ RdV neurons is still unclear. We investigated the physiological and morphological properties of Phox2b+ RdV neurons using postnatal day 2-7 transgenic rats expressing yellow fluorescent protein under the control of Phox2b. Almost all of Phox2b+ RdV neurons were glutamatergic, whereas Phox2b-negative (Phox2b-) RdV neurons consisted of a few glutamatergic, many GABAergic, and many glycinergic neurons. The majority (48/56) of Phox2b+ neurons showed low-frequency firing (LF), while most of Phox2b- neurons (35/42) exhibited high-frequency firing (HF) in response to intracellularly injected currents. All, but one, Phox2b+ neurons (55/56) did not fire spontaneously, whereas three-fourths of the Phox2b- neurons (31/42) were spontaneously active. K+ channel and persistent Na+ current blockers affected the firing of LF and HF neurons. The majority of Phox2b+ (35/46) and half of the Phox2b- neurons (19/40) did not respond to stimulations of the mesencephalic trigeminal nucleus, the trigeminal tract, and the principal sensory trigeminal nucleus. Biocytin labeling revealed that about half of the Phox2b+ (5/12) and Phox2b- RdV neurons (5/10) send their axons to the trigeminal motor nucleus. These results suggest that Phox2b+ RdV neurons have distinct neurotransmitter phenotypes and firing properties from Phox2b- RdV neurons and might play important roles in feeding-related functions including suckling and possibly mastication.
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Affiliation(s)
- Kouta Nagoya
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan; Division of Oral Rehabilitation Medicine, Department of Special Needs Dentistry, Showa University School of Dentistry, 2-2-1 Kitasenzoku, Ota-ku, Tokyo 145-8515, Japan
| | - Shiro Nakamura
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
| | - Keiko Ikeda
- Division of Biology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Atsushi Yoshida
- Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, 1-8, Yamada-Oka, Suita, Osaka 565-0871, Japan
| | - Kiyomi Nakayama
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Ayako Mochizuki
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Masaaki Kiyomoto
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Fumihiko Sato
- Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, 1-8, Yamada-Oka, Suita, Osaka 565-0871, Japan
| | - Kiyoshi Kawakami
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Koji Takahashi
- Division of Oral Rehabilitation Medicine, Department of Special Needs Dentistry, Showa University School of Dentistry, 2-2-1 Kitasenzoku, Ota-ku, Tokyo 145-8515, Japan
| | - Tomio Inoue
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
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23
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Effects of a TRPV1 agonist capsaicin on respiratory rhythm generation in brainstem-spinal cord preparation from newborn rats. Pflugers Arch 2016; 469:327-338. [PMID: 27900462 DOI: 10.1007/s00424-016-1912-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 11/20/2016] [Accepted: 11/22/2016] [Indexed: 12/19/2022]
Abstract
The heat-sensitive transient receptor potential vanilloid 1 (TRPV1) channels are expressed in the peripheral and central nervous systems. However, there is no report on how the activation of TRPV1 causes the modulation of neuronal activity in the medullary respiratory center. We examined effects of capsaicin, a specific agonist of TRPV1 channels, on respiratory rhythm generation in brainstem-spinal cord preparation from newborn rats. Capsaicin induced a biphasic response in the respiratory rhythm (a transient decrease followed by an increase in the C4 rate). The second-phase excitatory effect (but not the initial inhibitory effect) in the biphasic response was partly blocked by capsazepine or AMG9810 (TRPV1 antagonists). Capsaicin caused strong desensitization. After its washout, the strength of C4 burst inspiratory activity was augmented once per four to five respiratory cycles. The preinspiratory and inspiratory neurons showed tonic firings due to membrane depolarization during the initial inhibitory phase. In the presence of TTX, capsaicin increased the fluctuation of the membrane potential of the CO2-sensitive preinspiratory neurons in the parafacial respiratory group (pFRG), accompanied by slight depolarization. The C4 inspiratory activity did not stop, even 60-90 min after the application of 50/100 μM capsaicin. Voltage-sensitive dye imaging demonstrated that the spatiotemporal pattern of the respiratory rhythm generating networks after application of capsaicin (50 μM, 70-90 min) was highly similar to the control. A histochemical analysis using TRPV1 channel protein antibodies and mRNA demonstrated that the TRPV1 channel-positive cells were widely distributed in the reticular formation of the medulla, including the pFRG. Our results showed that the application of capsaicin in the medulla has various influences on the respiratory center: transient inhibitory and subsequent excitatory effects on the respiratory rhythm and periodical augmentation of the inspiratory burst pattern. The effects of capsaicin were partially blocked by TRPV1 antagonists but could be also induced at least partially via the non-specific action. Our results also suggested a minor contribution of the TRPV1 channels to central chemoreception.
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24
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The neural control of respiration in lampreys. Respir Physiol Neurobiol 2016; 234:14-25. [PMID: 27562521 DOI: 10.1016/j.resp.2016.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 08/08/2016] [Accepted: 08/21/2016] [Indexed: 11/24/2022]
Abstract
This review focuses on past and recent findings that have contributed to characterize the neural networks controlling respiration in the lamprey, a basal vertebrate. As in other vertebrates, respiration in lampreys is generated centrally in the brainstem. It is characterized by the presence of a fast and a slow respiratory rhythm. The anatomical and the basic physiological properties of the neural networks underlying the generation of the fast rhythm have been more thoroughly investigated; less is known about the generation of the slow respiratory rhythm. Comparative aspects with respiratory generators in other vertebrates as well as the mechanisms of modulation of respiration in association with locomotion are discussed.
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Ikeda K, Kawakami K, Onimaru H, Okada Y, Yokota S, Koshiya N, Oku Y, Iizuka M, Koizumi H. The respiratory control mechanisms in the brainstem and spinal cord: integrative views of the neuroanatomy and neurophysiology. J Physiol Sci 2016; 67:45-62. [PMID: 27535569 PMCID: PMC5368202 DOI: 10.1007/s12576-016-0475-y] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 07/22/2016] [Indexed: 12/17/2022]
Abstract
Respiratory activities are produced by medullary respiratory rhythm generators and are modulated from various sites in the lower brainstem, and which are then output as motor activities through premotor efferent networks in the brainstem and spinal cord. Over the past few decades, new knowledge has been accumulated on the anatomical and physiological mechanisms underlying the generation and regulation of respiratory rhythm. In this review, we focus on the recent findings and attempt to elucidate the anatomical and functional mechanisms underlying respiratory control in the lower brainstem and spinal cord.
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Affiliation(s)
- Keiko Ikeda
- Division of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo, 663-8501, Japan.
| | - Kiyoshi Kawakami
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, 329-0498, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, Shinagawa, Tokyo, 142-8555, Japan.
| | - Yasumasa Okada
- Clinical Research Center, Murayama Medical Center, Musashimurayama, Tokyo, 208-0011, Japan.
| | - Shigefumi Yokota
- Department of Anatomy and Morphological Neuroscience, Shimane University School of Medicine, Izumo, Shimane, 693-8501, Japan
| | - Naohiro Koshiya
- Cellular and Systems Neurobiology Section, NINDS, NIH, Bethesda, MD, 20892, USA.
| | - Yoshitaka Oku
- Department of Physiology, Hyogo College of Medicine, Nishinomiya, Hyogo, 663-8501, Japan.
| | - Makito Iizuka
- Department of Physiology, Showa University School of Medicine, Shinagawa, Tokyo, 142-8555, Japan.
| | - Hidehiko Koizumi
- Cellular and Systems Neurobiology Section, NINDS, NIH, Bethesda, MD, 20892, USA
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26
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Huckstepp RT, Henderson LE, Cardoza KP, Feldman JL. Interactions between respiratory oscillators in adult rats. eLife 2016; 5. [PMID: 27300271 PMCID: PMC4907693 DOI: 10.7554/elife.14203] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 04/27/2016] [Indexed: 01/20/2023] Open
Abstract
Breathing in mammals is hypothesized to result from the interaction of two distinct oscillators: the preBötzinger Complex (preBötC) driving inspiration and the lateral parafacial region (pFL) driving active expiration. To understand the interactions between these oscillators, we independently altered their excitability in spontaneously breathing vagotomized urethane-anesthetized adult rats. Hyperpolarizing preBötC neurons decreased inspiratory activity and initiated active expiration, ultimately progressing to apnea, i.e., cessation of both inspiration and active expiration. Depolarizing pFL neurons produced active expiration at rest, but not when inspiratory activity was suppressed by hyperpolarizing preBötC neurons. We conclude that in anesthetized adult rats active expiration is driven by the pFL but requires an additional form of network excitation, i.e., ongoing rhythmic preBötC activity sufficient to drive inspiratory motor output or increased chemosensory drive. The organization of this coupled oscillator system, which is essential for life, may have implications for other neural networks that contain multiple rhythm/pattern generators. DOI:http://dx.doi.org/10.7554/eLife.14203.001 Mammals breathe air into and out of their lungs to absorb oxygen into the body and to remove carbon dioxide. The rhythm of breathing is most likely controlled by two groups of neurons in a part of the brain called the brain stem. One group called the preBötzinger Complex drives breathing in (inspiration), and normally, breathing out (expiration) occurs when the muscles responsible for inspiration relax. The other group of neurons – known as the lateral parafacial region – controls extra muscles that allow us to increase our breathing when we need to, such as during exercise. Huckstepp et al. set out to determine how these two groups of neurons interact with one another in anesthetized rats to produce a reliable and efficient pattern of breathing. The experiments provide further evidence that inspiration is mainly driven by the preBötzinger Complex. Whilst activity from the lateral parafacial region is needed to cause the rats to breathe out more forcefully than normal, a second low level of activity from another source is also required. This source could either be the preBötzinger Complex, or some unknown neurons that change their activity in response to the levels of oxygen and carbon dioxide in the blood or fluid of the brain. Further investigation is required to identify how these interactions go awry in diseases that affect breathing, such as sleep apneas. DOI:http://dx.doi.org/10.7554/eLife.14203.002
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Affiliation(s)
- Robert Tr Huckstepp
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Lauren E Henderson
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Kathryn P Cardoza
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Jack L Feldman
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
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27
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Guyenet PG, Bayliss DA, Stornetta RL, Ludwig MG, Kumar NN, Shi Y, Burke PGR, Kanbar R, Basting TM, Holloway BB, Wenker IC. Proton detection and breathing regulation by the retrotrapezoid nucleus. J Physiol 2016; 594:1529-51. [PMID: 26748771 PMCID: PMC4799966 DOI: 10.1113/jp271480] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 01/04/2016] [Indexed: 01/26/2023] Open
Abstract
We discuss recent evidence which suggests that the principal central respiratory chemoreceptors are located within the retrotrapezoid nucleus (RTN) and that RTN neurons are directly sensitive to [H(+) ]. RTN neurons are glutamatergic. In vitro, their activation by [H(+) ] requires expression of a proton-activated G protein-coupled receptor (GPR4) and a proton-modulated potassium channel (TASK-2) whose transcripts are undetectable in astrocytes and the rest of the lower brainstem respiratory network. The pH response of RTN neurons is modulated by surrounding astrocytes but genetic deletion of RTN neurons or deletion of both GPR4 and TASK-2 virtually eliminates the central respiratory chemoreflex. Thus, although this reflex is regulated by innumerable brain pathways, it seems to operate predominantly by modulating the discharge rate of RTN neurons, and the activation of RTN neurons by hypercapnia may ultimately derive from their intrinsic pH sensitivity. RTN neurons increase lung ventilation by stimulating multiple aspects of breathing simultaneously. They stimulate breathing about equally during quiet wake and non-rapid eye movement (REM) sleep, and to a lesser degree during REM sleep. The activity of RTN neurons is regulated by inhibitory feedback and by excitatory inputs, notably from the carotid bodies. The latter input operates during normo- or hypercapnia but fails to activate RTN neurons under hypocapnic conditions. RTN inhibition probably limits the degree of hyperventilation produced by hypocapnic hypoxia. RTN neurons are also activated by inputs from serotonergic neurons and hypothalamic neurons. The absence of RTN neurons probably underlies the sleep apnoea and lack of chemoreflex that characterize congenital central hypoventilation syndrome.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | | | - Natasha N Kumar
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Peter G R Burke
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Roy Kanbar
- Department of Pharmaceutical Sciences, Lebanese American University, Beyrouth, Lebanon
| | - Tyler M Basting
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Benjamin B Holloway
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Ian C Wenker
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
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Iizuka M, Onimaru H, Izumizaki M. Distribution of respiration-related neuronal activity in the thoracic spinal cord of the neonatal rat: An optical imaging study. Neuroscience 2015; 315:217-27. [PMID: 26704634 DOI: 10.1016/j.neuroscience.2015.12.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 12/07/2015] [Accepted: 12/08/2015] [Indexed: 11/28/2022]
Abstract
The inspiratory motor outputs are larger in the intercostal muscles positioned at more rostral segments. To obtain further insights into the involvement of the spinal interneurons in the generation of this rostrocaudal gradient, the respiratory-related neuronal activities were optically recorded from various thoracic segments in brainstem-spinal cord preparations from 0- to 2-day-old rats. The preparation was stained with a voltage-sensitive dye, and the optical signals from about 2.5s before to about 7.7s after the peak of the C4 inspiratory discharge were obtained. Respiratory-related depolarizing signals were detectable from the ventral surface of all thoracic segments. Since the local blockage of the synaptic transmission in the thoracic spinal cord induced by the low-Ca(2+) superfusate blocked all respiratory signals, it is likely that these signals came from spinal neurons. Under the-low Ca(2+) superfusate, ventral root stimulation, inducing antidromic activation of motoneurons, evoked depolarizing optical signals in a restricted middle area between the lateral edge and midline of the spinal cord. These areas were referred to as 'motoneuron areas'. The respiratory signals were observed not only in the motoneuron areas but also in areas medial to the motoneuron areas, where interneurons should exist; these were referred to as 'interneuron areas'. The upper thoracic segments showed significantly larger inspiratory-related signals than the lower thoracic segments in both the motoneuron and interneuron areas. These results suggest that the inspiratory interneurons in the thoracic spinal cord play a role in the generation of the rostrocaudal gradient in the inspiratory intercostal muscle activity.
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Affiliation(s)
- M Iizuka
- Center for Medical Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ibaraki 300-0394, Japan; Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
| | - H Onimaru
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
| | - M Izumizaki
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
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29
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Heitzmann D, Buehler P, Schweda F, Georgieff M, Warth R, Thomas J. The in vivo respiratory phenotype of the adenosine A1 receptor knockout mouse. Respir Physiol Neurobiol 2015; 222:16-28. [PMID: 26593641 DOI: 10.1016/j.resp.2015.11.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 11/09/2015] [Accepted: 11/09/2015] [Indexed: 10/22/2022]
Abstract
The nucleoside adenosine has been implicated in the regulation of respiration, especially during hypoxia in the newborn. In this study the role of adenosine A1 receptors for the control of respiration was investigated in vivo. To this end, respiration of unrestrained adult and neonatal adenosine A1 receptor knockout mice (A1R(-/-)) was measured in a plethysmographic device. Under control conditions (21% O2) and mild hypoxia (12-15% O2) no difference of respiratory parameters was observed between adult wildtype (A1R(+/+)) and A1R(-/-) mice. Under more severe hypoxia (6-10% O2) A1R(+/+) mice showed, after a transient increase of respiration, a decrease of respiration frequency (fR) and tidal volume (VT) leading to a decrease of minute volume (MV). This depression of respiration during severe hypoxia was absent in A1R(-/-) mice which displayed a stimulated respiration as indicated by the enhancement of MV by some 50-60%. During hypercapnia-hyperoxia (3-10% CO2/97-90 % O2), no obvious differences in respiration of A1R(-/-) and A1R(+/+) was observed. In neonatal mice, the respiratory response to hypoxia was surprisingly similar in both genotypes. However, neonatal A1R(-/-) mice appeared to have more frequently periods of apnea during hypoxia and in the post-hypoxic control period. In conclusion, these data indicate that the adenosine A1 receptor is an important molecular component mediating hypoxic depression in adult mice and it appears to stabilize respiration of neonatal mice.
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Affiliation(s)
- Dirk Heitzmann
- Medizinische Klinik, University hospital Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, D-68167 Mannheim, Germany
| | - Philipp Buehler
- University children's hospital, Steinwiesstr. 75, CH-8032 Zürich, Switzerland
| | - Frank Schweda
- Institute of Physiology, University of Regensburg, D-93053 Regensburg, Germany
| | - Michael Georgieff
- Department of Anaesthesiology, University of Ulm, D-89075 Ulm, Germany
| | - Richard Warth
- Institute of Physiology, University of Regensburg, D-93053 Regensburg, Germany
| | - Joerg Thomas
- University children's hospital, Steinwiesstr. 75, CH-8032 Zürich, Switzerland.
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30
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Abstract
Recent advances have clarified how the brain detects CO2 to regulate breathing (central respiratory chemoreception). These mechanisms are reviewed and their significance is presented in the general context of CO2/pH homeostasis through breathing. At rest, respiratory chemoreflexes initiated at peripheral and central sites mediate rapid stabilization of arterial PCO2 and pH. Specific brainstem neurons (e.g., retrotrapezoid nucleus, RTN; serotonergic) are activated by PCO2 and stimulate breathing. RTN neurons detect CO2 via intrinsic proton receptors (TASK-2, GPR4), synaptic input from peripheral chemoreceptors and signals from astrocytes. Respiratory chemoreflexes are arousal state dependent whereas chemoreceptor stimulation produces arousal. When abnormal, these interactions lead to sleep-disordered breathing. During exercise, central command and reflexes from exercising muscles produce the breathing stimulation required to maintain arterial PCO2 and pH despite elevated metabolic activity. The neural circuits underlying central command and muscle afferent control of breathing remain elusive and represent a fertile area for future investigation.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0735, USA.
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0735, USA
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31
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Ikeda K, Takahashi M, Sato S, Igarashi H, Ishizuka T, Yawo H, Arata S, Southard-Smith EM, Kawakami K, Onimaru H. A Phox2b BAC Transgenic Rat Line Useful for Understanding Respiratory Rhythm Generator Neural Circuitry. PLoS One 2015; 10:e0132475. [PMID: 26147470 PMCID: PMC4492506 DOI: 10.1371/journal.pone.0132475] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 06/15/2015] [Indexed: 11/21/2022] Open
Abstract
The key role of the respiratory neural center is respiratory rhythm generation to maintain homeostasis through the control of arterial blood pCO2/pH and pO2 levels. The neuronal network responsible for respiratory rhythm generation in neonatal rat resides in the ventral side of the medulla and is composed of two groups; the parafacial respiratory group (pFRG) and the pre-Bötzinger complex group (preBötC). The pFRG partially overlaps in the retrotrapezoid nucleus (RTN), which was originally identified in adult cats and rats. Part of the pre-inspiratory (Pre-I) neurons in the RTN/pFRG serves as central chemoreceptor neurons and the CO2 sensitive Pre-I neurons express homeobox gene Phox2b. Phox2b encodes a transcription factor and is essential for the development of the sensory-motor visceral circuits. Mutations in human PHOX2B cause congenital hypoventilation syndrome, which is characterized by blunted ventilatory response to hypercapnia. Here we describe the generation of a novel transgenic (Tg) rat harboring fluorescently labeled Pre-I neurons in the RTN/pFRG. In addition, the Tg rat showed fluorescent signals in autonomic enteric neurons and carotid bodies. Because the Tg rat expresses inducible Cre recombinase in PHOX2B-positive cells during development, it is a potentially powerful tool for dissecting the entire picture of the respiratory neural network during development and for identifying the CO2/O2 sensor molecules in the adult central and peripheral nervous systems.
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Affiliation(s)
- Keiko Ikeda
- Division of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
- * E-mail:
| | - Masanori Takahashi
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
| | - Shigeru Sato
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
| | - Hiroyuki Igarashi
- Department of Physiology, and Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Toru Ishizuka
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences and JST/CREST, Sendai, Miyagi, Japan
| | - Hiromu Yawo
- Department of Physiology, and Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences and JST/CREST, Sendai, Miyagi, Japan
| | - Satoru Arata
- Center for Biotechnology, Showa University, Shinagawa, Tokyo, Japan
| | - E. Michelle Southard-Smith
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Kiyoshi Kawakami
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, Shinagawa, Tokyo, Japan
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32
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Ruffault PL, D'Autréaux F, Hayes JA, Nomaksteinsky M, Autran S, Fujiyama T, Hoshino M, Hägglund M, Kiehn O, Brunet JF, Fortin G, Goridis C. The retrotrapezoid nucleus neurons expressing Atoh1 and Phox2b are essential for the respiratory response to CO₂. eLife 2015; 4. [PMID: 25866925 PMCID: PMC4429526 DOI: 10.7554/elife.07051] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 04/09/2015] [Indexed: 01/08/2023] Open
Abstract
Maintaining constant CO2 and H+ concentrations in the arterial blood is critical for life. The principal mechanism through which this is achieved in mammals is the respiratory chemoreflex whose circuitry is still elusive. A candidate element of this circuitry is the retrotrapezoid nucleus (RTN), a collection of neurons at the ventral medullary surface that are activated by increased CO2 or low pH and project to the respiratory rhythm generator. Here, we use intersectional genetic strategies to lesion the RTN neurons defined by Atoh1 and Phox2b expression and to block or activate their synaptic output. Photostimulation of these neurons entrains the respiratory rhythm. Conversely, abrogating expression of Atoh1 or Phox2b or glutamatergic transmission in these cells curtails the phrenic nerve response to low pH in embryonic preparations and abolishes the respiratory chemoreflex in behaving animals. Thus, the RTN neurons expressing Atoh1 and Phox2b are a necessary component of the chemoreflex circuitry. DOI:http://dx.doi.org/10.7554/eLife.07051.001 An adult at rest will typically breathe in and out up to 20 times per minute, inhaling oxygen and exhaling carbon dioxide in a process that, for the most part, occurs automatically. While we can choose to override this process and exert voluntary control over our breathing, we cannot suppress it indefinitely. Attempting to do so will ultimately trigger a reflex that forces us to start breathing again. This reflex is mostly a response to the rise of carbon dioxide (CO2) in the blood, which lowers the pH of the blood. This rise in CO2 is toxic and triggers an increase in breathing so that the excess CO2 is exhaled. The majority of the sensors that detect CO2 are in the brainstem, which is at the junction of the brain and the spinal cord. However, the precise location of these sensors is not clear. Ruffault et al. now argue that the sensors are in a region called the ‘retrotrapezoid nucleus’, and that they can be identified by the presence of two proteins, Atoh1 and Phox2b. In the brains of foetal mice, Ruffault et al. recorded cells in the retrotrapezoid nucleus and found that they fired in a rhythmic pattern, as would be expected for cells that control breathing. Moreover, the firing rate of these cells increased when the pH was lowered. Ruffault et al. then created genetically modified mice with mutations in genes for Atoh1 or Phox2b. The retrotrapezoid nucleus was either absent or abnormal in these mutant mice. Moreover, new-born pups with these mutations were not able to increase their breathing when the level of CO2 in their blood rose. These results shed light on the respiratory distress experienced by patients with a rare disorder called congenital central hypoventilation syndrome (CCHS) that is caused by mutations in Phox2b. More commonly, unstable or irregular breathing is seen in human infants that are born prematurely, and sometimes in infants born at full term. In the light of the new findings by Ruffault et al., it is possible that abnormal development or immaturity of the retrotrapezoid nucleus is the cause. DOI:http://dx.doi.org/10.7554/eLife.07051.002
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Affiliation(s)
- Pierre-Louis Ruffault
- Université Paris-Saclay, Université Paris-Sud, CNRS, UMR 9197, Institut des Neurosciences Paris-Saclay, Gif-sur-Yvette, France
| | - Fabien D'Autréaux
- Institut de Biologie de l'École Normale Supérieure, Inserm U1024, and CNRS UMR 8197, Paris, France
| | - John A Hayes
- Université Paris-Saclay, Université Paris-Sud, CNRS, UMR 9197, Institut des Neurosciences Paris-Saclay, Gif-sur-Yvette, France
| | - Marc Nomaksteinsky
- Institut de Biologie de l'École Normale Supérieure, Inserm U1024, and CNRS UMR 8197, Paris, France
| | - Sandra Autran
- Université Paris-Saclay, Université Paris-Sud, CNRS, UMR 9197, Institut des Neurosciences Paris-Saclay, Gif-sur-Yvette, France
| | - Tomoyuki Fujiyama
- Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Mikio Hoshino
- Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Martin Hägglund
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Ole Kiehn
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Jean-François Brunet
- Institut de Biologie de l'École Normale Supérieure, Inserm U1024, and CNRS UMR 8197, Paris, France
| | - Gilles Fortin
- Université Paris-Saclay, Université Paris-Sud, CNRS, UMR 9197, Institut des Neurosciences Paris-Saclay, Gif-sur-Yvette, France
| | - Christo Goridis
- Institut de Biologie de l'École Normale Supérieure, Inserm U1024, and CNRS UMR 8197, Paris, France
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Mulkey DK, Hawkins VE, Hawryluk JM, Takakura AC, Moreira TS, Tzingounis AV. Molecular underpinnings of ventral surface chemoreceptor function: focus on KCNQ channels. J Physiol 2015; 593:1075-81. [PMID: 25603782 DOI: 10.1113/jphysiol.2014.286500] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 01/12/2015] [Indexed: 12/12/2022] Open
Abstract
Central chemoreception is the mechanism by which CO₂/H(+) -sensitive neurons (i.e. chemoreceptors) regulate breathing in response to changes in tissue CO₂/H(+) . Neurons in the retrotrapezoid nucleus (RTN) directly regulate breathing in response to changes in tissue CO₂/H(+) and function as a key locus of respiratory control by integrating information from several respiratory centres, including the medullary raphe. Therefore, chemosensitive RTN neurons appear to be critically important for maintaining breathing, thus understanding molecular mechanisms that regulate RTN chemoreceptor function may identify therapeutic targets for the treatment of respiratory control disorders. We have recently shown that KCNQ (Kv7) channels in the RTN are essential determinants of spontaneous activity ex vivo, and downstream effectors for serotonergic modulation of breathing. Considering that loss of function mutations in KCNQ channels can cause certain types of epilepsy including those associated with sudden unexplained death in epilepsy (SUDEP), we propose that dysfunctions of KCNQ channels may be one cause for epilepsy and respiratory problems associated with SUDEP. In this review, we will summarize the role of KCNQ channels in the regulation of RTN chemoreceptor function, and suggest that these channels represent useful therapeutic targets for the treatment of respiratory control disorders.
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Affiliation(s)
- Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, 06269, USA
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34
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Moreira TS, Wenker IC, Sobrinho CR, Barna BF, Takakura AC, Mulkey DK. Independent purinergic mechanisms of central and peripheral chemoreception in the rostral ventrolateral medulla. J Physiol 2015; 593:1067-74. [PMID: 25524282 DOI: 10.1113/jphysiol.2014.284430] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 12/15/2014] [Indexed: 01/02/2023] Open
Abstract
The rostral ventrolateral medulla oblongata (RVLM) contains two functionally distinct types of neurons that control and orchestrate cardiovascular and respiratory responses to hypoxia and hypercapnia. One group is composed of the central chemoreceptor neurons of the retrotrapezoid nucleus, which provides a CO₂/H(+) -dependent drive to breathe and serves as an integration centre and a point of convergence of chemosensory information from other central and peripheral sites, including the carotid bodies. The second cluster of RVLM cells forms a population of neurons belonging to the C1 catecholaminergic group that controls sympathetic vasomotor tone in resting conditions and in conditions of hypoxia and hypercapnia. Recent evidence suggests that ATP-mediated purinergic signalling at the level of the RVLM co-ordinates cardiovascular and respiratory responses triggered by hypoxia and hypercapnia by activating retrotrapezoid nucleus and C1 neurons, respectively. The role of ATP-mediated signalling in the RVLM mechanisms of cardiovascular and respiratory activities is the main subject of this short review.
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Affiliation(s)
- Thiago S Moreira
- Department of Physiology and Biophysics, University of São Paulo, São Paulo, SP, 05508, Brazil
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35
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Tsuzawa K, Yazawa I, Shakuo T, Ikeda K, Kawakami K, Onimaru H. Effects of ouabain on respiratory rhythm generation in brainstem-spinal cord preparation from newborn rats and in decerebrate and arterially perfused in situ preparation from juvenile rats. Neuroscience 2014; 286:404-11. [PMID: 25512246 DOI: 10.1016/j.neuroscience.2014.12.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 10/31/2014] [Accepted: 12/05/2014] [Indexed: 11/25/2022]
Abstract
The significance of Na/K-ATPase on respiratory rhythm generation is not well understood. We investigated the effects of the Na/K-ATPase blocker, ouabain, on respiratory rhythm. Experiments were performed with brainstem-spinal cord preparation from 0 to 3-day-old Wistar rats and with decerebrate and arterially perfused in situ preparation from juvenile rats (postnatal day 11-13). Newborn rat preparations were superfused at a rate of 3.0 ml/min with artificial cerebrospinal fluid, equilibrated with 95% O2 and 5% CO2, pH 7.4, at 26-27 °C. Inspiratory activity was monitored from the fourth cervical ventral root (C4). Application of ouabain (15-20 min) resulted in a dose-dependent increase in the burst rate of C4 inspiratory activity. After washout, the burst rate further increased to reach quasi-maximum values under each condition (e.g. 183% of control in 1 μM, 253% in 10 μM, and 303% in 20 μM at 30 min washout). Inspiratory or pre-inspiratory neurons in the rostral ventrolateral medulla were depolarized. We obtained similar results (i.e. increased phrenic burst rate) in an in situ perfused preparation of juvenile rats. Genes encoding the Na/K-ATPase α subunit were expressed in the region of the parafacial respiratory group (pFRG) in neonatal rats, suggesting that cells (neurons and/or glias) in the pFRG were one of the targets of ouabain. We concluded that Na/K-ATPase activity could be an important factor in respiratory rhythm modulation.
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Affiliation(s)
- K Tsuzawa
- Department of Physiology, Showa University School of Medicine, Tokyo 142-8555, Japan
| | - I Yazawa
- Department of Anatomy, Showa University School of Medicine, Tokyo 142-8555, Japan
| | - T Shakuo
- Department of Physiology, Showa University School of Medicine, Tokyo 142-8555, Japan
| | - K Ikeda
- Division of Biology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan
| | - K Kawakami
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - H Onimaru
- Department of Physiology, Showa University School of Medicine, Tokyo 142-8555, Japan.
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Abstract
Lung ventilation fluctuates widely with behavior but arterial PCO2 remains stable. Under normal conditions, the chemoreflexes contribute to PaCO2 stability by producing small corrective cardiorespiratory adjustments mediated by lower brainstem circuits. Carotid body (CB) information reaches the respiratory pattern generator (RPG) via nucleus solitarius (NTS) glutamatergic neurons which also target rostral ventrolateral medulla (RVLM) presympathetic neurons thereby raising sympathetic nerve activity (SNA). Chemoreceptors also regulate presympathetic neurons and cardiovagal preganglionic neurons indirectly via inputs from the RPG. Secondary effects of chemoreceptors on the autonomic outflows result from changes in lung stretch afferent and baroreceptor activity. Central respiratory chemosensitivity is caused by direct effects of acid on neurons and indirect effects of CO2 via astrocytes. Central respiratory chemoreceptors are not definitively identified but the retrotrapezoid nucleus (RTN) is a particularly strong candidate. The absence of RTN likely causes severe central apneas in congenital central hypoventilation syndrome. Like other stressors, intense chemosensory stimuli produce arousal and activate circuits that are wake- or attention-promoting. Such pathways (e.g., locus coeruleus, raphe, and orexin system) modulate the chemoreflexes in a state-dependent manner and their activation by strong chemosensory stimuli intensifies these reflexes. In essential hypertension, obstructive sleep apnea and congestive heart failure, chronically elevated CB afferent activity contributes to raising SNA but breathing is unchanged or becomes periodic (severe CHF). Extreme CNS hypoxia produces a stereotyped cardiorespiratory response (gasping, increased SNA). The effects of these various pathologies on brainstem cardiorespiratory networks are discussed, special consideration being given to the interactions between central and peripheral chemoreflexes.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia
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Remote control of respiratory neural network by spinal locomotor generators. PLoS One 2014; 9:e89670. [PMID: 24586951 PMCID: PMC3930745 DOI: 10.1371/journal.pone.0089670] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 01/21/2014] [Indexed: 12/03/2022] Open
Abstract
During exercise and locomotion, breathing rate rapidly increases to meet the suddenly enhanced oxygen demand. The extent to which direct central interactions between the spinal networks controlling locomotion and the brainstem networks controlling breathing are involved in this rhythm modulation remains unknown. Here, we show that in isolated neonatal rat brainstem-spinal cord preparations, the increase in respiratory rate observed during fictive locomotion is associated with an increase in the excitability of pre-inspiratory neurons of the parafacial respiratory group (pFRG/Pre-I). In addition, this locomotion-induced respiratory rhythm modulation is prevented both by bilateral lesion of the pFRG region and by blockade of neurokinin 1 receptors in the brainstem. Thus, our results assign pFRG/Pre-I neurons a new role as elements of a previously undescribed pathway involved in the functional interaction between respiratory and locomotor networks, an interaction that also involves a substance P-dependent modulating mechanism requiring the activation of neurokinin 1 receptors. This neurogenic mechanism may take an active part in the increased respiratory rhythmicity produced at the onset and during episodes of locomotion in mammals.
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Substance P differentially modulates firing rate of solitary complex (SC) neurons from control and chronic hypoxia-adapted adult rats. PLoS One 2014; 9:e88161. [PMID: 24516602 PMCID: PMC3917864 DOI: 10.1371/journal.pone.0088161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 01/03/2014] [Indexed: 11/19/2022] Open
Abstract
NK1 receptors, which bind substance P, are present in the majority of brainstem regions that contain CO2/H(+)-sensitive neurons that play a role in central chemosensitivity. However, the effect of substance P on the chemosensitive response of neurons from these regions has not been studied. Hypoxia increases substance P release from peripheral afferents that terminate in the caudal nucleus tractus solitarius (NTS). Here we studied the effect of substance P on the chemosensitive responses of solitary complex (SC: NTS and dorsal motor nucleus) neurons from control and chronic hypoxia-adapted (CHx) adult rats. We simultaneously measured intracellular pH and electrical responses to hypercapnic acidosis in SC neurons from control and CHx adult rats using the blind whole cell patch clamp technique and fluorescence imaging microscopy. Substance P significantly increased the basal firing rate in SC neurons from control and CHx rats, although the increase was smaller in CHx rats. However, substance P did not affect the chemosensitive response of SC neurons from either group of rats. In conclusion, we found that substance P plays a role in modulating the basal firing rate of SC neurons but the magnitude of the effect is smaller for SC neurons from CHx adult rats, implying that NK1 receptors may be down regulated in CHx adult rats. Substance P does not appear to play a role in modulating the firing rate response to hypercapnic acidosis of SC neurons from either control or CHx adult rats.
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Sobrinho CR, Wenker IC, Poss EM, Takakura AC, Moreira TS, Mulkey DK. Purinergic signalling contributes to chemoreception in the retrotrapezoid nucleus but not the nucleus of the solitary tract or medullary raphe. J Physiol 2014; 592:1309-23. [PMID: 24445316 DOI: 10.1113/jphysiol.2013.268490] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Several brain regions are thought to function as important sites of chemoreception including the nucleus of the solitary tract (NTS), medullary raphe and retrotrapezoid nucleus (RTN). In the RTN, mechanisms of chemoreception involve direct H(+)-mediated activation of chemosensitive neurons and indirect modulation of chemosensitive neurons by purinergic signalling. Evidence suggests that RTN astrocytes are the source of CO2-evoked ATP release. However, it is not clear whether purinergic signalling also influences CO2/H(+) responsiveness of other putative chemoreceptors. The goals of this study are to determine if CO2/H(+)-sensitive neurons in the NTS and medullary raphe respond to ATP, and whether purinergic signalling in these regions influences CO2 responsiveness in vitro and in vivo. In brain slices, cell-attached recordings of membrane potential show that CO2/H(+)-sensitive NTS neurons are activated by focal ATP application; however, purinergic P2-receptor blockade did not affect their CO2/H(+) responsiveness. CO2/H(+)-sensitive raphe neurons were unaffected by ATP or P2-receptor blockade. In vivo, ATP injection into the NTS increased cardiorespiratory activity; however, injection of a P2-receptor blocker into this region had no effect on baseline breathing or CO2/H(+) responsiveness. Injections of ATP or a P2-receptor blocker into the medullary raphe had no effect on cardiorespiratory activity or the chemoreflex. As a positive control we confirmed that ATP injection into the RTN increased breathing and blood pressure by a P2-receptor-dependent mechanism. These results suggest that purinergic signalling is a unique feature of RTN chemoreception.
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Affiliation(s)
- Cleyton R Sobrinho
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo, 1524, Prof. Lineu Prestes Avenue, 05508-000, São Paulo, SP, Brazil. ; D. K. Mulkey: Department of Physiology and Neurobiology, University of Connecticut, 75 N Eagleville Rd, Unit 3156, Storrs, CT 06269-3156, USA.
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Onimaru H, Ikeda K, Mariho T, Kawakami K. Cytoarchitecture and CO(2) sensitivity of Phox2b-positive Parafacial neurons in the newborn rat medulla. PROGRESS IN BRAIN RESEARCH 2014; 209:57-71. [PMID: 24746043 DOI: 10.1016/b978-0-444-63274-6.00004-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Preinspiratory (Pre-I) neurons in the parafacial respiratory group (pFRG) compose one of the respiratory rhythm generators in the medulla of the newborn rat. It has been shown that a subgroup of pFRG/Pre-I neurons could also work as central chemoreceptor neurons, because the CO(2) sensitivity of these Pre-I neurons was preserved even after blockade of Na(+) channels and Ca(2+) channels, and the membrane depolarization induced by hypercapnic stimulation was mainly because of the closing of K(+) channels. These neurons, some of which were identified to be glutamatergic, express the transcription factor Phox2b. Phox2b expression was one of the most noticeable characteristics of pFRG/Pre-I neurons. We also found that Phox2b-expressing neurons in the parafacial region of the rostral ventral medulla tended to assemble around capillary blood vessels. In contrast, another subclass of the pFRG/Pre-I neurons was Phox2b-negative and CO(2)-insensitive. Some of these neurons were identified to be glycinergic or GABAergic. Thus, Phox2b expression is a key genetic marker that can be used to more clearly establish the cell architecture of the pFRG, which consists of heterogeneous neuronal subtypes. In this chapter, we elaborate on the CO(2) sensitivity of Phox2b-positive/negative parafacial neurons and the cytoarchitecture in the newborn rat medulla, and discuss ionic mechanisms of CO(2) responsiveness.
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Affiliation(s)
- Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, Shinagawa-ku, Tokyo, Japan.
| | - Keiko Ikeda
- Division of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan
| | - Tani Mariho
- Department of Physiology, Showa University School of Medicine, Shinagawa-ku, Tokyo, Japan
| | - Kiyoshi Kawakami
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
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TASK-2 channels contribute to pH sensitivity of retrotrapezoid nucleus chemoreceptor neurons. J Neurosci 2013; 33:16033-44. [PMID: 24107938 DOI: 10.1523/jneurosci.2451-13.2013] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Phox2b-expressing glutamatergic neurons of the retrotrapezoid nucleus (RTN) display properties expected of central respiratory chemoreceptors; they are directly activated by CO2/H(+) via an unidentified pH-sensitive background K(+) channel and, in turn, facilitate brainstem networks that control breathing. Here, we used a knock-out mouse model to examine whether TASK-2 (K2P5), an alkaline-activated background K(+) channel, contributes to RTN neuronal pH sensitivity. We made patch-clamp recordings in brainstem slices from RTN neurons that were identified by expression of GFP (directed by the Phox2b promoter) or β-galactosidase (from the gene trap used for TASK-2 knock-out). Whereas nearly all RTN cells from control mice were pH sensitive (95%, n = 58 of 61), only 56% of GFP-expressing RTN neurons from TASK-2(-/-) mice (n = 49 of 88) could be classified as pH sensitive (>30% reduction in firing rate from pH 7.0 to pH 7.8); the remaining cells were pH insensitive (44%). Moreover, none of the recorded RTN neurons from TASK-2(-/-) mice selected based on β-galactosidase activity (a subpopulation of GFP-expressing neurons) were pH sensitive. The alkaline-activated background K(+) currents were reduced in amplitude in RTN neurons from TASK-2(-/-) mice that retained some pH sensitivity but were absent from pH-insensitive cells. Finally, using a working heart-brainstem preparation, we found diminished inhibition of phrenic burst amplitude by alkalization in TASK-2(-/-) mice, with apneic threshold shifted to higher pH levels. In conclusion, alkaline-activated TASK-2 channels contribute to pH sensitivity in RTN neurons, with effects on respiration in situ that are particularly prominent near apneic threshold.
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42
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Abstract
The main functions of the respiratory neural network are to produce a coordinated, efficient, rhythmic motor behavior and maintain homeostatic control over blood oxygen and CO2/pH levels. Purinergic (ATP) signaling features prominently in these homeostatic reflexes. The signaling actions of ATP are produced through its binding to a diversity of ionotropic P2X and metabotropic P2Y receptors. However, its net effect on neuronal and network excitability is determined by the interaction between the three limbs of a complex system comprising the signaling actions of ATP at P2Rs, the distribution of multiple ectonucleotidases that differentially metabolize ATP into ADP, AMP, and adenosine (ADO), and the signaling actions of ATP metabolites, especially ADP at P2YRs and ADO at P1Rs. Understanding the significance of purinergic signaling is further complicated by the fact that neurons, glia, and the vasculature differentially express P2 and P1Rs, and that both neurons and glia release ATP. This article reviews at cellular, synaptic, and network levels, current understanding and emerging concepts about the diverse roles played by this three-part signaling system in: mediating the chemosensitivity of respiratory networks to hypoxia and CO2/pH; modulating the activity of rhythm generating networks and inspiratory motoneurons, and; controlling blood flow through the cerebral vasculature.
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Affiliation(s)
- Gregory D Funk
- Department of Physiology, Centre for Neuroscience, Women & Children's Health Research Institute (WCHRI), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
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Guyenet PG, Abbott SBG. Chemoreception and asphyxia-induced arousal. Respir Physiol Neurobiol 2013; 188:333-43. [PMID: 23608705 PMCID: PMC3749262 DOI: 10.1016/j.resp.2013.04.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 04/02/2013] [Accepted: 04/06/2013] [Indexed: 02/07/2023]
Abstract
Arousal protects against the adverse and potentially fatal effects of asphyxia during sleep. Asphyxia stimulates the carotid bodies and central chemoreceptors but the sequence of events leading to arousal is uncertain. In this review, the theoretical mechanisms leading to arousal from sleep are briefly summarized and the issue of whether central respiratory chemoreceptors (CRCs) or other types of CO2-responsive CNS neurons contribute to asphyxia-induced arousal is discussed. We focus on the role of the retrotrapezoid nucleus, the raphe and the locus coeruleus and emphasize the anatomical and neurophysiological evidence which suggests that these putative central chemoreceptors could contribute to arousal independently of their effects on breathing. Finally, we describe recent attempts to test the contribution of specific brainstem pathways to asphyxia-induced arousal using optogenetic and other tools and the possible contribution of a group of hypoxia-sensitive brainstem neurons (the C1 cells) to breathing and arousal.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, United States.
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44
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Abstract
Central respiratory chemoreceptors sense changes in CO2/H(+) and initiate the adjustments to ventilation required to preserve brain and tissue pH. The cellular nature of the sensors (neurons and/or glia) and their CNS location are not conclusively established but the glutamatergic, Phox2b-expressing neurons located in the retrotrapezoid nucleus (RTN) are strong candidates. However, a direct demonstration that RTN neurons are intrinsically sensitive to CO2/H(+), required for designation as a chemosensor, has been lacking. To address this, we tested the pH sensitivity of RTN neurons that were acutely dissociated from two lines of Phox2b-GFP BAC transgenic mice. All GFP-labeled cells assayed by reverse transcriptase-PCR (n = 40) were Phox2b+, VGlut2+, TH-, and ChAT-, the neurochemical phenotype previously defined for chemosensitive RTN neurons in vivo. We found that most dissociated RTN neurons from both lines of mice were CO2/H(+)-sensitive (∼79%), with discharge increasing during acidification and decreasing during alkalization. The pH-sensitive cells could be grouped into two populations characterized by similar pH sensitivity but different basal firing rates, as previously observed in recordings from GFP-labeled RTN neurons in slice preparations. In conclusion, these data indicate that RTN neurons are inherently pH-sensitive, as expected for a respiratory chemoreceptor.
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45
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Smith JC, Abdala APL, Borgmann A, Rybak IA, Paton JFR. Brainstem respiratory networks: building blocks and microcircuits. Trends Neurosci 2012; 36:152-62. [PMID: 23254296 DOI: 10.1016/j.tins.2012.11.004] [Citation(s) in RCA: 269] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 11/10/2012] [Accepted: 11/12/2012] [Indexed: 01/18/2023]
Abstract
Breathing movements in mammals are driven by rhythmic neural activity generated within spatially and functionally organized brainstem neural circuits comprising the respiratory central pattern generator (CPG). This rhythmic activity provides homeostatic regulation of gases in blood and tissues and integrates breathing with other motor acts. We review new insights into the spatial-functional organization of key neural microcircuits of this CPG from recent multidisciplinary experimental and computational studies. The emerging view is that the microcircuit organization within the CPG allows the generation of multiple rhythmic breathing patterns and adaptive switching between them, depending on physiological or pathophysiological conditions. These insights open the possibility for site- and mechanism-specific interventions to treat various disorders of the neural control of breathing.
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Affiliation(s)
- Jeffrey C Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, MD, USA.
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46
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Abstract
Breathing is an essential behavior that presents a unique opportunity to understand how the nervous system functions normally, how it balances inherent robustness with a highly regulated lability, how it adapts to both rapidly and slowly changing conditions, and how particular dysfunctions result in disease. We focus on recent advancements related to two essential sites for respiratory rhythmogenesis: (a) the preBötzinger Complex (preBötC) as the site for the generation of inspiratory rhythm and (b) the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG) as the site for the generation of active expiration.
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Affiliation(s)
- Jack L Feldman
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095-1763, USA.
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48
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Abstract
Extracellular adenosine 5' triphosphate (ATP) is a widespread cell-to-cell signaling molecule in the brain, where it activates cell surface P2X and P2Y receptors. P2X receptors define a protein family unlike other neurotransmitter-gated ion channels in terms of sequence, subunit topology, assembly, and architecture. Within milliseconds of binding ATP, they catalyze the opening of a cation-selective pore. However, recent data show that P2X receptors often underlie neuromodulatory responses on slower time scales of seconds or longer. Herein, we review these findings at molecular, cellular and systems levels. We propose that, while P2X receptors are fast ligand-gated cation channels, they are most adept at mediating slow neuromodulatory functions that are more widespread and more physiologically utilized than fast ATP synaptic transmission in the CNS.
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Affiliation(s)
- Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1751, USA.
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49
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Onimaru H, Ikeda K, Kawakami K. Relationship between the distribution of the paired-like homeobox gene (Phox2b) expressing cells and blood vessels in the parafacial region of the ventral medulla of neonatal rats. Neuroscience 2012; 212:131-9. [DOI: 10.1016/j.neuroscience.2012.03.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 03/15/2012] [Accepted: 03/16/2012] [Indexed: 10/28/2022]
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50
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Wenker IC, Sobrinho CR, Takakura AC, Moreira TS, Mulkey DK. Regulation of ventral surface CO2/H+-sensitive neurons by purinergic signalling. J Physiol 2012; 590:2137-50. [PMID: 22411009 DOI: 10.1113/jphysiol.2012.229666] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Central chemoreception is the mechanism by which the brain regulates breathing in response to changes in tissue CO(2)H+. A brainstem region called the retrotrapezoid nucleus (RTN) contains a population of CO2/H+-sensitive neurons that appears to function as an important chemoreceptor. Evidence also indicates that CO2-evoked ATP release from RTN astrocytes modulates activity of CO2/H+-sensitive neurons; however, the extent to which purinergic signalling contributes to chemoreception by RTN neurons is not clear and the mechanism(s) underlying CO2/H+-evoked ATP release is not fully elucidated. The goals of this study are to determine the extent to which ATP contributes to RTN chemoreception both in vivo and in vitro, and whether purinergic drive to chemoreceptors relies on extracellular Ca(2+) or gap junction hemichannels. We also examine the possible contribution of P2Y1 receptors expressed in the RTN to the purinergic drive to breathe.We show that purinergic signalling contributes, in part, to the CO(2)/H+ sensitivity of RTN neurons. In vivo, phrenic nerve recordings of respiratory activity in adult rats show that bilateral injections of pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS, a P2 receptor blocker) decreased the ventilatory response to CO2 by 30%. In vitro, loose-patch recordings from RTN neurons show that P2 receptor blockers decreased responsiveness to both 10% and 15% CO2 also by 30%. In the slice, the contribution of purinergic signalling to RTN chemoreception did not increase with temperature (22–35◦C) and was retained in low extracellular Ca2+ medium. Conversely, the gap junction blockers carbenoxolone and cobalt decreased neuronal CO2/H+ sensitivity by an amount similar to P2 receptor antagonists. Inhibition of the P2Y1 receptor in the RTN had no effect on CO2 responsivness in vitro or in vivo; thus, the identity of P2 receptors underlying the purinergic component of RTN chemoreception remains unknown. These results support the possibility that CO2/H+-evoked ATP release is mediated by a mechanism involving gap junction hemichannels.
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Affiliation(s)
- Ian C Wenker
- University of Connecticut, Department of Physiology and Neurobiology, Storrs, CT 06269, USA.
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