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Cui K, Xia Y, Patnaik A, Salivara A, Lowenstein ED, Isik EG, Knorz AL, Airaghi L, Crotti M, Garratt AN, Meng F, Schmitz D, Studer M, Rijli FM, Nothwang HG, Rost BR, Strauß U, Hernandez-Miranda LR. Genetic identification of medullary neurons underlying congenital hypoventilation. SCIENCE ADVANCES 2024; 10:eadj0720. [PMID: 38896627 PMCID: PMC11186509 DOI: 10.1126/sciadv.adj0720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 05/14/2024] [Indexed: 06/21/2024]
Abstract
Mutations in the transcription factors encoded by PHOX2B or LBX1 correlate with congenital central hypoventilation disorders. These conditions are typically characterized by pronounced hypoventilation, central apnea, and diminished chemoreflexes, particularly to abnormally high levels of arterial PCO2. The dysfunctional neurons causing these respiratory disorders are largely unknown. Here, we show that distinct, and previously undescribed, sets of medullary neurons coexpressing both transcription factors (dB2 neurons) account for specific respiratory functions and phenotypes seen in congenital hypoventilation. By combining intersectional chemogenetics, intersectional labeling, lineage tracing, and conditional mutagenesis, we uncovered subgroups of dB2 neurons with key functions in (i) respiratory tidal volumes, (ii) the hypercarbic reflex, (iii) neonatal respiratory stability, and (iv) neonatal survival. These data provide functional evidence for the critical role of distinct medullary dB2 neurons in neonatal respiratory physiology. In summary, our work identifies distinct subgroups of dB2 neurons regulating breathing homeostasis, dysfunction of which causes respiratory phenotypes associated with congenital hypoventilation.
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Affiliation(s)
- Ke Cui
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Yiling Xia
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Abhisarika Patnaik
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Aikaterini Salivara
- German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | | | - Eser G. Isik
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Adrian L. Knorz
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Laura Airaghi
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Michela Crotti
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Alistair N. Garratt
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Fanqi Meng
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Dietmar Schmitz
- German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Michèle Studer
- Université Côte d'Azur (UCA), CNRS, Inserm, Institute of Biology Valrose (iBV), Nice, France
| | - Filippo M. Rijli
- Laboratory of Developmental Neuroepigenetics, Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Hans G. Nothwang
- Division of Neurogenetics, Cluster of Excellence Hearing4all, Carl von Ossietzky University, Oldenburg, Germany
| | - Benjamin R. Rost
- German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ulf Strauß
- Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Luis R. Hernandez-Miranda
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
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Janes TA, Cardani S, Saini JK, Pagliardini S. Etonogestrel promotes respiratory recovery in an in vivo rat model of central chemoreflex impairment. Acta Physiol (Oxf) 2024; 240:e14093. [PMID: 38258900 DOI: 10.1111/apha.14093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/11/2023] [Accepted: 01/01/2024] [Indexed: 01/24/2024]
Abstract
AIM The central CO2 chemoreflex is a vital component of respiratory control networks, providing excitatory drive during resting conditions and challenges to blood gas homeostasis. The retrotrapezoid nucleus is a crucial hub for CO2 chemosensitivity; its ablation or inhibition attenuates CO2 chemoreflexes and diminishes restful breathing. Similar phenotypes characterize certain hypoventilation syndromes, suggesting underlying retrotrapezoid nucleus impairment in these disorders. Progesterone stimulates restful breathing and CO2 chemoreflexes. However, its mechanisms and sites of actions remain unknown and the experimental use of synthetic progestins in patients and animal models have been met with mixed respiratory outcomes. METHODS We investigated whether acute or chronic administration of the progestinic drug, etonogestrel, could rescue respiratory chemoreflexes following selective lesion of the retrotrapezoid nucleus with saporin toxin. Adult female Sprague Dawley rats were grouped based on lesion size determined by the number of surviving chemosensitive neurons, and ventilatory responses were measured by whole body plethysmography. RESULTS Ventilatory responses to hypercapnia (but not hypoxia) were compromised in a lesion-dependent manner. Chronic etonogestrel treatment improved CO2 chemosensitivity selectively in rats with moderate lesion, suggesting that a residual number of chemosensitive neurons are required for etonogestrel-induced CO2 chemoreflex recovery. CONCLUSION This study provides new evidence for the use of progestins as respiratory stimulants under conditions of central hypoventilation and provides a new testable model for assessing the mechanism of action of progestins in the respiratory network.
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Affiliation(s)
- Tara A Janes
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Silvia Cardani
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Jasmeen K Saini
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Silvia Pagliardini
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
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Souza GMPR, Abbott SBG. Loss-of-function of chemoreceptor neurons in the retrotrapezoid nucleus: What have we learned from it? Respir Physiol Neurobiol 2024; 322:104217. [PMID: 38237884 PMCID: PMC10922619 DOI: 10.1016/j.resp.2024.104217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Revised: 01/11/2024] [Accepted: 01/13/2024] [Indexed: 01/23/2024]
Abstract
Central respiratory chemoreceptors are cells in the brain that regulate breathing in relation to arterial pH and PCO2. Neurons located at the retrotrapezoid nucleus (RTN) have been hypothesized to be central chemoreceptors and/or to be part of the neural network that drives the central respiratory chemoreflex. The inhibition or ablation of RTN chemoreceptor neurons has offered important insights into the role of these cells on central respiratory chemoreception and the neural control of breathing over almost 60 years since the original identification of acid-sensitive properties of this ventral medullary site. Here, we discuss the current definition of chemoreceptor neurons in the RTN and describe how this definition has evolved over time. We then summarize the results of studies that use loss-of-function approaches to evaluate the effects of disrupting the function of RTN neurons on respiration. These studies offer evidence that RTN neurons are indispensable for the central respiratory chemoreflex in mammals and exert a tonic drive to breathe at rest. Moreover, RTN has an interdependent relationship with oxygen sensing mechanisms for the maintenance of the neural drive to breathe and blood gas homeostasis. Collectively, RTN neurons are a genetically-defined group of putative central respiratory chemoreceptors that generate CO2-dependent drive that supports eupneic breathing and stimulates the hypercapnic ventilatory reflex.
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Goldstein DS. Linking the Extended Autonomic System with the Homeostat Theory: New Perspectives about Dysautonomias. J Pers Med 2024; 14:123. [PMID: 38276245 PMCID: PMC10817591 DOI: 10.3390/jpm14010123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 01/14/2024] [Accepted: 01/20/2024] [Indexed: 01/27/2024] Open
Abstract
Dysautonomias are conditions in which altered functions of one or more components of the autonomic nervous system (ANS) adversely affect health. This essay is about how elucidating mechanisms of dysautonomias may rationalize personalized treatments. Emphasized here are two relatively new ideas-the "extended" autonomic system (EAS) and the "homeostat" theory as applied to the pathophysiology and potential treatments of dysautonomias. The recently promulgated concept of the EAS updates Langley's ANS to include neuroendocrine, immune/inflammatory, and central components. The homeostat theory builds on Cannon's theory of homeostasis by proposing the existence of comparators (e.g., a thermostat, glucostat, carbistat, barostat) that receive information about regulated variables (e.g., core temperature, blood glucose, blood gases, delivery of blood to the brain). Homeostats sense discrepancies between the information and response algorithms. The presentation links the EAS with the homeostat theory to understand pathophysiological mechanisms of dysautonomias. Feed-forward anticipatory processes shift input-output curves and maintain plateau levels of regulated variables within different bounds of values-"allostasis". Sustained allostatic processes increase long-term wear-and-tear on effectors and organs-allostatic load. They decreaseing thresholds for destabilizing and potentially fatal positive feedback loops. The homeostat theory enables mathematical models that define stress, allostasis, and allostatic load. The present discussion applies the EAS and homeostat concepts to specific examples of pediatric, adolescent/adult, and geriatric dysautonomias-familial dysautonomia, chronic orthostatic intolerance, and Lewy body diseases. Computer modeling has the potential to take into account the complexity and dynamics of allostatic processes and may yield testable predictions about individualized treatments and outcomes.
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Affiliation(s)
- David S Goldstein
- Autonomic Medicine Section, Clinical Neurosciences Program, Division of Intramural Research, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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Conde SV, Polotsky VY, Joseph V, Kinkead R. On the origins of sleep disordered breathing, cardiorespiratory and metabolic dysfunction: which came first, the chicken or the egg? J Physiol 2023; 601:5509-5525. [PMID: 36988138 PMCID: PMC10539476 DOI: 10.1113/jp284113] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 03/08/2023] [Indexed: 03/30/2023] Open
Abstract
Sleep disordered breathing (SDB) is a complex, sex specific and highly heterogeneous group of respiratory disorders. Nevertheless, sleep fragmentation and repeated fluctuations of arterial blood gases for several hours per night are at the core of the problem; together, they impose significant stress to the organism with deleterious consequences on physical and mental health. SDB increases the risk of obesity, diabetes, depression and anxiety disorders; however, the same health issues are risk factors for SDB. So, which came first, the chicken or the egg? What causes the appearance of the first significant apnoeic events during sleep? These are important questions because although moderate to severe SDB affects ∼500 million adults globally, we still have a poor understanding of the origins of the disease, and the main treatments (and animal models) focus on the symptoms rather than the cause. Because obesity, metabolic dysfunction and stress-related neurological disorders generally appear progressively, we discuss how the development of these diseases can lead to specific anatomical and non-anatomical traits of SDB in males and females while considering the impacts of sex steroids. In light of the growing evidence indicating that the carotid bodies are important sensors of key metabolic and endocrine signals associated with stress and dysmetabolism, we propose that these organs play a key role in the process.
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Affiliation(s)
- Silvia V. Conde
- NOVA Medical School, Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisboa, Portugal
| | - Vsevolod Y Polotsky
- Department of Anesthesiology and Critical Care Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Vincent Joseph
- Département de Pédiatrie, Université Laval & Research Center of the Québec Heart and Lung Institute, Québec, QC. Canada
| | - Richard Kinkead
- Département de Pédiatrie, Université Laval & Research Center of the Québec Heart and Lung Institute, Québec, QC. Canada
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Xie Y, Zhang L, Guo S, Peng R, Gong H, Yang M. Changes in respiratory structure and function after traumatic cervical spinal cord injury: observations from spinal cord and brain. Front Neurol 2023; 14:1251833. [PMID: 37869136 PMCID: PMC10587692 DOI: 10.3389/fneur.2023.1251833] [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: 07/02/2023] [Accepted: 09/18/2023] [Indexed: 10/24/2023] Open
Abstract
Respiratory difficulties and mortality following severe cervical spinal cord injury (CSCI) result primarily from malfunctions of respiratory pathways and the paralyzed diaphragm. Nonetheless, individuals with CSCI can experience partial recovery of respiratory function through respiratory neuroplasticity. For decades, researchers have revealed the potential mechanism of respiratory nerve plasticity after CSCI, and have made progress in tissue healing and functional recovery. While most existing studies on respiratory plasticity after spinal cord injuries have focused on the cervical spinal cord, there is a paucity of research on respiratory-related brain structures following such injuries. Given the interconnectedness of the spinal cord and the brain, traumatic changes to the former can also impact the latter. Consequently, are there other potential therapeutic targets to consider? This review introduces the anatomy and physiology of typical respiratory centers, explores alterations in respiratory function following spinal cord injuries, and delves into the structural foundations of modified respiratory function in patients with CSCI. Additionally, we propose that magnetic resonance neuroimaging holds promise in the study of respiratory function post-CSCI. By studying respiratory plasticity in the brain and spinal cord after CSCI, we hope to guide future clinical work.
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Affiliation(s)
- Yongqi Xie
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
| | - Liang Zhang
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
| | - Shuang Guo
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
- Department of Rehabilitation, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Run Peng
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
| | - Huiming Gong
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
- Department of Spinal and Neural Functional Reconstruction, China Rehabilitation Research Center, Beijing, China
| | - Mingliang Yang
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
- Department of Spinal and Neural Functional Reconstruction, China Rehabilitation Research Center, Beijing, China
- Center of Neural Injury and Repair, Beijing Institute for Brain Disorders, Beijing, China
- Beijing Key Laboratory of Neural Injury and Rehabilitation, Beijing, China
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Goldman M, Lucke-Wold B, Katz J, Dawoud B, Dagra A. Respiratory Patterns in Neurological Injury, Pathophysiology, Ventilation Management, and Future Innovations: A Systematic Review. EXPLORATORY RESEARCH AND HYPOTHESIS IN MEDICINE 2023; 8:338-349. [PMID: 38130817 PMCID: PMC10735242 DOI: 10.14218/erhm.2022.00081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Traumatic brain injuries (TBI), ischemic stroke, hemorrhagic stroke, brain tumors, and seizures have diverse and sometimes overlapping associated breathing patterns. Homeostatic mechanisms for respiratory control are intertwined with complex neurocircuitry, both centrally and peripherally. This paper summarizes the neurorespiratory control and pathophysiology of its disruption. It also reviews the clinical presentation, ventilatory management, and emerging therapeutics. This review additionally serves to update all recent preclinical and clinical research regarding the spectrum of respiratory dysfunction. Having a solid pathophysiological foundation of disruptive mechanisms would permit further therapeutic development. This novel review bridges experimental/physiological data with bedside management, thus allowing neurosurgeons and intensivists alike to rapidly diagnose and treat respiratory sequelae of acute brain injury.
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Affiliation(s)
| | | | | | - Bavly Dawoud
- Neurosurgical Resident, University of Illinois, Peoria Illinois, United States
| | - Abeer Dagra
- Research Assistant, University of Florida, Gainesville, United States
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Souza GMPR, Stornetta DS, Shi Y, Lim E, Berry FE, Bayliss DA, Abbott SBG. Neuromedin B-Expressing Neurons in the Retrotrapezoid Nucleus Regulate Respiratory Homeostasis and Promote Stable Breathing in Adult Mice. J Neurosci 2023; 43:5501-5520. [PMID: 37290937 PMCID: PMC10376939 DOI: 10.1523/jneurosci.0386-23.2023] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 06/01/2023] [Accepted: 06/05/2023] [Indexed: 06/10/2023] Open
Abstract
Respiratory chemoreceptor activity encoding arterial Pco2 and Po2 is a critical determinant of ventilation. Currently, the relative importance of several putative chemoreceptor mechanisms for maintaining eupneic breathing and respiratory homeostasis is debated. Transcriptomic and anatomic evidence suggests that bombesin-related peptide Neuromedin-B (Nmb) expression identifies chemoreceptor neurons in the retrotrapezoid nucleus (RTN) that mediate the hypercapnic ventilatory response, but functional support is missing. In this study, we generated a transgenic Nmb-Cre mouse and used Cre-dependent cell ablation and optogenetics to test the hypothesis that RTN Nmb neurons are necessary for the CO2-dependent drive to breathe in adult male and female mice. Selective ablation of ∼95% of RTN Nmb neurons causes compensated respiratory acidosis because of alveolar hypoventilation, as well as profound breathing instability and respiratory-related sleep disruption. Following RTN Nmb lesion, mice were hypoxemic at rest and were prone to severe apneas during hyperoxia, suggesting that oxygen-sensitive mechanisms, presumably the peripheral chemoreceptors, compensate for the loss of RTN Nmb neurons. Interestingly, ventilation following RTN Nmb -lesion was unresponsive to hypercapnia, but behavioral responses to CO2 (freezing and avoidance) and the hypoxia ventilatory response were preserved. Neuroanatomical mapping shows that RTN Nmb neurons are highly collateralized and innervate the respiratory-related centers in the pons and medulla with a strong ipsilateral preference. Together, this evidence suggests that RTN Nmb neurons are dedicated to the respiratory effects of arterial Pco2/pH and maintain respiratory homeostasis in intact conditions and suggest that malfunction of these neurons could underlie the etiology of certain forms of sleep-disordered breathing in humans.SIGNIFICANCE STATEMENT Respiratory chemoreceptors stimulate neural respiratory motor output to regulate arterial Pco2 and Po2, thereby maintaining optimal gas exchange. Neurons in the retrotrapezoid nucleus (RTN) that express the bombesin-related peptide Neuromedin-B are proposed to be important in this process, but functional evidence has not been established. Here, we developed a transgenic mouse model and demonstrated that RTN neurons are fundamental for respiratory homeostasis and mediate the stimulatory effects of CO2 on breathing. Our functional and anatomic data indicate that Nmb-expressing RTN neurons are an integral component of the neural mechanisms that mediate CO2-dependent drive to breathe and maintain alveolar ventilation. This work highlights the importance of the interdependent and dynamic integration of CO2- and O2-sensing mechanisms in respiratory homeostasis of mammals.
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Affiliation(s)
- George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Daniel S Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Eunu Lim
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Faye E Berry
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
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Pereyra K, Díaz-Jara E, Arias P, Bravo L, Toledo C, Schwarz K, Del Rio R. Role of Peripheral Chemoreceptors on Enhanced Central Chemoreflex Drive in Nonischemic Heart Failure. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1427:107-114. [PMID: 37322341 DOI: 10.1007/978-3-031-32371-3_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Heart failure (HF) is a prevalent disease in elderly population. Potentiation of the ventilatory chemoreflex drive plays a pivotal role in disease progression, at least in part, through their contribution to the generation/maintenance of breathing disorders. Peripheral and central chemoreflexes are mainly regulated by carotid body (CB) and the retrotrapezoid nuclei (RTN), respectively. Recent evidence showed an enhanced central chemoreflex drive in rats with nonischemic HF along with breathing disorders. Importantly, increase activity from RTN chemoreceptors contribute to the potentiation of central chemoreflex response to hypercapnia. The precise mechanism driving RTN potentiation in HF is still elusive. Since interdependency of RTN and CB chemoreceptors has been described, we hypothesized that CB afferent activity is required to increase RTN chemosensitivity in the setting of HF. Accordingly, we studied central/peripheral chemoreflex drive and breathing disorders in HF rats with and without functional CBs (CB denervation). We found that CB afferent activity was required to increase central chemoreflex drive in HF. Indeed, CB denervation restored normal central chemoreflex drive and reduced the incidence of apneas by twofold. Our results support the notion that CB afferent activity plays an important role in central chemoreflex potentiation in rats with HF.
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Affiliation(s)
- Katherin Pereyra
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Esteban Díaz-Jara
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Paulina Arias
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Liena Bravo
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Camilo Toledo
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Karla Schwarz
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile.
- Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile.
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A Methodological Perspective on the Function and Assessment of Peripheral Chemoreceptors in Heart Failure: A Review of Data from Clinical Trials. Biomolecules 2022; 12:biom12121758. [PMID: 36551186 PMCID: PMC9775522 DOI: 10.3390/biom12121758] [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: 11/04/2022] [Revised: 11/22/2022] [Accepted: 11/24/2022] [Indexed: 11/29/2022] Open
Abstract
Augmented peripheral chemoreceptor sensitivity (PChS) is a common feature of many sympathetically mediated diseases, among others, and it is an important mechanism of the pathophysiology of heart failure (HF). It is related not only to the greater severity of symptoms, especially to dyspnea and lower exercise tolerance but also to a greater prevalence of complications and poor prognosis. The causes, mechanisms, and impact of the enhanced activity of peripheral chemoreceptors (PChR) in the HF population are subject to intense research. Several methodologies have been established and utilized to assess the PChR function. Each of them presents certain advantages and limitations. Furthermore, numerous factors could influence and modulate the response from PChR in studied subjects. Nevertheless, even with the impressive number of studies conducted in this field, there are still some gaps in knowledge that require further research. We performed a review of all clinical trials in HF human patients, in which the function of PChR was evaluated. This review provides an extensive synthesis of studies evaluating PChR function in the HF human population, including methods used, factors potentially influencing the results, and predictors of increased PChS.
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Toledo C, Ortolani D, Ortiz FC, Marcus NJ, Del Rio R. Potential Role of the Retrotrapezoid Nucleus in Mediating Cardio-Respiratory Dysfunction in Heart Failure With Preserved Ejection Fraction. Front Physiol 2022; 13:863963. [PMID: 35492622 PMCID: PMC9039230 DOI: 10.3389/fphys.2022.863963] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 03/29/2022] [Indexed: 01/15/2023] Open
Abstract
A strong association between chemoreflex hypersensitivity, disordered breathing, and elevated sympathetic activity has been shown in experimental and human heart failure (HF). The contribution of chemoreflex hypersensitivity in HF pathophysiology is incompletely understood. There is ample evidence that increased peripheral chemoreflex drive in HF with reduced ejection fraction (HFrEF; EF<40%) leads to pathophysiological changes in autonomic and cardio-respiratory control, but less is known about the neural mechanisms mediating cardio-respiratory disturbances in HF with preserved EF (HFpEF; EF>50%). Importantly, it has been shown that activation of the central chemoreflex worsens autonomic dysfunction in experimental HFpEF, an effect mediated in part by the activation of C1 catecholaminergic neurons neighboring the retrotrapezoid nucleus (RTN), an important region for central chemoreflex control of respiratory and autonomic function. Accordingly, the main purpose of this brief review is to discuss the possible role played by activation of central chemoreflex pathways on autonomic function and its potential role in precipitating disordered breathing in HFpEF. Improving understanding of the contribution of the central chemoreflex to the pathophysiology of HFpEF may help in development of novel interventions intended to improve cardio-respiratory outcomes in HFpEF.
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Affiliation(s)
- Camilo Toledo
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
| | - Domiziana Ortolani
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Fernando C. Ortiz
- Mechanisms of Myelin Formation and Repair Laboratory, Facultad de Ciencias de Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Santiago, Chile
| | - Noah J. Marcus
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, IA, United States
| | - Rodrigo Del Rio
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
- Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile
- *Correspondence: Rodrigo Del Rio,
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Abstract
This paper uses a unique dataset from Lebanon, a developing country with unstable political conditions, to explore the drivers of research outcomes. We use the Negative Binomial model to empirically examine the determinants of the total number of publications and single and co-authored articles. The results indicate that males are more likely to publish co-authored papers than females. Moreover, our findings show a quadratic relationship between age and the number of published papers with a peak at the age of 40. After this turning point, the publication rate starts to decrease at an increasing rate. When we run the model by gender, we find that females in large departments tend to publish more co-authored papers. We also find that full professors tend to publish more papers in Q1 and Q2 journals, while associate professors have more papers in Q2 and Q3 journals.
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13
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Turk AZ, Bishop M, Adeck A, SheikhBahaei S. Astrocytic modulation of central pattern generating motor circuits. Glia 2022; 70:1506-1519. [PMID: 35212422 DOI: 10.1002/glia.24162] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 12/26/2022]
Abstract
Central pattern generators (CPGs) generate the rhythmic and coordinated neural features necessary for the proper conduction of complex behaviors. In particular, CPGs are crucial for complex motor behaviors such as locomotion, mastication, respiration, and vocal production. While the importance of these networks in modulating behavior is evident, the mechanisms driving these CPGs are still not fully understood. On the other hand, accumulating evidence suggests that astrocytes have a significant role in regulating the function of some of these CPGs. Here, we review the location, function, and role of astrocytes in locomotion, respiration, and mastication CPGs and propose that, similarly, astrocytes may also play a significant role in the vocalization CPG.
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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, Maryland, USA
| | - Mitchell Bishop
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Afuh Adeck
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
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14
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Li Z, Ballance W, Joy M, Patel S, Hwang J, Kong H, Saif TA. Adaptive biohybrid pumping machine with flow loop feedback. Biofabrication 2022; 14. [PMID: 35045402 DOI: 10.1088/1758-5090/ac4d19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 01/19/2022] [Indexed: 11/11/2022]
Abstract
Tissue-engineered living machines is an emerging discipline that employs complex interactions between living cells and engineered scaffolds to self-assemble biohybrid systems for diverse scientific research and technological applications. Here, we report an adaptive, autonomous biohybrid pumping machine with flow loop feedback powered by engineered living muscles. The tissue is made from skeletal muscle cells (C2C12) and collagen /Matrigel matrix, which self-assembles into a ring that compresses a soft tube connected at both ends to a rigid fluidic platform. The muscle ring contracts in a cyclic fashion autonomously, squeezing the tube forming an impedance pump. The resulting flow is circulated back to the muscle ring forming a feedback loop, which allows the pump to respond to the cues received from the flow it generates and adaptively manage its pumping performances based on the feedback. The developed biohybrid pumping system may have broad utility and impact in health, medicine and bioengineering.
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Affiliation(s)
- Zhengwei Li
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 W Green St, Urbana, Urbana, Illinois, 61801-2946, UNITED STATES
| | - William Ballance
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 1206 W Green St, Urbana, Urbana, 61801-3028, UNITED STATES
| | - Md Joy
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 W Green St, Urbana, Illinois, 61801, UNITED STATES
| | - Shrey Patel
- Department of Bioengineering, University of Illinois at Urbana-Champaign, 1206 W Green St, Urbana, Urbana, 61801-3028, UNITED STATES
| | - Joanne Hwang
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 1206 W Green St, Urbana, Urbana, 61801-3028, UNITED STATES
| | - Hyunjoon Kong
- Department of Chemical and Biomolecular Engineering, University of Illinois - Urbana-Champaign, 600 S Mathew Street, 108 RAL, Urbana, IL 61801, USA, Urbana, Illinois, 61801, UNITED STATES
| | - Taher A Saif
- Mechanical Science and Engineering, University of Illinois - Urbana-Champaign, Mechanical Eng. Building, 1206 West Green Street, Urbana, IL 61801, USA, Urbana, 61801, UNITED STATES
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15
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Abstract
Obstructive sleep apnea (OSA) is a disease that results from loss of upper airway muscle tone leading to upper airway collapse during sleep in anatomically susceptible persons, leading to recurrent periods of hypoventilation, hypoxia, and arousals from sleep. Significant clinical consequences of the disorder cover a wide spectrum and include daytime hypersomnolence, neurocognitive dysfunction, cardiovascular disease, metabolic dysfunction, respiratory failure, and pulmonary hypertension. With escalating rates of obesity a major risk factor for OSA, the public health burden from OSA and its sequalae are expected to increase, as well. In this chapter, we review the mechanisms responsible for the development of OSA and associated neurocognitive and cardiometabolic comorbidities. Emphasis is placed on the neural control of the striated muscles that control the pharyngeal passages, especially regulation of hypoglossal motoneuron activity throughout the sleep/wake cycle, the neurocognitive complications of OSA, and the therapeutic options available to treat OSA including recent pharmacotherapeutic developments.
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Affiliation(s)
- Luu V Pham
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, MD, United States.
| | - Jonathan Jun
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, MD, United States
| | - Vsevolod Y Polotsky
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, MD, United States
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16
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Abstract
Brain PCO2 is sensed primarily via changes in [H+]. Small pH changes are detected in the medulla oblongata and trigger breathing adjustments that help maintain arterial PCO2 constant. Larger perturbations of brain CO2/H+, possibly also sensed elsewhere in the CNS, elicit arousal, dyspnea, and stress, and cause additional breathing modifications. The retrotrapezoid nucleus (RTN), a rostral medullary cluster of glutamatergic neurons identified by coexpression of Phoxb and Nmb transcripts, is the lynchpin of the central respiratory chemoreflex. RTN regulates breathing frequency, inspiratory amplitude, and active expiration. It is exquisitely responsive to acidosis in vivo and maintains breathing autorhythmicity during quiet waking, slow-wave sleep, and anesthesia. The RTN response to [H+] is partly an intrinsic neuronal property mediated by proton sensors TASK-2 and GPR4 and partly a paracrine effect mediated by astrocytes and the vasculature. The RTN also receives myriad excitatory or inhibitory synaptic inputs including from [H+]-responsive neurons (e.g., serotonergic). RTN is silenced by moderate hypoxia. RTN inactivity (periodic or sustained) contributes to periodic breathing and, likely, to central sleep apnea. RTN development relies on transcription factors Egr2, Phox2b, Lbx1, and Atoh1. PHOX2B mutations cause congenital central hypoventilation syndrome; they impair RTN development and consequently the central respiratory chemoreflex.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States.
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States
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17
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Stewart JM, Pianosi PT. Postural orthostatic tachycardia syndrome: A respiratory disorder? Curr Res Physiol 2021; 4:1-6. [PMID: 34746821 PMCID: PMC8562237 DOI: 10.1016/j.crphys.2021.01.002] [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: 12/07/2020] [Revised: 01/12/2021] [Accepted: 01/13/2021] [Indexed: 11/28/2022] Open
Abstract
Postural orthostatic tachycardia syndrome (POTS) is a disorder epitomized by the story of the blind men and the elephant. Patients may see primary care internists or pediatricians due to fatigue, be referred to neurologists for “spells”, to cardiologists for evaluation of pre-syncope or chest pain, to gastroenterologists for nausea or dyspepsia, and even pulmonologists for dyspnea. Adoption of a more systematic approach to their evaluation and better characterization of patients has led to greater understanding of comorbidities, hypotheses prompting mechanistic investigations, and pharmacologic trials. Recent work has implicated disordered sympathetic nervous system activation in response to central (thoracic) hypovolemia. It is this pathway that leads one zero in on a putative focal point from which many of the clinical manifestations can be explained – specifically the carotid body. Despite heterogeneity in etiopathogenesis of a POTS phenotype, we propose that aberrant activation and response of the carotid body represents one potential common pathway in evolution. To understand this postulate, one must jettison isolationist or reductionist ideas of chemoreceptor and baroreceptor functions of the carotid body or sinus, respectively, and consider their interaction and interdependence both locally and centrally where some of its efferents merge. Doing so enables one to connect the dots and appreciate origins of diverse manifestations of POTS, including dyspnea for which the concept of neuro-mechanical uncoupling is wanting, thereby expanding our construct of this symptom. This perspective expounds our premise that POTS has a prominent respiratory component. Dyspnea affects ~⅓ patients with postural orthostatic tachycardia syndrome (POTS). POTS is characterized by thoracic hypovolemia and compromised cephalad perfusion when upright. Carotid body and adjacent carotid sinus mediate chemo- and baro- reflexes, respectively. These are not independent and stimulation of either activates sympathetic discharge. We speculate that carotid body mediates hyperventilation and dyspnea in POTS.
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Affiliation(s)
- Julian M Stewart
- Department of Pediatrics, New York Medical College, Valhalla, NY, USA.,Department of Physiology, New York Medical College, Valhalla, NY, USA
| | - Paolo T Pianosi
- Department of Pediatrics, Division of Pulmonary & Sleep Medicine, University of Minnesota, VCRC, 401 E River Parkway Rm 413, Minneapolis, UK
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18
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Palkovic B, Marchenko V, Zuperku EJ, Stuth EAE, Stucke AG. Multi-Level Regulation of Opioid-Induced Respiratory Depression. Physiology (Bethesda) 2021; 35:391-404. [PMID: 33052772 DOI: 10.1152/physiol.00015.2020] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Opioids depress minute ventilation primarily by reducing respiratory rate. This results from direct effects on the preBötzinger Complex as well as from depression of the Parabrachial/Kölliker-Fuse Complex, which provides excitatory drive to preBötzinger Complex neurons mediating respiratory phase-switch. Opioids also depress awake drive from the forebrain and chemodrive.
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Affiliation(s)
- Barbara Palkovic
- Medical College of Wisconsin, Milwaukee, Wisconsin.,Faculty of Medicine, University of Osijek, Osijek, Croatia
| | | | - Edward J Zuperku
- Medical College of Wisconsin, Milwaukee, Wisconsin.,Zablocki VA Medical Center, Milwaukee, Wisconsin
| | - Eckehard A E Stuth
- Medical College of Wisconsin, Milwaukee, Wisconsin.,Children's Hospital of Wisconsin, Milwaukee, Wisconsin
| | - Astrid G Stucke
- Medical College of Wisconsin, Milwaukee, Wisconsin.,Children's Hospital of Wisconsin, Milwaukee, Wisconsin
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19
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Pho H, Berger S, Freire C, Kim LJ, Shin MK, Streeter SR, Hosamane N, Cabassa ME, Anokye-Danso F, Dergacheva O, Amorim MR, Fleury-Curado T, Jun JC, Schwartz AR, Ahima RS, Mendelowitz D, Polotsky VY. Leptin receptor expression in the dorsomedial hypothalamus stimulates breathing during NREM sleep in db/db mice. Sleep 2021; 44:6149135. [PMID: 33624805 PMCID: PMC8193564 DOI: 10.1093/sleep/zsab046] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 02/06/2021] [Indexed: 12/12/2022] Open
Abstract
STUDY OBJECTIVES Obesity leads to obstructive sleep apnea (OSA), which is recurrent upper airway obstruction during sleep, and obesity hypoventilation syndrome (OHS), hypoventilation during sleep resulting in daytime hypercapnia. Impaired leptin signaling in the brain was implicated in both conditions, but mechanisms are unknown. We have previously shown that leptin stimulates breathing and treats OSA and OHS in leptin-deficient ob/ob mice and leptin-resistant diet-induced obese mice and that leptin's respiratory effects may occur in the dorsomedial hypothalamus (DMH). We hypothesized that leptin receptor LepRb-deficient db/db mice have obesity hypoventilation and that restoration of leptin signaling in the DMH will increase ventilation during sleep in these animals. METHODS We measured arterial blood gas in unanesthetized awake db/db mice. We subsequently infected these animals with Ad-LepRb or control Ad-mCherry virus into the DMH and measured ventilation during sleep as well as CO2 production after intracerebroventricular (ICV) infusions of phosphate-buffered saline or leptin. RESULTS Awake db/db mice had elevated CO2 levels in the arterial blood. Ad-LepRb infection resulted in LepRb expression in the DMH neurons in a similar fashion to wildtype mice. In LepRb-DMH db/db mice, ICV leptin shortened REM sleep and increased inspiratory flow, tidal volume, and minute ventilation during NREM sleep without any effect on the quality of NREM sleep or CO2 production. Leptin had no effect on upper airway obstruction in these animals. CONCLUSION Leptin stimulates breathing and treats obesity hypoventilation acting on LepRb-positive neurons in the DMH.
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Affiliation(s)
- Huy Pho
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Slava Berger
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Carla Freire
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Lenise J Kim
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Mi-Kyung Shin
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Stone R Streeter
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Nishitha Hosamane
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Meaghan E Cabassa
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Frederick Anokye-Danso
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Olga Dergacheva
- Department of Pharmacology and Physiology, George Washington University, Washington, DC, USA
| | - Mateus R Amorim
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Thomaz Fleury-Curado
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jonathan C Jun
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Alan R Schwartz
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Otorhinolaryngology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Rexford S Ahima
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - David Mendelowitz
- Department of Pharmacology and Physiology, George Washington University, Washington, DC, USA
| | - Vsevolod Y Polotsky
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Corresponding author. Vsevolod (Seva) Y. Polotsky, Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Johns Hopkins Asthma and Allergy Center, Rm 4B65, Baltimore, MD 21224.
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20
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Carr JMJR, Caldwell HG, Ainslie PN. Cerebral blood flow, cerebrovascular reactivity and their influence on ventilatory sensitivity. Exp Physiol 2021; 106:1425-1448. [PMID: 33932955 DOI: 10.1113/ep089446] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 04/26/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the topic of this review? Cerebrovascular reactivity to CO2 , which is a principal factor in determining ventilatory responses to CO2 through the role reactivity plays in determining cerebral extra- and intracellular pH. What advances does it highlight? Recent animal evidence suggests central chemoreceptor vasculature may demonstrate regionally heterogeneous cerebrovascular reactivity to CO2 , potentially as a protective mechanism against excessive CO2 washout from the central chemoreceptors, thereby allowing ventilation to reflect the systemic acid-base balance needs (respiratory changes in P aC O 2 ) rather than solely the cerebral needs. Ventilation per se does not influence cerebrovascular reactivity independent of changes in P aC O 2 . ABSTRACT Alveolar ventilation and cerebral blood flow are both predominantly regulated by arterial blood gases, especially arterial P C O 2 , and so are intricately entwined. In this review, the fundamental mechanisms underlying cerebrovascular reactivity and central chemoreceptor control of breathing are covered. We discuss the interaction of cerebral blood flow and its reactivity with the control of ventilation and ventilatory responsiveness to changes in P C O 2 , as well as the lack of influence of ventilation itself on cerebrovascular reactivity. We briefly summarize the effects of arterial hypoxaemia on the relationship between ventilatory and cerebrovascular response to both P C O 2 and P O 2 . We then highlight key methodological considerations regarding the interaction of reactivity and ventilatory sensitivity, including the following: regional heterogeneity of cerebrovascular reactivity; a pharmacological approach for the reduction of cerebral blood flow; reactivity assessment techniques; the influence of mean arterial blood pressure; and sex-related differences. Finally, we discuss ventilatory and cerebrovascular control in the context of high altitude and congestive heart failure. Future research directions and pertinent questions of interest are highlighted throughout.
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Affiliation(s)
- Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, University of British Columbia - Okanagan Campus, British Columbia, Canada
| | - Hannah G Caldwell
- Centre for Heart, Lung and Vascular Health, University of British Columbia - Okanagan Campus, British Columbia, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia - Okanagan Campus, British Columbia, Canada
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21
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Pereyra KV, Schwarz KG, Andrade DC, Toledo C, Rios-Gallardo A, Díaz-Jara E, Bastías SS, Ortiz FC, Ortolani D, Del Rio R. Paraquat herbicide diminishes chemoreflex sensitivity, induces cardiac autonomic imbalance and impair cardiac function in rats. Am J Physiol Heart Circ Physiol 2021; 320:H1498-H1509. [PMID: 33513085 DOI: 10.1152/ajpheart.00710.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 01/21/2021] [Indexed: 11/22/2022]
Abstract
Paraquat (PQT) herbicide is widely used in agricultural practices despite being highly toxic to humans. It has been proposed that PQT exposure may promote cardiorespiratory impairment. However, the physiological mechanisms involved in cardiorespiratory dysfunction following PQT exposure are poorly known. We aimed to determine the effects of PQT on ventilatory chemoreflex control, cardiac autonomic control, and cardiac function in rats. Male Sprague-Dawley rats received two injections/week of PQT (5 mg·kg-1 ip) for 4 wk. Cardiac function was assessed through echocardiography and pressure-volume loops. Ventilatory function was evaluated using whole body plethysmography. Autonomic control was indirectly evaluated by heart rate variability (HRV). Cardiac electrophysiology (EKG) and exercise capacity were also measured. Four weeks of PQT administration markedly enlarged the heart as evidenced by increases in ventricular volumes and induced cardiac diastolic dysfunction. Indeed, end-diastolic pressure was significantly higher in PQT rats compared with control (2.42 ± 0.90 vs. 4.01 ± 0.92 mmHg, PQT vs. control, P < 0.05). In addition, PQT significantly reduced both the hypercapnic and hypoxic ventilatory chemoreflex response and induced irregular breathing. Also, PQT induced autonomic imbalance and reductions in the amplitude of EKG waves. Finally, PQT administration impaired exercise capacity in rats as evidenced by a ∼2-fold decrease in times-to-fatigue compared with control rats. Our results showed that 4 wk of PQT treatment induces cardiorespiratory dysfunction in rats and suggests that repetitive exposure to PQT may induce harmful mid/long-term cardiovascular, respiratory, and cardiac consequences.NEW & NOREWORTHY Paraquat herbicide is still employed in agricultural practices in several countries. Here, we showed for the first time that 1 mo paraquat administration results in cardiac adverse remodeling, blunts ventilatory chemoreflex drive, and promotes irregular breathing at rest in previously healthy rats. In addition, paraquat exposure induced cardiac autonomic imbalance and cardiac electrophysiology alterations. Lastly, cardiac diastolic dysfunction was overt in rats following 1 mo of paraquat treatment.
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Affiliation(s)
- Katherin V Pereyra
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Karla G Schwarz
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Envejecimiento y Regeneración, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - David C Andrade
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Fisiología y Medicina de Altura, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Camilo Toledo
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
| | - Angélica Rios-Gallardo
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Esteban Díaz-Jara
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Sussy S Bastías
- Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
| | - Fernando C Ortiz
- Mechanism of Myelin Formation and Repair Laboratory, Instituto de Ciencias Biomédicas, Facultad de Ciencias de Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Domiziana Ortolani
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Envejecimiento y Regeneración, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
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22
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Keir DA, Duffin J, Floras JS. Measuring Peripheral Chemoreflex Hypersensitivity in Heart Failure. Front Physiol 2020; 11:595486. [PMID: 33447244 PMCID: PMC7802759 DOI: 10.3389/fphys.2020.595486] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 11/30/2020] [Indexed: 01/08/2023] Open
Abstract
Heart failure with reduced ejection fraction (HFrEF) induces chronic sympathetic activation. This disturbance is a consequence of both compensatory reflex disinhibition in response to lower cardiac output and patient-specific activation of one or more excitatory stimuli. The result is the net adrenergic output that exceeds homeostatic need, which compromises cardiac, renal, and vascular function and foreshortens lifespan. One such sympatho-excitatory mechanism, evident in ~40-45% of those with HFrEF, is the augmentation of carotid (peripheral) chemoreflex ventilatory and sympathetic responsiveness to reductions in arterial oxygen tension and acidosis. Recognition of the contribution of increased chemoreflex gain to the pathophysiology of HFrEF and to patients' prognosis has focused attention on targeting the carotid body to attenuate sympathetic drive, alleviate heart failure symptoms, and prolong life. The current challenge is to identify those patients most likely to benefit from such interventions. Two assumptions underlying contemporary test protocols are that the ventilatory response to acute hypoxic exposure quantifies accurately peripheral chemoreflex sensitivity and that the unmeasured sympathetic response mirrors the determined ventilatory response. This Perspective questions both assumptions, illustrates the limitations of conventional transient hypoxic tests for assessing peripheral chemoreflex sensitivity and demonstrates how a modified rebreathing test capable of comprehensively quantifying both the ventilatory and sympathoneural efferent responses to peripheral chemoreflex perturbation, including their sensitivities and recruitment thresholds, can better identify individuals most likely to benefit from carotid body intervention.
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Affiliation(s)
- Daniel A. Keir
- University Health Network and Mount Sinai Hospital Division of Cardiology and Department of Medicine, University of Toronto, Toronto General Research Institute, Toronto, ON, Canada
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - James Duffin
- Department of Anesthesia and Pain Management, University of Toronto, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Thornhill Research Inc., Toronto, ON, Canada
| | - John S. Floras
- University Health Network and Mount Sinai Hospital Division of Cardiology and Department of Medicine, University of Toronto, Toronto General Research Institute, Toronto, ON, Canada
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23
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Guyenet PG, Stornetta RL, Souza GMPR, Abbott SBG, Brooks VL. Neuronal Networks in Hypertension: Recent Advances. Hypertension 2020; 76:300-311. [PMID: 32594802 DOI: 10.1161/hypertensionaha.120.14521] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurogenic hypertension is associated with excessive sympathetic nerve activity to the kidneys and portions of the cardiovascular system. Here we examine the brain regions that cause heightened sympathetic nerve activity in animal models of neurogenic hypertension, and we discuss the triggers responsible for the changes in neuronal activity within these regions. We highlight the limitations of the evidence and, whenever possible, we briefly address the pertinence of the findings to human hypertension. The arterial baroreflex reduces arterial blood pressure variability and contributes to the arterial blood pressure set point. This set point can also be elevated by a newly described cerebral blood flow-dependent and astrocyte-mediated sympathetic reflex. Both reflexes converge on the presympathetic neurons of the rostral medulla oblongata, and both are plausible causes of neurogenic hypertension. Sensory afferent dysfunction (reduced baroreceptor activity, increased renal, or carotid body afferent) contributes to many forms of neurogenic hypertension. Neurogenic hypertension can also result from activation of brain nuclei or sensory afferents by excess circulating hormones (leptin, insulin, Ang II [angiotensin II]) or sodium. Leptin raises blood vessel sympathetic nerve activity by activating the carotid bodies and subsets of arcuate neurons. Ang II works in the lamina terminalis and probably throughout the brain stem and hypothalamus. Sodium is sensed primarily in the lamina terminalis. Regardless of its cause, the excess sympathetic nerve activity is mediated to some extent by activation of presympathetic neurons located in the rostral ventrolateral medulla or the paraventricular nucleus of the hypothalamus. Increased activity of the orexinergic neurons also contributes to hypertension in selected models.
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Affiliation(s)
- Patrice G Guyenet
- From the Department of Pharmacology, University of Virginia, Charlottesville (P.G.G., R.L.S., G.M.P.R.S., S.B.G.A.)
| | - Ruth L Stornetta
- From the Department of Pharmacology, University of Virginia, Charlottesville (P.G.G., R.L.S., G.M.P.R.S., S.B.G.A.)
| | - George M P R Souza
- From the Department of Pharmacology, University of Virginia, Charlottesville (P.G.G., R.L.S., G.M.P.R.S., S.B.G.A.)
| | - Stephen B G Abbott
- From the Department of Pharmacology, University of Virginia, Charlottesville (P.G.G., R.L.S., G.M.P.R.S., S.B.G.A.)
| | - Virginia L Brooks
- Department of Chemical Physiology and Biochemistry, Oregon Health & Sciences University, Portland (V.L.B.)
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24
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Dempsey JA, Smith CA. Update on Chemoreception: Influence on Cardiorespiratory Regulation and Pathophysiology. Clin Chest Med 2020; 40:269-283. [PMID: 31078209 DOI: 10.1016/j.ccm.2019.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We examine recent findings that have revealed interdependence of function within the chemoreceptor pathway regulating breathing and sympathetic vasomotor activity and the hypersensitization of these reflexes in chronic disease states. Recommendations are made as to how these states of hyperreflexia in chemoreceptors and muscle afferents might be modified in treating sleep apnea, drug-resistant hypertension, chronic heart failure-induced sympathoexcitation, and the exertional dyspnea of chronic obstructive pulmonary disease.
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Affiliation(s)
- Jerome A Dempsey
- Department Population Health Sciences, University of Wisconsin-Madison, 707 WARF Building, 610 N. Walnut Street, WI 53726, USA.
| | - Curtis A Smith
- Department Population Health Sciences, University of Wisconsin-Madison, 707 WARF Building, 610 N. Walnut Street, WI 53726, USA
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25
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Melo MR, Gasparini S, Silva EF, Karlen-Amarante M, Speretta GF, Lauar MR, Pedrino GR, Menani JV, Colombari DSA, Zoccal DB, Colombari E. Renovascular hypertension elevates pulmonary ventilation in rats by carotid body-dependent mechanisms. Am J Physiol Regul Integr Comp Physiol 2020; 318:R730-R742. [PMID: 32022595 DOI: 10.1152/ajpregu.00134.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The two kidney-one clip (2K1C) renovascular hypertension depends on the renin-angiotensin system and sympathetic overactivity. The maintenance of 2K1C hypertension also depends on inputs from the carotid bodies (CB), which when activated stimulate the respiratory activity. In the present study, we investigated the importance of CB afferent activity for the ventilatory responses in 2K1C hypertensive rats and for phrenic and hypoglossal activities in in situ preparations of normotensive rats treated with angiotensin II. Silver clips were implanted around the left renal artery of male Holtzman rats (150 g) to induce renovascular hypertension. Six weeks after clipping, hypertensive 2K1C rats showed, in conscious state, elevated resting tidal volume and minute ventilation compared with the normotensive group. 2K1C rats also presented arterial alkalosis, urinary acidification, and amplified hypoxic ventilatory response. Carotid body removal (CBR), 2 wk before the experiments (4th week after clipping), significantly reduced arterial pressure and pulmonary ventilation in 2K1C rats but not in normotensive rats. Intra-arterial administration of angiotensin II in the in situ preparation of normotensive rats increased phrenic and hypoglossal activities, responses that were also reduced after CBR. Results show that renovascular hypertensive rats exhibit increased resting ventilation that depends on CB inputs. Similarly, angiotensin II increases phrenic and hypoglossal activities in in situ preparations of normotensive rats, responses that also depend on CB inputs. Results suggest that mechanisms that depend on CB inputs in renovascular hypertensive rats or during angiotensin II administration in normotensive animals increase respiratory drive.
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Affiliation(s)
- Mariana Rosso Melo
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Silvia Gasparini
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Elaine F Silva
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil.,Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás, Goiânia, Goiás, Brazil
| | - Marlusa Karlen-Amarante
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Guilherme F Speretta
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Mariana R Lauar
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Gustavo R Pedrino
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goiás, Goiânia, Goiás, Brazil
| | - Jose V Menani
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Debora S A Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
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26
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Clayson MS, Devereaux MEM, Pamenter ME. Neurokinin-1 receptor activation is sufficient to restore the hypercapnic ventilatory response in the Substance P-deficient naked mole-rat. Am J Physiol Regul Integr Comp Physiol 2020; 318:R712-R721. [PMID: 31967860 DOI: 10.1152/ajpregu.00251.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Naked mole-rats (NMRs) live in large colonies within densely populated underground burrows. Their collective respiration generates significant metabolic carbon dioxide (CO2) that diffuses slowly out of the burrow network, creating a hypercapnic environment. Currently, the physiological mechanisms that underlie the ability of NMRs to tolerate environmental hypercapnia are largely unknown. To address this, we used whole-body plethysmography and respirometry to elucidate the hypercapnic ventilatory and metabolic responses of awake, freely behaving NMRs to 0%-10% CO2. We found that NMRs have a blunted hypercapnic ventilatory response (HCVR): ventilation increased only in 10% CO2. Conversely, metabolism was unaffected by hypercapnia. NMRs are insensitive to cutaneous acid-based pain caused by modified substance P (SP)-mediated peripheral neurotransmission, and SP is also an important neuromodulator of ventilation. Therefore, we re-evaluated physiological responses to hypercapnia in NMRs after an intraperitoneal injection of exogenous substance P (2 mg/kg) or a long-lived isoform of substance P {[pGlu5-MePhe8-MeGly9]SP(5-11), DiMe-C7; 40-400 μg/kg}. We found that both drugs restored hypercapnia sensitivity and unmasked an HCVR in animals breathing 2%-10% CO2. Taken together, our findings indicate that NMRs are remarkably tolerant of hypercapnic environments and have a blunted HCVR; however, the signaling network architecture required for a "normal" HCVR is retained but endogenously inactive. This muting of chemosensitivity likely suits the ecophysiology of this species, which presumably experiences hypercapnia regularly in their underground niche.
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Affiliation(s)
- Maxwell S Clayson
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.,University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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27
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Souza GMPR, Kanbar R, Stornetta DS, Abbott SBG, Stornetta RL, Guyenet PG. Breathing regulation and blood gas homeostasis after near complete lesions of the retrotrapezoid nucleus in adult rats. J Physiol 2019; 596:2521-2545. [PMID: 29667182 DOI: 10.1113/jp275866] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 04/04/2018] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS The retrotrapezoid nucleus (RTN) drives breathing proportionally to brain PCO2 but its role during various states of vigilance needs clarification. Under normoxia, RTN lesions increased the arterial PCO2 set-point, lowered the PO2 set-point and reduced alveolar ventilation relative to CO2 production. Tidal volume was reduced and breathing frequency increased to a comparable degree during wake, slow-wave sleep and REM sleep. RTN lesions did not produce apnoeas or disordered breathing during sleep. RTN lesions in rats virtually eliminated the central respiratory chemoreflex (CRC) while preserving the cardiorespiratory responses to hypoxia; the relationship between CRC and number of surviving RTN Nmb neurons was an inverse exponential. The CRC does not function without the RTN. In the quasi-complete absence of the RTN and CRC, alveolar ventilation is reduced despite an increased drive to breathe from the carotid bodies. ABSTRACT The retrotrapezoid nucleus (RTN) is one of several CNS nuclei that contribute, in various capacities (e.g. CO2 detection, neuronal modulation) to the central respiratory chemoreflex (CRC). Here we test how important the RTN is to PCO2 homeostasis and breathing during sleep or wake. RTN Nmb-positive neurons were killed with targeted microinjections of substance P-saporin conjugate in adult rats. Under normoxia, rats with large RTN lesions (92 ± 4% cell loss) had normal blood pressure and arterial pH but were hypoxic (-8 mmHg PaO2 ) and hypercapnic (+10 mmHg ). In resting conditions, minute volume (VE ) was normal but breathing frequency (fR ) was elevated and tidal volume (VT ) reduced. Resting O2 consumption and CO2 production were normal. The hypercapnic ventilatory reflex in 65% FiO2 had an inverse exponential relationship with the number of surviving RTN neurons and was decreased by up to 92%. The hypoxic ventilatory reflex (HVR; FiO2 21-10%) persisted after RTN lesions, hypoxia-induced sighing was normal and hypoxia-induced hypotension was reduced. In rats with RTN lesions, breathing was lowest during slow-wave sleep, especially under hyperoxia, but apnoeas and sleep-disordered breathing were not observed. In conclusion, near complete RTN destruction in rats virtually eliminates the CRC but the HVR persists and sighing and the state dependence of breathing are unchanged. Under normoxia, RTN lesions cause no change in VE but alveolar ventilation is reduced by at least 21%, probably because of increased physiological dead volume. RTN lesions do not cause sleep apnoea during slow-wave sleep, even under hyperoxia.
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Affiliation(s)
- George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| | - Roy Kanbar
- Department of Pharmaceutical Sciences, Lebanese American University, Beyrouth, Lebanon
| | - Daniel S Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| | - Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
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28
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Guyenet PG, Stornetta RL, Souza GMPR, Abbott SBG, Shi Y, Bayliss DA. The Retrotrapezoid Nucleus: Central Chemoreceptor and Regulator of Breathing Automaticity. Trends Neurosci 2019; 42:807-824. [PMID: 31635852 DOI: 10.1016/j.tins.2019.09.002] [Citation(s) in RCA: 123] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/28/2019] [Accepted: 09/05/2019] [Indexed: 12/15/2022]
Abstract
The ventral surface of the rostral medulla oblongata has been suspected since the 1960s to harbor central respiratory chemoreceptors [i.e., acid-activated neurons that regulate breathing to maintain a constant arterial PCO2 (PaCO2)]. The key neurons, a.k.a. the retrotrapezoid nucleus (RTN), have now been identified. In this review we describe their transcriptome, developmental lineage, and anatomical projections. We also review their contribution to CO2 homeostasis and to the regulation of breathing automaticity during sleep and wake. Finally, we discuss several mechanisms that contribute to the activation of RTN neurons by CO2in vivo: cell-autonomous effects of protons; paracrine effects of pH mediated by surrounding astrocytes and blood vessels; and excitatory inputs from other CO2-responsive CNS neurons.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
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29
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Bruce RM, Jolley C, White MJ. Control of exercise hyperpnoea: Contributions from thin-fibre skeletal muscle afferents. Exp Physiol 2019; 104:1605-1621. [PMID: 31429500 DOI: 10.1113/ep087649] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/16/2019] [Indexed: 12/16/2022]
Abstract
NEW FINDINGS What is the topic of this review? In this review, we examine the evidence for control mechanisms underlying exercise hyperpnoea, giving attention to the feedback from thin-fibre skeletal muscle afferents, and highlight the frequently conflicting findings and difficulties encountered by researchers using a variety of experimental models. What advances does it highlight? There has been a recent resurgence of interest in the role of skeletal muscle afferent involvement, not only as a mechanism of healthy exercise hyperpnoea but also in the manifestation of breathlessness and exercise intolerance in chronic disease. ABSTRACT The ventilatory response to dynamic submaximal exercise is immediate and proportional to metabolic rate, which maintains isocapnia. How these respiratory responses are controlled remains poorly understood, given that the most tightly controlled variable (arterial partial pressure of CO2 /H+ ) provides no error signal for arterial chemoreceptors to trigger reflex increases in ventilation. This review discusses evidence for different postulated control mechanisms, with a focus on the feedback from group III/IV skeletal muscle mechanosensitive and metabosensitive afferents. This concept is attractive, because the stimulation of muscle mechanoreceptors might account for the immediate increase in ventilation at the onset of exercise, and signals from metaboreceptors might be proportional to metabolic rate. A variety of experimental models have been used to establish the contribution of thin-fibre muscle afferents in ventilatory control during exercise, with equivocal results. The inhibition of afferent feedback via the application of lumbar intrathecal fentanyl during exercise suppresses ventilation, which provides the most compelling supportive evidence to date. However, stimulation of afferent feedback at rest has no consistent effect on respiratory output. However, evidence is emerging for synergistic interactions between muscle afferent feedback and other stimulatory inputs to the central respiratory neuronal pool. These seemingly hyperadditive effects might explain the conflicting findings encountered when using different experimental models. We also discuss the increasing evidence that patients with certain chronic diseases exhibit exaggerated muscle afferent activation during exercise, resulting in enhanced cardiorespiratory responses. This might provide a neural link between the well-established limb muscle dysfunction and the associated exercise intolerance and exertional dyspnoea, which might offer therapeutic targets for these patients.
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Affiliation(s)
- Richard M Bruce
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Sciences, King's College London, London, UK
| | - Caroline Jolley
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Sciences, King's College London, London, UK
| | - Michael J White
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
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30
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Abstract
Central sleep apnea is prevalent in patients with heart failure, healthy individuals at high altitudes, and chronic opiate users and in the initiation of "mixed" (that is, central plus obstructive apneas). This brief review focuses on (a) the causes of repetitive, cyclical central apneas as mediated primarily through enhanced sensitivities in the respiratory control system and (b) treatment of central sleep apnea through modification of key components of neurochemical control as opposed to the current universal use of positive airway pressure.
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Affiliation(s)
- Jerome A. Dempsey
- Department of Population Health Sciences, University of Wisconsin - Madison, WARF Building, 7th Floor, 614 Walnut Street, Madison, WI 53726, USA
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31
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Ben-Tal A, Wang Y, Leite MCA. The logic behind neural control of breathing pattern. Sci Rep 2019; 9:9078. [PMID: 31235701 PMCID: PMC6591426 DOI: 10.1038/s41598-019-45011-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 05/29/2019] [Indexed: 01/09/2023] Open
Abstract
The respiratory rhythm generator is spectacular in its ability to support a wide range of activities and adapt to changing environmental conditions, yet its operating mechanisms remain elusive. We show how selective control of inspiration and expiration times can be achieved in a new representation of the neural system (called a Boolean network). The new framework enables us to predict the behavior of neural networks based on properties of neurons, not their values. Hence, it reveals the logic behind the neural mechanisms that control the breathing pattern. Our network mimics many features seen in the respiratory network such as the transition from a 3-phase to 2-phase to 1-phase rhythm, providing novel insights and new testable predictions.
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Affiliation(s)
- Alona Ben-Tal
- School of Natural and Computational Sciences, Massey University, Auckland, New Zealand.
| | - Yunjiao Wang
- Department of Mathematics, Texas Southern University, Houston, TX, USA
| | - Maria C A Leite
- Mathematics and Statistics Unit, University of South Florida St Petersburg, St Petersburg, FL, USA
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32
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Guyenet PG, Stornetta RL, Holloway BB, Souza GMPR, Abbott SBG. Rostral Ventrolateral Medulla and Hypertension. Hypertension 2019; 72:559-566. [PMID: 30354763 DOI: 10.1161/hypertensionaha.118.10921] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Patrice G Guyenet
- From the Department of Pharmacology, University of Virginia, Charlottesville
| | - Ruth L Stornetta
- From the Department of Pharmacology, University of Virginia, Charlottesville
| | - Benjamin B Holloway
- From the Department of Pharmacology, University of Virginia, Charlottesville
| | - George M P R Souza
- From the Department of Pharmacology, University of Virginia, Charlottesville
| | - Stephen B G Abbott
- From the Department of Pharmacology, University of Virginia, Charlottesville
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33
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Lindsey BG, Nuding SC, Segers LS, Morris KF. Carotid Bodies and the Integrated Cardiorespiratory Response to Hypoxia. Physiology (Bethesda) 2019; 33:281-297. [PMID: 29897299 DOI: 10.1152/physiol.00014.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Advances in our understanding of brain mechanisms for the hypoxic ventilatory response, coordinated changes in blood pressure, and the long-term consequences of chronic intermittent hypoxia as in sleep apnea, such as hypertension and heart failure, are giving impetus to the search for therapies to "erase" dysfunctional memories distributed in the carotid bodies and central nervous system. We review current network models, open questions, sex differences, and implications for translational research.
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Affiliation(s)
- Bruce G Lindsey
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Sarah C Nuding
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Lauren S Segers
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Kendall F Morris
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
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34
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Benarroch EE. Brainstem integration of arousal, sleep, cardiovascular, and respiratory control. Neurology 2018; 91:958-966. [PMID: 30355703 DOI: 10.1212/wnl.0000000000006537] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
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35
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Andrade DC, Haine L, Toledo C, Diaz HS, Quintanilla RA, Marcus NJ, Iturriaga R, Richalet JP, Voituron N, Del Rio R. Ventilatory and Autonomic Regulation in Sleep Apnea Syndrome: A Potential Protective Role for Erythropoietin? Front Physiol 2018; 9:1440. [PMID: 30374309 PMCID: PMC6196773 DOI: 10.3389/fphys.2018.01440] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 09/21/2018] [Indexed: 12/20/2022] Open
Abstract
Obstructive sleep apnea (OSA) is the most common form of sleep disordered breathing and is associated with wide array of cardiovascular morbidities. It has been proposed that during OSA, the respiratory control center (RCC) is affected by exaggerated afferent signals coming from peripheral/central chemoreceptors which leads to ventilatory instability and may perpetuate apnea generation. Treatments focused on decreasing hyperactivity of peripheral/central chemoreceptors may be useful to improving ventilatory instability in OSA patients. Previous studies indicate that oxidative stress and inflammation are key players in the increased peripheral/central chemoreflex drive associated with OSA. Recent data suggest that erythropoietin (Epo) could also be involved in modulating chemoreflex activity as functional Epo receptors are constitutively expressed in peripheral and central chemoreceptors cells. Additionally, there is some evidence that Epo has anti-oxidant/anti-inflammatory effects. Accordingly, we propose that Epo treatment during OSA may reduce enhanced peripheral/central chemoreflex drive and normalize the activity of the RCC which in turn may help to abrogate ventilatory instability. In this perspective article we discuss the potential beneficial effects of Epo administration on ventilatory regulation in the setting of OSA.
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Affiliation(s)
- David C Andrade
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Liasmine Haine
- Laboratoire Hypoxie and Poumon - EA2363, Université Paris 13, Paris, France
| | - Camilo Toledo
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Hugo S Diaz
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Investigación Biomédica, Universidad Autónoma de Chile, Santiago, Chile
| | | | - Noah J Marcus
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, IA, United States
| | - Rodrigo Iturriaga
- Laboratorio de Neurobiología, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Jean-Paul Richalet
- Laboratoire Hypoxie and Poumon - EA2363, Université Paris 13, Paris, France
| | - Nicolas Voituron
- Laboratoire Hypoxie and Poumon - EA2363, Université Paris 13, Paris, France
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
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36
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Ramirez JM, Severs LJ, Ramirez SC, Agosto‐Marlin IM. Advances in cellular and integrative control of oxygen homeostasis within the central nervous system. J Physiol 2018; 596:3043-3065. [PMID: 29742297 PMCID: PMC6068258 DOI: 10.1113/jp275890] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 04/04/2018] [Indexed: 12/31/2022] Open
Abstract
Mammals must continuously regulate the levels of O2 and CO2 , which is particularly important for the brain. Failure to maintain adequate O2 /CO2 homeostasis has been associated with numerous disorders including sleep apnoea, Rett syndrome and sudden infant death syndrome. But, O2 /CO2 homeostasis poses major regulatory challenges, even in the healthy brain. Neuronal activities change in a differentiated, spatially and temporally complex manner, which is reflected in equally complex changes in O2 demand. This raises important questions: is oxygen sensing an emergent property, locally generated within all active neuronal networks, and/or the property of specialized O2 -sensitive CNS regions? Increasing evidence suggests that the regulation of the brain's redox state involves properties that are intrinsic to many networks, but that specialized regions in the brainstem orchestrate the integrated control of respiratory and cardiovascular functions. Although the levels of O2 in arterial blood and the CNS are very different, neuro-glial interactions and purinergic signalling are critical for both peripheral and CNS chemosensation. Indeed, the specificity of neuroglial interactions seems to determine the differential responses to O2 , CO2 and the changes in pH.
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Affiliation(s)
- Jan Marino Ramirez
- Center for Integrative Brain ResearchSeattle Children's Research InstituteDepartment of Neurological SurgeryUniversity of Washington School of MedicineSeattleWAUSA
- Department of Physiology and BiophysicsUniversity of WashingtonSeattleWAUSA
| | - Liza J. Severs
- Department of Physiology and BiophysicsUniversity of WashingtonSeattleWAUSA
| | - Sanja C. Ramirez
- Center for Integrative Brain ResearchSeattle Children's Research InstituteDepartment of Neurological SurgeryUniversity of Washington School of MedicineSeattleWAUSA
| | - Ibis M. Agosto‐Marlin
- Center for Integrative Brain ResearchSeattle Children's Research InstituteDepartment of Neurological SurgeryUniversity of Washington School of MedicineSeattleWAUSA
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37
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Schultz HD. Advances in cellular and integrative control of oxygen and carbon dioxide homeostasis. J Physiol 2018; 596:2933-2934. [PMID: 30239019 PMCID: PMC6068245 DOI: 10.1113/jp276326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 06/01/2018] [Indexed: 11/08/2022] Open
Affiliation(s)
- Harold D. Schultz
- Department of Cellular and Integrative PhysiologyUniveristy of Nebraska Medical CenterOmahaNE 68198USA
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