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Bhat AA, Afzal M, Moglad E, Thapa R, Ali H, Almalki WH, Kazmi I, Alzarea SI, Gupta G, Subramaniyan V. lncRNAs as prognostic markers and therapeutic targets in cuproptosis-mediated cancer. Clin Exp Med 2024; 24:226. [PMID: 39325172 DOI: 10.1007/s10238-024-01491-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2024] [Accepted: 09/16/2024] [Indexed: 09/27/2024]
Abstract
Long non-coding RNAs (lncRNAs) have emerged as crucial regulators in various cellular processes, including cancer progression and stress response. Recent studies have demonstrated that copper accumulation induces a unique form of cell death known as cuproptosis, with lncRNAs playing a key role in regulating cuproptosis-associated pathways. These lncRNAs may trigger cell-specific responses to copper stress, presenting new opportunities as prognostic markers and therapeutic targets. This paper delves into the role of lncRNAs in cuproptosis-mediated cancer, underscoring their potential as biomarkers and targets for innovative therapeutic strategies. A thorough review of scientific literature was conducted, utilizing databases such as PubMed, Google Scholar, and ScienceDirect, with search terms like 'lncRNAs,' 'cuproptosis,' and 'cancer.' Studies were selected based on their relevance to lncRNA regulation of cuproptosis pathways and their implications for cancer prognosis and treatment. The review highlights the significant contribution of lncRNAs in regulating cuproptosis-related genes and pathways, impacting copper metabolism, mitochondrial stress responses, and apoptotic signaling. Specific lncRNAs are potential prognostic markers in breast, lung, liver, ovarian, pancreatic, and gastric cancers. The objective of this article is to explore the role of lncRNAs as potential prognostic markers and therapeutic targets in cancers mediated by cuproptosis.
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Affiliation(s)
- Asif Ahmad Bhat
- Uttaranchal Institute of Pharmaceutical Sciences, Uttaranchal University, Dehradun, India
| | - Muhammad Afzal
- Department of Pharmaceutical Sciences, Pharmacy Program, Batterjee Medical College, P.O. Box 6231, 21442, Jeddah, Saudi Arabia
| | - Ehssan Moglad
- Department of Pharmaceutics, College of Pharmacy, Prince Sattam Bin Abdulaziz University, 11942, Al Kharj, Saudi Arabia
| | - Riya Thapa
- Uttaranchal Institute of Pharmaceutical Sciences, Uttaranchal University, Dehradun, India
| | - Haider Ali
- Centre for Global Health Research, Saveetha Medical College, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, India
- Department of Pharmacology, Kyrgyz State Medical College, Bishkek, Kyrgyzstan
| | - Waleed Hassan Almalki
- Department of Pharmacology, College of Pharmacy, Umm Al-Qura University, Makkah, Saudi Arabia
| | - Imran Kazmi
- Department of Biochemistry, Faculty of Science, King Abdulaziz University, 21589, Jeddah, Saudi Arabia
| | - Sami I Alzarea
- Department of Pharmacology, College of Pharmacy, Jouf University, 72341, Sakaka, Aljouf, Saudi Arabia
| | - Gaurav Gupta
- Centre for Research Impact & Outcome, Chitkara College of Pharmacy, Chitkara University, Rajpura, Punjab, 140401, India
- Centre of Medical and Bio-Allied Health Sciences Research, Ajman University, Ajman, United Arab Emirates
| | - Vetriselvan Subramaniyan
- Pharmacology Unit, Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor Darul Ehsan, Malaysia.
- Department of Medical Sciences, School of Medical and Life Sciences, Sunway University, Bandar Sunway, 47500, Subang Jaya, Selangor, Malaysia.
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Yazawa I, Yoshida Y, Yoshimi R, Ozato K. Immature functional development of lumbar locomotor networks in adult Irf8-/- mice. Front Neurosci 2024; 17:1234215. [PMID: 38239832 PMCID: PMC10794560 DOI: 10.3389/fnins.2023.1234215] [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: 06/03/2023] [Accepted: 12/11/2023] [Indexed: 01/22/2024] Open
Abstract
To date, research on the role of the brainstem and spinal cord in motor behavior has relied on in vitro preparations of the neonatal rodent spinal cord, with or without the brainstem; their spatial and temporal scope are subject to technical limitations imposed by low oxygen tension in deep tissues. Therefore, we created an arterially perfused in situ preparation that allowed us to investigate functional interactions in the CNS from the neonatal to adult period. Decerebrated rodents were kept alive via total artificial cardiopulmonary bypass for extracorporeal circulation; the plasma oxygen and ion components needed for survival were supplied through the blood vessels. Interferon regulatory factor 8 (IRF8) is a transcription factor that promotes myeloid cell development and stimulates innate immune responses. In the brain, IRF8 is expressed only in microglia and directs the expression of many genes that serve microglial functions. Recent evidence indicates that IRF8 affects behavior and modulates Alzheimer's disease progression in a mouse model. However, whether this immune deficiency arising from the absence of IRF8 influences the development of the neuronal network in the spinal cord is unknown. We applied the above methodology to mice of all ages and electrophysiologically explored whether the absence of IRF8 influences the development of lumbar central pattern generator (CPG) networks. In mice of all ages, bilateral neuronal discharges by the normal CPG networks activated by the modulated sympathetic tone via descending pathways at high flow rates became organized into discharge episodes punctuated by periods of quiescence. Similar discharge episodes were generated by the adult CPG networks (≥P14 days) activated by drug application. However, discharge episodes elicited by activating the neonatal-juvenile CPG networks (
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Affiliation(s)
- Itaru Yazawa
- Department of Food and Nutrition, Kyushu Nutrition Welfare University, Kitakyushu, Japan
- Laboratory of Neural Control, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, MD, United States
| | - Yuko Yoshida
- Division of Developmental Biology, National Institute of Child Health and Human Development (NICHD), NIH, Bethesda, MD, United States
| | - Ryusuke Yoshimi
- Division of Developmental Biology, National Institute of Child Health and Human Development (NICHD), NIH, Bethesda, MD, United States
- Department of Stem Cell and Immune Regulation, Graduate School of Medicine, Yokohama City University, Yokohama, Japan
| | - Keiko Ozato
- Division of Developmental Biology, National Institute of Child Health and Human Development (NICHD), NIH, Bethesda, MD, United States
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Cummins EP, Strowitzki MJ, Taylor CT. Mechanisms and Consequences of Oxygen and Carbon Dioxide Sensing in Mammals. Physiol Rev 2019; 100:463-488. [PMID: 31539306 DOI: 10.1152/physrev.00003.2019] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Molecular oxygen (O2) and carbon dioxide (CO2) are the primary gaseous substrate and product of oxidative phosphorylation in respiring organisms, respectively. Variance in the levels of either of these gasses outside of the physiological range presents a serious threat to cell, tissue, and organism survival. Therefore, it is essential that endogenous levels are monitored and kept at appropriate concentrations to maintain a state of homeostasis. Higher organisms such as mammals have evolved mechanisms to sense O2 and CO2 both in the circulation and in individual cells and elicit appropriate corrective responses to promote adaptation to commonly encountered conditions such as hypoxia and hypercapnia. These can be acute and transient nontranscriptional responses, which typically occur at the level of whole animal physiology or more sustained transcriptional responses, which promote chronic adaptation. In this review, we discuss the mechanisms by which mammals sense changes in O2 and CO2 and elicit adaptive responses to maintain homeostasis. We also discuss crosstalk between these pathways and how they may represent targets for therapeutic intervention in a range of pathological states.
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Affiliation(s)
- Eoin P Cummins
- UCD Conway Institute, Systems Biology Ireland and the School of Medicine, University College Dublin, Belfield, Dublin, Ireland
| | - Moritz J Strowitzki
- UCD Conway Institute, Systems Biology Ireland and the School of Medicine, University College Dublin, Belfield, Dublin, Ireland
| | - Cormac T Taylor
- UCD Conway Institute, Systems Biology Ireland and the School of Medicine, University College Dublin, Belfield, Dublin, Ireland
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Patrone LGA, Duarte JB, Bícego KC, Steiner AA, Romanovsky AA, Gargaglioni LH. TRPV1 Inhibits the Ventilatory Response to Hypoxia in Adult Rats, but Not the CO₂-Drive to Breathe. Pharmaceuticals (Basel) 2019; 12:ph12010019. [PMID: 30682830 PMCID: PMC6469189 DOI: 10.3390/ph12010019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 11/27/2018] [Accepted: 12/07/2018] [Indexed: 12/31/2022] Open
Abstract
Receptors of the transient receptor potential (TRP) channels superfamily are expressed in many tissues and have different physiological functions. However, there are few studies investigating the role of these channels in cardiorespiratory control in mammals. We assessed the role of central and peripheral TRPV1 receptors in the cardiorespiratory responses to hypoxia (10% O2) and hypercapnia (7% CO2) by measuring pulmonary ventilation (V˙E), heart rate (HR), mean arterial pressure (MAP) and body temperature (Tb) of male Wistar rats before and after intraperitoneal (AMG9810 [2.85 µg/kg, 1 mL/kg]) or intracebroventricular (AMG9810 [2.85 µg/kg, 1 µL] or AMG7905 [28.5 μg/kg, 1 µL]) injections of TRPV1 antagonists. Central or peripheral injection of TRPV1 antagonists did not change cardiorespiratory parameters or Tb during room air and hypercapnic conditions. However, the hypoxic ventilatory response was exaggerated by both central and peripheral injection of AMG9810. In addition, the peripheral antagonist blunted the drop in Tb induced by hypoxia. Therefore, the current data provide evidence that TRPV1 channels exert an inhibitory modulation on the hypoxic drive to breathe and stimulate the Tb reduction during hypoxia.
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Affiliation(s)
- Luis Gustavo A Patrone
- Department of Animal Morphology and Physiology, Faculty of Agricultural and Veterinarian Sciences, UNESP at Jaboticabal, Rod. Prof. Paulo Donato Castellane s/n, Jaboticabal SP 14870-000, Brazil.
| | - Jaime B Duarte
- Department of Animal Morphology and Physiology, Faculty of Agricultural and Veterinarian Sciences, UNESP at Jaboticabal, Rod. Prof. Paulo Donato Castellane s/n, Jaboticabal SP 14870-000, Brazil.
| | - Kênia Cardoso Bícego
- Department of Animal Morphology and Physiology, Faculty of Agricultural and Veterinarian Sciences, UNESP at Jaboticabal, Rod. Prof. Paulo Donato Castellane s/n, Jaboticabal SP 14870-000, Brazil.
| | - Alexandre A Steiner
- Department of Immunology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-090, Brazil.
| | - Andrej A Romanovsky
- Thermoregulation and Systemic Inflammation Laboratory (FeverLab), Trauma Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ 85013, USA.
| | - Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, Faculty of Agricultural and Veterinarian Sciences, UNESP at Jaboticabal, Rod. Prof. Paulo Donato Castellane s/n, Jaboticabal SP 14870-000, Brazil.
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Faull OK, Subramanian HH, Ezra M, Pattinson KTS. The midbrain periaqueductal gray as an integrative and interoceptive neural structure for breathing. Neurosci Biobehav Rev 2019; 98:135-144. [PMID: 30611797 DOI: 10.1016/j.neubiorev.2018.12.020] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 11/08/2018] [Accepted: 12/18/2018] [Indexed: 01/25/2023]
Abstract
The periaqueductal gray (PAG) plays a critical role in autonomic function and behavioural responses to threatening stimuli. Recent evidence has revealed the PAG's potential involvement in the perception of breathlessness, a highly threatening respiratory symptom. In this review, we outline the current evidence in animals and humans on the role of the PAG in respiratory control and in the perception of breathlessness. While recent work has unveiled dissociable brain activity within the lateral PAG during perception of breathlessness and ventrolateral PAG during conditioned anticipation in healthy humans, this is yet to be translated into diseases dominated by breathlessness symptomology, such as chronic obstructive pulmonary disease. Understanding how the sub-structures of the PAG differentially interact with interoceptive brain networks involved in the perception of breathlessness will help towards understanding discordant symptomology, and may reveal treatment targets for those debilitated by chronic and pervasive breathlessness.
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Affiliation(s)
- Olivia K Faull
- Translational Neuromodeling Unit, University of Zürich and ETH Zürich, Zürich, Switzerland; Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | | | - Martyn Ezra
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Kyle T S Pattinson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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Beltrán-Castillo S, Morgado-Valle C, Eugenín J. The Onset of the Fetal Respiratory Rhythm: An Emergent Property Triggered by Chemosensory Drive? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1015:163-192. [PMID: 29080027 DOI: 10.1007/978-3-319-62817-2_10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The mechanisms responsible for the onset of respiratory activity during fetal life are unknown. The onset of respiratory rhythm may be a consequence of the genetic program of each of the constituents of the respiratory network, so they start to interact and generate respiratory cycles when reaching a certain degree of maturation. Alternatively, generation of cycles might require the contribution of recently formed sensory inputs that will trigger oscillatory activity in the nascent respiratory neural network. If this hypothesis is true, then sensory input to the respiratory generator must be already formed and become functional before the onset of fetal respiration. In this review, we evaluate the timing of the onset of the respiratory rhythm in comparison to the appearance of receptors, neurotransmitter machinery, and afferent projections provided by two central chemoreceptive nuclei, the raphe and locus coeruleus nuclei.
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Affiliation(s)
- Sebastián Beltrán-Castillo
- Laboratorio de Sistemas Neurales, Facultad de Química y Biología, Departamento de Biología, Universidad de Santiago de Chile, USACH, PO 9170022, Santiago, Chile
| | - Consuelo Morgado-Valle
- Centro de Investigaciones Cerebrales, Universidad Veracruzana, Campus Xalapa, Berlin 7, Fracc., Monte Magno Animas, C.P. 91190, Xalapa, Veracruz, Mexico.
| | - Jaime Eugenín
- Laboratorio de Sistemas Neurales, Facultad de Química y Biología, Departamento de Biología, Universidad de Santiago de Chile, USACH, PO 9170022, Santiago, Chile.
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Zbrzeski A, Bornat Y, Hillen B, Siu R, Abbas J, Jung R, Renaud S. Bio-Inspired Controller on an FPGA Applied to Closed-Loop Diaphragmatic Stimulation. Front Neurosci 2016; 10:275. [PMID: 27378844 PMCID: PMC4909776 DOI: 10.3389/fnins.2016.00275] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 06/01/2016] [Indexed: 12/02/2022] Open
Abstract
Cervical spinal cord injury can disrupt connections between the brain respiratory network and the respiratory muscles which can lead to partial or complete loss of ventilatory control and require ventilatory assistance. Unlike current open-loop technology, a closed-loop diaphragmatic pacing system could overcome the drawbacks of manual titration as well as respond to changing ventilation requirements. We present an original bio-inspired assistive technology for real-time ventilation assistance, implemented in a digital configurable Field Programmable Gate Array (FPGA). The bio-inspired controller, which is a spiking neural network (SNN) inspired by the medullary respiratory network, is as robust as a classic controller while having a flexible, low-power and low-cost hardware design. The system was simulated in MATLAB with FPGA-specific constraints and tested with a computational model of rat breathing; the model reproduced experimentally collected respiratory data in eupneic animals. The open-loop version of the bio-inspired controller was implemented on the FPGA. Electrical test bench characterizations confirmed the system functionality. Open and closed-loop paradigm simulations were simulated to test the FPGA system real-time behavior using the rat computational model. The closed-loop system monitors breathing and changes in respiratory demands to drive diaphragmatic stimulation. The simulated results inform future acute animal experiments and constitute the first step toward the development of a neuromorphic, adaptive, compact, low-power, implantable device. The bio-inspired hardware design optimizes the FPGA resource and time costs while harnessing the computational power of spike-based neuromorphic hardware. Its real-time feature makes it suitable for in vivo applications.
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Affiliation(s)
- Adeline Zbrzeski
- Bordeaux INP, IMS, UMR 5218Talence, France; Univ. Bordeaux, IMS, UMR 5218Talence, France
| | - Yannick Bornat
- Bordeaux INP, IMS, UMR 5218Talence, France; Univ. Bordeaux, IMS, UMR 5218Talence, France
| | - Brian Hillen
- Department of Biomedical Engineering, Florida International University Miami, FL, USA
| | - Ricardo Siu
- Department of Biomedical Engineering, Florida International University Miami, FL, USA
| | - James Abbas
- School of Biological and Health Systems Engineering, Arizona State University Tempe, AZ, USA
| | - Ranu Jung
- Department of Biomedical Engineering, Florida International University Miami, FL, USA
| | - Sylvie Renaud
- Bordeaux INP, IMS, UMR 5218Talence, France; Univ. Bordeaux, IMS, UMR 5218Talence, France
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Yazawa I, Shioda S. Reciprocal functional interactions between the respiration/circulation center, the upper spinal cord, and the trigeminal system. Transl Neurosci 2015; 6:87-102. [PMID: 28123792 PMCID: PMC4936616 DOI: 10.1515/tnsci-2015-0008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Accepted: 01/19/2015] [Indexed: 11/15/2022] Open
Abstract
The interplay of neural discharge patterns involved in "respiration", "circulation", "opening movements in the mandible", and "locomotion" was investigated electrophysiologically in a decerebrate and arterially perfused in situ rat preparation. Sympathetic tone increased with increases in perfusion flow rate. All nerve discharges became clearly organized into discharge episodes of increasing frequency and duration punctuated by quiescent periods as the perfusion flow rate increased at 26°C. The modulated sympathetic tone at 10× total blood volume/ min activated the forelimb pattern generator and spontaneously generated fictive forelimb movement during discharge episodes. The coupling rhythm of respiration and locomotion during motion occurred at frequency ratios ranges of 1:2 and 1:3. Small increases in systemic pressure were always generated after the initiation of motion. Opening movements in the mandible, occurring during the inspiratory phase at all tested flow rates, were generated in both the inspiratory and expiratory phases during motion. Although the central mechanism for the entrainment of respiratory and locomotor rhythms has not been identified, a spinal-feedback mechanism generating fictive locomotion in the upper spinal cord contributed to generating the opening movement in the mandible in the expiratory phase during motion. The existence of this mechanism implies that there is a reciprocal functional interaction between the brainstem and the spinal cord, whereby the intake and output of air by the lungs is efficiently improved during movement by both nasal and mouth breathing. These results suggest that this reciprocal functional interaction plays an important role in increasing oxygenated blood flow during locomotion.
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Affiliation(s)
- Itaru Yazawa
- Department of Anatomy, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
| | - Seiji Shioda
- Department of Anatomy, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
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Warren PM, Awad BI, Alilain WJ. Reprint of "Drawing breath without the command of effectors: the control of respiration following spinal cord injury". Respir Physiol Neurobiol 2014; 204:120-30. [PMID: 25266395 DOI: 10.1016/j.resp.2014.09.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The maintenance of blood gas and pH homeostasis is essential to life. As such breathing, and the mechanisms which control ventilation, must be tightly regulated yet highly plastic and dynamic. However, injury to the spinal cord prevents the medullary areas which control respiration from connecting to respiratory effectors and feedback mechanisms below the level of the lesion. This trauma typically leads to severe and permanent functional deficits in the respiratory motor system. However, endogenous mechanisms of plasticity occur following spinal cord injury to facilitate respiration and help recover pulmonary ventilation. These mechanisms include the activation of spared or latent pathways, endogenous sprouting or synaptogenesis, and the possible formation of new respiratory control centres. Acting in combination, these processes provide a means to facilitate respiratory support following spinal cord trauma. However, they are by no means sufficient to return pulmonary function to pre-injury levels. A major challenge in the study of spinal cord injury is to understand and enhance the systems of endogenous plasticity which arise to facilitate respiration to mediate effective treatments for pulmonary dysfunction.
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Affiliation(s)
- Philippa M Warren
- Department of Neurosciences, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, OH 44109, USA
| | - Basem I Awad
- Department of Neurosciences, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, OH 44109, USA; Department of Neurological Surgery, Mansoura University School of Medicine, Mansoura, Egypt
| | - Warren J Alilain
- Department of Neurosciences, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, OH 44109, USA.
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Yazawa I. Reciprocal functional interactions between the brainstem and the lower spinal cord. Front Neurosci 2014; 8:124. [PMID: 24910591 PMCID: PMC4039168 DOI: 10.3389/fnins.2014.00124] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 05/07/2014] [Indexed: 11/18/2022] Open
Abstract
The interplay of the neuronal discharge patterns regarding respiration and locomotion was investigated using electrophysiological techniques in a decerebrate and arterially perfused in situ mouse preparation. The phrenic, tibial, and/or peroneal nerve discharge became clearly organized into discharge episodes of increasing frequency and duration, punctuated by periods of quiescence as the perfusion flow rate increased at room temperature. The modulated sympathetic tone induced by the hyperoxic/normocapnic state was found to activate the locomotor pattern generator (LPG) via descending pathways and generate a left and right alternating discharge during discharge episodes in the motor nerves. The rhythm coupling of respiration and locomotion occurred at a 1:1 frequency ratio. Although the phrenic discharge synchronized with the tibial discharge at all flow rates tested, the time lag between peaks of the two discharges during locomotion was ≈400 ms rather than ≈200 ms, suggesting spinal feedback via ascending pathways. The incidence of the phrenic and tibial discharge episodes decreased by ≈50% after spinalization at the twelfth thoracic cord and the respiratory rhythm was more regular. These results indicate that: (i) locomotion can be generated in a hyperoxic/normocapnic state induced by specific respiratory conditions, (ii) the central mechanism regarding entrainment of respiratory and locomotor rhythms relies on spinal feedback via ascending pathways, initiated by the activated LPG generating locomotion, and (iii) the increase in respiratory rate seen during locomotion is caused not only by afferent mechanical and nociceptive inputs but also by impulses from the activated spinal cord producing a locomotor-like discharge via ascending pathways.
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Affiliation(s)
- Itaru Yazawa
- Laboratory of Neural Control, National Institute of Neurological Disorders and Stroke, National Institutes of Health , Bethesda, MD, USA
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11
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Respiratory and sympathetic chemoreflex regulation by Kölliker-Fuse neurons in rats. Pflugers Arch 2014; 467:231-9. [DOI: 10.1007/s00424-014-1525-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 03/31/2014] [Accepted: 04/16/2014] [Indexed: 11/26/2022]
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Edwards BA, Sands SA, Berger PJ. Postnatal maturation of breathing stability and loop gain: the role of carotid chemoreceptor development. Respir Physiol Neurobiol 2012; 185:144-55. [PMID: 22705011 DOI: 10.1016/j.resp.2012.06.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 05/16/2012] [Accepted: 06/01/2012] [Indexed: 11/17/2022]
Abstract
Any general model of respiratory control must explain a puzzling array of breathing patterns that are observed during the course of a lifetime. Particular challenges are to understand why periodic breathing is rarely seen in the first few days after birth, reaches a peak at 2-4 weeks postnatal age, and disappears by 6 months, why it is prevalent in preterm infants, and why it reappears in adults at altitude or with heart failure. In this review we use the concept of loop gain to obtain quantitative insight into the genesis of unstable breathing patterns with a particular focus on how changes in carotid body function could underlie the age-related dependence of periodic breathing.
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Affiliation(s)
- Bradley A Edwards
- Division of Sleep Medicine, Brigham and Women's Hospital & Harvard Medical School, Boston, MA, USA.
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Periaqueductal gray matter modulates the hypercapnic ventilatory response. Pflugers Arch 2012; 464:155-66. [PMID: 22665049 DOI: 10.1007/s00424-012-1119-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 05/16/2012] [Accepted: 05/22/2012] [Indexed: 01/15/2023]
Abstract
The periaqueductal gray (PAG) is a midbrain structure directly involved in the modulation of defensive behaviors. It has direct projections to several central nuclei that are involved in cardiorespiratory control. Although PAG stimulation is known to elicit respiratory responses, the role of the PAG in the CO(2)-drive to breathe is still unknown. The present study assessed the effect of chemical lesion of the dorsolateral and dorsomedial and ventrolateral/lateral PAG (dlPAG, dmPAG, and vPAG, respectively) on cardiorespiratory and thermal responses to hypercapnia. Ibotenic acid (IBO) or vehicle (PBS, Sham group) was injected into the dlPAG, dmPAG, or vPAG of male Wistar rats. Rats with lesions outside the dlPAG, dmPAG, or vPAG were considered as negative controls (NC). Pulmonary ventilation (VE: ), mean arterial pressure (MAP), heart rate (HR), and body temperature (Tb) were measured in unanesthetized rats during normocapnia and hypercapnic exposure (5, 15, 30 min, 7 % CO(2)). IBO lesioning of the dlPAG/dmPAG caused 31 % and 26.5 % reductions of the respiratory response to CO(2) (1,094.3 ± 115 mL/kg/min) compared with Sham (1,589.5 ± 88.1 mL/kg/min) and NC groups (1,488.2 ± 47.7 mL/kg/min), respectively. IBO lesioning of the vPAG caused 26.6 % and 21 % reductions of CO(2) hyperpnea (1,215.3 ± 108.6 mL/kg/min) compared with Sham (1,657.3 ± 173.9 mL/kg/min) and NC groups (1,537.6 ± 59.3). Basal VE: , MAP, HR, and Tb were not affected by dlPAG, dmPAG, or vPAG lesioning. The results suggest that dlPAG, dmPAG, and vPAG modulate hypercapnic ventilatory responses in rats but do not affect MAP, HR, or Tb regulation in resting conditions or during hypercapnia.
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Taxini CL, Takakura AC, Gargaglioni LH, Moreira TS. Control of the central chemoreflex by A5 noradrenergic neurons in rats. Neuroscience 2011; 199:177-86. [PMID: 22015927 DOI: 10.1016/j.neuroscience.2011.09.068] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 09/05/2011] [Accepted: 09/30/2011] [Indexed: 11/16/2022]
Abstract
Central chemoreflex stimulation produces an increase in phrenic nerve activity (PNA) and sympathetic nerve activity (SNA). The A5 noradrenergic region projects to several brainstem areas involved in autonomic regulation and contributes to the increase in SNA elicited by peripheral chemoreflex activation. The aim of the present study was to further test the hypothesis that the A5 noradrenergic region could contribute to central chemoreflex activation. In urethane-anesthetized, sino-aortic denervated, and vagotomized male Wistar rats (n=6-8/group), hypercapnia (end-expiratory CO₂ from 5% to 10%) increased mean arterial pressure (MAP; Δ=+33±4 mmHg, P<0.05), splanchnic SNA (sSNA; Δ=+97±13%, P<0.05), and PNA frequency and amplitude. Bilateral injection of muscimol (GABA-A agonist; 2 mM) into the A5 noradrenergic region reduced the rise in MAP (Δ=+19±3 mmHg, P<0.05), sSNA (Δ=+63±5%, P<0.05), and PNA frequency and amplitude produced by hypercapnia. Injections of the immunotoxin anti-dopamine β-hydroxylase-saporin (anti-DβH-SAP) into the A5 region destroyed TH⁺ neurons but spared facial motoneurons and the chemosensitive neurons in the retrotrapezoid nucleus that express the transcription factor Phox2b and that are non-catecholaminergic (TH⁻Phox2b⁺). Two weeks after selective destruction of the A5 region with the anti-DβH-SAP toxin, the increase in MAP (Δ=+22±5 mmHg, P<0.05), sSNA (Δ=+68±9%, P<0.05), and PNA amplitude was reduced after central chemoreflex activation. These results suggest that A5 noradrenergic neurons contribute to the increase in MAP, sSNA, and PNA activation during central chemoreflex stimulation.
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Affiliation(s)
- C L Taxini
- Department of Morphology and Animal Physiology, São Paulo State University (UNESP), 14884-900 Jaboticabal, SP, Brazil
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15
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Lavezzi AM, Mehboob R, Matturri L. Developmental alterations of the spinal trigeminal nucleus disclosed by substance P immunohistochemistry in fetal and infant sudden unexplained deaths. Neuropathology 2011; 31:405-13. [PMID: 21276082 DOI: 10.1111/j.1440-1789.2010.01190.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated the immunohistochemical expression of substance P (SP) in the brainstems of 56 subjects aged from 17 gestational weeks to 10 post natal months, who died of unknown (sudden unexplained fetal deaths and SIDS) and known causes (controls). The goals of this study were: (i) to obtain basic information about the expression of SP during the first phases of human nervous system development; (ii) to evaluate whether there are alterations of this neuromodulator in victims of sudden death; and (iii) to verify any correlation with maternal cigarette smoking. Immunohistochemistry demonstrated SP immunoreactivity in the caudal trigeminal nucleus area, with a progressive increase in the density of SP-positive fibers of the corresponding tract during normal development from fetal life to the first post natal months. Delineation of the structure of the human trigeminal nucleus, little investigated so far, provided essential data on its morphologic and functional development. Instead, a negative or low SP expression was detectable in the fibers of this tract in a wide subset of SIDS victims and, conversely, a high SP-expression in a wide subset of sudden fetal deaths. We postulate, on the basis of these results, that SP has a functional importance in the early phases of central nervous system development and in the regulation of autonomic functions. In addition, the observation of a significant correlation between sudden unexplained death, altered SP staining and maternal smoking leads us to suggest a close relation between the absorption of cigarette smoke in utero and a decreased functional activity of the trigeminal nucleus, that can trigger sudden death of the fetus during pregnancy or of the infant in the first months of life.
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Affiliation(s)
- Anna M Lavezzi
- Lino Rossi Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, Department of Surgical, Reconstructive and Diagnostic Sciences, University of Milan, Milan, Italy.
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16
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Niblock MM, Gao H, Li A, Jeffress EC, Murphy M, Nattie EE. Fos-Tau-LacZ mice reveal sex differences in brainstem c-fos activation in response to mild carbon dioxide exposure. Brain Res 2010; 1311:51-63. [PMID: 19932690 PMCID: PMC2812580 DOI: 10.1016/j.brainres.2009.11.037] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 11/13/2009] [Accepted: 11/17/2009] [Indexed: 01/13/2023]
Abstract
There are sex differences in the neurochemistry of brainstem nuclei that participate in the control of breathing as well as sex differences in respiratory responses to hypoxia. Central chemoreception refers to the detection within the brain of minute changes in carbon dioxide (CO(2)) levels and the subsequent modulation of breathing. Putative central chemoreceptor sites are widespread and include cells located near the ventral surface of the brainstem in the retrotrapezoid nucleus (RTN), in the medullary midline raphe nuclei, and, more dorsally in the medulla, in the nucleus of the solitary tract and in the locus caeruleus at the pontomedullary junction as well as in the fastigial nucleus of the cerebellum. In this study, we ask if the cells that respond to CO(2) differ between the sexes. We used a transgenic mouse with a c-fos promoter driven tau-lacZ reporter construct (FTL) to map the locations of cells in the mouse brainstem and cerebellum that responded to exposure of mice of both sexes to 5% CO(2) or room air (control). X-gal (5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside) histochemical staining to detect the beta-galactosidase enzyme produced staining in the brains of mice of both sexes in all of the previously identified putative chemoreceptor sites, with the exception of the fastigial nucleus. Notably, the male RTN region contained significantly more x-gal-labeled cells than the female RTN region. In addition to new observations regarding potential sex differences in the retrotrapezoid region, we found the FTL mouse to be a useful tool for identifying cells that respond to the exposure of the whole animal to relatively low concentrations of CO(2).
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Affiliation(s)
- Mary Melissa Niblock
- Biology Department and Neuroscience Program, Dickinson College, Carlisle, PA, USA.
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17
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Ondicova K, Mravec B. Do monoamine-synthesizing cells constitute a complex network of oxygen sensors? Med Hypotheses 2009; 74:547-51. [PMID: 19846259 DOI: 10.1016/j.mehy.2009.09.045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 09/23/2009] [Indexed: 11/17/2022]
Abstract
Oxygen represents an essential molecule for organisms. Because of this, sophisticated systems of sensors have evolved to monitor oxygenation of tissues. We propose that monoamine-synthesizing cells represent an important part of this system. It is well known that the carotid body, which contains chromaffin cells, serves as a chemical sensor of blood oxygenation. Similarly, the activity of adrenal medullary chromaffin cells is increased during hypoxia. Moreover, neurons located in the central nervous system containing catecholamines, serotonin, and histamine are also sensitive to hypoxia. On the basis of this common sensitivity of monoamine-synthesizing cells to changes in oxygenation we propose the hypothesis that these cells constitute a widely distributed network of sensors that monitor oxygen levels. The role of monoamine-synthesizing cells in monitoring tissue oxygen supply during both physiological and pathological conditions is also discussed.
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Affiliation(s)
- K Ondicova
- Faculty of Medicine, Institute of Pathophysiology, Comenius University, Slovak Academy of Sciences, Bratislava, Slovakia
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18
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Johnson SM, Haxhiu MA, Richerson GB. GFP-expressing locus ceruleus neurons from Prp57 transgenic mice exhibit CO2/H+ responses in primary cell culture. J Appl Physiol (1985) 2008; 105:1301-11. [PMID: 18635881 PMCID: PMC2576037 DOI: 10.1152/japplphysiol.90414.2008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Accepted: 07/12/2008] [Indexed: 11/22/2022] Open
Abstract
The locus ceruleus (LC) contains neurons that increase their firing rate (FR) in vitro when exposed to elevated CO(2)/H(+) and have been proposed to influence the respiratory network to make compensatory adjustments in ventilation. Prp57 transgenic mice express green fluorescent protein (GFP) in the LC and were used to isolate, culture, and target LC neurons for electrophysiological recording. We hypothesized that GFP-LC neurons would exhibit CO(2)/H(+) chemosensitivity under primary culture conditions, evidenced as a change in FR. This is the first study to quantify CO(2)/H(+) responses in LC neuron FR in cell culture. Neurons were continuously bathed with solutions containing antagonists of glutamate and GABA receptors, and the acid-base status was changed from control (5% CO(2); pH approximately 7.4) to hypercapnic acidosis (9% CO(2); pH approximately 7.2) and hypocapnic alkalosis (3% CO(2); pH approximately 7.6). FR was quantified during perforated patch current clamp recordings. Approximately 86% of GFP-LC neurons were stimulated, and approximately 14% were insensitive to changes in CO(2)/H(+). The magnitude of the response of these neurons depended on the baseline FR, ranging from 155.9 +/- 6% when FR started at 2.95 +/- 0.49 Hz to 381 +/- 55.6% when FR started at 1.32 +/- 0.31 Hz. These results demonstrate that cultured LC neurons from Prp57 transgenic mice retain functional sensing molecules necessary for CO(2)/H(+) responses. Prp57 transgenic mice will serve as a valuable model to delineate mechanisms involved in CO(2)/H(+) responsiveness in catecholaminergic neurons.
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Affiliation(s)
- Shereé M Johnson
- Department of Physiology and Biophysics, Howard University College of Medicine, 520 W Street Northwest, Washington, DC 20059, USA.
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19
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Lavezzi AM, Matturri L. Functional neuroanatomy of the human pre-Bötzinger complex with particular reference to sudden unexplained perinatal and infant death. Neuropathology 2008; 28:10-6. [DOI: 10.1111/j.1440-1789.2007.00824.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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20
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Aging-related changes in the sensitivity of the system of respiratory control and the intensity of free-radical processes in humans. NEUROPHYSIOLOGY+ 2008. [DOI: 10.1007/s11062-008-9017-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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21
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Zimmer MB, Nantwi K, Goshgarian HG. Effect of spinal cord injury on the respiratory system: basic research and current clinical treatment options. J Spinal Cord Med 2007; 203:98-108. [PMID: 17853653 DOI: 10.1016/j.resp.2014.08.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 08/11/2014] [Accepted: 08/12/2014] [Indexed: 02/09/2023] Open
Abstract
Spinal cord injury (SCI) often leads to an impairment of the respiratory system. The more rostral the level of injury, the more likely the injury will affect ventilation. In fact, respiratory insufficiency is the number one cause of mortality and morbidity after SCI. This review highlights the progress that has been made in basic and clinical research, while noting the gaps in our knowledge. Basic research has focused on a hemisection injury model to examine methods aimed at improving respiratory function after SCI, but contusion injury models have also been used. Increasing synaptic plasticity, strengthening spared axonal pathways, and the disinhibition of phrenic motor neurons all result in the activation of a latent respiratory motor pathway that restores function to a previously paralyzed hemidiaphragm in animal models. Human clinical studies have revealed that respiratory function is negatively impacted by SCI. Respiratory muscle training regimens may improve inspiratory function after SCI, but more thorough and carefully designed studies are needed to adequately address this issue. Phrenic nerve and diaphragm pacing are options available to wean patients from standard mechanical ventilation. The techniques aimed at improving respiratory function in humans with SCI have both pros and cons, but having more options available to the clinician allows for more individualized treatment, resulting in better patient care. Despite significant progress in both basic and clinical research, there is still a significant gap in our understanding of the effect of SCI on the respiratory system.
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Affiliation(s)
- M Beth Zimmer
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan 48201, USA.
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22
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Biancardi V, Bícego KC, Almeida MC, Gargaglioni LH. Locus coeruleus noradrenergic neurons and CO2 drive to breathing. Pflugers Arch 2007; 455:1119-28. [PMID: 17851683 DOI: 10.1007/s00424-007-0338-8] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Revised: 08/08/2007] [Accepted: 08/27/2007] [Indexed: 01/17/2023]
Abstract
The Locus coeruleus (LC) has been suggested as a CO(2) chemoreceptor site in mammals. In the present study, we assessed the role of LC noradrenergic neurons in the cardiorespiratory and thermal responses to hypercapnia. To selectively destroy LC noradrenergic neurons, we administered 6-hydroxydopamine (6-OHDA) bilaterally into the LC of male Wistar rats. Control animals had vehicle (ascorbic acid) injected (sham group) into the LC. Pulmonary ventilation (plethysmograph), mean arterial pressure (MAP), heart rate (HR), and body core temperature (T (c), data loggers) were measured followed by 60 min of hypercapnic exposure (7% CO(2) in air). To verify the correct placement and effectiveness of the chemical lesions, tyrosine hydroxylase immunoreactivity was performed. Hypercapnia caused an increase in pulmonary ventilation in all groups, which resulted from increases in respiratory frequency and tidal volume (V (T)) in sham-operated and 6-OHDA-lesioned groups. The hypercapnic ventilatory response was significantly decreased in 6-OHDA-lesioned rats compared with sham group. This difference was due to a decreased V (T) in 6-OHDA rats. LC chemical lesion or hypercapnia did not affect MAP, HR, and T (c). Thus, we conclude that LC noradrenergic neurons modulate hypercapnic ventilatory response but play no role in cardiovascular and thermal regulation under resting conditions.
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Affiliation(s)
- Vivian Biancardi
- Department of Animal Morphology and Physiology, Sao Paulo State University-UNESP FCAV, Jaboticabal, SP, Brazil
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23
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Zimmer MB, Goshgarian HG. Spinal cord injury in neonates alters respiratory motor output via supraspinal mechanisms. Exp Neurol 2007; 206:137-45. [PMID: 17559837 DOI: 10.1016/j.expneurol.2007.05.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Revised: 04/27/2007] [Accepted: 05/02/2007] [Indexed: 02/03/2023]
Abstract
Upper cervical spinal cord injury (SCI) alters respiratory output and results in a blunted respiratory response to pH/CO2. Many SCI studies have concentrated on respiratory changes in neural function caudal to injury; however few have examined whether neural plasticity occurs rostral to SCI. Golder et al. (2001a) showed that supraspinal changes occur to alter respiratory output after SCI. Furthermore, Brown et al. (2004) showed that neural receptors change rostral to a thoracic SCI. We hypothesized that SCI in neonates will alter supraspinal output, show a blunted response to pH and alter receptor protein levels in the medulla. On postnatal day 0/1, a C2 SCI surgery was performed. Two days later, neonates were anesthetized and brainstem-spinal cords removed. Respiratory-related activity was recorded using the in vitro brainstem-spinal cord preparation and the superfusate pH was changed (pH 7.2, 7.4 and 7.8). The respiratory-like frequency was significantly reduced in SCI rats indicating supraspinal plasticity. Increasing the pH decreased respiratory-like frequency and peak amplitude in injured and sham controls. Increasing the pH increased burst duration and area in sham controls, whereas in injured rats, the burst duration and area decreased. Western blot analysis demonstrated significant changes in glutamate receptor subunits (NR1, NR2B and GluR2), adenosine receptors (A1, A2A), glutamic acid decarboxylase (65) and neurokinin-1 receptors in medullary tissue ipsilateral and contralateral to injury. These data show that supraspinal plasticity in the respiratory system occurs after SCI in neonate rats. The mechanisms remain unknown, but may involve alterations in receptor proteins involved in neurotransmission.
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Affiliation(s)
- M Beth Zimmer
- Wayne State University, Department of Anatomy and Cell Biology, Detroit, MI 48201, USA.
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24
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Marchenko V, Rogers RF. Selective loss of high-frequency oscillations in phrenic and hypoglossal activity in the decerebrate rat during gasping. Am J Physiol Regul Integr Comp Physiol 2006; 291:R1414-29. [PMID: 16825420 DOI: 10.1152/ajpregu.00217.2006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Respiratory motor outputs contain medium-(MFO) and high-frequency oscillations (HFO) that are much faster than the fundamental breathing rhythm. However, the associated changes in power spectral characteristics of the major respiratory outputs in unanesthetized animals during the transition from normal eupneic breathing to hypoxic gasping have not been well characterized. Experiments were performed on nine unanesthetized, chemo- and barodenervated, decerebrate adult rats, in which asphyxia elicited hyperpnea, followed by apnea and gasping. A gated fast Fourier transform (FFT) analysis and a novel time-frequency representation (TFR) analysis were developed and applied to whole phrenic and to medial branch hypoglossal nerve recordings. Our results revealed one MFO and one HFO peak in the phrenic output during eupnea, where HFO was prominent in the first two-thirds of the burst and MFO was prominent in the latter two-thirds of the burst. The hypoglossal activity contained broadband power distribution with several distinct peaks. During gasping, two high-amplitude MFO peaks were present in phrenic activity, and this state was characterized by a conspicuous loss in HFO power. Hypoglossal activity showed a significant reduction in power and a shift in its distribution toward lower frequencies during gasping. TFR analysis of phrenic activity revealed the increasing importance of an initial low-frequency “start-up” burst that grew in relative intensity as hypoxic conditions persisted. Significant changes in MFO and HFO rhythm generation during the transition from eupnea to gasping presumably reflect a reconfiguration of the respiratory network and/or alterations in signal processing by the circuitry associated with the two motor pools.
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Affiliation(s)
- Vitaliy Marchenko
- Dept. of Electrical and Computer Engineering, Univ. of Delaware, Newark, DE 19716, USA
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25
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Rosin DL, Chang DA, Guyenet PG. Afferent and efferent connections of the rat retrotrapezoid nucleus. J Comp Neurol 2006; 499:64-89. [PMID: 16958085 DOI: 10.1002/cne.21105] [Citation(s) in RCA: 208] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The rat retrotrapezoid nucleus (RTN) contains candidate central chemoreceptors that have extensive dendrites within the marginal layer (ML). This study describes the axonal projections of RTN neurons and their probable synaptic inputs. The ML showed a dense plexus of nerve terminals immunoreactive (ir) for markers of glutamatergic (vesicular glutamate transporters VGLUT1-3), gamma-aminobutyric acid (GABA)-ergic, adrenergic, serotonergic, cholinergic, and peptidergic transmission. The density of VGLUT3-ir terminals tracked the location of RTN chemoreceptors. The efferent and afferent projections of RTN were studied by placing small iontophoretic injections of anterograde (biotinylated dextran amine; BDA) and retrograde (cholera toxin B) tracers where RTN chemoreceptors have been previously recorded. BDA did not label the nearby C1 cells. BDA-ir varicosities were found in the solitary tract nucleus (NTS), all ventral respiratory column (VRC) subdivisions, A5 noradrenergic area, parabrachial complex, and spinal cord. In each target region, a large percentage of the BDA-ir varicosities was VGLUT2-ir (41-83%). Putative afferent input to RTN originated from spinal cord, caudal NTS, area postrema, VRC, dorsolateral pons, raphe nuclei, lateral hypothalamus, central amygdala, and insular cortex. The results suggest that 1) whether or not the ML is specialized for CO(2) sensing, its complex neuropil likely regulates the activity of RTN chemosensitive neurons; 2) the catecholaminergic, cholinergic, and serotonergic innervation of RTN represents a possible substrate for the known state-dependent control of RTN chemoreceptors; 3) VGLUT3-ir terminals are a probable marker of RTN; and 4) the chemosensitive neurons of RTN may provide a chemical drive to multiple respiratory outflows, insofar as RTN innervates the entire VRC.
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Affiliation(s)
- Diane L Rosin
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA.
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26
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Eugenín J, von Bernhardi R, Muller KJ, Llona I. Development and pH sensitivity of the respiratory rhythm of fetal mice in vitro. Neuroscience 2006; 141:223-31. [PMID: 16675136 DOI: 10.1016/j.neuroscience.2006.03.046] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 03/01/2006] [Accepted: 03/23/2006] [Indexed: 10/24/2022]
Abstract
In newborn and adult mammals, chemosensory drive exerted by CO(2) and H(+) provides an essential tonic input: without it the rhythm of respiration is abolished. It is not known, however, whether this chemosensory drive and the respiratory rhythm appear simultaneously during development. In isolated brainstem-spinal cord preparations from fetal mice, we determined at what stage of fetal life the respiratory rhythm appeared in third to fifth cervical ventral roots (phrenic motoneurons) and whether this fetal rhythm was sensitive to chemosensory inputs. A respiratory-like rhythm consisting of short duration bursts of discharges recurring at 2-16 min(-1) was detected in two of nine embryonic day 13 fetuses; it was abolished by transection of the spinal cord between the first to second cervical segments and was phase-related to rhythmic activity from medullary units of the ventral respiratory group. At embryonic day 13, it coexisted with a slow rhythm (0.1-2.0 min(-1)) of long duration bursts of action potentials which was generated by the spinal cord. At later fetal stages, the respiratory-like rhythm became more robust and of higher frequency, while the spinal cord rhythm became less obvious. At all fetal stages, acidification of the superfusion medium from pH 7.5-7.2 or 7.4-7.3 or 7.4 to 7.2 increased the frequency of both the respiratory-like and the spinal cord rhythms. In addition, acidification reduced the amplitude of the integrated burst activity of the spinal cord rhythm of embryonic day 13-embryonic day 16 fetuses and the respiratory-like rhythm of embryonic day 17 and older fetuses. Our results indicate that the rhythms transmitted by phrenic motoneurons during fetal development are chemosensitive from early fetal stages. Through its effects on induction and patterning of the rhythm, chemosensory drive may play a role in activity-dependent formation of respiratory neural networks.
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Affiliation(s)
- J Eugenín
- Laboratory of Neural Systems, Department of Biology, USACH, Casilla 40, Correo 33, Santiago 1, Santiago, Chile.
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27
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Ritucci NA, Dean JB, Putnam RW. Somatic vs. dendritic responses to hypercapnia in chemosensitive locus coeruleus neurons from neonatal rats. Am J Physiol Cell Physiol 2005; 289:C1094-104. [PMID: 16014703 PMCID: PMC1262647 DOI: 10.1152/ajpcell.00329.2004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiorespiratory control is mediated in part by central chemosensitive neurons that respond to increased CO(2) (hypercapnia). Activation of these neurons is thought to involve hypercapnia-induced decreases in intracellular pH (pH(i)). All previous measurements of hypercapnia-induced pH(i) changes in chemosensitive neurons have been obtained from the soma, but chemosensitive signaling could be initiated in the dendrites of these neurons. In this study, membrane potential (V(m)) and pH(i) were measured simultaneously in chemosensitive locus coeruleus (LC) neurons from neonatal rat brain stem slices using whole cell pipettes and the pH-sensitive fluorescent dye pyranine. We measured pH(i) from the soma as well as from primary dendrites to a distance 160 mum from the edge of the soma. Hypercapnia [15% CO(2), external pH (pH(o)) 7.00; control, 5% CO(2), pH(o) 7.45] resulted in an acidification of similar magnitude in dendrites and soma ( approximately 0.26 pH unit), but acidification was faster in the more distal regions of the dendrites. Neither the dendrites nor the soma exhibited pH(i) recovery during hypercapnia-induced acidification; but both regions contained pH-regulating transporters, because they exhibited pH(i) recovery from an NH(4)Cl prepulse-induced acidification (at constant pH(o) 7.45). Exposure of a portion of the dendrites to hypercapnic solution did not increase the firing rate, but exposing the soma to hypercapnic solution resulted in a near-maximal increase in firing rate. These data show that while the pH(i) response to hypercapnia is similar in the dendrites and soma, somatic exposure to hypercapnia plays a major role in the activation of chemosensitive LC neurons from neonatal rats.
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Affiliation(s)
- Nick A. Ritucci
- Department of Neuroscience, Cell Biology and Physiology Wright State University School of Medicine 3640 Colonel Glenn Highway Dayton, OH 45435
| | - Jay B. Dean
- Department of Neuroscience, Cell Biology and Physiology Wright State University School of Medicine 3640 Colonel Glenn Highway Dayton, OH 45435
| | - Robert W. Putnam
- Department of Neuroscience, Cell Biology and Physiology Wright State University School of Medicine 3640 Colonel Glenn Highway Dayton, OH 45435
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28
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Gaultier C, Gallego J. Development of respiratory control: Evolving concepts and perspectives. Respir Physiol Neurobiol 2005; 149:3-15. [PMID: 15941676 DOI: 10.1016/j.resp.2005.04.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Revised: 04/22/2005] [Accepted: 04/25/2005] [Indexed: 10/25/2022]
Abstract
The mechanisms underlying respiratory system immaturity in newborns have been investigated, both in vivo and in vitro, in humans and in animals. Immaturity affects breathing rhythmicity and its modulation by suprapontine influences and by afferents from central and peripheral chemoreceptors. Recent research has moved from bedside tools to sophisticated technologies, bringing new insights into the plasticity and genetics of respiratory control development. Genetic research has benefited from investigations of newborn mice having targeted deletions of genes involved in respiratory control. Genetic variability may govern the normal programming of development and the processes underlying adaptation to homeostasis disturbances induced by prenatal and postnatal insults. Studies of plasticity have emphasized the role of neurotrophic factors. Improvements in our understanding of the mechanistic effects of these factors should lead to new neuroprotective strategies for infants at risk for early respiratory control disturbances, such as apnoeas of prematurity, sudden infant death syndrome and congenital central hypoventilation syndrome.
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Affiliation(s)
- Claude Gaultier
- Service de Physiologie, Hôpital Robert Debré, 48 Boulevard Serurier, 75019 Paris, France.
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29
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Longobardo G, Evangelisti CJ, Cherniack NS. Introduction of respiratory pattern generators into models of respiratory control. Respir Physiol Neurobiol 2005; 148:285-301. [PMID: 16143285 DOI: 10.1016/j.resp.2005.02.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Revised: 02/07/2005] [Accepted: 02/07/2005] [Indexed: 10/25/2022]
Abstract
We have adapted two models previously proposed as respiratory pattern generators (RPGs) into a neurochemical feed back control model of ventilation. The RPG models, non-dimensional as originally presented, consisted of oscillating circuits of either two or five interconnected neurons [Matsugu, M., Duffin, J., Poon, C.-S., 1998. Entrainment, instability, quasi-periodicity, and chaos in a compound neural oscillator. J. Comput. Neurosci. 5, 35-51; Botros, S.M., Bruce, E.N., 1990. Neural network implementation of a three-phase model of respiratory rhythm generation. Biol. Cybern. 63, 143-153]. The neurochemical model into which they were integrated [Longobardo, G., Evangelisti, C.J., Cherniack, N.S., 2002. Effects of neural drives on breathing in the awake state in humans. Respir. Physiol. 129, 317-333] included the effects of cerebral blood flow variation with CO2, vagal stretch receptors input and a multicompartment model of carbon dioxide stores. The methodology is described whereby these neuronal oscillator networks were quantified, a necessary step for their inclusion as RPGs in broader models of the overall control of respiration. Subsequent simulations of the ventilation response to carbon dioxide with either respiratory pattern generator model exhibited only a limited range in which tidal volume and frequency increased with increasing respiratory drive. With both models, frequency peaked and then declined, as did ventilation when P CO2 was greater than normal. The range of the models was extended if the respiratory pattern generators were considered to be composed of multiple neuronal oscillators or a single oscillator in which there was increasing phasic input that was gated or pacemaker driven.
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Affiliation(s)
- Guy Longobardo
- Department of Medicine, UDMNJ-New Jersey Medical School, 185 South Orange Avenue, MSB/I-510n Newark, NJ 07103, USA.
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30
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Hopwood SE, Trapp S. TASK-like K+ channels mediate effects of 5-HT and extracellular pH in rat dorsal vagal neurones in vitro. J Physiol 2005; 568:145-54. [PMID: 16020457 PMCID: PMC1474773 DOI: 10.1113/jphysiol.2005.093070] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Dorsal vagal neurones (DVN) receive serotonergic projections from the medullary raphé nuclei, suggesting that 5-HT modulates vagal activity. A previous study has shown that 5-HT excites DVN in part by inhibition of a K+ current via postsynaptic 5-HT2A receptors. As mRNA for the two-pore-domain K+ channels TASK-1 (KCNK3) and TASK-3 (KCNK9) has been found in DVN, we investigated the possibility that 5-HT exerts its effects via inhibition of these K+ channels using whole-cell patch-clamp techniques. In current clamp, 5-HT (20 microM) elicited a depolarization by 5.1+/-1.5 mV and an increase in firing rate. In voltage clamp, 5-HT reduced the standing outward current (ISO) at -20 mV by 106+/-17 pA, inhibiting a conductance (reversal, -95+/-4 mV) which displayed Goldman-Hodgkin-Katz outward rectification, supportive of a TASK-like K+ current. Since TASK channels are modulated by extracellular pH (pHo), we next investigated the pH sensitivity of ISO in Hepes-buffered ACSF. At pHo 7.3, DVN exhibited an ISO of 147+/-15 pA at -20 mV. Acidification to pHo 6.3 reduced ISO to 85+/-13 pA, whereas raising pHo to 8.5 increased ISO to 216+/-26 pA. At pHo 7.3, ISO was inhibited by BaCl2 (IC50 465 microM), but unaffected by ZnCl2 (100 microM). 5-HT (10 microM) reduced ISO by 114+/-17 pA at pHo 7.3, but at pHo 6.3 the 5-HT-induced inhibition of ISO was significantly smaller. The present data suggest that the excitatory effects of 5-HT on DVN are mediated in part by inhibition of a TASK-like, pH-sensitive K+ conductance. The pharmacological profile of this conductance excludes TASK-3 homomers, but rather implicates TASK-1-containing channels.
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MESH Headings
- Action Potentials/drug effects
- Animals
- Barium Compounds/pharmacology
- Chlorides/pharmacology
- Dose-Response Relationship, Drug
- Hydrogen-Ion Concentration
- In Vitro Techniques
- Nerve Tissue Proteins
- Neurons/drug effects
- Neurons/physiology
- Potassium/metabolism
- Potassium Channels, Inwardly Rectifying/drug effects
- Potassium Channels, Inwardly Rectifying/metabolism
- Potassium Channels, Tandem Pore Domain/antagonists & inhibitors
- Potassium Channels, Tandem Pore Domain/physiology
- Rats
- Rats, Sprague-Dawley
- Receptors, Serotonin, 5-HT2/drug effects
- Receptors, Serotonin, 5-HT2/physiology
- Serotonin/pharmacology
- Time Factors
- Vagus Nerve/drug effects
- Vagus Nerve/physiology
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Affiliation(s)
- Sarah E Hopwood
- Department of Anaesthetics, Pain Medicine and Intensive Care, Division of Surgery, Oncology, Reproductive Biology, Blackett Laboratory, South Kensington Campus, Imperial College London, London SW7 2AZ, UK
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Young JK, Dreshaj IA, Wilson CG, Martin RJ, Zaidi SIA, Haxhiu MA. An astrocyte toxin influences the pattern of breathing and the ventilatory response to hypercapnia in neonatal rats. Respir Physiol Neurobiol 2005; 147:19-30. [PMID: 15848120 DOI: 10.1016/j.resp.2005.01.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Revised: 01/18/2005] [Accepted: 01/31/2005] [Indexed: 11/24/2022]
Abstract
Recent in vitro data suggest that astrocytes may modulate respiration. To examine this question in vivo, we treated 5-day-old rat pups with methionine sulfoximine (MS), a compound that alters carbohydrate and glutamate metabolism in astrocytes, but not neurons. MS-treated pups displayed a reduced breathing frequency (f) in baseline conditions relative to saline-treated pups. Hypercapnia (5% CO(2)) increased f in both groups, but f still remained significantly lower in the MS-treated group. No differences between treatment groups in the responses to hypoxia (8% O(2)) were observed. Also, MS-treated rats showed an enhanced accumulation of glycogen in neurons of the facial nucleus, the nucleus ambiguus, and the hypoglossal nucleus, structures that regulate respiratory activity and airway patency. An altered transfer of nutrient molecules from astrocytes to neurons may underlie these effects of MS, although direct effects of MS upon neurons or upon peripheral structures that regulate respiration cannot be completely ruled out as an explanation.
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Affiliation(s)
- John K Young
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA.
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Okada Y, Kuwana SI, Kawai A, Mückenhoff K, Scheid P. Significance of extracellular potassium in central respiratory control studied in the isolated brainstem-spinal cord preparation of the neonatal rat. Respir Physiol Neurobiol 2005; 146:21-32. [PMID: 15733776 DOI: 10.1016/j.resp.2004.10.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2004] [Indexed: 10/26/2022]
Abstract
The significance of extracellular potassium in central respiratory control was investigated using the isolated brainstem-spinal cord preparation of the neonatal rat. Depth profiles of extracellular potassium activity ([K+])ECF in the medulla were measured with ion-sensitive microelectrodes. Although [K+]ECF increased with depth in medullary tissue during control (4 mM) and low (1 mM) potassium concentration ([K+])CSF superfusion, this gradient disappeared with higher [K+]CSF. With low [K+]CSF (1 mM), respiratory CO2 responsiveness was abolished, and increased with high [K+]CSF (8 mM). Respiratory frequency (fR) was diminished at low [K+]CSF (1 mM), and increased with elevated [K+]CSF (8 and 16 mM); with yet higher [K+]CSF (32 mM) apnea occurred after a transient increase in fR. Perforated patch recording revealed that high [K+]ECF decreased membrane resistance, depolarized membrane potential, and increased firing frequency in most of the recorded medullary neurons. High [K+]ECF also increased excitatory and inhibitory post-synaptic potentials of medullary neurons and augmented the functional connectivity among neurons. It is concluded that [K+]ECF is of importance in the maintenance of respiratory rhythm and central chemosensitivity.
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Affiliation(s)
- Yasumasa Okada
- Department of Medicine, Keio University Tsukigase Rehabilitation Center, Tsukigase 380-2, Izu City, Shizuoka-ken 410-3215, Japan.
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Wu M, Haxhiu MA, Johnson SM. Hypercapnic and hypoxic responses require intact neural transmission from the pre-Bötzinger complex. Respir Physiol Neurobiol 2005; 146:33-46. [PMID: 15733777 DOI: 10.1016/j.resp.2004.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2004] [Indexed: 11/15/2022]
Abstract
The central respiratory network that includes the pre-Bötzinger complex (pre-BötC), a region believed to contain rhythmogenic neurons, is capable of responding to fluctuations in CO2 and pH. However, the role of inputs from this site in mediating ventilatory responses to hypercapnia and/or hypoxia in nonsedated animals is not well established. Therefore, in the present study we tested the hypothesis that altered transmission from the pre-BötC to its target sites would decrease chemosensory responsiveness to acute hypercapnia and modulate the ventilatory response to hypoxia. Colchicine was used to block axonal transport. At 48 h after bilateral microinjections of colchicine into the pre-BötC (100 microg/uL, 100 nL/site), but not saline, the baseline frequency of breathing decreased; however, rhythmicity was not altered. In addition, there was a significant fall in the ventilatory response to hypercapnia (5 and 12% CO2) and hypoxia (8% O2). These findings indicate that, inputs from pre-BötC neurons are of critical importance in providing the normal ventilatory response to both hypercapnia and hypoxia.
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Affiliation(s)
- Mingfei Wu
- Department of Physiology and Biophysics, College of Medicine, Howard University, 520 W Street, Northwest, Washington, DC 20059, USA
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The Cardiorespiratory System in Tropical Fishes: Structure, Function, and Control. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s1546-5098(05)21006-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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35
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Putnam RW, Filosa JA, Ritucci NA. Cellular mechanisms involved in CO(2) and acid signaling in chemosensitive neurons. Am J Physiol Cell Physiol 2004; 287:C1493-526. [PMID: 15525685 DOI: 10.1152/ajpcell.00282.2004] [Citation(s) in RCA: 221] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An increase in CO(2)/H(+) is a major stimulus for increased ventilation and is sensed by specialized brain stem neurons called central chemosensitive neurons. These neurons appear to be spread among numerous brain stem regions, and neurons from different regions have different levels of chemosensitivity. Early studies implicated changes of pH as playing a role in chemosensitive signaling, most likely by inhibiting a K(+) channel, depolarizing chemosensitive neurons, and thereby increasing their firing rate. Considerable progress has been made over the past decade in understanding the cellular mechanisms of chemosensitive signaling using reduced preparations. Recent evidence has pointed to an important role of changes of intracellular pH in the response of central chemosensitive neurons to increased CO(2)/H(+) levels. The signaling mechanisms for chemosensitivity may also involve changes of extracellular pH, intracellular Ca(2+), gap junctions, oxidative stress, glial cells, bicarbonate, CO(2), and neurotransmitters. The normal target for these signals is generally believed to be a K(+) channel, although it is likely that many K(+) channels as well as Ca(2+) channels are involved as targets of chemosensitive signals. The results of studies of cellular signaling in central chemosensitive neurons are compared with results in other CO(2)- and/or H(+)-sensitive cells, including peripheral chemoreceptors (carotid body glomus cells), invertebrate central chemoreceptors, avian intrapulmonary chemoreceptors, acid-sensitive taste receptor cells on the tongue, and pain-sensitive nociceptors. A multiple factors model is proposed for central chemosensitive neurons in which multiple signals that affect multiple ion channel targets result in the final neuronal response to changes in CO(2)/H(+).
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Affiliation(s)
- Robert W Putnam
- Department of Anatomy and Physiology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA.
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36
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Lorier AR, Peebles K, Brosenitsch T, Robinson DM, Housley GD, Funk GD. P2 receptors modulate respiratory rhythm but do not contribute to central CO2 sensitivity in vitro. Respir Physiol Neurobiol 2004; 142:27-42. [PMID: 15351302 DOI: 10.1016/j.resp.2004.04.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2004] [Indexed: 11/25/2022]
Abstract
Multiple brainstem sites are proposed to contribute to central respiratory chemosensitivity, however, the underlying molecular mechanisms remain unknown. P2X2 subunit-containing ATP receptors, which mediate pH-sensitive currents, appear to contribute to central chemosensitivity in vivo [J. Physiol. 523 (2000) 441]. However, recent data from P2X2 knockout mice [J. Neurosci. 23 (2003) 11315] indicate that they are not essential. To further explore the role of P2 receptors in central chemosensitivity, we examined the effects of P2 receptor agonists/antagonists on respiratory-related activity and CO2-sensitivity of rhythmically-active in vitro preparations from neonatal rat. Our main findings: (i) that putative chemosensitive regions of the ventrolateral medulla are immunoreactive for the P2X2 subunit; (ii) that ATP potentiates respiratory frequency in a dose-dependent, and PPADS-sensitive (P2 receptor antagonist), manner; and (iii) that the increase in burst frequency produced by increasing CO2 is unaffected by PPADS, indicate that ATP is a potent modulator of respiratory activity, but that P2 receptors do not contribute to central chemosensitivity in vitro.
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Affiliation(s)
- A R Lorier
- Department of Physiology, Faculty of Medicine and Health Science, University of Auckland, Private Bag 92019, New Zealand
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Mulkey DK, Stornetta RL, Weston MC, Simmons JR, Parker A, Bayliss DA, Guyenet PG. Respiratory control by ventral surface chemoreceptor neurons in rats. Nat Neurosci 2004; 7:1360-9. [PMID: 15558061 DOI: 10.1038/nn1357] [Citation(s) in RCA: 432] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Accepted: 10/08/2004] [Indexed: 11/09/2022]
Abstract
A long-standing theory posits that central chemoreception, the CNS mechanism for CO(2) detection and regulation of breathing, involves neurons located at the ventral surface of the medulla oblongata (VMS). Using in vivo and in vitro electrophysiological recordings, we identify VMS neurons within the rat retrotrapezoid nucleus (RTN) that have characteristics befitting these elusive chemoreceptors. These glutamatergic neurons are vigorously activated by CO(2) in vivo, whereas serotonergic neurons are not. Their CO(2) sensitivity is unaffected by pharmacological blockade of the respiratory pattern generator and persists without carotid body input. RTN CO(2)-sensitive neurons have extensive dendrites along the VMS and they innervate key pontomedullary respiratory centers. In brainstem slices, a subset of RTN neurons with markedly similar morphology is robustly activated by acidification and CO(2). Their pH sensitivity is intrinsic and involves a background K(+) current. In short, the CO(2)-sensitive neurons of the RTN are good candidates for the long sought-after VMS chemoreceptors.
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Affiliation(s)
- Daniel K Mulkey
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA
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Vesely AE, Somogyi RB, Sasano H, Sasano N, Fisher JA, Duffin J. The effects of carbon monoxide on respiratory chemoreflexes in humans. ENVIRONMENTAL RESEARCH 2004; 94:227-33. [PMID: 15016588 DOI: 10.1016/s0013-9351(03)00107-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2002] [Accepted: 05/08/2003] [Indexed: 05/05/2023]
Abstract
As protection against low-oxygen and high-carbon-dioxide environments, the respiratory chemoreceptors reflexly increase breathing. Since CO is also frequently present in such environments, it is important to know whether CO affects the respiratory chemoreflexes responsiveness. Although the peripheral chemoreceptors fail to detect hypoxia produced by CO poisoning, whether CO affects the respiratory chemoreflex responsiveness to carbon dioxide is unknown. The responsiveness of 10 healthy male volunteers were assessed before and after inhalation of approximately 1200 ppm CO in air using two iso-oxic rebreathing tests; hypoxic, to emphasize the peripheral chemoreflex, and hyperoxic, to emphasize the central chemoreflex. Although mean (SEM) COHb values of 10.2 (0.2)% were achieved, no statistically significant effects of CO were observed. The average differences between pre- and post-CO values for ventilation response threshold and sensitivity were -0.5 (0.9) mmHg and 0.8 (0.3) L/min/mmHg, respectively, for hyperoxia, and 0.7 (1.1) mmHg and 1.2 (0.8) L/min/mmHg, respectively, for hypoxia. The 95% confidence intervals for the effect of CO were small. We conclude that environments with low levels of CO do not have a clinically significant effect acutely on either the central or the peripheral chemoreflex responsiveness to carbon dioxide.
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Affiliation(s)
- Alex E Vesely
- Department of Physiology, 1 King's College Circle, University of Toronto, Toronto, Ont., Canada M5S 1A8
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Nattie EE, Li A, Richerson GB, Richerson G, Lappi DA. Medullary serotonergic neurones and adjacent neurones that express neurokinin-1 receptors are both involved in chemoreception in vivo. J Physiol 2004; 556:235-53. [PMID: 14724193 PMCID: PMC1664900 DOI: 10.1113/jphysiol.2003.059766] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Neurokinin-1 receptor (NK1R)-expressing neurones that are involved in chemoreception at the retrotrapezoid nucleus (Nattie & Li, 2002b) are also prominent at locations that contain medullary serotonergic neurones, which are chemosensitive in vitro. In medullary regions containing both types, we evaluated their role in central chemoreception by specific cell killing. We injected (2 x 100 nl) (a) substance P-saporin (SP-SAP; 1 microm) to kill NK1R-expressing neurones, (b) a novel conjugate of a monoclonal antibody to the serotonin transporter (SERT) and saporin (anti-SERT-SAP; 1 microm) to kill serotonergic neurones, or (c) SP-SAP and anti-SERT-SAP together to kill both types. Controls received IgG-SAP injections (1 microm). There was no double-labelling of NK1R-immunoreactive (ir) and tryptophan-hydroxylase (TPOH)-ir neurones. Cell (somatic profile) counts showed that NK1R-ir neurones in the SP-SAP group were reduced by 31%; TPOH-ir neurones in the anti-SERT-SAP group by 28%; and NK1R-ir and TPOH-ir neurones, respectively, in the combined lesion group by 55% and 31% (P < 0.001; two-way ANOVA; P < 0.05, Tukey's post hoc test). The treatments had no significant effect on sleep/wake time, body temperature, or oxygen consumption but all three reduced the ventilatory response to 7% inspired CO(2) in wakefulness and sleep by a similar amount. SP-SAP treatment decreased the averaged CO(2) responses (3, 7 and 14 days after lesions) in wakefulness and sleep by 21% and 16%, anti-SERT-SAP decreased the responses by 15% and 18%, and the combined treatment decreased the responses by 12% and 12% (P < 0.001; two-way ANOVA; P < 0.05, Tukey's post hoc test). We conclude that separate populations of serotonergic and adjacent NK1R-expressing neurones in the medulla are both involved in central chemoreception in vivo.
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Affiliation(s)
- Eugene E Nattie
- Department of Physiology, Dartmouth Medical School, Borwell Bldg, Lebanon, NH 03756-0001, USA.
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Washburn CP, Bayliss DA, Guyenet PG. Cardiorespiratory neurons of the rat ventrolateral medulla contain TASK-1 and TASK-3 channel mRNA. Respir Physiol Neurobiol 2003; 138:19-35. [PMID: 14519375 DOI: 10.1016/s1569-9048(03)00185-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The potassium channels TASK-1 and TASK-3 are neuronal 'leak' channels that are inhibited by extracellular acidification and numerous neurotransmitters. Here we tested whether in the rat TASK-1 and TASK-3 mRNAs are present in ventrolateral medulla neurons that regulate respiration or circulation (C1 adrenergic neurons). The mRNAs were identified by in situ hybridization. Respiratory neurons were identified by anatomical markers (neurokinin-1 receptors, NK1R, or somatostatin) or directly by juxtacellular labeling of bulbospinal neurons. C1 neurons were identified by the presence of tyrosine-hydroxylase. TASK-1 and TASK-3 transcripts were present in all hypoglossal and facial motor neurons, in most C1 cells (85-95%), in most small and large NK1R-ir neurons (>90%) of the ventral respiratory group (VRG) and in all the inspiratory-augmenting bulbospinal neurons of the rostral ventral respiratory group. In conclusion, TASK channels are expressed by respiratory cells with putative rhythmogenic function and by premotor and motor neurons. TASK channels presumably mediate excitatory effects of numerous transmitters on these neurons and may contribute to their pH-sensitivity.
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Affiliation(s)
- Christopher P Washburn
- Department of Pharmacology, University of Virginia, Health Sciences Center, 1300 Jefferson Park Avenue P.O. Box 800735, Charlottesville, VA 22908-0735, USA
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Abstract
H(+) is maintained constant in the internal environment at a given body temperature independent of external environment according to Bernard's principle of "milieu interieur". But CO2 relates to ventilation and H(+) to kidney. Hence, the title of the chapter. In order to do this, sensors for H(+) in the internal environment are needed. The sensor-receptor is CO2/H(+) sensing. The sensor-receptor is coupled to integrate and to maintain the body's chemical environment at equilibrium. This chapter dwells on this theme of constancy of H(+) of the blood and of the other internal environments. [H(+)] is regulated jointly by respiratory and renal systems. The respiratory response to [H(+)] originates from the activities of two groups of chemoreceptors in two separate body fluid compartments: (A) carotid and aortic bodies which sense arterial P(O2) and H(+); and (B) the medullary H(+) receptors on the ventrolateral medulla of the central nervous system (CNS). The arterial chemoreceptors function to maintain arterial P(O2) and H(+) constant, and medullary H(+) receptors to maintain H(+) of the brain fluid constant. Any acute change of H(+) in these compartments is taken care of almost instantly by pulmonary ventilation, and slowly by the kidney. This general theme is considered in Section 1. The general principles involving cellular CO2 reactions mediated by carbonic anhydrase (CA), transport of CO2 and H(+) are described in Section 2. Since the rest of the chapter is dependent on these key mechanisms, they are given in detail, including the role of Jacobs-Stewart Cycle and its interaction with carbonic anhydrase. Also, this section deals briefly with the mechanisms of membrane depolarization of the chemoreceptor cells because this is one mechanism on which the responses depend. The metabolic impact of endogenous CO2 appears in the section with a historical twist, in the context of acclimatization to high altitude (Section 3). Because low P(O2) at high altitude stimulates the peripheral chemoreceptors (PC) increasing ventilation, the endogenous CO2 is blown off, making the internal milieu alkaline. With acclimatization however ventilation increases. This alkalinity is compensated in the course of time by the kidney and the acidity tends to be restored, but the acidification is not great enough to increase ventilation further. The question is what drives ventilation during acclimatization when the central pH is alkaline? The peripheral chemoreceptor came to the rescue. Its sensitivity to P(O2) is increased which continues to drive ventilation further during acclimatization at high altitude even when pH is alkaline. This link of CO2 through the O2 chemoreceptor is described in Section 4 which led to hypoxia-inducible factor (HIF-1). HIF-1 is stabilized during hypoxia, including the carotid body (CB) and brain cells, the seat of CO2 chemoreception. The cells are always hypoxic even at sea level. But how CO2 can affect the HIF-1 in the brain is considered in this section. CO2 sensing in the central chemoreceptors (CC) is given in Section 5. CO(2)/H(+) is sensed by the various structures in the central nervous system but its respiratory and cardiovascular responses are restricted only to some areas. How the membranes are depolarized by CO2 or how it works through Na(+)/Ca(2+) exchange are discussed in this section. It is obvious, however, that CO2 is not maintained constant, decreasing with altitude as alveolar P(O2) decreases and ventilation increases. Rather, it is the [H(+)] that the organism strives to maintain at the expense of CO2. But then again, [H(+)] where? Perhaps it is in the intracellular environment. Gap junctions in the carotid body and in the brain are ubiquitous. What functions they perform have been considered in Section 6. CO2 changes take place in lung alveoli where inspired air mixes with the CO2 from the returning venous blood. It is the interface between the inspired and expired air in the lungs where CO2 change is most dramatic. As a result, various investigators have looked for CO2 receptors in the lung, but none have been found in the mammals. Instead, CO2/H(+) receptors were found in birds and amphibians. However, they are inhibited by increasing CO2/H(+), instead of stimulated. But the afferent impulses transmitted to the brain produced stimulation in the efferents. This reversal of afferent-efferent inputs is a curious situation in nature, and this is considered in Section 7. The NO and CO effects on CO2 sensing are interesting and have been briefly mentioned in Section 8. A model for CO2/H(+) sensing by cells, neurons and bare nerve endings are also considered. These NO effects, models for CO2/H(+) and O2-sensitive cells in the CNS have been considered in the perspectives. Finally, in conclusion, the general theme of constancy of internal environment for CO2/H(+) is reiterated, and for that CO2/H(+) sensors-receptors systems are essential. Since CO2/H(+) sensing as such has not been reviewed before, the recent findings in addition to defining basic CO2/H(+) reactions in the cells have been briefly summarized.
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Affiliation(s)
- Sukhamay Lahiri
- Department of Physiology, University of Pennsylvania Medical Center, Richards Building, Philadelphia, PA 19104, USA.
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Gourine AV, Atkinson L, Deuchars J, Spyer KM. Purinergic signalling in the medullary mechanisms of respiratory control in the rat: respiratory neurones express the P2X2 receptor subunit. J Physiol 2003; 552:197-211. [PMID: 12878756 PMCID: PMC2343330 DOI: 10.1113/jphysiol.2003.045294] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
ATP is involved in central respiratory control and may mediate changes in the activity of medullary respiratory neurones during hypercapnia, thus playing an important role in central chemoreception. The main objective of this study was to explore further the role of ATP-mediated signalling in respiratory control and central chemoreception by characterising the profile of the P2X receptors expressed by physiologically identified respiratory neurones. In particular we determined whether respiratory neurones in the rostral ventrolateral medulla (VLM) express P2X2 receptor subunits of the ATP-gated ion channel, since ATP currents evoked at recombinant P2X2 receptors are potentiated by lowering extracellular pH. Experiments were performed on anaesthetised (pentobarbitone sodium 60 mg kg-1 I.P., then 10 mg kg-1 I.V. as required), gallamine-triethiodide-treated (10 mg kg-1 I.V., then 2-4 mg kg-1 h-1 I.V.) and artificially ventilated rats. The VLM respiratory neurones were classified according to the timing of their discharge pattern in relation to that of the phrenic nerve and by the exclusion of pump cells from the study population; these were labelled with Neurobiotin using the juxtacellular method, and visualised with fluorescence microscopy. It was found that a substantial proportion of the VLM respiratory neurones express the P2X2 receptor subunit. P2X2 receptor subunit immunoreactivity was detected in approximately 50 % (six out of 12) of expiratory neurones and in approximately 20 % (two out of 11) of neurones with inspiratory-related discharge (pre-inspiratory and inspiratory). In contrast, no Neurobiotin-labelled VLM respiratory neurones (n = 19) were detectably immunoreactive for the P2X1 receptor subunit. Microionophoretic application of ATP (0.2 M, 20-80 nA for 40 s) increased the activity of approximately 80 % (13 out of 16) of expiratory neurones and of approximately 30 % (five out of 18) of VLM neurones with inspiratory-related discharge. These effects were abolished by the P2 receptor blocker suramin (0.02 M, 80 nA), which also reduced the baseline firing in some expiratory neurones. These data indicate that modulation of P2X2 receptor function, such as that evoked by acidification of the extracellular environment during hypercapnia, may contribute to the changes in activity of the VLM respiratory neurones that express these receptors.
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Affiliation(s)
- Alexander V Gourine
- Department of Physiology, Royal Free and University College London Medical School, Rowland Hill Street, London NW3 2PF, U.K.
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Infante CD, von Bernhardi R, Rovegno M, Llona I, Eugenín JL. Respiratory responses to pH in the absence of pontine and dorsal medullary areas in the newborn mouse in vitro. Brain Res 2003; 984:198-205. [PMID: 12932854 DOI: 10.1016/s0006-8993(03)03155-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The contribution of pons and dorsal medulla in establishing the pattern of fictive respiration and in mediating the respiratory response to acidification was studied using the isolated brainstem-spinal cord preparation from neonatal mouse. About 40% of ponto-medullary preparations (retaining pons) showed spontaneous, but irregular respiratory-like rhythm. In the other 60%, the elimination of the pons often was followed by the initiation of a respiratory-like rhythm. Medullary preparations, derived from either inactive or rhythmic ponto-medullary preparations, showed a regular respiratory-like rhythm, which was also of a higher frequency and a bigger amplitude than that observed in ponto-medullary preparations. In contrast, ventral medullary preparations, derived from medullary preparations by eliminating the dorsal medulla, showed an irregular rhythm with a reduced amplitude of the integrated inspiratory burst. In ponto-medullary and ventral medullary preparations, acidification of the superfusion medium increased the respiratory frequency, while in medullary preparations, it increased the frequency and reduced the amplitude of the inspiratory burst. Our results suggest that pontine structures influence negatively the rate and depth of the respiratory-like rhythm, while dorsal medullary structures influence positively the depth of the rhythm. They also suggest that the pattern of response to pH supported by the ventral medulla is modified by the input provided from pons and dorsal medulla.
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Affiliation(s)
- Claudia D Infante
- Laboratory of Neural Systems, Department of Biology, Universidad de Santiago de Chile, Casilla 40, Correo 33, Santiago, Chile
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Abstract
Breathing is a vital behavior that is particularly amenable to experimental investigation. We review recent progress on three problems of broad interest. (i) Where and how is respiratory rhythm generated? The preBötzinger Complex is a critical site, whereas pacemaker neurons may not be essential. The possibility that coupled oscillators are involved is considered. (ii) What are the mechanisms that underlie the plasticity necessary for adaptive changes in breathing? Serotonin-dependent long-term facilitation following intermittent hypoxia is an important example of such plasticity, and a model that can account for this adaptive behavior is discussed. (iii) Where and how are the regulated variables CO2 and pH sensed? These sensors are essential if breathing is to be appropriate for metabolism. Neurons with appropriate chemosensitivity are spread throughout the brainstem; their individual properties and collective role are just beginning to be understood.
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Affiliation(s)
- Jack L. Feldman
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095-1763
| | - Gordon S. Mitchell
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin 53706
| | - Eugene E. Nattie
- Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire 03756-0001
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Nakayama H, Smith CA, Rodman JR, Skatrud JB, Dempsey JA. Carotid body denervation eliminates apnea in response to transient hypocapnia. J Appl Physiol (1985) 2003; 94:155-64. [PMID: 12391082 DOI: 10.1152/japplphysiol.00722.2002] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We determined the effects on breathing of transient ventilatory overshoots and concomitant hypocapnia, as produced by pressure support mechanical ventilation (PSV), in intact and carotid body chemoreceptor denervated (CBX) sleeping dogs. In the intact dog, PSV-induced transient increases in tidal volume and hypocapnia caused apnea within 10-11 s, followed by repetitive two-breath clusters separated by apneas, i.e., periodic breathing (PB). After CBX, significant expiratory time prolongation did not occur until after 30 s of PSV-induced hypocapnia, and PB never occurred. Average apneas of 8.4 +/- 1-s duration after a ventilatory overshoot required a decrease below eupnea of end-tidal Pco(2) 5.1 +/- 0.4 Torr below eupnea in the intact animal and 10.1 +/- 2 Torr in the CBX dog, where the former reflected peripheral and the latter central dynamic CO(2) chemoresponsiveness, as tested in the absence of peripheral chemoreceptor input. Hyperoxia when the dogs were intact shortened PSV-induced apneas and reduced PB but did not mimic the effects of CBX. We conclude that, during non-rapid eye movement sleep, carotid chemoreceptors are required to produce apneas that normally occur after a transient ventilatory overshoot and for PB.
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Affiliation(s)
- Hideaki Nakayama
- John Rankin Laboratory of Pulmonary Medicine, Madison, Wisconsin 53726, USA
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Li A, Nattie E. CO2 dialysis in one chemoreceptor site, the RTN: stimulus intensity and sensitivity in the awake rat. Respir Physiol Neurobiol 2002; 133:11-22. [PMID: 12385727 DOI: 10.1016/s1569-9048(02)00134-9] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We stimulate single central chemoreceptor sites in the unanesthetized rat by focal microdialysis of artificial cerebrospinal fluid (aCSF) equilibrated with 25% CO(2). Here, in the retrotrapezoid nucleus (RTN) we measured the focal stimulus intensity with a pH electrode adjacent to the dialysis probe. During 25% CO(2) dialysis, RTN pH decreased by 0.069 (0.013, SEM) pH units (N=5), 44% of the change observed during 7% CO(2) breathing, -0.157 (0.019) pH units (N=4). During 7% CO(2) breathing, Pa(CO(2)) increased by 15 Torr (N=5). We calculate the deltaPa(CO(2)) that would produce a deltapH at the RTN approximately like that observed during 25% CO(2) dialysis as 44% of 15 Torr, or 6.6 Torr deltaPa(CO(2)). Using ventilatory response data from our lab, we estimate overall chemoreceptor sensitivity as 13% deltaVE/Torr deltaPa(CO(2)) and RTN sensitivity as 3% deltaVE/Torr deltaPa(CO(2)). The RTN provides 23% of the overall response. This may be an underestimate. During RTN stimulation Pa(CO(2)) decreases by 4.9 (0.7) Torr (N=5), which may inhibit other chemoreceptor sites. Multiple chemoreceptor sites may interact to provide high sensitivity in systemic hypercapnia and stability during heterogeneous stimulation and inhibition.
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Affiliation(s)
- Aihua Li
- Department of Physiology, Dartmouth Medical School, 706E Borwell Building, Lebanon, NH 03756-0001, USA
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Nattie EE, Li A. Substance P-saporin lesion of neurons with NK1 receptors in one chemoreceptor site in rats decreases ventilation and chemosensitivity. J Physiol 2002; 544:603-16. [PMID: 12381830 PMCID: PMC2290611 DOI: 10.1113/jphysiol.2002.020032] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
All medullary central chemoreceptor sites contain neurokinin-1 receptor immunoreactivity (NK1R-ir). We ask if NK1R-ir neurons and processes are involved in chemoreception. At one site, the retrotrapezoid nucleus/parapyramidal region (RTN/Ppy), we injected a substance P-saporin conjugate (SP-SAP; 0.1 pmol in 100 nl) to kill NK1R-ir neurons specifically, or SAP alone as a control. We made measurements for 15 days after the injections in two groups of rats. In group 1, with unilateral injections made in the awake state via a pre-implanted guide cannula, we compared responses within rats using initial baseline data. In group 2, with bilateral injections made under anaesthesia at surgery, we compared responses between SP-SAP- and SAP-treated rats. SP-SAP treatment reduced the volume of the RTN/Ppy region that contained NK1R-ir neuronal somata and processes by 44 % (group 1) and by 47 and 40 % on each side, respectively (group 2). Ventilation (.V(E)) and tidal volume (V(T)) were decreased during air breathing in sleep and wakefulness (group 2; P < 0.001; two-way ANOVA) and P(a,CO2) was increased (group 2; P < 0.05; Student's t test). When rats breathed an air mixture containing 7 % CO(2) during sleep and wakefulness, .V(E) and V(T) were lower (groups 1 and 2; P < 0.001; ANOVA) and the Delta.V(E) in air containing 7 % CO(2) compared to air was decreased by 28-30 % (group 1) and 17-22 % (group 2). SP-SAP-treated rats also slept less during air breathing. We conclude that neurons with NK1R-ir somata or processes in the RTN/Ppy region are either chemosensitive or they modulate chemosensitivity. They also provide a tonic drive to breathe and may affect arousal.
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Affiliation(s)
- Eugene E Nattie
- Department of Physiology, Dartmouth Medical School, Borwell Building, Lebanon, NH 03756-0001, USA.
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Abstract
Whereas in vitro techniques have contributed greatly to our understanding of detailed neuronal mechanisms of respiratory control, the integrated function of respiratory behavior requires studying conscious, unsedated subjects. Noninvasive approaches, meticulous chronic instrumentation for the recording of multiple respiratory indices, and correlations with brain studies performed after physiological manipulations in vivo can all be employed to get to some understanding of the maturation of respiratory control in the mammal. This article is a selective and critical overview of recent literature on methodologies that can be used in behaving subjects, the relationship of respiration to sleep-wake states, respiratory patterns during normoxia, and on respiratory responsiveness to hypercarbia and hypoxia, all emphasizing processes during development. It is hoped that this review will encourage new investigators interested in the regulation of breathing to resort to experimental approaches that will reveal the mysteries of respiratory behavior in the integrated organism.
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Affiliation(s)
- Immanuela Ravé Moss
- McGill University, The Montreal Children's Hospital, Developmental Respiratory Laboratory, Room A-707, 2300 Tupper Street, H3H 1P3 Montreal, Quebec, Canada.
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