1
|
Javaheri S, Randerath WJ, Safwan Badr M, Javaheri S. Medication-induced central sleep apnea: a unifying concept. Sleep 2024; 47:zsae038. [PMID: 38334297 DOI: 10.1093/sleep/zsae038] [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: 12/06/2023] [Revised: 01/17/2024] [Indexed: 02/10/2024] Open
Abstract
Medication-induced central sleep apnea (CSA) is one of the eight categories of causes of CSA but in the absence of awareness and careful history may be misclassified as primary CSA. While opioids are a well-known cause of respiratory depression and CSA, non-opioid medications including sodium oxybate, baclofen, valproic acid, gabapentin, and ticagrelor are less well-recognized. Opioids-induced respiratory depression and CSA are mediated primarily by µ-opioid receptors, which are abundant in the pontomedullary centers involved in breathing. The non-opioid medications, sodium oxybate, baclofen, valproic acid, and gabapentin, act upon brainstem gamma-aminobutyric acid (GABA) receptors, which co-colonize with µ-opioid receptors and mediate CSA. The pattern of ataxic breathing associated with these medications is like that induced by opioids on polysomnogram. Finally, ticagrelor also causes periodic breathing and CSA by increasing central chemosensitivity and ventilatory response to carbon dioxide. Given the potential consequences of CSA and the association between some of these medications with mortality, it is critical to recognize these adverse drug reactions, particularly because discontinuation of the offending agents has been shown to eliminate CSA.
Collapse
Affiliation(s)
- Shahrokh Javaheri
- Division of Pulmonary and Sleep Medicine, Bethesda North Hospital, Cincinnati, OH, USA
- Adjunct Professor of Medicine, Division of Cardiology, The Ohio State University, Columbus, Ohio, USA
- Emeritus Professor of Medicine, Division of Pulmonary and Sleep Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Winfried J Randerath
- Professor and Head Physician, Institute of Pneumology, University of Cologne, Bethanien Hospital, Solingen, Germany
| | - M Safwan Badr
- Professor and Chair, Department of Internal Medicine, Wayne State University School of Medicine Detroit, Staff Physician, John D. Dingell VA Medical Center, MI, USA
| | - Sogol Javaheri
- Assistant Professor of Sleep Medicine, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| |
Collapse
|
2
|
Furdui A, da Silveira Scarpellini C, Montandon G. Anatomical distribution of µ-opioid receptors, neurokinin-1 receptors, and vesicular glutamate transporter 2 in the mouse brainstem respiratory network. J Neurophysiol 2024; 132:108-129. [PMID: 38748514 DOI: 10.1152/jn.00478.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 05/08/2024] [Accepted: 05/12/2024] [Indexed: 07/03/2024] Open
Abstract
µ-Opioid receptors (MORs) are responsible for mediating both the analgesic and respiratory effects of opioid drugs. By binding to MORs in brainstem regions involved in controlling breathing, opioids produce respiratory depressive effects characterized by slow and shallow breathing, with potential cardiorespiratory arrest and death during overdose. To better understand the mechanisms underlying opioid-induced respiratory depression, thorough knowledge of the regions and cellular subpopulations that may be vulnerable to modulation by opioid drugs is needed. Using in situ hybridization, we determined the distribution and coexpression of Oprm1 (gene encoding MORs) mRNA with glutamatergic (Vglut2) and neurokinin-1 receptor (Tacr1) mRNA in medullary and pontine regions involved in breathing control and modulation. We found that >50% of cells expressed Oprm1 mRNA in the preBötzinger complex (preBötC), nucleus tractus solitarius (NTS), nucleus ambiguus (NA), postinspiratory complex (PiCo), locus coeruleus (LC), Kölliker-Fuse nucleus (KF), and the lateral and medial parabrachial nuclei (LBPN and MPBN, respectively). Among Tacr1 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, Bötzinger complex (BötC), PiCo, LC, raphe magnus nucleus, KF, LPBN, and MPBN, whereas among Vglut2 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, BötC, PiCo, LC, KF, LPBN, and MPBN. Taken together, our study provides a comprehensive map of the distribution and coexpression of Oprm1, Tacr1, and Vglut2 mRNA in brainstem regions that control and modulate breathing and identifies Tacr1 and Vglut2 mRNA-expressing cells as subpopulations with potential vulnerability to modulation by opioid drugs.NEW & NOTEWORTHY Opioid drugs can cause serious respiratory side-effects by binding to µ-opioid receptors (MORs) in brainstem regions that control breathing. To better understand the regions and their cellular subpopulations that may be vulnerable to modulation by opioids, we provide a comprehensive map of Oprm1 (gene encoding MORs) mRNA expression throughout brainstem regions that control and modulate breathing. Notably, we identify glutamatergic and neurokinin-1 receptor-expressing cells as potentially vulnerable to modulation by opioid drugs and worthy of further investigation using targeted approaches.
Collapse
Affiliation(s)
- Andreea Furdui
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | | | - Gaspard Montandon
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Division of Respirology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| |
Collapse
|
3
|
Nakamura NH, Oku Y, Fukunaga M. "Brain-breath" interactions: respiration-timing-dependent impact on functional brain networks and beyond. Rev Neurosci 2024; 35:165-182. [PMID: 37651646 DOI: 10.1515/revneuro-2023-0062] [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: 06/05/2023] [Accepted: 08/06/2023] [Indexed: 09/02/2023]
Abstract
Breathing is a natural daily action that one cannot do without, and it sensitively and intensely changes under various situations. What if this essential act of breathing can impact our overall well-being? Recent studies have demonstrated that breathing oscillations couple with higher brain functions, i.e., perception, motor actions, and cognition. Moreover, the timing of breathing, a phase transition from exhalation to inhalation, modulates specific cortical activity and accuracy in cognitive tasks. To determine possible respiratory roles in attentional and memory processes and functional neural networks, we discussed how breathing interacts with the brain that are measured by electrophysiology and functional neuroimaging: (i) respiration-dependent modulation of mental health and cognition; (ii) respiratory rhythm generation and respiratory pontomedullary networks in the brainstem; (iii) respiration-dependent effects on specific brainstem regions and functional neural networks (e.g., glutamatergic PreBötzinger complex neurons, GABAergic parafacial neurons, adrenergic C1 neurons, parabrachial nucleus, locus coeruleus, temporoparietal junction, default-mode network, ventral attention network, and cingulo-opercular salience network); and (iv) a potential application of breathing manipulation in mental health care. These outlines and considerations of "brain-breath" interactions lead to a better understanding of the interoceptive and cognitive mechanisms that underlie brain-body interactions in health conditions and in stress-related and neuropsychiatric disorders.
Collapse
Affiliation(s)
- Nozomu H Nakamura
- Division of Physiome, Department of Physiology, Hyogo Medical University, 1-1, Mukogawa cho, Nishinomiya, Hyogo 663-8501, Japan
| | - Yoshitaka Oku
- Division of Physiome, Department of Physiology, Hyogo Medical University, 1-1, Mukogawa cho, Nishinomiya, Hyogo 663-8501, Japan
| | - Masaki Fukunaga
- Section of Brain Function Information, National Institute of Physiological Sciences, 38 Nishigonaka Myodaiji, Okazaki, Aichi 444-8585, Japan
| |
Collapse
|
4
|
Karlen-Amarante M, Bassi M, Barbosa RM, Sá JM, Menani JV, Colombari E, Zoccal DB, Colombari DSA. Maternal high-fat diet changes breathing pattern and causes excessive sympathetic discharge in juvenile offspring rat. Am J Physiol Lung Cell Mol Physiol 2023; 325:L662-L674. [PMID: 37786934 DOI: 10.1152/ajplung.00013.2023] [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: 01/11/2023] [Revised: 06/28/2023] [Accepted: 09/13/2023] [Indexed: 10/04/2023] Open
Abstract
Early life over-nutrition, as experienced in maternal obesity, is a risk factor for developing cardiorespiratory and metabolic diseases. Here we investigated the effects of high-fat diet (HFD) consumption on the breathing pattern and sympathetic discharge to blood vessels in juvenile offspring from dams fed with HFD (O-HFD). Adult female Holtzman rats were given a standard diet (SD) or HFD from 6 wk before gestation to weaning. At weaning (P21), the male offspring from SD dams (O-SD) and O-HFD received SD until the experimental day (P28-P45). Nerve recordings performed in decerebrated in situ preparations demonstrated that O-HFD animals presented abdominal expiratory hyperactivity under resting conditions and higher vasoconstrictor sympathetic activity levels. The latter was associated with blunted respiratory-related oscillations in sympathetic activity, especially in control animals. When exposed to elevated hypercapnia or hypoxia levels, the O-HFD animals mounted similar ventilatory and respiratory motor responses as the control animals. Hypercapnia and hypoxia exposure also increased sympathetic activity in both groups but did not reinstate the respiratory-sympathetic coupling in the O-HFD rats. In freely behaving conditions, O-HFD animals exhibited higher resting pulmonary ventilation and larger variability of arterial pressure levels than the O-SD animals due to augmented sympathetic modulation of blood vessel diameter. Maternal obesity modified the functioning of cardiorespiratory systems in offspring at a young age, inducing active expiration and sympathetic overactivity under resting conditions. These observations represent new evidence about pregnancy-related complications that lead to the development of respiratory distress and hypertension in children of obese mothers.NEW & NOTEWORTHY Maternal obesity is a risk factor for developing cardiorespiratory and metabolic diseases. This study highlights the changes on the breathing pattern and sympathetic discharge to blood vessels in juvenile offspring from dams fed with HFD. Maternal obesity modified the functioning of cardiorespiratory systems in offspring, inducing active expiration and sympathetic overactivity. These observations represent new evidence about pregnancy-related complications that lead to the development of respiratory distress and hypertension in children of obese mothers.
Collapse
Affiliation(s)
- Marlusa Karlen-Amarante
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Mirian Bassi
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Rafaela Moreira Barbosa
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Jéssica Matheus Sá
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - José Vanderlei Menani
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, Brazil
| | | |
Collapse
|
5
|
Xie Y, Zhang L, Guo S, Peng R, Gong H, Yang M. Changes in respiratory structure and function after traumatic cervical spinal cord injury: observations from spinal cord and brain. Front Neurol 2023; 14:1251833. [PMID: 37869136 PMCID: PMC10587692 DOI: 10.3389/fneur.2023.1251833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Accepted: 09/18/2023] [Indexed: 10/24/2023] Open
Abstract
Respiratory difficulties and mortality following severe cervical spinal cord injury (CSCI) result primarily from malfunctions of respiratory pathways and the paralyzed diaphragm. Nonetheless, individuals with CSCI can experience partial recovery of respiratory function through respiratory neuroplasticity. For decades, researchers have revealed the potential mechanism of respiratory nerve plasticity after CSCI, and have made progress in tissue healing and functional recovery. While most existing studies on respiratory plasticity after spinal cord injuries have focused on the cervical spinal cord, there is a paucity of research on respiratory-related brain structures following such injuries. Given the interconnectedness of the spinal cord and the brain, traumatic changes to the former can also impact the latter. Consequently, are there other potential therapeutic targets to consider? This review introduces the anatomy and physiology of typical respiratory centers, explores alterations in respiratory function following spinal cord injuries, and delves into the structural foundations of modified respiratory function in patients with CSCI. Additionally, we propose that magnetic resonance neuroimaging holds promise in the study of respiratory function post-CSCI. By studying respiratory plasticity in the brain and spinal cord after CSCI, we hope to guide future clinical work.
Collapse
Affiliation(s)
- Yongqi Xie
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
| | - Liang Zhang
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
| | - Shuang Guo
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
- Department of Rehabilitation, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Run Peng
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
| | - Huiming Gong
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
- Department of Spinal and Neural Functional Reconstruction, China Rehabilitation Research Center, Beijing, China
| | - Mingliang Yang
- School of Rehabilitation Medicine, Capital Medical University, Beijing, China
- Department of Spinal and Neural Functional Reconstruction, China Rehabilitation Research Center, Beijing, China
- Center of Neural Injury and Repair, Beijing Institute for Brain Disorders, Beijing, China
- Beijing Key Laboratory of Neural Injury and Rehabilitation, Beijing, China
| |
Collapse
|
6
|
Thoby-Brisson M. Central respiratory command and microglia: An early-life partnership. Curr Opin Neurobiol 2023; 82:102756. [PMID: 37544078 DOI: 10.1016/j.conb.2023.102756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 07/12/2023] [Accepted: 07/12/2023] [Indexed: 08/08/2023]
Abstract
Microglia, brain-resident macrophages, are key players in brain development, regulating synapse density, shaping neural circuits, contributing to plasticity, and maintaining nervous tissue homeostasis. These functions are ensured from early prenatal development until maturity, in normal and pathological states of the central nervous system. Microglia dysfunction can be involved in several neurodevelopmental disorders, some of which are associated with respiratory deficits. Breathing is a rhythmic motor behavior generated and controlled by hindbrain neuronal networks. The operation of the central respiratory command relies on the proper development of these rhythmogenic networks, formation of their appropriate interactions, and their lifelong constant adaptation to physiological needs. This review, focusing exclusively on the perinatal period, outlines recent advances obtained in rodents in determining the roles of microglia in the establishment and functioning of the respiratory networks and their involvement in certain pathologies.
Collapse
Affiliation(s)
- Muriel Thoby-Brisson
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, CNRS UMR 5287, Université de Bordeaux, 146 Rue Léo Saignat, 33076, Bordeaux, France. mailto:
| |
Collapse
|
7
|
Hérent C, Diem S, Usseglio G, Fortin G, Bouvier J. Upregulation of breathing rate during running exercise by central locomotor circuits in mice. Nat Commun 2023; 14:2939. [PMID: 37217517 DOI: 10.1038/s41467-023-38583-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 05/02/2023] [Indexed: 05/24/2023] Open
Abstract
While respiratory adaptation to exercise is compulsory to cope with the increased metabolic demand, the neural signals at stake remain poorly identified. Using neural circuit tracing and activity interference strategies in mice, we uncover here two systems by which the central locomotor network can enable respiratory augmentation in relation to running activity. One originates in the mesencephalic locomotor region (MLR), a conserved locomotor controller. Through direct projections onto the neurons of the preBötzinger complex that generate the inspiratory rhythm, the MLR can trigger a moderate increase of respiratory frequency, prior to, or even in the absence of, locomotion. The other is the lumbar enlargement of the spinal cord containing the hindlimb motor circuits. When activated, and through projections onto the retrotrapezoid nucleus (RTN), it also potently upregulates breathing rate. On top of identifying critical underpinnings for respiratory hyperpnea, these data also expand the functional implication of cell types and pathways that are typically regarded as "locomotor" or "respiratory" related.
Collapse
Affiliation(s)
- Coralie Hérent
- Université Paris-Saclay, CNRS, Institut des Neurosciences Paris-Saclay, 91400, Saclay, France
- Champalimaud Research, Champalimaud Foundation, 1400-038, Lisbon, Portugal
| | - Séverine Diem
- Université Paris-Saclay, CNRS, Institut des Neurosciences Paris-Saclay, 91400, Saclay, France
- Institute of Functional Genomics, University of Montpellier, CNRS, INSERM, 34094, Montpellier, France
| | - Giovanni Usseglio
- Université Paris-Saclay, CNRS, Institut des Neurosciences Paris-Saclay, 91400, Saclay, France
| | - Gilles Fortin
- Institut de Biologie de l'École Normale Supérieure (IBENS), École Normale Supérieure, CNRS, INSERM, PSL Research University, 75005, Paris, France
| | - Julien Bouvier
- Université Paris-Saclay, CNRS, Institut des Neurosciences Paris-Saclay, 91400, Saclay, France.
| |
Collapse
|
8
|
Krohn F, Novello M, van der Giessen RS, De Zeeuw CI, Pel JJM, Bosman LWJ. The integrated brain network that controls respiration. eLife 2023; 12:83654. [PMID: 36884287 PMCID: PMC9995121 DOI: 10.7554/elife.83654] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 01/29/2023] [Indexed: 03/09/2023] Open
Abstract
Respiration is a brain function on which our lives essentially depend. Control of respiration ensures that the frequency and depth of breathing adapt continuously to metabolic needs. In addition, the respiratory control network of the brain has to organize muscular synergies that integrate ventilation with posture and body movement. Finally, respiration is coupled to cardiovascular function and emotion. Here, we argue that the brain can handle this all by integrating a brainstem central pattern generator circuit in a larger network that also comprises the cerebellum. Although currently not generally recognized as a respiratory control center, the cerebellum is well known for its coordinating and modulating role in motor behavior, as well as for its role in the autonomic nervous system. In this review, we discuss the role of brain regions involved in the control of respiration, and their anatomical and functional interactions. We discuss how sensory feedback can result in adaptation of respiration, and how these mechanisms can be compromised by various neurological and psychological disorders. Finally, we demonstrate how the respiratory pattern generators are part of a larger and integrated network of respiratory brain regions.
Collapse
Affiliation(s)
- Friedrich Krohn
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
| | - Manuele Novello
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
| | | | - Chris I De Zeeuw
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands.,Netherlands Institute for Neuroscience, Royal Academy of Arts and Sciences, Amsterdam, Netherlands
| | - Johan J M Pel
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
| | | |
Collapse
|
9
|
Casarrubios AM, Pérez-Atencio LF, Martín C, Ibarz JM, Mañas E, Paul DL, Barrio LC. Neural bases for the genesis and CO 2 therapy of periodic Cheyne-Stokes breathing in neonatal male connexin-36 knockout mice. Front Neurosci 2023; 17:1045269. [PMID: 36845442 PMCID: PMC9944137 DOI: 10.3389/fnins.2023.1045269] [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: 09/15/2022] [Accepted: 01/16/2023] [Indexed: 02/11/2023] Open
Abstract
Periodic Cheyne-Stokes breathing (CSB) oscillating between apnea and crescendo-decrescendo hyperpnea is the most common central apnea. Currently, there is no proven therapy for CSB, probably because the fundamental pathophysiological question of how the respiratory center generates this form of breathing instability is still unresolved. Therefore, we aimed to determine the respiratory motor pattern of CSB resulting from the interaction of inspiratory and expiratory oscillators and identify the neural mechanism responsible for breathing regularization induced by the supplemental CO2 administration. Analysis of the inspiratory and expiratory motor pattern in a transgenic mouse model lacking connexin-36 electrical synapses, the neonatal (P14) Cx36 knockout male mouse, with a persistent CSB, revealed that the reconfigurations recurrent between apnea and hyperpnea and vice versa result from cyclical turn on/off of active expiration driven by the expiratory oscillator, which acts as a master pacemaker of respiration and entrains the inspiratory oscillator to restore ventilation. The results also showed that the suppression of CSB by supplemental 12% CO2 in inhaled air is due to the stabilization of coupling between expiratory and inspiratory oscillators, which causes the regularization of respiration. CSB rebooted after washout of CO2 excess when the inspiratory activity depressed again profoundly, indicating that the disability of the inspiratory oscillator to sustain ventilation is the triggering factor of CSB. Under these circumstances, the expiratory oscillator activated by the cyclic increase of CO2 behaves as an "anti-apnea" center generating the crescendo-decrescendo hyperpnea and periodic breathing. The neurogenic mechanism of CSB identified highlights the plasticity of the two-oscillator system in the neural control of respiration and provides a rationale base for CO2 therapy.
Collapse
Affiliation(s)
- Ana M. Casarrubios
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain,Ph.D. Program in Neuroscience, Autonoma de Madrid University-Cajal Institute, Madrid, Spain
| | - Leonel F. Pérez-Atencio
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain
| | - Cristina Martín
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain
| | - José M. Ibarz
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain
| | - Eva Mañas
- Sleep Apnea Unit, Respiratory Department, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain
| | - David L. Paul
- Department of Neurobiology, Medical School, Harvard University, Boston, MA, United States
| | - Luis C. Barrio
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain,Center for Biomedical Technology, Universidad Politécnica de Madrid, Madrid, Spain,*Correspondence: Luis C. Barrio, ; orcid.org/0000-0002-9016-3510
| |
Collapse
|
10
|
Wiese BM, Alvarez Reyes A, Vanderah TW, Largent-Milnes TM. The endocannabinoid system and breathing. Front Neurosci 2023; 17:1126004. [PMID: 37144090 PMCID: PMC10153446 DOI: 10.3389/fnins.2023.1126004] [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: 12/16/2022] [Accepted: 03/16/2023] [Indexed: 05/06/2023] Open
Abstract
Recent changes in cannabis accessibility have provided adjunct therapies for patients across numerous disease states and highlights the urgency in understanding how cannabinoids and the endocannabinoid (EC) system interact with other physiological structures. The EC system plays a critical and modulatory role in respiratory homeostasis and pulmonary functionality. Respiratory control begins in the brainstem without peripheral input, and coordinates the preBötzinger complex, a component of the ventral respiratory group that interacts with the dorsal respiratory group to synchronize burstlet activity and drive inspiration. An additional rhythm generator: the retrotrapezoid nucleus/parafacial respiratory group drives active expiration during conditions of exercise or high CO2. Combined with the feedback information from the periphery: through chemo- and baroreceptors including the carotid bodies, the cranial nerves, stretch of the diaphragm and intercostal muscles, lung tissue, and immune cells, and the cranial nerves, our respiratory system can fine tune motor outputs that ensure we have the oxygen necessary to survive and can expel the CO2 waste we produce, and every aspect of this process can be influenced by the EC system. The expansion in cannabis access and potential therapeutic benefits, it is essential that investigations continue to uncover the underpinnings and mechanistic workings of the EC system. It is imperative to understand the impact cannabis, and exogenous cannabinoids have on these physiological systems, and how some of these compounds can mitigate respiratory depression when combined with opioids or other medicinal therapies. This review highlights the respiratory system from the perspective of central versus peripheral respiratory functionality and how these behaviors can be influenced by the EC system. This review will summarize the literature available on organic and synthetic cannabinoids in breathing and how that has shaped our understanding of the role of the EC system in respiratory homeostasis. Finally, we look at some potential future therapeutic applications the EC system has to offer for the treatment of respiratory diseases and a possible role in expanding the safety profile of opioid therapies while preventing future opioid overdose fatalities that result from respiratory arrest or persistent apnea.
Collapse
Affiliation(s)
- Beth M. Wiese
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States
| | - Angelica Alvarez Reyes
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States
- College of Medicine, University of Arizona, Tucson, AZ, United States
| | - Todd W. Vanderah
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States
| | - Tally M. Largent-Milnes
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States
- *Correspondence: Tally M. Largent-Milnes,
| |
Collapse
|
11
|
Oku Y. Temporal variations in the pattern of breathing: techniques, sources, and applications to translational sciences. J Physiol Sci 2022; 72:22. [PMID: 36038825 DOI: 10.1186/s12576-022-00847-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Accepted: 08/12/2022] [Indexed: 11/10/2022]
Abstract
The breathing process possesses a complex variability caused in part by the respiratory central pattern generator in the brainstem; however, it also arises from chemical and mechanical feedback control loops, network reorganization and network sharing with nonrespiratory motor acts, as well as inputs from cortical and subcortical systems. The notion that respiratory fluctuations contain hidden information has prompted scientists to decipher respiratory signals to better understand the fundamental mechanisms of respiratory pattern generation, interactions with emotion, influences on the cortical neuronal networks associated with cognition, and changes in variability in healthy and disease-carrying individuals. Respiration can be used to express and control emotion. Furthermore, respiration appears to organize brain-wide network oscillations via cross-frequency coupling, optimizing cognitive performance. With the aid of information theory-based techniques and machine learning, the hidden information can be translated into a form usable in clinical practice for diagnosis, emotion recognition, and mental conditioning.
Collapse
Affiliation(s)
- Yoshitaka Oku
- Division of Physiome, Department of Physiology, Hyogo Medical University, Nishinomiya, Hyogo, 663-8501, Japan.
| |
Collapse
|
12
|
Gumnit MG, Watters JJ, Baker TL, Johnson SM, Johnson SM. Mu-opioid receptor-dependent transformation of respiratory motor pattern in neonates in vitro. Front Physiol 2022; 13:921466. [PMID: 35936900 PMCID: PMC9353126 DOI: 10.3389/fphys.2022.921466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 06/30/2022] [Indexed: 11/29/2022] Open
Abstract
Endogenous opioid peptides activating mu-opioid receptors (MORs) are part of an intricate neuromodulatory system that coordinates and optimizes respiratory motor output to maintain blood-gas homeostasis. MOR activation is typically associated with respiratory depression but also has excitatory effects on breathing and respiratory neurons. We hypothesized that low level MOR activation induces excitatory effects on the respiratory motor pattern. Thus, low concentrations of an MOR agonist drug (DAMGO, 10–200 nM) were bath-applied to neonatal rat brainstem-spinal cord preparations while recording inspiratory-related motor output on cervical spinal roots (C4-C5). Bath-applied DAMGO (50–200 nM) increased inspiratory motor burst amplitude by 40–60% during (and shortly following) drug application with decreased burst frequency and minute activity. Reciprocal changes in inspiratory burst amplitude and frequency were balanced such that 20 min after DAMGO (50–200 nM) application, minute activity was unaltered compared to pre-DAMGO levels. The DAMGO-induced inspiratory burst amplitude increase did not require crossed cervical spinal pathways, was expressed on thoracic ventral spinal roots (T4-T8) and remained unaltered by riluzole pretreatment (blocks persistent sodium currents associated with gasping). Split-bath experiments showed that the inspiratory burst amplitude increase was induced only when DAMGO was bath-applied to the brainstem and not the spinal cord. Thus, MOR activation in neonates induces a respiratory burst amplitude increase via brainstem-specific mechanisms. The burst amplitude increase counteracts the expected MOR-dependent frequency depression and may represent a new mechanism by which MOR activation influences respiratory motor output.
Collapse
|
13
|
Abstract
Breathing is a vital rhythmic motor behavior with a surprisingly broad influence on the brain and body. The apparent simplicity of breathing belies a complex neural control system, the breathing central pattern generator (bCPG), that exhibits diverse operational modes to regulate gas exchange and coordinate breathing with an array of behaviors. In this review, we focus on selected advances in our understanding of the bCPG. At the core of the bCPG is the preBötzinger complex (preBötC), which drives inspiratory rhythm via an unexpectedly sophisticated emergent mechanism. Synchronization dynamics underlying preBötC rhythmogenesis imbue the system with robustness and lability. These dynamics are modulated by inputs from throughout the brain and generate rhythmic, patterned activity that is widely distributed. The connectivity and an emerging literature support a link between breathing, emotion, and cognition that is becoming experimentally tractable. These advances bring great potential for elucidating function and dysfunction in breathing and other mammalian neural circuits.
Collapse
Affiliation(s)
- Sufyan Ashhad
- Department of Neurobiology, University of California at Los Angeles, Los Angeles, California, USA;
| | - Kaiwen Kam
- Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | | | - Jack L Feldman
- Department of Neurobiology, University of California at Los Angeles, Los Angeles, California, USA;
| |
Collapse
|
14
|
Lavezzi AM, Pusiol T, Paradiso B. Harmful Effect of Intrauterine Smoke Exposure on Neuronal Control of "Fetal Breathing System" in Stillbirths. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19074164. [PMID: 35409845 PMCID: PMC8999022 DOI: 10.3390/ijerph19074164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 03/29/2022] [Accepted: 03/30/2022] [Indexed: 02/04/2023]
Abstract
This article is aimed to contribute to the current knowledge on the role of toxic substances such as nicotine on sudden intrauterine unexplained deaths’ (SIUDS’) pathogenetic mechanisms. The in-depth histopathological examination of the autonomic nervous system in wide groups of victims of SIUDS (47 cases) and controls (20 cases), with both smoking and no-smoking mothers, highlighted the frequent presence of the hypodevelopment of brainstem structures checking the vital functions. In particular, the hypoplasia of the pontine parafacial nucleus together with hypoplastic lungs for gestational age were observed in SIUDS cases with mothers who smoked cigarettes, including electronic ones. The results allow us to assume that the products of cigarette smoke during pregnancy can easily cross the placental barrier, thus entering the fetal circulation and damaging the most sensitive organs, such as lungs and brain. In a non-negligible percentage of SIUDS, the mothers did not smoke. Furthermore, based on previous and ongoing studies conducted through analytical procedures and the use of scanning electron microscopy, the authors envisage the involvement of toxic nanoparticles (such as agricultural pesticides and nanomaterials increasingly used in biomedicine, bioscience and biotechnology) in the death pathogenesis, with similar mechanisms to those of nicotine.
Collapse
Affiliation(s)
- Anna M. Lavezzi
- “Lino Rossi” Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20121 Milan, Italy;
- Correspondence:
| | - Teresa Pusiol
- Institute of Anatomic Pathology, APSS, 38122 Trento, Italy;
| | - Beatrice Paradiso
- “Lino Rossi” Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20121 Milan, Italy;
- General Pathology Unit, Dolo Hospital, 30031 Dolo, Italy
| |
Collapse
|
15
|
Turk AZ, Bishop M, Adeck A, SheikhBahaei S. Astrocytic modulation of central pattern generating motor circuits. Glia 2022; 70:1506-1519. [PMID: 35212422 DOI: 10.1002/glia.24162] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 12/26/2022]
Abstract
Central pattern generators (CPGs) generate the rhythmic and coordinated neural features necessary for the proper conduction of complex behaviors. In particular, CPGs are crucial for complex motor behaviors such as locomotion, mastication, respiration, and vocal production. While the importance of these networks in modulating behavior is evident, the mechanisms driving these CPGs are still not fully understood. On the other hand, accumulating evidence suggests that astrocytes have a significant role in regulating the function of some of these CPGs. Here, we review the location, function, and role of astrocytes in locomotion, respiration, and mastication CPGs and propose that, similarly, astrocytes may also play a significant role in the vocalization CPG.
Collapse
Affiliation(s)
- Ariana Z Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Mitchell Bishop
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Afuh Adeck
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| |
Collapse
|
16
|
Patterns of cardio-respiratory motor outputs during acute and subacute exposure to chlorpyrifos in an ex-vivo in situ preparation in rats. Toxicol Appl Pharmacol 2022; 436:115862. [PMID: 34998853 DOI: 10.1016/j.taap.2022.115862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 12/08/2021] [Accepted: 01/02/2022] [Indexed: 10/19/2022]
Abstract
While a considerable body of literature has characterized the clinical features induced by organophosphate pesticides, the field lacks scrutiny into cardio-respiratory changes in different phases of poisoning. Herein, we evaluated the impact of chlorpyrifos (CPF) and its active metabolite chlorpyrifos-oxon (CPO) on the cardiorespiratory system during acute and subacute phases of poisoning using an in situ experimental rodent model. CPF (30 mg/kg) was injected intraperitoneally to rats beforehand (24 h) whereas CPO (15 mg/kg) was added into the perfusate reservoir to evaluate the effects on the motor outputs throughout the three phases of the respiratory cycle: inspiration, post-inspiration and late expiration. Phrenic, recurrent laryngeal (RLN) and thoracic sympathetic nerve activity (tSNA) were recorded. Heart rate was derived from the electrocardiogram (ECG) and the baro- and chemo-reflexes tested. CPF and CPO led to a time-dependent change in cardiorespiratory motor outputs. In the acute phase, the CPO induced bradypnea, transiently reduced the inspiratory time (TI), and increased the amplitude of phrenic. Post-inspiratory (PI) discharge recorded from the RLN was progressively reduced while tSNA was increased. CPO significantly depressed the chemoreflex but had no effect on baroreflex. During subacute phase, CPF prolongated TI with no effect on respiratory rate. Both the RLN PI discharge, the chemoreflex and the baroreflex sympathetic gain were reduced. In addition, both CPF and CPO shifted the cardiac sympatho-vagal balance towards sympathetic dominance. Our data show that different phases of poisoning are associated with specific changes in the cardio-respiratory system and might therefore demand distinct approaches by health care providers.
Collapse
|
17
|
Smith JC. Respiratory rhythm and pattern generation: Brainstem cellular and circuit mechanisms. HANDBOOK OF CLINICAL NEUROLOGY 2022; 188:1-35. [PMID: 35965022 DOI: 10.1016/b978-0-323-91534-2.00004-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Breathing movements in mammals are driven by rhythmic neural activity automatically generated within spatially and functionally organized brainstem neural circuits comprising the respiratory central pattern generator (CPG). This chapter reviews up-to-date experimental information and theoretical studies of the cellular and circuit mechanisms of respiratory rhythm and pattern generation operating within critical components of this CPG in the lower brainstem. Over the past several decades, there have been substantial advances in delineating the spatial architecture of essential medullary regions and their regional cellular and circuit properties required to understand rhythm and pattern generation mechanisms. A fundamental concept is that the circuits in these regions have rhythm-generating capabilities at multiple cellular and circuit organization levels. The regional cellular properties, circuit organization, and control mechanisms allow flexible expression of neural activity patterns for a repertoire of respiratory behaviors under various physiologic conditions that are dictated by requirements for homeostatic regulation and behavioral integration. Many mechanistic insights have been provided by computational modeling studies driven by experimental results and have advanced understanding in the field. These conceptual and theoretical developments are discussed.
Collapse
Affiliation(s)
- Jeffrey C Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States.
| |
Collapse
|
18
|
Abstract
Brain PCO2 is sensed primarily via changes in [H+]. Small pH changes are detected in the medulla oblongata and trigger breathing adjustments that help maintain arterial PCO2 constant. Larger perturbations of brain CO2/H+, possibly also sensed elsewhere in the CNS, elicit arousal, dyspnea, and stress, and cause additional breathing modifications. The retrotrapezoid nucleus (RTN), a rostral medullary cluster of glutamatergic neurons identified by coexpression of Phoxb and Nmb transcripts, is the lynchpin of the central respiratory chemoreflex. RTN regulates breathing frequency, inspiratory amplitude, and active expiration. It is exquisitely responsive to acidosis in vivo and maintains breathing autorhythmicity during quiet waking, slow-wave sleep, and anesthesia. The RTN response to [H+] is partly an intrinsic neuronal property mediated by proton sensors TASK-2 and GPR4 and partly a paracrine effect mediated by astrocytes and the vasculature. The RTN also receives myriad excitatory or inhibitory synaptic inputs including from [H+]-responsive neurons (e.g., serotonergic). RTN is silenced by moderate hypoxia. RTN inactivity (periodic or sustained) contributes to periodic breathing and, likely, to central sleep apnea. RTN development relies on transcription factors Egr2, Phox2b, Lbx1, and Atoh1. PHOX2B mutations cause congenital central hypoventilation syndrome; they impair RTN development and consequently the central respiratory chemoreflex.
Collapse
Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States.
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States
| |
Collapse
|
19
|
Abstract
Opiates, such as morphine, and synthetic opioids, such as fentanyl, constitute a class of drugs acting on opioid receptors which have been used therapeutically and recreationally for centuries. Opioid drugs have strong analgesic properties and are used to treat moderate to severe pain, but also present side effects including opioid dependence, tolerance, addiction, and respiratory depression, which can lead to lethal overdose if not treated. This chapter explores the pathophysiology, the neural circuits, and the cellular mechanisms underlying opioid-induced respiratory depression and provides a translational perspective of the most recent research. The pathophysiology discussed includes the effects of opioid drugs on the respiratory system in patients, as well as the animal models used to identify underlying mechanisms. Using a combination of gene editing and pharmacology, the neural circuits and molecular pathways mediating neuronal inhibition by opioids are examined. By using pharmacology and neuroscience approaches, new therapies to prevent or reverse respiratory depression by opioid drugs have been identified and are currently being developed. Considering the health and economic burden associated with the current opioid epidemic, innovative research is needed to better understand the side effects of opioid drugs and to discover new therapeutic solutions to reduce the incidence of lethal overdoses.
Collapse
|
20
|
Pérez‐Atencio LF, Casarrubios AM, Ibarz JM, Barios JA, Medrano C, Pestaña D, Paul DL, Barrio LC. Respiratory disturbances and high risk of sudden death in the neonatal connexin-36 knockout mouse. Physiol Rep 2021; 9:e15109. [PMID: 34755471 PMCID: PMC8579078 DOI: 10.14814/phy2.15109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 10/10/2021] [Indexed: 11/24/2022] Open
Abstract
Neural circuits at the brainstem involved in the central generation of the motor patterns of respiration and cardiorespiratory chemoreflexes organize as cell assemblies connected by chemical and electrical synapses. However, the role played by the electrical connectivity mainly mediated by connexin36 (Cx36), which expression reaches peak value during the postnatal period, is still unknown. To address this issue, we analyzed here the respiratory phenotype of a mouse strain devoid constitutively of Cx36 at P14. Male Cx36-knockout mice at rest showed respiratory instability of variable degree, including a periodic Cheyne-Stokes breathing. Moreover, mice lacking Cx36 exhibited exacerbated chemoreflexes to normoxic and hypoxic hypercapnia characterized by a stronger inspiratory/expiratory coupling due to an increased sensitivity to CO2 . Deletion of Cx36 also impaired the generation of the recurrent episodes of transient bradycardia (ETBs) evoked during hypercapnic chemoreflexes; these EBTs constituted a powerful mechanism of cardiorespiratory coupling capable of improving alveolar gaseous exchange under hypoxic hypercapnia conditions. Approximately half of the homo- and heterozygous Cx36KO, but none WT, mice succumbed by respiratory arrest when submitted to hypoxia-hypercapnia, the principal exogenous stressor causing sudden infant death syndrome (SIDS). The early suppression of EBTs, which worsened arterial O2 saturation, and the generation of a paroxysmal generalized clonic-tonic activity, which provoked the transition from eupneic to gasping respiration, were the critical events causing sudden death in the Cx36KO mice. These results indicate that Cx36 expression plays a pivotal role in respiratory control, cardiorespiratory coordination, and protection against SIDS at the postnatal period.
Collapse
Affiliation(s)
| | - Ana M. Casarrubios
- Unit of Experimental Neurology“Ramón y Cajal” Hospital (IRYCIS)MadridSpain
| | - José M. Ibarz
- Unit of Experimental Neurology“Ramón y Cajal” Hospital (IRYCIS)MadridSpain
| | - Juan A. Barios
- Biomedical Neuroengineering Research Group (nBio)Systems Engineering and Automation Department of Miguel Hernández UniversityElcheSpain
| | - Cristina Medrano
- Anesthesiology Service“Ramón y Cajal” Hospital (IRYCIS)MadridSpain
| | - David Pestaña
- Anesthesiology Service“Ramón y Cajal” Hospital (IRYCIS)MadridSpain
| | - David L. Paul
- Department of NeurobiologyHarvard Medical SchoolBostonMassachusettsUSA
| | - Luis C. Barrio
- Unit of Experimental Neurology“Ramón y Cajal” Hospital (IRYCIS)MadridSpain
- Centro de Tecnología Biomédica de la Universidad PolitécnicaMadridSpain
| |
Collapse
|
21
|
Magalhães KS, da Silva MP, Mecawi AS, Paton JFR, Machado BH, Moraes DJA. Intrinsic and synaptic mechanisms controlling the expiratory activity of excitatory lateral parafacial neurones of rats. J Physiol 2021; 599:4925-4948. [PMID: 34510468 DOI: 10.1113/jp281545] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 09/07/2021] [Indexed: 12/21/2022] Open
Abstract
Active expiration is essential for increasing pulmonary ventilation during high chemical drive (hypercapnia). The lateral parafacial (pFL ) region, which contains expiratory neurones, drives abdominal muscles during active expiration in response to hypercapnia. However, the electrophysiological properties and synaptic mechanisms determining the activity of pFL expiratory neurones, as well as the specific conditions for their emergence, are not fully understood. Using whole cell electrophysiology and single cell quantitative RT-PCR techniques, we describe the intrinsic electrophysiological properties, the phenotype and the respiratory-related synaptic inputs to the pFL expiratory neurones, as well as the mechanisms for the expression of their expiratory activity under conditions of hypercapnia-induced active expiration, using in situ preparations of juvenile rats. We also evaluated whether these neurones possess intrinsic CO2 /[H+ ] sensitivity and burst generating properties. GABAergic and glycinergic inhibition during inspiration and expiration suppressed the activity of glutamatergic pFL expiratory neurones in normocapnia. In hypercapnia, these neurones escape glycinergic inhibition and generate burst discharges at the end of expiration. Evidence for the contribution of post-inhibitory rebound, CaV 3.2 isoform of T-type Ca2+ channels and intracellular [Ca2+ ] is presented. Neither intrinsic bursting properties, mediated by persistent Na+ current, nor CO2 /[H+ ] sensitivity or expression of CO2 /[H+ ] sensitive ion channels/receptors (TASK or GPR4) were observed. On the other hand, hyperpolarisation-activated cyclic nucleotide-gated and twik-related K+ leak channels were recorded. Post-synaptic disinhibition and the intrinsic electrophysiological properties of glutamatergic neurones play important roles in the generation of the expiratory oscillations in the pFL region during hypercapnia in rats. KEY POINTS: Hypercapnia induces active expiration in rats and the recruitment of a specific population of expiratory neurones in the lateral parafacial (pFL ) region. Post-synaptic GABAergic and glycinergic inhibition both suppress the activity of glutamatergic pFL neurones during inspiratory and expiratory phases in normocapnia. Hypercapnia reduces glycinergic inhibition during expiration leading to burst generation by pFL neurones; evidence for a contribution of post-inhibitory rebound, voltage-gated Ca2+ channels and intracellular [Ca2+ ] is presented. pFL glutamatergic expiratory neurones are neither intrinsic burster neurones, nor CO2 /[H+ ] sensors, and do not express CO2 /[H+ ] sensitive ion channels or receptors. Post-synaptic disinhibition and the intrinsic electrophysiological properties of glutamatergic neurones both play important roles in the generation of the expiratory oscillations in the pFL region during hypercapnia in rats.
Collapse
Affiliation(s)
- Karolyne S Magalhães
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Melina P da Silva
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - André S Mecawi
- Department of Biophysics, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Julian F R Paton
- Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland, Park Road, Grafton, Auckland, New Zealand
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| |
Collapse
|
22
|
Milsom WK, Kinkead R, Hedrick MS, Gilmour K, Perry S, Gargaglioni L, Wang T. Evolution of vertebrate respiratory central rhythm generators. Respir Physiol Neurobiol 2021; 295:103781. [PMID: 34481078 DOI: 10.1016/j.resp.2021.103781] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/03/2021] [Accepted: 08/29/2021] [Indexed: 12/01/2022]
Abstract
Tracing the evolution of the central rhythm generators associated with ventilation in vertebrates is hindered by a lack of information surrounding key transitions. To begin with, central rhythm generation has been studied in detail in only a few species from four vertebrate groups, lamprey, anuran amphibians, turtles, and mammals (primarily rodents). Secondly, there is a lack of information regarding the transition from water breathing fish to air breathing amniotes (reptiles, birds, and mammals). Specifically, the respiratory rhythm generators of fish appear to be single oscillators capable of generating both phases of the respiratory cycle (expansion and compression) and projecting to motoneurons in cranial nerves innervating bucco-pharyngeal muscles. In the amniotes we find oscillators capable of independently generating separate phases of the respiratory cycle (expiration and inspiration) and projecting to pre-motoneurons in the ventrolateral medulla that in turn project to spinal motoneurons innervating thoracic and abdominal muscles (reptiles, birds, and mammals). Studies of the one group of amphibians that lie at this transition (the anurans), raise intriguing possibilities but, for a variety of reasons that we explore, also raise unanswered questions. In this review we summarize what is known about the rhythm generating circuits associated with breathing that arise from the different rhombomeric segments in each of the different vertebrate classes. Assuming oscillating circuits form in every pair of rhombomeres in every vertebrate during development, we trace what appears to be the evolutionary fate of each and highlight the questions that remain to be answered to properly understand the evolutionary transitions in vertebrate central respiratory rhythm generation.
Collapse
Affiliation(s)
- W K Milsom
- Department of Zoology, University of British Columbia, Canada.
| | - R Kinkead
- Département de Pédiatrie, Université Laval, Canada
| | - M S Hedrick
- Department of Biological Sciences, California State University, Hayward, CA, USA
| | - K Gilmour
- Department of Biology, University of Ottawa, Canada
| | - S Perry
- Department of Biology, University of Ottawa, Canada
| | - L Gargaglioni
- Departamento de Morfologia e Fisiologia Animal, UNESP, Jaboticabal, Brazil
| | - T Wang
- Department of Zoophysiology, Aarhus University, Denmark
| |
Collapse
|
23
|
Acute intermittent hypoxia evokes ventilatory long-term facilitation and active expiration in unanesthetized rats. Respir Physiol Neurobiol 2021; 294:103768. [PMID: 34343692 DOI: 10.1016/j.resp.2021.103768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Revised: 07/23/2021] [Accepted: 07/29/2021] [Indexed: 11/23/2022]
Abstract
Acute intermittent hypoxia (AIH) modifies the functioning of the respiratory network, causing respiratory motor facilitation in anesthetized animals and a compensatory increase in pulmonary ventilation in freely behaving animals. However, it is still unclear whether the ventilatory facilitation induced by AIH in unanesthetized animals is associated with changes in the respiratory pattern. We found that Holtzman male rats (80-150 g) exposed to AIH (10 × 6% O2 for 30-40 s every 5 min, n = 9) exhibited a prolonged (30 min) increase in baseline minute ventilation (P < 0.05) compared to control animals (n = 13), combined with the occurrence of late expiratory peak flow events, suggesting the presence of active expiration. The increase in ventilation after AIH was also accompanied by reductions in arterial CO2 and body temperature (n = 5-6, P < 0.05). The systemic treatment with ketanserin (a 5-HT2 receptor antagonist) before AIH prevented the changes in ventilation and active expiration (n = 11) but potentiated the hypothermic response (n = 5, P < 0.05) when compared to appropriate control rats (n = 13). Our findings indicate that the ventilatory long-term facilitation elicited by AIH exposure in unanesthetized rats is linked to the generation of active expiration by mechanisms that may depend on the activation of serotonin receptors. In contrast, the decrease in body temperature induced by AIH may not require 5-HT2 receptor activation.
Collapse
|
24
|
The lamprey respiratory network: Some evolutionary aspects. Respir Physiol Neurobiol 2021; 294:103766. [PMID: 34329767 DOI: 10.1016/j.resp.2021.103766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/19/2021] [Accepted: 07/25/2021] [Indexed: 01/25/2023]
Abstract
Breathing is a complex behaviour that involves rhythm generating networks. In this review, we examine the main characteristics of respiratory rhythm generation in vertebrates and, in particular, we describe the main results of our studies on the role of neural mechanisms involved in the neuromodulation of the lamprey respiration. The lamprey respiratory rhythm generator is located in the paratrigeminal respiratory group (pTRG) and shows similarities with the mammalian preBötzinger complex. In fact, within the pTRG a major role is played by glutamate, but also GABA and glycine display important contributions. In addition, neuromodulatory influences are exerted by opioids, substance P, acetylcholine and serotonin. Both structures respond to exogenous ATP with a biphasic response and astrocytes there located strongly contribute to the modulation of the respiratory pattern. The results emphasize that some important characteristics of the respiratory rhythm generating network are, to a great extent, maintained throughout evolution.
Collapse
|
25
|
Cinelli E, Mutolo D, Pantaleo T, Bongianni F. Neural mechanisms underlying respiratory regulation within the preBötzinger complex of the rabbit. Respir Physiol Neurobiol 2021; 293:103736. [PMID: 34224867 DOI: 10.1016/j.resp.2021.103736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 07/01/2021] [Accepted: 07/01/2021] [Indexed: 11/29/2022]
Abstract
The preBötzinger complex (preBötC) is a medullary area essential for normal breathing and widely recognized as necessary and sufficient to generate the inspiratory phase of respiration. It has been studied mainly in rodents. Here we report the main results of our studies revealing the characteristics of the rabbit preBötC identified by means of neuronal recordings, D,L-homocysteic acid microinjections and histological controls. A crucial role in the respiratory rhythmogenesis within this neural substrate is played by excitatory amino acids, but also GABA and glycine display important contributions. Increases in respiratory frequency are induced by microinjections of neurokinins, somatostatin as well by serotonin (5-HT) through an action on 5-HT1A and 5-HT3 receptors or the disinhibition of a GABAergic circuit. Respiratory depression is observed in response to microinjections of the μ-opioid receptor agonist DAMGO. Our results show similarities and differences with the rodent preBötC and emphasize the importance of comparative studies on the mechanisms underlying respiratory rhythmogenesis in different animal species.
Collapse
Affiliation(s)
- Elenia Cinelli
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Donatella Mutolo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Tito Pantaleo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Fulvia Bongianni
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy.
| |
Collapse
|
26
|
Wang D, Yee BJ, Grunstein RR, Chung F. Chronic Opioid Use and Central Sleep Apnea, Where Are We Now and Where To Go? A State of the Art Review. Anesth Analg 2021; 132:1244-1253. [PMID: 33857966 DOI: 10.1213/ane.0000000000005378] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Opioids are commonly used for pain management, perioperative procedures, and addiction treatment. There is a current opioid epidemic in North America that is paralleled by a marked increase in related deaths. Since 2000, chronic opioid users have been recognized to have significant central sleep apnea (CSA). After heart failure-related Cheyne-Stokes breathing (CSB), opioid-induced CSA is now the second most commonly seen CSA. It occurs in around 24% of chronic opioid users, typically after opioids have been used for more than 2 months, and usually corresponds in magnitude to opioid dose/plasma concentration. Opioid-induced CSA events often mix with episodes of ataxic breathing. The pathophysiology of opioid-induced CSA is based on dysfunction in respiratory rhythm generation and ventilatory chemoreflexes. Opioids have a paradoxical effect on different brain regions, which result in irregular respiratory rhythm. Regarding ventilatory chemoreflexes, chronic opioid use induces hypoxia that appears to stimulate an augmented hypoxic ventilatory response (high loop gain) and cause a narrow CO2 reserve, a combination that promotes respiratory instability. To date, no direct evidence has shown any major clinical consequence from CSA in chronic opioid users. A line of evidence suggested increased morbidity and mortality in overall chronic opioid users. CSA in chronic opioid users is likely to be a compensatory mechanism to avoid opioid injury and is potentially beneficial. The current treatments of CSA in chronic opioid users mainly focus on continuous positive airway pressure (CPAP) and adaptive servo-ventilation (ASV) or adding oxygen. ASV is more effective in reducing CSA events than CPAP. However, a recent ASV trial suggested an increased all-cause and cardiovascular mortality with the removal of CSA/CSB in cardiac failure patients. A major reason could be counteracting of a compensatory mechanism. No similar trial has been conducted for chronic opioid-related CSA. Future studies should focus on (1) investigating the phenotypes and genotypes of opioid-induced CSA that may have different clinical outcomes; (2) determining if CSA in chronic opioid users is beneficial or detrimental; and (3) assessing clinical consequences on different treatment options on opioid-induced CSA.
Collapse
Affiliation(s)
- David Wang
- From the Centre for Integrated Research and Understanding of Sleep (CIRUS), Woolcock Institute of Medical Research, Sydney Medical School, the University of Sydney, Australia.,Department of Respiratory and Sleep Medicine, Royal Prince Alfred Hospital, Sydney Local Health District, Sydney, Australia
| | - Brendon J Yee
- From the Centre for Integrated Research and Understanding of Sleep (CIRUS), Woolcock Institute of Medical Research, Sydney Medical School, the University of Sydney, Australia.,Department of Respiratory and Sleep Medicine, Royal Prince Alfred Hospital, Sydney Local Health District, Sydney, Australia
| | - Ronald R Grunstein
- From the Centre for Integrated Research and Understanding of Sleep (CIRUS), Woolcock Institute of Medical Research, Sydney Medical School, the University of Sydney, Australia.,Department of Respiratory and Sleep Medicine, Royal Prince Alfred Hospital, Sydney Local Health District, Sydney, Australia
| | - Frances Chung
- Department of Anesthesiology and Pain Management, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada
| |
Collapse
|
27
|
Hocker AD, Morrison NR, Selby ML, Huxtable AG. Maternal Methadone Destabilizes Neonatal Breathing and Desensitizes Neonates to Opioid-Induced Respiratory Frequency Depression. Front Physiol 2021; 12:604593. [PMID: 33716765 PMCID: PMC7946987 DOI: 10.3389/fphys.2021.604593] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 02/08/2021] [Indexed: 11/28/2022] Open
Abstract
Pregnant women and developing infants are understudied populations in the opioid crisis, despite the rise in opioid use during pregnancy. Maternal opioid use results in diverse negative outcomes for the fetus/newborn, including death; however, the effects of perinatal (maternal and neonatal) opioids on developing respiratory circuitry are not well understood. Given the profound depressive effects of opioids on central respiratory networks controlling breathing, we tested the hypothesis that perinatal opioid exposure impairs respiratory neural circuitry, creating breathing instability. Our data demonstrate maternal opioids increase apneas and destabilize neonatal breathing. Maternal opioids also blunted opioid-induced respiratory frequency depression acutely in neonates; a unique finding since adult respiratory circuity does not desensitize to opioids. This desensitization normalized rapidly between postnatal days 1 and 2 (P1 and P2), the same age quantal slowing emerged in respiratory rhythm. These data suggest significant reorganization of respiratory rhythm generating circuits at P1-2, the same time as the preBötzinger Complex (key site of respiratory rhythm generation) becomes the dominant respiratory rhythm generator. Thus, these studies provide critical insight relevant to the normal developmental trajectory of respiratory circuits and suggest changes to mutual coupling between respiratory oscillators, while also highlighting how maternal opioids alter these developing circuits. In conclusion, the results presented demonstrate neurorespiratory disruption by maternal opioids and blunted opioid-induced respiratory frequency depression with neonatal opioids, which will be important for understanding and treating the increasing population of neonates exposed to gestational opioids.
Collapse
|
28
|
Moreira TS, Sobrinho CR, Falquetto B, Oliveira LM, Lima JD, Mulkey DK, Takakura AC. The retrotrapezoid nucleus and the neuromodulation of breathing. J Neurophysiol 2020; 125:699-719. [PMID: 33427575 DOI: 10.1152/jn.00497.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Breathing is regulated by a host of arousal and sleep-wake state-dependent neuromodulators to maintain respiratory homeostasis. Modulators such as acetylcholine, norepinephrine, histamine, serotonin (5-HT), adenosine triphosphate (ATP), substance P, somatostatin, bombesin, orexin, and leptin can serve complementary or off-setting functions depending on the target cell type and signaling mechanisms engaged. Abnormalities in any of these modulatory mechanisms can destabilize breathing, suggesting that modulatory mechanisms are not overly redundant but rather work in concert to maintain stable respiratory output. The present review focuses on the modulation of a specific cluster of neurons located in the ventral medullary surface, named retrotrapezoid nucleus, that are activated by changes in tissue CO2/H+ and regulate several aspects of breathing, including inspiration and active expiration.
Collapse
Affiliation(s)
- Thiago S Moreira
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Cleyton R Sobrinho
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Barbara Falquetto
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Luiz M Oliveira
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Janayna D Lima
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Ana C Takakura
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| |
Collapse
|
29
|
Freire C, Pho H, Kim LJ, Wang X, Dyavanapalli J, Streeter SR, Fleury-Curado T, Sennes LU, Mendelowitz D, Polotsky VY. Intranasal Leptin Prevents Opioid-induced Sleep-disordered Breathing in Obese Mice. Am J Respir Cell Mol Biol 2020; 63:502-509. [PMID: 32603263 DOI: 10.1165/rcmb.2020-0117oc] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Respiratory depression is the main cause of morbidity and mortality associated with opioids. Obesity increases opioid-related mortality, which is mostly related to comorbid obstructive sleep apnea. Naloxone, a μ-opioid receptor blocker, is an effective antidote, but it reverses analgesia. Like humans with obesity, mice with diet-induced obesity hypoventilate during sleep and develop obstructive sleep apnea, which can be treated with intranasal leptin. We hypothesized that intranasal leptin reverses opioid-induced sleep-disordered breathing in obese mice without decreasing analgesia. To test this hypothesis, mice with diet-induced obesity were treated with morphine at 10 mg/kg subcutaneously and with leptin or placebo intranasally. Sleep and breathing were recorded by barometric plethysmography, and pain sensitivity was measured by the tail-flick test. Excitatory postsynaptic currents were recorded in vitro from hypoglossal motor neurons after the application of the μ-opioid receptor agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin and leptin. Morphine dramatically increased the frequency of apneas and greatly increased the severity of hypoventilation and obstructive sleep apnea. Leptin decreased the frequency of apneas, improved obstructive sleep apnea, and completely reversed hypoventilation, whereas morphine analgesia was enhanced. Our in vitro studies demonstrated that [D-Ala2, N-MePhe4, Gly-ol]-enkephalin reduced the frequency of excitatory postsynaptic currents in hypoglossal motoneurons and that application of leptin restored excitatory synaptic neurotransmission. Our findings suggest that intranasal leptin may prevent opioid respiratory depression during sleep in patients with obesity receiving opioids without reducing analgesia.
Collapse
Affiliation(s)
- Carla Freire
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.,Department of Otolaryngology, University of São Paulo, São Paulo, Brazil; and
| | - Huy Pho
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Lenise J Kim
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Xin Wang
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC
| | - Jhansi Dyavanapalli
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC
| | - Stone R Streeter
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Thomaz Fleury-Curado
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.,Department of Otolaryngology, University of São Paulo, São Paulo, Brazil; and
| | - Luiz U Sennes
- Department of Otolaryngology, University of São Paulo, São Paulo, Brazil; and
| | - David Mendelowitz
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC
| | - Vsevolod Y Polotsky
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| |
Collapse
|
30
|
Leirão IP, Zoccal DB, Gargaglioni LH, da Silva GSF. Differential modulation of active expiration during hypercapnia by the medullary raphe in unanesthetized rats. Pflugers Arch 2020; 472:1563-1576. [PMID: 32914212 DOI: 10.1007/s00424-020-02455-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 07/30/2020] [Accepted: 08/27/2020] [Indexed: 11/26/2022]
Abstract
Active expiration represents an important mechanism to improve ventilation in conditions of augmented ventilatory demand, such as hypercapnia. While a rostral ventromedullary region, the parafacial respiratory group (pFRG), has been identified as a conditional expiratory oscillator, little is known about how central chemosensitive sites contribute to modulate active expiration under hypercapnia. In this study, we investigated the influence of the medullary raphe in the emergence of phasic expiratory abdominal activity during hypercapnia in unanesthetized adult male rats, in a state-dependent manner. To do so, reverse microdialysis of muscimol (GABAA receptor agonist, 1 mM) or 8-OH-DPAT (5-HT1A agonist, 1 mM) was applied in the MR during sleep and wakefulness periods, both in normocapnic (room air) and hypercapnic conditions (7% CO2). Electromyography (EMG) of diaphragm and abdominal muscles was performed to measure inspiratory and expiratory motor outputs. We found that active expiration did not occur in room air exposure during wakefulness or sleep. However, hypercapnia did recruit active expiration, and differential effects were observed with the drug dialyses in the medullary raphe. Muscimol increased the diaphragm inspiratory motor output and also increased the amplitude and frequency of abdominal expiratory rhythmic activity during hypercapnia in wakefulness periods. On the other hand, the microdialysis of 8-OH-DPAT attenuated hypercapnia-induced active expiration in a state-dependent manner. Our data suggest that the medullary raphe can either inhibit or potentiate respiratory motor activity during hypercapnia, and the balance of these inhibitory or excitatory outputs may determine the expression of active expiration.
Collapse
Affiliation(s)
- Isabela P Leirão
- Department of Physiology and Pathology, School of Dentistry of Araraquara (FOAR), São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry of Araraquara (FOAR), São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinary Sciences, São Paulo State University (FCAV-UNESP), Jaboticabal, SP, Brazil
| | - Glauber S F da Silva
- Department of Physiology and Biophysics. Institute of Biological Sciences, Federal University of Minas Gerais (ICB/UFMG), Belo Horizonte, MG, Brazil.
- Departamento de Fisiologia e Biofísica, ICB/UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG, 31270-901, Brazil.
| |
Collapse
|
31
|
Biancardi V, Saini J, Pageni A, Prashaad M. H, Funk GD, Pagliardini S. Mapping of the excitatory, inhibitory, and modulatory afferent projections to the anatomically defined active expiratory oscillator in adult male rats. J Comp Neurol 2020; 529:853-884. [DOI: 10.1002/cne.24984] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/29/2020] [Accepted: 07/05/2020] [Indexed: 01/21/2023]
Affiliation(s)
- Vivian Biancardi
- Department of Physiology University of Alberta Edmonton Canada
- Women and Children's Health Research Institute, Faculty of Medicine and Dentistry University of Alberta Edmonton Canada
| | - Jashan Saini
- Department of Physiology University of Alberta Edmonton Canada
| | - Anileen Pageni
- Department of Physiology University of Alberta Edmonton Canada
| | | | - Gregory D. Funk
- Department of Physiology University of Alberta Edmonton Canada
- Women and Children's Health Research Institute, Faculty of Medicine and Dentistry University of Alberta Edmonton Canada
- Neuroscience and Mental Health Institute University of Alberta Edmonton Canada
| | - Silvia Pagliardini
- Department of Physiology University of Alberta Edmonton Canada
- Women and Children's Health Research Institute, Faculty of Medicine and Dentistry University of Alberta Edmonton Canada
- Neuroscience and Mental Health Institute University of Alberta Edmonton Canada
| |
Collapse
|
32
|
Flor KC, Barnett WH, Karlen-Amarante M, Molkov YI, Zoccal DB. Inhibitory control of active expiration by the Bötzinger complex in rats. J Physiol 2020; 598:4969-4994. [PMID: 32621515 DOI: 10.1113/jp280243] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 06/21/2020] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Contraction of abdominal muscles at the end of expiration during metabolic challenges (such as hypercapnia and hypoxia) improves pulmonary ventilation. The emergence of this active expiratory pattern requires the recruitment of the expiratory oscillator located on the ventral surface of the medulla oblongata. Here we show that an inhibitory circuitry located in the Bötzinger complex is an important source of inhibitory drive to the expiratory oscillator. This circuitry, mediated by GABAergic and glycinergic synapses, provides expiratory inhibition that restrains the expiratory oscillator under resting condition and regulates the formation of abdominal expiratory activity during active expiration. By combining experimental and modelling approaches, we propose the organization and connections within the respiratory network that control the changes in the breathing pattern associated with elevated metabolic demand. ABSTRACT The expiratory neurons of the Bötzinger complex (BötC) provide inhibitory inputs to the respiratory network, which, during eupnoea, are critically important for respiratory phase transition and duration control. Here, we investigated how the BötC neurons interact with the expiratory oscillator located in the parafacial respiratory group (pFRG) and control the abdominal activity during active expiration. Using the decerebrated, arterially perfused in situ preparations of juvenile rats, we recorded the activity of expiratory neurons and performed pharmacological manipulations of the BötC and pFRG during hypercapnia or after the exposure to short-term sustained hypoxia - conditions that generate active expiration. The experimental data were integrated in a mathematical model to gain new insights into the inhibitory connectome within the respiratory central pattern generator. Our results indicate that the BötC neurons may establish mutual connections with the pFRG, providing expiratory inhibition during the first stage of expiration and receiving excitatory inputs during late expiration. Moreover, we found that application of GABAergic and glycinergic antagonists in the BötC caused opposing effects on abdominal expiratory activity, suggesting complex inhibitory circuitry within the BötC. Using mathematical modelling, we propose that the BötC network organization and its interactions with the pFRG restrain abdominal activity under resting conditions and contribute to abdominal expiratory pattern formation during active expiration observed during hypercapnia or after the exposure to short-term sustained hypoxia.
Collapse
Affiliation(s)
- Karine C Flor
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, Brazil
| | - William H Barnett
- Department of Mathematics and Statistics, Georgia State University, Atlanta, GA, USA
| | - Marlusa Karlen-Amarante
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, Brazil
| | - Yaroslav I Molkov
- Department of Mathematics and Statistics, Georgia State University, Atlanta, GA, USA.,Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, Brazil
| |
Collapse
|
33
|
Ghali MGZ. Retracted: Control of hypoglossal pre‐inspiratory discharge. Exp Physiol 2020; 105:1232-1255. [DOI: 10.1113/ep087329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Accepted: 06/11/2020] [Indexed: 12/22/2022]
Affiliation(s)
- Michael George Zaki Ghali
- Departments of Neurological Surgery, Internal Medicine, General Surgery, and Neuroscience Karolinska Institutet Huddinge Stockholm Sweden
- Departments of Neurological Surgery, Neurophysiology, Neuroscience University of Oslo Oslo Norway
- Departments of Neurological Surgery and Neurochemistry University of Helsinki Helsinki Finland
- Departments of Neurological Surgery, Internal Medicine, Cardiothoracic Surgery, and Neuroscience University of California Francisco San Francisco CA USA
- Departments of Neurological Surgery and Neuroscience Barrow Neurological Institute Phoenix AZ USA
| |
Collapse
|
34
|
Gauda EB, Conde S, Bassi M, Zoccal DB, Almeida Colombari DS, Colombari E, Despotovic N. Leptin: Master Regulator of Biological Functions that Affects Breathing. Compr Physiol 2020; 10:1047-1083. [PMID: 32941688 DOI: 10.1002/cphy.c190031] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Obesity is a global epidemic in developed countries accounting for many of the metabolic and cardiorespiratory morbidities that occur in adults. These morbidities include type 2 diabetes, sleep-disordered breathing (SDB), obstructive sleep apnea, chronic intermittent hypoxia, and hypertension. Leptin, produced by adipocytes, is a master regulator of metabolism and of many other biological functions including central and peripheral circuits that control breathing. By binding to receptors on cells and neurons in the brainstem, hypothalamus, and carotid body, leptin links energy and metabolism to breathing. In this comprehensive article, we review the central and peripheral locations of leptin's actions that affect cardiorespiratory responses during health and disease, with a particular focus on obesity, SDB, and its effects during early development. Obesity-induced hyperleptinemia is associated with centrally mediated hypoventilation with decrease CO2 sensitivity. On the other hand, hyperleptinemia augments peripheral chemoreflexes to hypoxia and induces sympathoexcitation. Thus, "leptin resistance" in obesity is relative. We delineate the circuits responsible for these divergent effects, including signaling pathways. We review the unique effects of leptin during development on organogenesis, feeding behavior, and cardiorespiratory responses, and how undernutrition and overnutrition during critical periods of development can lead to cardiorespiratory comorbidities in adulthood. We conclude with suggestions for future directions to improve our understanding of leptin dysregulation and associated clinical diseases and possible therapeutic targets. Lastly, we briefly discuss the yin and the yang, specifically the contribution of relative adiponectin deficiency in adults with hyperleptinemia to the development of metabolic and cardiovascular disease. © 2020 American Physiological Society. Compr Physiol 10:1047-1083, 2020.
Collapse
Affiliation(s)
- Estelle B Gauda
- Division of Neonatology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Silvia Conde
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Lisboa, Portugal
| | - Mirian Bassi
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, São Paulo, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, São Paulo, Brazil
| | - Debora Simoes Almeida Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, São Paulo, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, São Paulo, Brazil
| | - Nikola Despotovic
- Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| |
Collapse
|
35
|
Silva JDN, Oliveira LM, Souza FC, Moreira TS, Takakura AC. GABAergic neurons of the medullary raphe regulate active expiration during hypercapnia. J Neurophysiol 2020; 123:1933-1943. [PMID: 32267190 DOI: 10.1152/jn.00698.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The parafacial respiratory group (pFRG), located in the lateral aspect of the rostroventral lateral medulla, has been described as a conditional expiratory oscillator that emerges mainly in conditions of high metabolic challenges to increase breathing. The convergence of inhibitory and excitatory inputs to pFRG and the generation of active expiration may be more complex than previously thought. We hypothesized that the medullary raphe, a region that has long been described to be involved in breathing activity, is also responsible for the expiratory activity under hypercapnic condition. To test this hypothesis, we performed anatomical and physiological experiments in urethane-anesthetized adult male Wistar rats. Our data showed anatomical projections from serotonergic (5-HT-ergic) and GABAergic neurons of raphe magnus (RMg) and obscurus (ROb) to the pFRG region. Pharmacological inhibition of RMg or ROb with muscimol (60 pmol/30 nL) did not change the frequency or amplitude of diaphragm activity and did not generate active expiration. However, under hypercapnia (9-10% CO2), the inhibition of RMg or ROb increased the amplitude of abdominal activity, without changing the increased amplitude of diaphragm activity. Depletion of serotonergic neurons with saporin anti-SERT injections into ROb and RMg did not increase the amplitude of abdominal activity during hypercapnia. These results show that the presumably GABAergic neurons within the RMg and ROb may be the inhibitory source to modulate the activity of pFRG during hypercapnia condition.NEW & NOTEWORTHY Medullary raphe has been involved in the inspiratory response to central chemoreflex; however, these reports have never addressed the role of raphe neurons on active expiration induced by hypercapnia. Here, we showed that a subset of GABA cells within the medullary raphe directly project to the parafacial respiratory region, modulating active expiration under high levels of CO2.
Collapse
Affiliation(s)
- Josiane do N Silva
- Departamento de Farmacologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, São Paulo, Brazil
| | - Luiz M Oliveira
- Departamento de Farmacologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, São Paulo, Brazil
| | - Felipe C Souza
- Departamento de Farmacologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, São Paulo, Brazil
| | - Thiago S Moreira
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biomedicas, Universidade de São Paulo, São Paulo, Brazil
| | - Ana C Takakura
- Departamento de Farmacologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, São Paulo, Brazil
| |
Collapse
|
36
|
Mitchell L, MacFarlane PM. Mechanistic actions of oxygen and methylxanthines on respiratory neural control and for the treatment of neonatal apnea. Respir Physiol Neurobiol 2020; 273:103318. [PMID: 31626973 PMCID: PMC6986994 DOI: 10.1016/j.resp.2019.103318] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 10/07/2019] [Accepted: 10/08/2019] [Indexed: 12/14/2022]
Abstract
Apnea remains one of the most concerning and prevalent respiratory disorders spanning all ages from infants (particularly those born preterm) to adults. Although the pathophysiological consequences of apnea are fairly well described, the neural mechanisms underlying the etiology of the different types of apnea (central, obstructive, and mixed) still remain incompletely understood. From a developmental perspective, however, research into the respiratory neural control system of immature animals has shed light on both central and peripheral neural pathways underlying apnea of prematurity (AOP), a highly prevalent respiratory disorder of preterm infants. Animal studies have also been fundamental in furthering our understanding of how clinical interventions (e.g. pharmacological and mechanical) exert their beneficial effects in the clinical treatment of apnea. Although current clinical interventions such as supplemental O2 and positive pressure respiratory support are critically important for the infant in respiratory distress, they are not fully effective and can also come with unfortunate, unintended (and long-term) side-effects. In this review, we have chosen AOP as one of the most common clinical scenarios involving apnea to highlight the mechanistic basis behind how some of the interventions could be both beneficial and also deleterious to the respiratory neural control system. We have included a section on infants with critical congenital heart diseases (CCHD), in whom apnea can be a clinical concern due to treatment with prostaglandin, and who may benefit from some of the treatments used for AOP.
Collapse
Affiliation(s)
- Lisa Mitchell
- Department of Pediatrics, Case Western Reserve University, Rainbow Babies & Children's Hospital, Cleveland, OH 44106, USA
| | - Peter M MacFarlane
- Department of Pediatrics, Case Western Reserve University, Rainbow Babies & Children's Hospital, Cleveland, OH 44106, USA.
| |
Collapse
|
37
|
Malheiros-Lima MR, Silva JN, Souza FC, Takakura AC, Moreira TS. C1 neurons are part of the circuitry that recruits active expiration in response to the activation of peripheral chemoreceptors. eLife 2020; 9:52572. [PMID: 31971507 PMCID: PMC7010411 DOI: 10.7554/elife.52572] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 01/21/2020] [Indexed: 12/18/2022] Open
Abstract
Breathing results from the interaction of two distinct oscillators: the pre-Bötzinger Complex (preBötC), which drives inspiration; and the lateral parafacial region (pFRG), which drives active expiration. The pFRG is silent at rest and becomes rhythmically active during the stimulation of peripheral chemoreceptors, which also activates adrenergic C1 cells. We postulated that the C1 cells and the pFRG may constitute functionally distinct but interacting populations for controlling expiratory activity during hypoxia. We found in rats that: a) C1 neurons are activated by hypoxia and project to the pFRG region; b) active expiration elicited by hypoxia was blunted after blockade of ionotropic glutamatergic receptors at the level of the pFRG; and c) selective depletion of C1 neurons eliminated the active expiration elicited by hypoxia. These results suggest that C1 cells may regulate the respiratory cycle, including active expiration, under hypoxic conditions.
Collapse
Affiliation(s)
- Milene R Malheiros-Lima
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
| | - Josiane N Silva
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
| | - Felipe C Souza
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
| |
Collapse
|
38
|
Varga AG, Reid BT, Kieffer BL, Levitt ES. Differential impact of two critical respiratory centres in opioid-induced respiratory depression in awake mice. J Physiol 2020; 598:189-205. [PMID: 31589332 PMCID: PMC6938533 DOI: 10.1113/jp278612] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 10/03/2019] [Indexed: 12/29/2022] Open
Abstract
KEY POINTS The main cause of death from opioid overdose is respiratory depression due to the activation of µ-opioid receptors (MORs). We conditionally deleted MORs from neurons in two key areas of the brainstem respiratory circuitry (the Kölliker-Fuse nucleus (KF) and pre-Bötzinger complex (preBötC)) to determine their role in opioid-induced respiratory disturbances in adult, awake mice. Deletion of MORs from KF neurons attenuated respiratory rate depression at all doses of morphine. Deletion of MORs from preBötC neurons attenuated rate depression at the low dose, but had no effect on rate following high doses of morphine. Instead, high doses of morphine increased the occurrence of apnoeas. The results indicate that opioids affect distributed key areas of the respiratory network in a dose-dependent manner and countering the respiratory effects of high dose opioids via the KF may be an effective approach to combat overdose. ABSTRACT The primary cause of death from opioid overdose is respiratory failure. High doses of opioids cause severe rate depression and increased risk of fatal apnoea, which correlate with increasing irregularities in breathing pattern. µ-Opioid receptors (MORs) are widely distributed throughout the brainstem respiratory network, but the mechanisms underlying respiratory depression are poorly understood. The medullary pre-Bötzinger complex (preBötC) and the pontine Kölliker-Fuse nucleus (KF) are considered critical for inducing opioid-related respiratory disturbances. We used a conditional knockout approach to investigate the roles and relative contribution of MORs in KF and preBötC neurons in opioid-induced respiratory depression in awake adult mice. The results revealed dose-dependent and region-specific opioid effects on the control of both respiratory rate and pattern. Respiratory depression induced by an anti-nociceptive dose of morphine was significantly attenuated following deletion of MORs from either the KF or the preBötC, suggesting cumulative network effects on respiratory rate control at low opioid doses. Deletion of MORs from KF neurons also relieved rate depression at near-maximal respiratory depressant doses of morphine. Meanwhile, deletion of MORs from the preBötC had no effect on rate following administration of high doses of morphine. Instead, a severe ataxic breathing pattern emerged with many apnoeas. We conclude that opioids affect distributed areas of the respiratory network and opioid-induced respiratory depression cannot be attributed to only one area in isolation. However, countering the effects of near maximal respiratory depressant doses of opioids in the KF may be a powerful approach to combat opioid overdose.
Collapse
Affiliation(s)
- Adrienn G. Varga
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy, University of Florida, Gainesville, FL 32610
| | - Brandon T. Reid
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610
| | | | - Erica S. Levitt
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy, University of Florida, Gainesville, FL 32610
| |
Collapse
|
39
|
Gupta S, Otero JJ, Sundaresan VB, Czeisler CM. Near field non-invasive electrophysiology of retrotrapezoid nucleus using amperometric cation sensor. Biosens Bioelectron 2019; 151:111975. [PMID: 31999582 DOI: 10.1016/j.bios.2019.111975] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/13/2019] [Accepted: 12/16/2019] [Indexed: 11/29/2022]
Abstract
Central chemoreception is the process whereby the brainstem senses blood gas levels and adjusts homeostatic functions such as breathing and cardiovascular tone accordingly. Rodent evidence suggests that the retrotrapezoid nucleus (RTN) is a master regulator of central chemoreception, in particular, through direct sensation of acidosis induced by CO2 levels. The oscillatory dynamics caused by pH changes as sensed by the RTN surface and its relationship to the fluctuations in cation flux is not clearly understood due to the current limitations of electrophysiology tools and this article presents our investigations to address this need. A cation selective sensor fabricated from polypyrrole doped with dodecyl benzenesulfonate (PPy (DBS)) is placed over RTN in an ex-vivo en bloc brain and changes in cation concentration in the diffusion limited region above the RTN is measured due to changes in externally imposed basal pH. The novelty of this technique lies in its feasibility to detect cation fluxes from the cells in the RTN region without having to access either sides of the cell membrane. Owing to the placement of the sensor in close proximity to the tissue, we refer to this technique as near-field electrophysiology. It is observed that lowering the pH in the physiological range (7.4-7.2) results in a significant increase in cation concentration in the vicinity of RTN with a median value of ~5 μM. The utilization of such quantifiable measurement techniques to detect sub-threshold brain activity may help provide a platform for future neural network architectures. Findings from this paper present a quantifiable, sensitive, and robust electrophysiology technique with minimal damage to the underlying tissue.
Collapse
Affiliation(s)
- Sujasha Gupta
- Department of Mechanical and Aerospace Engineering, The Ohio State University, 201 W 19(th) Ave, Columbus, 43210, Ohio, United States.
| | - José Javier Otero
- Department of Pathology, Neuropathology, The Ohio State University, 333 W 10(th) Ave, Columbus, 43210, Ohio, United States.
| | - Vishnu Baba Sundaresan
- Department of Mechanical and Aerospace Engineering, The Ohio State University, 201 W 19(th) Ave, Columbus, 43210, Ohio, United States.
| | - Catherine Miriam Czeisler
- Division of Department of Pathology, The Ohio State University, 333 W 10(th) Ave, Columbus, 43210, Ohio, United States.
| |
Collapse
|
40
|
Sun X, Thörn Pérez C, Halemani D N, Shao XM, Greenwood M, Heath S, Feldman JL, Kam K. Opioids modulate an emergent rhythmogenic process to depress breathing. eLife 2019; 8:e50613. [PMID: 31841107 PMCID: PMC6938398 DOI: 10.7554/elife.50613] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Accepted: 12/11/2019] [Indexed: 12/13/2022] Open
Abstract
How mammalian neural circuits generate rhythmic activity in motor behaviors, such as breathing, walking, and chewing, remains elusive. For breathing, rhythm generation is localized to a brainstem nucleus, the preBötzinger Complex (preBötC). Rhythmic preBötC population activity consists of strong inspiratory bursts, which drive motoneuronal activity, and weaker burstlets, which we hypothesize reflect an emergent rhythmogenic process. If burstlets underlie inspiratory rhythmogenesis, respiratory depressants, such as opioids, should reduce burstlet frequency. Indeed, in medullary slices from neonatal mice, the μ-opioid receptor (μOR) agonist DAMGO slowed burstlet generation. Genetic deletion of μORs in a glutamatergic preBötC subpopulation abolished opioid-mediated depression, and the neuropeptide Substance P, but not blockade of inhibitory synaptic transmission, reduced opioidergic effects. We conclude that inspiratory rhythmogenesis is an emergent process, modulated by opioids, that does not rely on strong bursts of activity associated with motor output. These findings also point to strategies for ameliorating opioid-induced depression of breathing.
Collapse
Affiliation(s)
- Xiaolu Sun
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Carolina Thörn Pérez
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Nagaraj Halemani D
- Department of Cell Biology and AnatomyChicago Medical School, Rosalind Franklin University of Medicine and ScienceNorth ChicagoUnited States
| | - Xuesi M Shao
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Morgan Greenwood
- RFUMS/DePaul Research Internship ProgramRosalind Franklin University of Medicine and ScienceNorth ChicagoUnited States
| | - Sarah Heath
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Jack L Feldman
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Kaiwen Kam
- Department of Cell Biology and AnatomyChicago Medical School, Rosalind Franklin University of Medicine and ScienceNorth ChicagoUnited States
| |
Collapse
|
41
|
van der Heijden ME, Zoghbi HY. Development of the brainstem respiratory circuit. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2019; 9:e366. [PMID: 31816185 DOI: 10.1002/wdev.366] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 02/01/2023]
Abstract
The respiratory circuit is comprised of over a dozen functionally and anatomically segregated brainstem nuclei that work together to control respiratory rhythms. These respiratory rhythms emerge prenatally but only acquire vital importance at birth, which is the first time the respiratory circuit faces the sole responsibility for O2 /CO2 homeostasis. Hence, the respiratory circuit has little room for trial-and-error-dependent fine tuning and relies on a detailed genetic blueprint for development. This blueprint is provided by transcription factors that have specific spatiotemporal expression patterns along the rostral-caudal or dorsal-ventral axis of the developing brainstem, in proliferating precursor cells and postmitotic neurons. Studying these transcription factors in mice has provided key insights into the functional segregation of respiratory control and the vital importance of specific respiratory nuclei. Many studies converge on just two respiratory nuclei that each have rhythmogenic properties during the prenatal period: the preBötzinger complex (preBötC) and retrotrapezoid nucleus/parafacial nucleus (RTN/pF). Here, we discuss the transcriptional regulation that guides the development of these nuclei. We also summarize evidence showing that normal preBötC development is necessary for neonatal survival, and that neither the preBötC nor the RTN/pF alone is sufficient to sustain normal postnatal respiratory rhythms. Last, we highlight several studies that use intersectional genetics to assess the necessity of transcription factors only in subregions of their expression domain. These studies independently demonstrate that lack of RTN/pF neurons weakens the respiratory circuit, yet these neurons are not necessary for neonatal survival because developmentally related populations can compensate for abnormal RTN/pF function at birth. This article is categorized under: Nervous System Development > Vertebrates: Regional Development.
Collapse
Affiliation(s)
- Meike E van der Heijden
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas.,Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas
| | - Huda Y Zoghbi
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas.,Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas.,Department of Pediatrics, Baylor College of Medicine, Houston, Texas.,Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas
| |
Collapse
|
42
|
Guyenet PG, Stornetta RL, Souza GMPR, Abbott SBG, Shi Y, Bayliss DA. The Retrotrapezoid Nucleus: Central Chemoreceptor and Regulator of Breathing Automaticity. Trends Neurosci 2019; 42:807-824. [PMID: 31635852 DOI: 10.1016/j.tins.2019.09.002] [Citation(s) in RCA: 122] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/28/2019] [Accepted: 09/05/2019] [Indexed: 12/15/2022]
Abstract
The ventral surface of the rostral medulla oblongata has been suspected since the 1960s to harbor central respiratory chemoreceptors [i.e., acid-activated neurons that regulate breathing to maintain a constant arterial PCO2 (PaCO2)]. The key neurons, a.k.a. the retrotrapezoid nucleus (RTN), have now been identified. In this review we describe their transcriptome, developmental lineage, and anatomical projections. We also review their contribution to CO2 homeostasis and to the regulation of breathing automaticity during sleep and wake. Finally, we discuss several mechanisms that contribute to the activation of RTN neurons by CO2in vivo: cell-autonomous effects of protons; paracrine effects of pH mediated by surrounding astrocytes and blood vessels; and excitatory inputs from other CO2-responsive CNS neurons.
Collapse
Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| |
Collapse
|
43
|
Díaz HS, Andrade DC, Toledo C, Pereyra KV, Schwarz KG, Díaz-Jara E, Lucero C, Arce-Álvarez A, Schultz HD, Silva JN, Takakura AC, Moreira TS, Marcus NJ, Del Rio R. Episodic stimulation of central chemoreceptor neurons elicits disordered breathing and autonomic dysfunction in volume overload heart failure. Am J Physiol Lung Cell Mol Physiol 2019; 318:L27-L40. [PMID: 31617729 PMCID: PMC6985876 DOI: 10.1152/ajplung.00007.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Enhanced central chemoreflex (CC) gain is observed in volume overload heart failure (HF) and is correlated with autonomic dysfunction and breathing disorders. The aim of this study was to determine the role of the CC in the development of respiratory and autonomic dysfunction in HF. Volume overload was surgically created to induce HF in male Sprague-Dawley rats. Radiotelemetry transmitters were implanted for continuous monitoring of blood pressure and heart rate. After recovering from surgery, conscious unrestrained rats were exposed to episodic hypercapnic stimulation [EHS; 10 cycles/5 min, inspiratory fraction of carbon dioxide (FICO2) 7%] in a whole body plethysmograph for recording of cardiorespiratory function. To determine the contribution of CC to cardiorespiratory variables, selective ablation of chemoreceptor neurons within the retrotrapezoid nucleus (RTN) was performed via injection of saporin toxin conjugated to substance P (SSP-SAP). Vehicle-treated rats (HF+Veh and Sham+Veh) were used as controls for SSP-SAP experiments. Sixty minutes post-EHS, minute ventilation was depressed in sham animals relative to HF animals (ΔV̇e: -5.55 ± 2.10 vs. 1.24 ± 1.35 mL/min 100 g, P < 0.05; Sham+Veh vs. HF+Veh). Furthermore, EHS resulted in autonomic imbalance, cardiorespiratory entrainment, and ventilatory disturbances in HF+Veh but not Sham+Veh rats, and these effects were significantly attenuated by SSP-SAP treatment. Also, the apnea-hypopnea index (AHI) was significantly lower in HF+SSP-SAP rats compared with HF+Veh rats (AHI: 5.5 ± 0.8 vs. 14.4 ± 1.3 events/h, HF+SSP-SAP vs. HF+Veh, respectively, P < 0.05). Finally, EHS-induced respiratory-cardiovascular coupling in HF rats depends on RTN chemoreceptor neurons because it was reduced by SSP-SAP treatment. Overall, EHS triggers ventilatory plasticity and elicits cardiorespiratory abnormalities in HF that are largely dependent on RTN chemoreceptor neurons.
Collapse
Affiliation(s)
- Hugo S Díaz
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - David C Andrade
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Investigación en Fisiología del Ejercicio (CIFE), Universidad Mayor, Santiago, Chile
| | - Camilo Toledo
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración (CARE-UC), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Katherin V Pereyra
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Karla G Schwarz
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Esteban Díaz-Jara
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Claudia Lucero
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alexis Arce-Álvarez
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Harold D Schultz
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Centre, Omaha, Nebraska
| | - Josiane N Silva
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Noah J Marcus
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, Iowa
| | - Rodrigo Del Rio
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración (CARE-UC), Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Excelencia de Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
| |
Collapse
|
44
|
Ayad S, Khanna AK, Iqbal SU, Singla N. Characterisation and monitoring of postoperative respiratory depression: current approaches and future considerations. Br J Anaesth 2019; 123:378-391. [DOI: 10.1016/j.bja.2019.05.044] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 05/06/2019] [Accepted: 05/24/2019] [Indexed: 01/19/2023] Open
|
45
|
The pre-Bötzinger complex: Generation and modulation of respiratory rhythm. NEUROLOGÍA (ENGLISH EDITION) 2019. [DOI: 10.1016/j.nrleng.2018.05.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
46
|
Garcia AJ, Viemari JC, Khuu MA. Respiratory rhythm generation, hypoxia, and oxidative stress-Implications for development. Respir Physiol Neurobiol 2019; 270:103259. [PMID: 31369874 DOI: 10.1016/j.resp.2019.103259] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 07/15/2019] [Accepted: 07/24/2019] [Indexed: 02/07/2023]
Abstract
Encountered in a number of clinical conditions, repeated hypoxia/reoxygenation during the neonatal period can pose both a threat to immediate survival as well as a diminished quality of living later in life. This review focuses on our current understanding of central respiratory rhythm generation and the role that hypoxia and reoxygenation play in influencing rhythmogenesis. Here, we examine the stereotypical response of the inspiratory rhythm from the preBötzinger complex (preBötC), basic neuronal mechanisms that support rhythm generation during the peri-hypoxic interval, and the physiological consequences of inspiratory network responsivity to hypoxia and reoxygenation, acute and chronic intermittent hypoxia, and oxidative stress. These topics are examined in the context of Sudden Infant Death Syndrome, apneas of prematurity, and neonatal abstinence syndrome.
Collapse
Affiliation(s)
- Alfredo J Garcia
- Institute for Integrative Physiology, Section of Emergency Medicine, The University of Chicago, Chicago, 60637, IL, United States
| | - Jean Charles Viemari
- Institut de Neurosciences de la Timone, P3M team, UMR7289 CNRS & AMU, Faculté de Médecine de la Timone, 27 Bd Jean Moulin, Marseille, 13005, France
| | - Maggie A Khuu
- Institute for Integrative Physiology, Section of Emergency Medicine, The University of Chicago, Chicago, 60637, IL, United States
| |
Collapse
|
47
|
Bazilio DS, Bonagamba LGH, Moraes DJA, Machado BH. Cardiovascular and respiratory profiles during the sleep-wake cycle of rats previously submitted to chronic intermittent hypoxia. Exp Physiol 2019; 104:1408-1419. [PMID: 31099915 DOI: 10.1113/ep087784] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 05/15/2019] [Indexed: 12/22/2022]
Abstract
NEW FINDINGS What is the central question of this study? Chronic intermittent hypoxia (CIH) causes increased arterial pressure (AP), sympathetic overactivity and changes in expiratory modulation of sympathetic activity. However, changes in the short-term sleep-wake cycle pattern after CIH and their potential impact on cardiorespiratory parameters have not been reported previously. What is the main finding and its importance? Exposure to CIH for 10 days elevates AP in wakefulness and sleep but does not cause major changes in short-term sleep-wake cycle pattern. A higher incidence of muscular expiratory activity was observed in rats exposed to CIH only during wakefulness, indicating that active expiration is not required for the increase in AP in rats submitted to CIH. ABSTRACT Chronic intermittent hypoxia (CIH) increases arterial pressure (AP) and changes sympathetic-respiratory coupling. However, the alterations in the sleep-wake cycle after CIH and their potential impact on cardiorespiratory parameters remain unknown. Here, we evaluated whether CIH-exposed rats present changes in their short-term sleep-wake cycle pattern and in cardiorespiratory parameters. Male Wistar rats (∼250 g) were divided into CIH and control groups. The CIH rats were exposed to 8 h day-1 of cycles of normoxia (fraction of inspired O2 = 0.208, 5 min) followed by hypoxia (fraction of inspired O2 = 0.06, 30-40 s) for 10 days. One day after CIH, electrocorticographic activity, cervical EMG, AP and heart rate were recorded for 3 h. Plethysmographic recordings were collected for 2 h. A subgroup of control and CIH rats also had the diaphragm and oblique abdominal muscle activities recorded. Chronic intermittent hypoxia did not alter the time for sleep onset, total time awake, durations of rapid eye movement (REM) and non-REM (NREM) sleep and number of REM episodes in the 3 h recordings. However, a significant increase in the duration of REM episodes was observed. The AP and heart rate were increased in all phases of the cycle in rats exposed to CIH. Respiratory frequency and ventilation were similar between groups in all phases, but tidal volume was increased during NREM and REM sleep in rats exposed to CIH. An increase in the incidence of active expiration during wakefulness was observed in rats exposed to CIH. The data show that CIH-related hypertension is not caused by changes in the sleep-wake cycle and suggest that active expiration is not required for the increase in AP in freely moving rats exposed to CIH.
Collapse
Affiliation(s)
- Darlan S Bazilio
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Leni G H Bonagamba
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| |
Collapse
|
48
|
Fogarty MJ, Sieck GC. Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals. Compr Physiol 2019; 9:715-766. [PMID: 30873594 PMCID: PMC7082849 DOI: 10.1002/cphy.c180012] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Symmorphosis is a concept of economy of biological design, whereby structural properties are matched to functional demands. According to symmorphosis, biological structures are never over designed to exceed functional demands. Based on this concept, the evolution of the diaphragm muscle (DIAm) in mammals is a tale of two structures, a membrane that separates and partitions the primitive coelomic cavity into separate abdominal and thoracic cavities and a muscle that serves as a pump to generate intra-abdominal (Pab ) and intrathoracic (Pth ) pressures. The DIAm partition evolved in reptiles from folds of the pleural and peritoneal membranes that was driven by the biological advantage of separating organs in the larger coelomic cavity into separate thoracic and abdominal cavities, especially with the evolution of aspiration breathing. The DIAm pump evolved from the advantage afforded by more effective generation of both a negative Pth for ventilation of the lungs and a positive Pab for venous return of blood to the heart and expulsive behaviors such as airway clearance, defecation, micturition, and child birth. © 2019 American Physiological Society. Compr Physiol 9:715-766, 2019.
Collapse
Affiliation(s)
- Matthew J Fogarty
- Mayo Clinic, Department of Physiology & Biomedical Engineering, Rochester, Minnesota, USA
| | - Gary C Sieck
- Mayo Clinic, Department of Physiology & Biomedical Engineering, Rochester, Minnesota, USA
| |
Collapse
|
49
|
Ramirez JM, Baertsch N. Defining the Rhythmogenic Elements of Mammalian Breathing. Physiology (Bethesda) 2019; 33:302-316. [PMID: 30109823 DOI: 10.1152/physiol.00025.2018] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Breathing's remarkable ability to adapt to changes in metabolic, environmental, and behavioral demands stems from a complex integration of its rhythm-generating network within the wider nervous system. Yet, this integration complicates identification of its specific rhythmogenic elements. Based on principles learned from smaller rhythmic networks of invertebrates, we define criteria that identify rhythmogenic elements of the mammalian breathing network and discuss how they interact to produce robust, dynamic breathing.
Collapse
Affiliation(s)
- Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine , Seattle, Washington
| | - Nathan Baertsch
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine , Seattle, Washington
| |
Collapse
|
50
|
da Silva MP, Moraes DJA, Bonagamba LGH, Mecawi ADS, Varanda WA, Machado BH. Hyperexcitability and plasticity induced by sustained hypoxia on rectus abdominis motoneurons. J Physiol 2019; 597:1935-1956. [PMID: 30747446 DOI: 10.1113/jp277030] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 02/06/2019] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Acute hypoxia induces active expiration in rectus abdominis (RA) muscles in conscious freely moving rats, although its overall contribution is smaller than in internal oblique (IO) muscles. Tonically active and silent RA motoneurons were identified in in vitro preparations of rat spinal cords. Sustained hypoxia (SH) increased the synaptic strength and induced morphological changes in tonically active RA motoneurons. Expiratory RA motoneurons were recorded in the in situ preparation and SH enhanced both the excitability and the synaptic transmission in those firing during the stage 2 expiration. The present study contributes to a better understanding of the mechanisms involved in SH recruitment of RA motoneurons to induce active expiration in rats. ABSTRACT Rectus abdominis (RA) motoneurons translate the complex respiratory brainstem inputs into effective muscle contractions. Despite their fundamental role in respiration, their functional and morphological properties are not fully understood. In the present study, we investigated for the first time the contribution of RA muscle to active expiration and characterized RA motoneurons regarding their electrical, molecular and morphological profiles in control rats and in rats submitted to sustained hypoxia (SH), which induces chronic recruitment of abdominal muscles. Electromyographic experiments in conscious freely moving control rats and SH rats showed that RA contributes to active expiration induced by acute hypoxia, although its contribution is smaller than in internal oblique muscles. in vitro whole-cell patch clamp recordings from RA motoneurons revealed two populations of cells: tonically active and silent. SH induced hyperexcitability in the tonically active cells by changing their action potential properties, and EPSCs. Three-dimensional morphological reconstructions of these cells showed that SH increased the dendritic complexity, stimulated the appearance of dendrite spines, and increased the somatic area and volume. Physiologically identified RA motoneurons, firing in two distinct phases of expiration, were recorded in the brainstem-spinal cord in situ preparation of rats. SH increased the firing frequency and EPSCs of neurons firing during stage 2 expiration. Taken together, our results show that RA motoneurons reconfigure their biophysical properties, morphology and synaptic strength to produce an appropriate expiratory drive in response to SH in rats.
Collapse
Affiliation(s)
- Melina P da Silva
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Davi José A Moraes
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Leni G H Bonagamba
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - André de Souza Mecawi
- Paulista School of Medicine, Department of Biophysics, Federal University of São Paulo, São Paulo, Brazil
| | - Wamberto A Varanda
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Benedito H Machado
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| |
Collapse
|