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Souza GMPR, Abbott SBG. Loss-of-function of chemoreceptor neurons in the retrotrapezoid nucleus: What have we learned from it? Respir Physiol Neurobiol 2024; 322:104217. [PMID: 38237884 PMCID: PMC10922619 DOI: 10.1016/j.resp.2024.104217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Revised: 01/11/2024] [Accepted: 01/13/2024] [Indexed: 01/23/2024]
Abstract
Central respiratory chemoreceptors are cells in the brain that regulate breathing in relation to arterial pH and PCO2. Neurons located at the retrotrapezoid nucleus (RTN) have been hypothesized to be central chemoreceptors and/or to be part of the neural network that drives the central respiratory chemoreflex. The inhibition or ablation of RTN chemoreceptor neurons has offered important insights into the role of these cells on central respiratory chemoreception and the neural control of breathing over almost 60 years since the original identification of acid-sensitive properties of this ventral medullary site. Here, we discuss the current definition of chemoreceptor neurons in the RTN and describe how this definition has evolved over time. We then summarize the results of studies that use loss-of-function approaches to evaluate the effects of disrupting the function of RTN neurons on respiration. These studies offer evidence that RTN neurons are indispensable for the central respiratory chemoreflex in mammals and exert a tonic drive to breathe at rest. Moreover, RTN has an interdependent relationship with oxygen sensing mechanisms for the maintenance of the neural drive to breathe and blood gas homeostasis. Collectively, RTN neurons are a genetically-defined group of putative central respiratory chemoreceptors that generate CO2-dependent drive that supports eupneic breathing and stimulates the hypercapnic ventilatory reflex.
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Turk AZ, Millwater M, SheikhBahaei S. Whole-brain analysis of CO 2 chemosensitive regions and identification of the retrotrapezoid and medullary raphé nuclei in the common marmoset ( Callithrix jacchus). BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.26.558361. [PMID: 37986845 PMCID: PMC10659419 DOI: 10.1101/2023.09.26.558361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Respiratory chemosensitivity is an important mechanism by which the brain senses changes in blood partial pressure of CO2 (PCO2). It is proposed that special neurons (and astrocytes) in various brainstem regions play key roles as CO2 central respiratory chemosensors in rodents. Although common marmosets (Callithrix jacchus), New-World non-human primates, show similar respiratory responses to elevated inspired CO2 as rodents, the chemosensitive regions in marmoset brain have not been defined yet. Here, we used c-fos immunostainings to identify brain-wide CO2-activated brain regions in common marmosets. In addition, we mapped the location of the retrotrapezoid nucleus (RTN) and raphé nuclei in the marmoset brainstem based on colocalization of CO2-induced c-fos immunoreactivity with Phox2b, and TPH immunostaining, respectively. Our data also indicated that, similar to rodents, marmoset RTN astrocytes express Phox2b and have complex processes that create a meshwork structure at the ventral surface of medulla. Our data highlight some cellular and structural regional similarities in brainstem of the common marmosets and rodents.
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Affiliation(s)
- Ariana Z. Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Marissa Millwater
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
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Abstract
Brain PCO2 is sensed primarily via changes in [H+]. Small pH changes are detected in the medulla oblongata and trigger breathing adjustments that help maintain arterial PCO2 constant. Larger perturbations of brain CO2/H+, possibly also sensed elsewhere in the CNS, elicit arousal, dyspnea, and stress, and cause additional breathing modifications. The retrotrapezoid nucleus (RTN), a rostral medullary cluster of glutamatergic neurons identified by coexpression of Phoxb and Nmb transcripts, is the lynchpin of the central respiratory chemoreflex. RTN regulates breathing frequency, inspiratory amplitude, and active expiration. It is exquisitely responsive to acidosis in vivo and maintains breathing autorhythmicity during quiet waking, slow-wave sleep, and anesthesia. The RTN response to [H+] is partly an intrinsic neuronal property mediated by proton sensors TASK-2 and GPR4 and partly a paracrine effect mediated by astrocytes and the vasculature. The RTN also receives myriad excitatory or inhibitory synaptic inputs including from [H+]-responsive neurons (e.g., serotonergic). RTN is silenced by moderate hypoxia. RTN inactivity (periodic or sustained) contributes to periodic breathing and, likely, to central sleep apnea. RTN development relies on transcription factors Egr2, Phox2b, Lbx1, and Atoh1. PHOX2B mutations cause congenital central hypoventilation syndrome; they impair RTN development and consequently the central respiratory chemoreflex.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States.
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States
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Bouvier C, Souedet N, Levy J, Jan C, You Z, Herard AS, Mergoil G, Rodriguez BH, Clouchoux C, Delzescaux T. Reduced and stable feature sets selection with random forest for neurons segmentation in histological images of macaque brain. Sci Rep 2021; 11:22973. [PMID: 34836996 PMCID: PMC8626511 DOI: 10.1038/s41598-021-02344-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 10/27/2021] [Indexed: 01/01/2023] Open
Abstract
In preclinical research, histology images are produced using powerful optical microscopes to digitize entire sections at cell scale. Quantification of stained tissue relies on machine learning driven segmentation. However, such methods require multiple additional information, or features, which are increasing the quantity of data to process. As a result, the quantity of features to deal with represents a drawback to process large series or massive histological images rapidly in a robust manner. Existing feature selection methods can reduce the amount of required information but the selected subsets lack reproducibility. We propose a novel methodology operating on high performance computing (HPC) infrastructures and aiming at finding small and stable sets of features for fast and robust segmentation of high-resolution histological images. This selection has two steps: (1) selection at features families scale (an intermediate pool of features, between spaces and individual features) and (2) feature selection performed on pre-selected features families. We show that the selected sets of features are stables for two different neuron staining. In order to test different configurations, one of these dataset is a mono-subject dataset and the other is a multi-subjects dataset to test different configurations. Furthermore, the feature selection results in a significant reduction of computation time and memory cost. This methodology will allow exhaustive histological studies at a high-resolution scale on HPC infrastructures for both preclinical and clinical research.
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Affiliation(s)
- C Bouvier
- CEA, CNRS, MIRCen, Laboratoire Des Maladies Neurodégénératives, Université Paris-Saclay, Fontenay-aux-Roses, France
- Witsee, Paris, France
| | - N Souedet
- CEA, CNRS, MIRCen, Laboratoire Des Maladies Neurodégénératives, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - J Levy
- Service de Médecine Physique Et de Réadaptation - APHP Hôpital Raymond Poincaré, Garches, France
- UMR 1179, Handicap Neuromusculaire - INSERM-UVSQ, Montigny le Bretonneux, France
| | - C Jan
- CEA, CNRS, MIRCen, Laboratoire Des Maladies Neurodégénératives, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - Z You
- CEA, CNRS, MIRCen, Laboratoire Des Maladies Neurodégénératives, Université Paris-Saclay, Fontenay-aux-Roses, France
- Shaanxi Key Laboratory for Network Computing and Security Technology, School of Computer Science and Engineering, Xi'an University of Technology, Xi'an, China
| | - A-S Herard
- CEA, CNRS, MIRCen, Laboratoire Des Maladies Neurodégénératives, Université Paris-Saclay, Fontenay-aux-Roses, France
| | | | | | - C Clouchoux
- CEA, CNRS, MIRCen, Laboratoire Des Maladies Neurodégénératives, Université Paris-Saclay, Fontenay-aux-Roses, France
- Witsee, Paris, France
| | - T Delzescaux
- CEA, CNRS, MIRCen, Laboratoire Des Maladies Neurodégénératives, Université Paris-Saclay, Fontenay-aux-Roses, France.
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Baizer JS, Webster CJ, Witelson SF. Individual variability in the size and organization of the human arcuate nucleus of the medulla. Brain Struct Funct 2021; 227:159-176. [PMID: 34613435 DOI: 10.1007/s00429-021-02396-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 09/23/2021] [Indexed: 12/11/2022]
Abstract
The arcuate nucleus (Arc) of the medulla is found in almost all human brains and in a small percentage of chimpanzee brains. It is absent in the brains of other mammalian species including mice, rats, cats, and macaque monkeys. The Arc is classically considered a precerebellar relay nucleus, receiving input from the cerebral cortex and projecting to the cerebellum via the inferior cerebellar peduncle. However, several studies have found aplasia of the Arc in babies who died of SIDS (Sudden Infant Death Syndrome), and it was suggested that the Arc is the locus of chemosensory neurons critical for brainstem control of respiration. Aplasia of the Arc, however, has also been reported in adults, suggesting that it is not critical for survival. We have examined the Arc in closely spaced Nissl-stained sections in thirteen adult human cases to acquire a better understanding of the degree of variability of its size and location in adults. We have also examined immunostained sections to look for neurochemical compartments in this nucleus. Caudally, neurons of the Arc are ventrolateral to the pyramidal tracts (py); rostrally, they are ventro-medial to the py and extend up along the midline. In some cases, the Arc is discontinuous, with a gap between sections with the ventrolaterally located and the ventromedially located neurons. In all cases, there is some degree of left-right asymmetry in Arc position, size, and shape at all rostro-caudal levels. Somata of neurons in the Arc express calretinin (CR), neuronal nitric oxide synthase (nNOS), and nonphosphorylated neurofilament protein (NPNFP). Calbindin (CB) is expressed in puncta whereas there is no expression of parvalbumin (PV) in somata or puncta. There is also immunostaining for GAD and GABA receptors suggesting inhibitory input to Arc neurons. These properties were consistent among cases. Our data show differences in location of caudal and rostral Arc neurons and considerable variability among cases in the size and shape of the Arc. The variability in size suggests that "hypoplasia" of the Arc is difficult to define. The discontinuity of the Arc in many cases suggests that establishing aplasia of the Arc requires examination of many closely spaced sections through the brainstem.
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Affiliation(s)
- Joan S Baizer
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, 123 Sherman Hall, South Campus, Buffalo, NY, 14214, USA.
| | - Charles J Webster
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, 123 Sherman Hall, South Campus, Buffalo, NY, 14214, USA
| | - Sandra F Witelson
- Department of Psychiatry and Behavioural Neurosciences, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON, L8S 4K1, Canada
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Levy J, Droz-Bartholet F, Achour M, Facchinetti P, Parratte B, Giuliano F. Parafacial neurons in the human brainstem express specific markers for neurons of the retrotrapezoid nucleus. J Comp Neurol 2021; 529:3313-3320. [PMID: 34008871 DOI: 10.1002/cne.25191] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 05/08/2021] [Accepted: 05/13/2021] [Indexed: 11/06/2022]
Abstract
The retrotrapezoid nucleus (RTN) is a hub for respiratory chemoregulation in the mammal brainstem that integrates chemosensory information from peripheral sites and central relays. Chemosensitive neurons of the RTN express specific genetic and molecular determinants, which have been used to identify RTN precise location within the brainstem of rodents and nonhuman primates. Based on a comparative approach, we hypothesized that among mammals, neurons exhibiting the same specific molecular and genetic signature would have the same function. The co-expression of preprogalanin (PPGAL) and SLC17A6 (VGluT2) mRNAs with duplex in situ hybridization has been studied in formalin fixed paraffin-embedded postmortem human brainstems. Two specimens were processed and analyzed in line with RTN descriptions in adult rats and macaques. Double-labeled PPGAL+/SLC17A6+ neurons were only identified in the parafacial region of the brainstem. These neurons were found surrounding the nucleus of the facial nerve, located ventrally to the nucleus VII on caudal sections, and slightly more dorsally on rostral sections. The expression of neuromedin B (NMB) mRNA as a single marker of chemosensitive RTN neurons has not been confirmed in humans. The location of the RTN in human adults is provided. This should help to develop investigation tools combining anatomic high-resolution imaging and respiratory functional investigations to explore the pathogenic role of the RTN in congenital or acquired neurodegenerative diseases.
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Affiliation(s)
- Jonathan Levy
- UMR 1179 (Inserm-UVSQ) Neuromuscular Handicap - UFR des sciences de la Santé Simone Veil, Université de Versailles St. Quentin, Montigny-le-Bretonneux, Paris Saclay campus, France.,Service de Médecine Physique et de Réadaptation - APHP, Hôpital Raymond Poincaré, Garches, France.,Fondation Garches - Hôpital Raymond Poincaré, Garches, France
| | - François Droz-Bartholet
- Laboratoire d'Anatomie - Faculté de Médecine de Besançon, Université de Franche-Comté, Besançon, France.,Service de Médecine Physique et de Réadaptation - CHRU Jean Minjoz, Besançon, France
| | - Melyna Achour
- UMR 1179 (Inserm-UVSQ) Neuromuscular Handicap - UFR des sciences de la Santé Simone Veil, Université de Versailles St. Quentin, Montigny-le-Bretonneux, Paris Saclay campus, France
| | - Patricia Facchinetti
- UMR 1179 (Inserm-UVSQ) Neuromuscular Handicap - UFR des sciences de la Santé Simone Veil, Université de Versailles St. Quentin, Montigny-le-Bretonneux, Paris Saclay campus, France
| | - Bernard Parratte
- Laboratoire d'Anatomie - Faculté de Médecine de Besançon, Université de Franche-Comté, Besançon, France.,Service de Médecine Physique et de Réadaptation - CHRU Jean Minjoz, Besançon, France
| | - François Giuliano
- UMR 1179 (Inserm-UVSQ) Neuromuscular Handicap - UFR des sciences de la Santé Simone Veil, Université de Versailles St. Quentin, Montigny-le-Bretonneux, Paris Saclay campus, France.,Service de Médecine Physique et de Réadaptation - APHP, Hôpital Raymond Poincaré, Garches, France
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Guyenet PG, Stornetta RL, Souza GMPR, Abbott SBG, Shi Y, Bayliss DA. The Retrotrapezoid Nucleus: Central Chemoreceptor and Regulator of Breathing Automaticity. Trends Neurosci 2019; 42:807-824. [PMID: 31635852 DOI: 10.1016/j.tins.2019.09.002] [Citation(s) in RCA: 120] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/28/2019] [Accepted: 09/05/2019] [Indexed: 12/15/2022]
Abstract
The ventral surface of the rostral medulla oblongata has been suspected since the 1960s to harbor central respiratory chemoreceptors [i.e., acid-activated neurons that regulate breathing to maintain a constant arterial PCO2 (PaCO2)]. The key neurons, a.k.a. the retrotrapezoid nucleus (RTN), have now been identified. In this review we describe their transcriptome, developmental lineage, and anatomical projections. We also review their contribution to CO2 homeostasis and to the regulation of breathing automaticity during sleep and wake. Finally, we discuss several mechanisms that contribute to the activation of RTN neurons by CO2in vivo: cell-autonomous effects of protons; paracrine effects of pH mediated by surrounding astrocytes and blood vessels; and excitatory inputs from other CO2-responsive CNS neurons.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
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