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John SR, Barnett WH, Abdala APL, Zoccal DB, Rubin JE, Molkov YI. Exploring the role of the Kölliker-Fuse nucleus in breathing variability by mathematical modelling. J Physiol 2024; 602:93-112. [PMID: 38063489 PMCID: PMC10847960 DOI: 10.1113/jp285158] [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: 06/15/2023] [Accepted: 11/09/2023] [Indexed: 12/19/2023] Open
Abstract
The Kölliker-Fuse nucleus (KF), which is part of the parabrachial complex, participates in the generation of eupnoea under resting conditions and the control of active abdominal expiration when increased ventilation is required. Moreover, dysfunctions in KF neuronal activity are believed to play a role in the emergence of respiratory abnormalities seen in Rett syndrome (RTT), a progressive neurodevelopmental disorder associated with an irregular breathing pattern and frequent apnoeas. Relatively little is known, however, about the intrinsic dynamics of neurons within the KF and how their synaptic connections affect breathing pattern control and contribute to breathing irregularities. In this study, we use a reduced computational model to consider several dynamical regimes of KF activity paired with different input sources to determine which combinations are compatible with known experimental observations. We further build on these findings to identify possible interactions between the KF and other components of the respiratory neural circuitry. Specifically, we present two models that both simulate eupnoeic as well as RTT-like breathing phenotypes. Using nullcline analysis, we identify the types of inhibitory inputs to the KF leading to RTT-like respiratory patterns and suggest possible KF local circuit organizations. When the identified properties are present, the two models also exhibit quantal acceleration of late-expiratory activity, a hallmark of active expiration featuring forced exhalation, with increasing inhibition to KF, as reported experimentally. Hence, these models instantiate plausible hypotheses about possible KF dynamics and forms of local network interactions, thus providing a general framework as well as specific predictions for future experimental testing. KEY POINTS: The Kölliker-Fuse nucleus (KF), a part of the parabrachial complex, is involved in regulating normal breathing and controlling active abdominal expiration during increased ventilation. Dysfunction in KF neuronal activity is thought to contribute to respiratory abnormalities seen in Rett syndrome (RTT). This study utilizes computational modelling to explore different dynamical regimes of KF activity and their compatibility with experimental observations. By analysing different model configurations, the study identifies inhibitory inputs to the KF that lead to RTT-like respiratory patterns and proposes potential KF local circuit organizations. Two models are presented that simulate both normal breathing and RTT-like breathing patterns. These models provide testable hypotheses and specific predictions for future experimental investigations, offering a general framework for understanding KF dynamics and potential network interactions.
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Affiliation(s)
- S R John
- University of Pittsburgh, Pittsburgh, PA, USA
| | - W H Barnett
- Indiana University Purdue University Indianapolis, Indianapolis, IN, USA
| | | | - D B Zoccal
- São Paulo State University, Araraquara, Brazil
| | - J E Rubin
- University of Pittsburgh, Pittsburgh, PA, USA
| | - Y I Molkov
- Georgia State University, Atlanta, GA, USA
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2
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Whitaker-Fornek JR, Jenkins PM, Levitt ES. Inhibitory synaptic transmission is impaired in the Kölliker-Fuse of male, but not female, Rett syndrome mice. J Neurophysiol 2023; 130:1578-1587. [PMID: 37965930 PMCID: PMC11068392 DOI: 10.1152/jn.00327.2023] [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: 08/30/2023] [Revised: 10/31/2023] [Accepted: 11/09/2023] [Indexed: 11/16/2023] Open
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder that mainly affects females due to silencing mutations in the X-linked MECP2 gene. One of the most troubling symptoms of RTT is breathing irregularity, including apneas, breath-holds, and hyperventilation. Mice with silencing mutations in Mecp2 exhibit breathing abnormalities similar to human patients and serve as useful models for studying mechanisms underlying breathing problems in RTT. Previous work implicated the pontine, respiratory-controlling Kölliker-Fuse (KF) in the breathing problems in RTT. The goal of this study was to test the hypothesis that inhibitory synaptic transmission is deficient in KF neurons from symptomatic male and female RTT mice. We performed whole cell voltage-clamp recordings from KF neurons in acute brain slices to examine spontaneous and electrically evoked inhibitory post-synaptic currents (IPSCs) in RTT mice and age- and sex-matched wild-type mice. The frequency of spontaneous IPSCs was reduced in KF neurons from male RTT mice but surprisingly not in female RTT mice. In addition, electrically evoked IPSCs were less reliable in KF neurons from male, but not female, RTT mice, which was positively correlated with paired-pulse facilitation, indicating decreased probability of release. KF neurons from male RTT mice were also more excitable and exhibited shorter-duration action potentials. Increased excitability of KF neurons from male mice was not explained by changes in axon initial segment length. These findings indicate impaired inhibitory neurotransmission and increased excitability of KF neurons in male but not female RTT mice and suggest that sex-dependent mechanisms contribute to breathing problems in RTT.NEW & NOTEWORTHY Kölliker-Fuse (KF) neurons in acute brain slices from male Rett syndrome (RTT) mice receive reduced inhibitory synaptic inputs compared with wild-type littermates. In female RTT mice, inhibitory transmission was not different in KF neurons compared with controls. The results from this study show that sex-specific alterations in synaptic transmission occur in the KF of RTT mice.
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Affiliation(s)
- Jessica R Whitaker-Fornek
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, United States
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida, United States
| | - Paul M Jenkins
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, United States
- Department of Psychiatry, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Erica S Levitt
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, United States
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida, United States
- Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan, United States
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3
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Khurram OU, Mantilla CB, Sieck GC. Neuromotor control of spontaneous quiet breathing in awake rats evaluated by assessments of diaphragm EMG stationarity. J Neurophysiol 2023; 130:1344-1357. [PMID: 37877195 DOI: 10.1152/jn.00267.2023] [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: 07/10/2023] [Revised: 10/23/2023] [Accepted: 10/23/2023] [Indexed: 10/26/2023] Open
Abstract
The neuromotor control of the diaphragm muscle (DIAm) is dynamic. The activity of the DIAm can be recorded via electromyography (EMG), which represents the temporal summation of motor unit action potentials. Our goal in the present study was to investigate DIAm neuromotor control during quiet spontaneous breathing (eupnea) in awake rats by evaluating DIAm EMG at specific temporal locations defined by motor unit recruitment and derecruitment. We evaluated the nonstationarity of DIAm EMG activity to identify DIAm motor unit recruitment and derecruitment durations. Combined with assessments of root mean square (RMS) and sum of squares (SS) EMG, the durations of these phases provide physiological information about the temporal aspects of motor control. During eupnea in awake rats (n = 10), the duration of motor unit recruitment comprised 61 ± 19 ms of the onset-to-peak duration (214 ± 62 ms) of the DIAm RMS EMG. The peak-to-offset duration of DIAm EMG activity was 453 ± 96 ms, with a terminating period of derecruitment of 161 ± 44 ms. The burst duration was 673 ± 128 ms. Both the RMS EMG amplitude and the SS EMG were higher at the completion of motor unit recruitment than at the start of motor unit derecruitment, suggesting that offset discharge rates were lower than onset discharge rates. Our analyses provide novel insights into the time domain aspects of DIAm neuromotor control and allow indirect estimates of the contribution of recruitment and frequency to RMS EMG amplitude during eupnea in awake rats.NEW & NOTEWORTHY We characterized three phases of neuromotor control-motor unit recruitment, sustained activity, and derecruitment-based on statistical assessments of stationarity of the diaphragm muscle (DIAm) EMG activity in awake rats. Our findings may allow indirect estimates of the contribution of motor unit recruitment and frequency coding toward generating force and provide novel insights about the temporal aspects of DIAm neuromotor control and descending respiratory drive in unanesthetized animals.
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Affiliation(s)
- Obaid U Khurram
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Carlos B Mantilla
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Gary C Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
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4
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Oluigbo DC. Rett Syndrome: A Tale of Altered Genetics, Synaptic Plasticity, and Neurodevelopmental Dynamics. Cureus 2023; 15:e41555. [PMID: 37554594 PMCID: PMC10405636 DOI: 10.7759/cureus.41555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/07/2023] [Indexed: 08/10/2023] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder that is a leading cause of severe cognitive and physical impairment. RTT typically occurs in females, although rare cases of males with the disease exist. Its genetic cause, symptoms, and clinical progression timeline have also become well-documented since its initial discovery. However, a relatively late diagnosis and lack of an available cure signify that our understanding of the disease is incomplete. Innovative research methods and tools are thereby helping to fill gaps in our knowledge of RTT. Specifically, mouse models of RTT, video analysis, and retrospective parental analysis are well-established tools that provide valuable insights into RTT. Moreover, current and anticipated treatment options are improving the quality of life of the RTT patient population. Collectively, these developments are creating optimistic future perspectives for RTT.
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Affiliation(s)
- David C Oluigbo
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, USA
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5
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John S, Barnett W, Abdala A, Zoccal D, Rubin J, Molkov Y. The role of Kölliker-Fuse nucleus in breathing variability. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.15.545086. [PMID: 37398197 PMCID: PMC10312726 DOI: 10.1101/2023.06.15.545086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
The Kölliker-Fuse nucleus (KF), which is part of the parabrachial complex, participates in the generation of eupnea under resting conditions and the control of active abdominal expiration when increased ventilation is required. Moreover, dysfunctions in KF neuronal activity are believed to play a role in the emergence of respiratory abnormalities seen in Rett syndrome (RTT), a progressive neurodevelopmental disorder associated with an irregular breathing pattern and frequent apneas. Relatively little is known, however, about the intrinsic dynamics of neurons within the KF and how their synaptic connections affect breathing pattern control and contribute to breathing irregularities. In this study, we use a reduced computational model to consider several dynamical regimes of KF activity paired with different input sources to determine which combinations are compatible with known experimental observations. We further build on these findings to identify possible interactions between the KF and other components of the respiratory neural circuitry. Specifically, we present two models that both simulate eupneic as well as RTT-like breathing phenotypes. Using nullcline analysis, we identify the types of inhibitory inputs to the KF leading to RTT-like respiratory patterns and suggest possible KF local circuit organizations. When the identified properties are present, the two models also exhibit quantal acceleration of late-expiratory activity, a hallmark of active expiration featuring forced exhalation, with increasing inhibition to KF, as reported experimentally. Hence, these models instantiate plausible hypotheses about possible KF dynamics and forms of local network interactions, thus providing a general framework as well as specific predictions for future experimental testing. Key points The Kölliker-Fuse nucleus (KF), a part of the parabrachial complex, is involved in regulating normal breathing and controlling active abdominal expiration during increased ventilation. Dysfunction in KF neuronal activity is thought to contribute to respiratory abnormalities seen in Rett syndrome (RTT). This study utilizes computational modeling to explore different dynamical regimes of KF activity and their compatibility with experimental observations. By analyzing different model configurations, the study identifies inhibitory inputs to the KF that lead to RTT-like respiratory patterns and proposes potential KF local circuit organizations. Two models are presented that simulate both normal breathing and RTT-like breathing patterns. These models provide plausible hypotheses and specific predictions for future experimental investigations, offering a general framework for understanding KF dynamics and potential network interactions.
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6
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Fogarty MJ. Inhibitory Synaptic Influences on Developmental Motor Disorders. Int J Mol Sci 2023; 24:ijms24086962. [PMID: 37108127 PMCID: PMC10138861 DOI: 10.3390/ijms24086962] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 04/05/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
During development, GABA and glycine play major trophic and synaptic roles in the establishment of the neuromotor system. In this review, we summarise the formation, function and maturation of GABAergic and glycinergic synapses within neuromotor circuits during development. We take special care to discuss the differences in limb and respiratory neuromotor control. We then investigate the influences that GABAergic and glycinergic neurotransmission has on two major developmental neuromotor disorders: Rett syndrome and spastic cerebral palsy. We present these two syndromes in order to contrast the approaches to disease mechanism and therapy. While both conditions have motor dysfunctions at their core, one condition Rett syndrome, despite having myriad symptoms, has scientists focused on the breathing abnormalities and their alleviation-to great clinical advances. By contrast, cerebral palsy remains a scientific quagmire or poor definitions, no widely adopted model and a lack of therapeutic focus. We conclude that the sheer abundance of diversity of inhibitory neurotransmitter targets should provide hope for intractable conditions, particularly those that exhibit broad spectra of dysfunction-such as spastic cerebral palsy and Rett syndrome.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55902, USA
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7
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Bateman JT, Saunders SE, Levitt ES. Understanding and countering opioid-induced respiratory depression. Br J Pharmacol 2023; 180:813-828. [PMID: 34089181 PMCID: PMC8997313 DOI: 10.1111/bph.15580] [Citation(s) in RCA: 30] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 05/06/2021] [Accepted: 05/23/2021] [Indexed: 02/06/2023] Open
Abstract
Respiratory depression is the proximal cause of death in opioid overdose, yet the mechanisms underlying this potentially fatal outcome are not well understood. The goal of this review is to provide a comprehensive understanding of the pharmacological mechanisms of opioid-induced respiratory depression, which could lead to improved therapeutic options to counter opioid overdose, as well as other detrimental effects of opioids on breathing. The development of tolerance in the respiratory system is also discussed, as are differences in the degree of respiratory depression caused by various opioid agonists. Finally, potential future therapeutic agents aimed at reversing or avoiding opioid-induced respiratory depression through non-opioid receptor targets are in development and could provide certain advantages over naloxone. By providing an overview of mechanisms and effects of opioids in the respiratory network, this review will benefit future research on countering opioid-induced respiratory depression. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.
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Affiliation(s)
- Jordan T Bateman
- Department of Pharmacology & Therapeutics, University of Florida, Gainesville, Florida, USA
| | - Sandy E Saunders
- Department of Pharmacology & Therapeutics, University of Florida, Gainesville, Florida, USA
| | - Erica S Levitt
- Department of Pharmacology & Therapeutics, University of Florida, Gainesville, Florida, USA
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, Florida, USA
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8
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Mafa-dependent GABAergic activity promotes mouse neonatal apneas. Nat Commun 2022; 13:3284. [PMID: 35672398 PMCID: PMC9174494 DOI: 10.1038/s41467-022-30825-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 05/19/2022] [Indexed: 01/17/2023] Open
Abstract
While apneas are associated with multiple pathological and fatal conditions, the underlying molecular mechanisms remain elusive. We report that a mutated form of the transcription factor Mafa (Mafa4A) that prevents phosphorylation of the Mafa protein leads to an abnormally high incidence of breath holding apneas and death in newborn Mafa4A/4A mutant mice. This apneic breathing is phenocopied by restricting the mutation to central GABAergic inhibitory neurons and by activation of inhibitory Mafa neurons while reversed by inhibiting GABAergic transmission centrally. We find that Mafa activates the Gad2 promoter in vitro and that this activation is enhanced by the mutation that likely results in increased inhibitory drives onto target neurons. We also find that Mafa inhibitory neurons are absent from respiratory, sensory (primary and secondary) and pontine structures but are present in the vicinity of the hypoglossal motor nucleus including premotor neurons that innervate the geniohyoid muscle, to control upper airway patency. Altogether, our data reveal a role for Mafa phosphorylation in regulation of GABAergic drives and suggest a mechanism whereby reduced premotor drives to upper airway muscles may cause apneic breathing at birth. Apneas are associated with many pathological conditions. Here, the authors show in a mouse model that stabilization of the transcription factor Mafa in brainstem GABAergic neurons may contribute to apnea, by decreasing motor drive to muscles controlling the airways.
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9
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Xia M, Owen B, Chiang J, Levitt A, Preisinger K, Yan WW, Huffman R, Nobis WP. Disruption of Synaptic Transmission in the Bed Nucleus of the Stria Terminalis Reduces Seizure-Induced Death in DBA/1 Mice and Alters Brainstem E/I Balance. ASN Neuro 2022; 14:17590914221103188. [PMID: 35611439 PMCID: PMC9136462 DOI: 10.1177/17590914221103188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in refractory epilepsy patients. Accumulating evidence from recent human studies and animal models suggests that seizure-related respiratory arrest may be important for initiating cardiorespiratory arrest and death. Prior evidence suggests that apnea onset can coincide with seizure spread to the amygdala and that stimulation of the amygdala can reliably induce apneas in epilepsy patients, potentially implicating amygdalar regions in seizure-related respiratory arrest and subsequent postictal hypoventilation and cardiorespiratory death. This study aimed to determine if an extended amygdalar structure, the dorsal bed nucleus of the stria terminalis (dBNST), is involved in seizure-induced respiratory arrest (S-IRA) and death using DBA/1 mice, a mouse strain which has audiogenic seizures (AGS) and a high incidence of postictal respiratory arrest and death. The presence of S-IRA significantly increased c-Fos expression in the dBNST of DBA/1 mice. Furthermore, disruption of synaptic output from the dBNST via viral-induced tetanus neurotoxin (TeNT) significantly improved survival following S-IRA in DBA/1 mice without affecting baseline breathing or hypercapnic (HCVR) and hypoxic ventilatory response (HVR). This disruption in the dBNST resulted in changes to the balance of excitatory/inhibitory (E/I) synaptic events in the downstream brainstem regions of the lateral parabrachial nucleus (PBN) and the periaqueductal gray (PAG). These findings suggest that the dBNST is a potential subcortical forebrain site necessary for the mediation of S-IRA, potentially through its outputs to brainstem respiratory regions.
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Affiliation(s)
| | | | | | | | | | | | | | - William P. Nobis
- Department of Neurology, Vanderbilt University Medical Center, 6130A MRB 3/Bio Sci Building, 465 21st Ave S, Nashville, TN 37235, USA.
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10
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Paton JFR, Machado BH, Moraes DJA, Zoccal DB, Abdala AP, Smith JC, Antunes VR, Murphy D, Dutschmann M, Dhingra RR, McAllen R, Pickering AE, Wilson RJA, Day TA, Barioni NO, Allen AM, Menuet C, Donnelly J, Felippe I, St-John WM. Advancing respiratory-cardiovascular physiology with the working heart-brainstem preparation over 25 years. J Physiol 2022; 600:2049-2075. [PMID: 35294064 PMCID: PMC9322470 DOI: 10.1113/jp281953] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 03/04/2022] [Indexed: 11/24/2022] Open
Abstract
Twenty‐five years ago, a new physiological preparation called the working heart–brainstem preparation (WHBP) was introduced with the claim it would provide a new platform allowing studies not possible before in cardiovascular, neuroendocrine, autonomic and respiratory research. Herein, we review some of the progress made with the WHBP, some advantages and disadvantages along with potential future applications, and provide photographs and technical drawings of all the customised equipment used for the preparation. Using mice or rats, the WHBP is an in situ experimental model that is perfused via an extracorporeal circuit benefitting from unprecedented surgical access, mechanical stability of the brain for whole cell recording and an uncompromised use of pharmacological agents akin to in vitro approaches. The preparation has revealed novel mechanistic insights into, for example, the generation of distinct respiratory rhythms, the neurogenesis of sympathetic activity, coupling between respiration and the heart and circulation, hypothalamic and spinal control mechanisms, and peripheral and central chemoreceptor mechanisms. Insights have been gleaned into diseases such as hypertension, heart failure and sleep apnoea. Findings from the in situ preparation have been ratified in conscious in vivo animals and when tested have translated to humans. We conclude by discussing potential future applications of the WHBP including two‐photon imaging of peripheral and central nervous systems and adoption of pharmacogenetic tools that will improve our understanding of physiological mechanisms and reveal novel mechanisms that may guide new treatment strategies for cardiorespiratory diseases.
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Affiliation(s)
- Julian F R Paton
- Manaaki Manawa - The Centre for Heart Research, Faculty of Medical & Health Science, University of Auckland, Park Road, Grafton, Auckland, 1142, New Zealand
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, São Paulo, Brazil
| | - Ana P Abdala
- School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol, Bristol, England, BS8 1TD, UK
| | - Jeffrey C Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Vagner R Antunes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - David Murphy
- Molecular Neuroendocrinology Research Group, Bristol Medical School: Translational Health Sciences, University of Bristol, Bristol, UK
| | - Mathias Dutschmann
- Florey institute of Neuroscience and Mental Health, University of Melbourne, 30, Royal Parade, Parkville, Victoria, 3052, Australia
| | - Rishi R Dhingra
- Florey institute of Neuroscience and Mental Health, University of Melbourne, 30, Royal Parade, Parkville, Victoria, 3052, Australia
| | - Robin McAllen
- Florey institute of Neuroscience and Mental Health, University of Melbourne, 30, Royal Parade, Parkville, Victoria, 3052, Australia
| | - Anthony E Pickering
- School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol, Bristol, England, BS8 1TD, UK
| | - Richard J A Wilson
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Trevor A Day
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Nicole O Barioni
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Andrew M Allen
- Department of Anatomy & Physiology, The University of Melbourne, Victoria, 3010, Australia
| | - Clément Menuet
- Institut de Neurobiologie de la Méditerranée, INMED UMR1249, INSERM, Aix-Marseille Université, Marseille, France
| | - Joseph Donnelly
- Department of Medicine, Faculty of Medical and Health Sciences, The University of Auckland, New Zealand
| | - Igor Felippe
- Manaaki Manawa - The Centre for Heart Research, Faculty of Medical & Health Science, University of Auckland, Park Road, Grafton, Auckland, 1142, New Zealand
| | - Walter M St-John
- Emeritus Professor, Department of Physiology and Neurobiology, Geisel School of Medicine at Dartmouth, Dartmouth, New Hampshire, USA
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11
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Ramirez JM, Karlen-Amarante M, Wang JDJ, Huff A, Burgraff N. Breathing disturbances in Rett syndrome. HANDBOOK OF CLINICAL NEUROLOGY 2022; 189:139-151. [PMID: 36031301 PMCID: PMC10029146 DOI: 10.1016/b978-0-323-91532-8.00018-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Rett Syndrome is an X-linked neurological disorder characterized by behavioral and neurological regression, seizures, motor deficits, and dysautonomia. A particularly prominent presentation includes breathing abnormalities characterized by breathing irregularities, hyperventilation, repetitive breathholding during wakefulness, obstructive and central apneas during sleep, and abnormal responses to hypoxia and hypercapnia. The condition and pathology of the respiratory system is further complicated by dysfunctions of breathing-motor coordination, which is reflected in dysphagia. The discovery of the X-linked mutations in the MECP2 gene has transformed our understanding of the cellular and molecular mechanisms that are at the root of various clinical phenotypes. However, the genotype-phenotype relationship is complicated by various factors which include not only X-inactivation but also consequences of the intermittent hypoxia and oxidative stress associated with the breathing abnormalities.
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Affiliation(s)
- Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, United States; Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA, United States.
| | - Marlusa Karlen-Amarante
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, United States
| | - Jia-Der Ju Wang
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, United States
| | - Alyssa Huff
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, United States
| | - Nicholas Burgraff
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, United States
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12
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Bach S, Shovlin S, Moriarty M, Bardoni B, Tropea D. Rett Syndrome and Fragile X Syndrome: Different Etiology With Common Molecular Dysfunctions. Front Cell Neurosci 2021; 15:764761. [PMID: 34867203 PMCID: PMC8640214 DOI: 10.3389/fncel.2021.764761] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 10/27/2021] [Indexed: 01/04/2023] Open
Abstract
Rett syndrome (RTT) and Fragile X syndrome (FXS) are two monogenetic neurodevelopmental disorders with complex clinical presentations. RTT is caused by mutations in the Methyl-CpG binding protein 2 gene (MECP2) altering the function of its protein product MeCP2. MeCP2 modulates gene expression by binding methylated CpG dinucleotides, and by interacting with transcription factors. FXS is caused by the silencing of the FMR1 gene encoding the Fragile X Mental Retardation Protein (FMRP), a RNA binding protein involved in multiple steps of RNA metabolism, and modulating the translation of thousands of proteins including a large set of synaptic proteins. Despite differences in genetic etiology, there are overlapping features in RTT and FXS, possibly due to interactions between MeCP2 and FMRP, and to the regulation of pathways resulting in dysregulation of common molecular signaling. Furthermore, basic physiological mechanisms are regulated by these proteins and might concur to the pathophysiology of both syndromes. Considering that RTT and FXS are disorders affecting brain development, and that most of the common targets of MeCP2 and FMRP are involved in brain activity, we discuss the mechanisms of synaptic function and plasticity altered in RTT and FXS, and we consider the similarities and the differences between these two disorders.
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Affiliation(s)
- Snow Bach
- School of Mathematical Sciences, Dublin City University, Dublin, Ireland.,Neuropsychiatric Genetics, Department of Psychiatry, School of Medicine, Trinity College Dublin, Trinity Translational Medicine Institute, St James's Hospital, Dublin, Ireland
| | - Stephen Shovlin
- Neuropsychiatric Genetics, Department of Psychiatry, School of Medicine, Trinity College Dublin, Trinity Translational Medicine Institute, St James's Hospital, Dublin, Ireland
| | | | - Barbara Bardoni
- Inserm, CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, Université Côte d'Azur, Valbonne, France
| | - Daniela Tropea
- Neuropsychiatric Genetics, Department of Psychiatry, School of Medicine, Trinity College Dublin, Trinity Translational Medicine Institute, St James's Hospital, Dublin, Ireland.,Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland.,FutureNeuro, The SFI Research Centre for Chronic and Rare Neurological Diseases, Dublin, Ireland
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13
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Wu Y, Cui N, Xing H, Zhong W, Arrowood C, Johnson CM, Jiang C. In vivo evidence for the cellular basis of central hypoventilation of Rett syndrome and pharmacological correction in the rat model. J Cell Physiol 2021; 236:8082-8098. [PMID: 34077559 DOI: 10.1002/jcp.30462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 04/13/2021] [Accepted: 05/08/2021] [Indexed: 12/29/2022]
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused mostly by mutations in the MECP2 gene. RTT patients show periodical hypoventilation attacks. The breathing disorder contributing to the high incidence of sudden death is thought to be due to depressed central inspiratory (I) activity via unknown cellular processes. Demonstration of such processes may lead to targets for pharmacological control of the RTT-type hypoventilation. We performed in vivo recordings from medullary respiratory neurons on the RTT rat model. To our surprise, both I and expiratory (E) neurons in the ventral respiratory column (VRC) increased their firing activity in Mecp2-null rats with severe hypoventilation. These I neurons including E-I phase-spanning and other I neurons remained active during apneas. Consistent with enhanced central I drive, ectopic phrenic discharges during expiration as well as apnea were observed in the Mecp2-null rats. Considering the increased I neuronal firing and ectopic phrenic activity, the RTT-type hypoventilation does not seem to be caused by depression in central I activity, neither reduced medullary I premotor output. This as well as excessive E neuronal firing as shown in our previous studies suggests inadequate synaptic inhibition for phase transition. We found that the abnormal respiratory neuronal firing, ectopic phrenic discharge as well as RTT-type hypoventilation all can be corrected by enhancing GABAergic inhibition. More strikingly, Mecp2-null rats reaching humane endpoints with severe hypoventilation can be rescued by GABAergic augmentation. Thus, defective GABAergic inhibition among respiratory neurons is likely to play a role in the RTT-type hypoventilation, which can be effectively controlled with pharmacological agents.
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Affiliation(s)
- Yang Wu
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Ningren Cui
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Hao Xing
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Weiwei Zhong
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Colin Arrowood
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | | | - Chun Jiang
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
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14
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Yan WW, Xia M, Chiang J, Levitt A, Hawkins N, Kearney J, Swanson GT, Chetkovich D, Nobis WP. Enhanced Synaptic Transmission in the Extended Amygdala and Altered Excitability in an Extended Amygdala to Brainstem Circuit in a Dravet Syndrome Mouse Model. eNeuro 2021; 8:ENEURO.0306-20.2021. [PMID: 34045209 PMCID: PMC8213443 DOI: 10.1523/eneuro.0306-20.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 04/29/2021] [Accepted: 05/11/2021] [Indexed: 12/13/2022] Open
Abstract
Dravet syndrome (DS) is a developmental and epileptic encephalopathy with an increased incidence of sudden death. Evidence of interictal breathing deficits in DS suggests that alterations in subcortical projections to brainstem nuclei may exist, which might be driving comorbidities in DS. The aim of this study was to determine whether a subcortical structure, the bed nucleus of the stria terminalis (BNST) in the extended amygdala, is activated by seizures, exhibits changes in excitability, and expresses any alterations in neurons projecting to a brainstem nucleus associated with respiration, stress response, and homeostasis. Experiments were conducted using F1 mice generated by breeding 129.Scn1a+/- mice with wild-type C57BL/6J mice. Immunohistochemistry was performed to quantify neuronal c-fos activation in DS mice after observed spontaneous seizures. Whole-cell patch-clamp and current-clamp electrophysiology recordings were conducted to evaluate changes in intrinsic and synaptic excitability in the BNST. Spontaneous seizures in DS mice significantly enhanced neuronal c-fos expression in the BNST. Further, the BNST had altered AMPA/NMDA postsynaptic receptor composition and showed changes in spontaneous neurotransmission, with greater excitation and decreased inhibition. BNST to parabrachial nucleus (PBN) projection neurons exhibited intrinsic excitability in wild-type mice, while these projection neurons were hypoexcitable in DS mice. The findings suggest that there is altered excitability in neurons of the BNST, including BNST-to-PBN projection neurons, in DS mice. These alterations could potentially be driving comorbid aspects of DS outside of seizures, including respiratory dysfunction and sudden death.
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Affiliation(s)
- Wen Wei Yan
- Department of Neurology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Maya Xia
- Department of Neurology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Jeremy Chiang
- Department of Neurology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Alyssa Levitt
- Department of Neurology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Nicole Hawkins
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
| | - Jennifer Kearney
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
| | - Geoffrey T Swanson
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
| | - Dane Chetkovich
- Department of Neurology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - William P Nobis
- Department of Neurology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
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15
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Ramirez JM, Burgraff NJ, Wei AD, Baertsch NA, Varga AG, Baghdoyan HA, Lydic R, Morris KF, Bolser DC, Levitt ES. Neuronal mechanisms underlying opioid-induced respiratory depression: our current understanding. J Neurophysiol 2021; 125:1899-1919. [PMID: 33826874 DOI: 10.1152/jn.00017.2021] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Opioid-induced respiratory depression (OIRD) represents the primary cause of death associated with therapeutic and recreational opioid use. Within the United States, the rate of death from opioid abuse since the early 1990s has grown disproportionally, prompting the classification as a nationwide "epidemic." Since this time, we have begun to unravel many fundamental cellular and systems-level mechanisms associated with opioid-related death. However, factors such as individual vulnerability, neuromodulatory compensation, and redundancy of opioid effects across central and peripheral nervous systems have created a barrier to a concise, integrative view of OIRD. Within this review, we bring together multiple perspectives in the field of OIRD to create an overarching viewpoint of what we know, and where we view this essential topic of research going forward into the future.
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Affiliation(s)
- Jan-Marino Ramirez
- Department of Neurological Surgery, University of Washington, Seattle, Washington.,Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Nicholas J Burgraff
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Aguan D Wei
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Nathan A Baertsch
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Adrienn G Varga
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida.,Center for Respiratory Research and Rehabilitation, Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Helen A Baghdoyan
- Department of Psychology, University of Tennessee, Knoxville, Tennessee.,Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Ralph Lydic
- Department of Psychology, University of Tennessee, Knoxville, Tennessee.,Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Kendall F Morris
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Donald C Bolser
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida
| | - Erica S Levitt
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida.,Center for Respiratory Research and Rehabilitation, Department of Physical Therapy, University of Florida, Gainesville, Florida
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16
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Ramirez JM, Karlen-Amarante M, Wang JDJ, Bush NE, Carroll MS, Weese-Mayer DE, Huff A. The Pathophysiology of Rett Syndrome With a Focus on Breathing Dysfunctions. Physiology (Bethesda) 2020; 35:375-390. [PMID: 33052774 PMCID: PMC7864239 DOI: 10.1152/physiol.00008.2020] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 06/21/2020] [Accepted: 06/22/2020] [Indexed: 02/07/2023] Open
Abstract
Rett syndrome (RTT), an X-chromosome-linked neurological disorder, is characterized by serious pathophysiology, including breathing and feeding dysfunctions, and alteration of cardiorespiratory coupling, a consequence of multiple interrelated disturbances in the genetic and homeostatic regulation of central and peripheral neuronal networks, redox state, and control of inflammation. Characteristic breath-holds, obstructive sleep apnea, and aerophagia result in intermittent hypoxia, which, combined with mitochondrial dysfunction, causes oxidative stress-an important driver of the clinical presentation of RTT.
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Affiliation(s)
- Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
- Departments of Neurological Surgery and Pediatrics, University of Washington School of Medicine, Seattle, Washington
| | - Marlusa Karlen-Amarante
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, Brazil
| | - Jia-Der Ju Wang
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
| | - Nicholas E Bush
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
| | - Michael S Carroll
- Data Analytics and Reporting, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois
- Division of Autonomic Medicine, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - Debra E Weese-Mayer
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois
- Division of Autonomic Medicine, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - Alyssa Huff
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington
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17
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Johnson CM, Cui N, Xing H, Wu Y, Jiang C. The antitussive cloperastine improves breathing abnormalities in a Rett Syndrome mouse model by blocking presynaptic GIRK channels and enhancing GABA release. Neuropharmacology 2020; 176:108214. [PMID: 32622786 DOI: 10.1016/j.neuropharm.2020.108214] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 06/12/2020] [Accepted: 06/14/2020] [Indexed: 12/21/2022]
Abstract
Rett Syndrome (RTT) is an X-linked neurodevelopmental disorder caused mainly by mutations in the MECP2 gene. One of the major RTT features is breathing dysfunction characterized by periodic hypo- and hyperventilation. The breathing disorders are associated with increased brainstem neuronal excitability, which can be alleviated with GABA agonists. Since neuronal hypoexcitability occurs in the forebrain of RTT models, it is necessary to find pharmacological agents with a relative preference to brainstem neurons. Here we show evidence for the improvement of breathing disorders of Mecp2-disrupted mice with the brainstem-acting drug cloperastine (CPS) and its likely neuronal targets. CPS is an over-the-counter cough medicine that has an inhibitory effect on brainstem neuronal networks. In Mecp2-disrupted mice, CPS (30 mg/kg, i.p.) decreased the occurrence of apneas/h and breath frequency variation. GIRK currents expressed in HEK cells were inhibited by CPS with IC50 1 μM. Whole-cell patch clamp recordings in locus coeruleus (LC) and dorsal tegmental nucleus (DTN) neurons revealed an overall inhibitory effect of CPS (10 μM) on neuronal firing activity. Such an effect was reversed by the GABAA receptor antagonist bicuculline (20 μM). Voltage clamp studies showed that CPS increased GABAergic sIPSCs in LC cells, which was blocked by the GABAB receptor antagonist phaclofen. Functional GABAergic connections of DTN neurons with LC cells were shown. These results suggest that CPS improves breathing dysfunction in Mecp2-null mice by blocking GIRK channels in synaptic terminals and enhancing GABA release.
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Affiliation(s)
- Christopher M Johnson
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA, 30303, USA
| | - Ningren Cui
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA, 30303, USA
| | - Hao Xing
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA, 30303, USA
| | - Yang Wu
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA, 30303, USA
| | - Chun Jiang
- Department of Biology, Georgia State University, 100 Piedmont Avenue, Atlanta, GA, 30303, USA.
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18
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Varga AG, Maletz SN, Bateman JT, Reid BT, Levitt ES. Neurochemistry of the Kölliker-Fuse nucleus from a respiratory perspective. J Neurochem 2020; 156:16-37. [PMID: 32396650 DOI: 10.1111/jnc.15041] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/27/2020] [Accepted: 05/04/2020] [Indexed: 12/11/2022]
Abstract
The Kölliker-Fuse nucleus (KF) is a functionally distinct component of the parabrachial complex, located in the dorsolateral pons of mammals. The KF has a major role in respiration and upper airway control. A comprehensive understanding of the KF and its contributions to respiratory function and dysfunction requires an appreciation for its neurochemical characteristics. The goal of this review is to summarize the diverse neurochemical composition of the KF, focusing on the neurotransmitters, neuromodulators, and neuropeptides present. We also include a description of the receptors expressed on KF neurons and transporters involved in each system, as well as their putative roles in respiratory physiology. Finally, we provide a short section reviewing the literature regarding neurochemical changes in the KF in the context of respiratory dysfunction observed in SIDS and Rett syndrome. By over-viewing the current literature on the neurochemical composition of the KF, this review will serve to aid a wide range of topics in the future research into the neural control of respiration in health and disease.
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Affiliation(s)
- Adrienn G Varga
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
| | - Sebastian N Maletz
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Jordan T Bateman
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
| | - Brandon T Reid
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Erica S Levitt
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
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19
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Dhingra RR, Dick TE, Furuya WI, Galán RF, Dutschmann M. Volumetric mapping of the functional neuroanatomy of the respiratory network in the perfused brainstem preparation of rats. J Physiol 2020; 598:2061-2079. [PMID: 32100293 DOI: 10.1113/jp279605] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 02/05/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The functional neuroanatomy of the mammalian respiratory network is far from being understood since experimental tools that measure neural activity across this brainstem-wide circuit are lacking. Here, we use silicon multi-electrode arrays to record respiratory local field potentials (rLFPs) from 196-364 electrode sites within 8-10 mm3 of brainstem tissue in single arterially perfused brainstem preparations with respect to the ongoing respiratory motor pattern of inspiration (I), post-inspiration (PI) and late-expiration (E2). rLFPs peaked specifically at the three respiratory phase transitions, E2-I, I-PI and PI-E2. We show, for the first time, that only the I-PI transition engages a brainstem-wide network, and that rLFPs during the PI-E2 transition identify a hitherto unknown role for the dorsal respiratory group. Volumetric mapping of pontomedullary rLFPs in single preparations could become a reliable tool for assessing the functional neuroanatomy of the respiratory network in health and disease. ABSTRACT While it is widely accepted that inspiratory rhythm generation depends on the pre-Bötzinger complex, the functional neuroanatomy of the neural circuits that generate expiration is debated. We hypothesized that the compartmental organization of the brainstem respiratory network is sufficient to generate macroscopic local field potentials (LFPs), and if so, respiratory (r) LFPs could be used to map the functional neuroanatomy of the respiratory network. We developed an approach using silicon multi-electrode arrays to record spontaneous LFPs from hundreds of electrode sites in a volume of brainstem tissue while monitoring the respiratory motor pattern on phrenic and vagal nerves in the perfused brainstem preparation. Our results revealed the expression of rLFPs across the pontomedullary brainstem. rLFPs occurred specifically at the three transitions between respiratory phases: (1) from late expiration (E2) to inspiration (I), (2) from I to post-inspiration (PI), and (3) from PI to E2. Thus, respiratory network activity was maximal at respiratory phase transitions. Spatially, the E2-I, and PI-E2 transitions were anatomically localized to the ventral and dorsal respiratory groups, respectively. In contrast, our data show, for the first time, that the generation of controlled expiration during the post-inspiratory phase engages a distributed neuronal population within ventral, dorsal and pontine network compartments. A group-wise independent component analysis demonstrated that all preparations exhibited rLFPs with a similar temporal structure and thus share a similar functional neuroanatomy. Thus, volumetric mapping of rLFPs could allow for the physiological assessment of global respiratory network organization in health and disease.
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Affiliation(s)
- Rishi R Dhingra
- The Florey Institute of Neuroscience & Mental Health, University of Melbourne, Melbourne, Australia
| | - Thomas E Dick
- Division of Pulmonary, Critical Care & Sleep, Department of Medicine, Case Western Reserve University, Cleveland, USA
| | - Werner I Furuya
- The Florey Institute of Neuroscience & Mental Health, University of Melbourne, Melbourne, Australia
| | - Roberto F Galán
- Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, USA
| | - Mathias Dutschmann
- The Florey Institute of Neuroscience & Mental Health, University of Melbourne, Melbourne, Australia
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20
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Kölliker-Fuse/Parabrachial complex mu opioid receptors contribute to fentanyl-induced apnea and respiratory rate depression. Respir Physiol Neurobiol 2020; 275:103388. [PMID: 31953234 DOI: 10.1016/j.resp.2020.103388] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 11/05/2019] [Accepted: 01/13/2020] [Indexed: 12/19/2022]
Abstract
Overdoses caused by the opioid agonist fentanyl have increased exponentially in recent years. Identifying mechanisms to counter progression to fatal respiratory apnea during opioid overdose is desirable, but difficult to study in vivo. The pontine Kölliker-Fuse/Parabrachial complex (KF/PB) provides respiratory drive and contains opioid-sensitive neurons. The contribution of the KF/PB complex to fentanyl-induced apnea was investigated using the in situ arterially perfused preparation of rat. Systemic application of fentanyl resulted in concentration-dependent respiratory disturbances. At low concentrations, respiratory rate slowed and subsequently transitioned to an apneustic-like, 2-phase pattern. Higher concentrations caused prolonged apnea, interrupted by occasional apneustic-like bursts. Application of CTAP, a selective mu opioid receptor antagonist, directly into the KF/PB complex reversed and prevented fentanyl-induced apnea by increasing the frequency of apneustic-like bursting. These results demonstrate that countering opioid effects in the KF/PB complex is sufficient to restore phasic respiratory output at a rate similar to pre-fentanyl conditions, which could be beneficial in opioid overdose.
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21
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Hinz L, Torrella Barrufet J, Heine VM. KCC2 expression levels are reduced in post mortem brain tissue of Rett syndrome patients. Acta Neuropathol Commun 2019; 7:196. [PMID: 31796123 PMCID: PMC6892240 DOI: 10.1186/s40478-019-0852-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 11/21/2019] [Indexed: 02/07/2023] Open
Abstract
Rett Syndrome (RTT) is a neurodevelopmental disorder caused by mutations in the Methyl CpG binding protein 2 (MECP2) gene. Deficient K+-Cl-co-transporter 2 (KCC2) expression is suggested to play a key role in the neurodevelopmental delay in RTT patients' neuronal networks. KCC2 is a major player in neuronal maturation by supporting the GABAergic switch, through the regulation of neuronal chlorine homeostasis. Previous studies suggest that MeCP2 mutations lead to changed KCC2 expression levels, thereby causing a disturbance in excitation/inhibition (E/I) balance. To investigate this, we performed protein and RNA expression analysis on post mortem brain tissue from RTT patients and healthy controls. We showed that KCC2 expression, in particular the KCC2a isoform, is relatively decreased in RTT patients. The expression of Na+-K+-Cl- co-transporter 1 (NKCC1), responsible for the inward transport of chlorine, is not affected, leading to a reduced KCC2/NKCC1 ratio in RTT brains. Our report confirms KCC2 expression alterations in RTT patients in human brain tissue, which is in line with other studies, suggesting affected E/I balance could underlie neurodevelopmental defects in RTT patients.
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Affiliation(s)
- Lisa Hinz
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, Vrije Universiteit, Amsterdam, The Netherlands
| | - Joan Torrella Barrufet
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, Vrije Universiteit, Amsterdam, The Netherlands
| | - Vivi M Heine
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, Vrije Universiteit, Amsterdam, The Netherlands.
- Pediatric Neurology, Emma Children's Hospital, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Neuroscience, Boelelaan 1085, 1081HV, Amsterdam, The Netherlands.
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22
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Banerjee A, Miller MT, Li K, Sur M, Kaufmann WE. Towards a better diagnosis and treatment of Rett syndrome: a model synaptic disorder. Brain 2019; 142:239-248. [PMID: 30649225 DOI: 10.1093/brain/awy323] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 10/31/2018] [Indexed: 12/21/2022] Open
Abstract
With the recent 50th anniversary of the first publication on Rett syndrome, and the almost 20 years since the first report on the link between Rett syndrome and MECP2 mutations, it is important to reflect on the tremendous advances in our understanding and their implications for the diagnosis and treatment of this neurodevelopmental disorder. Rett syndrome features an interesting challenge for biologists and clinicians, as the disorder lies at the intersection of molecular mechanisms of epigenetic regulation and neurophysiological alterations in synapses and circuits that together contribute to severe pathophysiological endophenotypes. Genetic, clinical, and neurobiological evidences support the notion that Rett syndrome is primarily a synaptic disorder, and a disease model for both intellectual disability and autism spectrum disorder. This review examines major developments in both recent neurobiological and preclinical findings of Rett syndrome, and to what extent they are beginning to impact our understanding and management of the disorder. It also discusses potential applications of knowledge on synaptic plasticity abnormalities in Rett syndrome to its diagnosis and treatment.
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Affiliation(s)
- Abhishek Banerjee
- Laboratory of Neural Circuit Dynamics, Brain Research Institute, University of Zürich, Zürich, Switzerland
| | - Meghan T Miller
- Roche Pharma Research and Early Development, Roche Innovation Center, F. Hoffman-La Roche, Basel, Switzerland
| | - Keji Li
- Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge MA, USA
| | - Mriganka Sur
- Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge MA, USA
| | - Walter E Kaufmann
- Department of Human Genetics, Emory University School of Medicine, Atlanta GA, USA
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23
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Dhingra RR, Furuya WI, Bautista TG, Dick TE, Galán RF, Dutschmann M. Increasing Local Excitability of Brainstem Respiratory Nuclei Reveals a Distributed Network Underlying Respiratory Motor Pattern Formation. Front Physiol 2019; 10:887. [PMID: 31396094 PMCID: PMC6664290 DOI: 10.3389/fphys.2019.00887] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 06/26/2019] [Indexed: 11/18/2022] Open
Abstract
The core circuit of the respiratory central pattern generator (rCPG) is located in the ventrolateral medulla, especially in the pre-Bötzinger complex (pre-BötC) and the neighboring Bötzinger complex (BötC). To test the hypothesis that this core circuit is embedded within an anatomically distributed pattern-generating network, we investigated whether local disinhibition of the nucleus tractus solitarius (NTS), the Kölliker-Fuse nuclei (KFn), or the midbrain periaqueductal gray area (PAG) can similarly affect the respiratory pattern compared to disinhibition of the pre-BötC/BötC core. In arterially-perfused brainstem preparations of rats, we recorded the three-phase respiratory pattern (inspiration, post-inspiration and late-expiration) from phrenic and vagal nerves before and after bilateral microinjections of the GABA(A)R antagonist bicuculline (50 nl, 10 mM). Local disinhibition of either NTS, pre-BötC/BötC, or KFn, but not PAG, triggered qualitatively similar disruptions of the respiratory pattern resulting in a highly significant increase in the variability of the respiratory cycle length, including inspiratory and expiratory phase durations. To quantitatively analyze these motor pattern perturbations, we measured the strength of phase synchronization between phrenic and vagal motor outputs. This analysis showed that local disinhibition of all brainstem target nuclei, but not the midbrain PAG, significantly decreased the strength of phase synchronization. The convergent perturbations of the respiratory pattern suggest that the rCPG expands rostrally and dorsally from the designated core but does not include higher mid-brain structures. Our data also suggest that excitation-inhibition balance of respiratory network synaptic interactions critically determines the network dynamics that underlie vital respiratory rhythm and pattern formation.
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Affiliation(s)
- Rishi R Dhingra
- Division of Systems Neurophysiology, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Werner I Furuya
- Division of Systems Neurophysiology, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Tara G Bautista
- Division of Systems Neurophysiology, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Thomas E Dick
- Division of Pulmonary, Critical Care and Sleep, Department of Medicine, Case Western Reserve University, Cleveland, OH, United States
| | - Roberto F Galán
- Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, OH, United States
| | - Mathias Dutschmann
- Division of Systems Neurophysiology, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
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Mouro FM, Miranda-Lourenço C, Sebastião AM, Diógenes MJ. From Cannabinoids and Neurosteroids to Statins and the Ketogenic Diet: New Therapeutic Avenues in Rett Syndrome? Front Neurosci 2019; 13:680. [PMID: 31333401 PMCID: PMC6614559 DOI: 10.3389/fnins.2019.00680] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 06/13/2019] [Indexed: 12/21/2022] Open
Abstract
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused mainly by mutations in the MECP2 gene, being one of the leading causes of mental disability in females. Mutations in the MECP2 gene are responsible for 95% of the diagnosed RTT cases and the mechanisms through which these mutations relate with symptomatology are still elusive. Children with RTT present a period of apparent normal development followed by a rapid regression in speech and behavior and a progressive deterioration of motor abilities. Epilepsy is one of the most common symptoms in RTT, occurring in 60 to 80% of RTT cases, being associated with worsening of other symptoms. At this point, no cure for RTT is available and there is a pressing need for the discovery of new drug candidates to treat its severe symptoms. However, despite being a rare disease, in the last decade research in RTT has grown exponentially. New and exciting evidence has been gathered and the etiopathogenesis of this complex, severe and untreatable disease is slowly being unfolded. Advances in gene editing techniques have prompted cure-oriented research in RTT. Nonetheless, at this point, finding a cure is a distant reality, highlighting the importance of further investigating the basic pathological mechanisms of this disease. In this review, we focus our attention in some of the newest evidence on RTT clinical and preclinical research, evaluating their impact in RTT symptomatology control, and pinpointing possible directions for future research.
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Affiliation(s)
- Francisco Melo Mouro
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Catarina Miranda-Lourenço
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Ana Maria Sebastião
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Maria José Diógenes
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
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25
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Wittman S, Abdala AP, Rubin JE. Reduced computational modelling of Kölliker-Fuse contributions to breathing patterns in Rett syndrome. J Physiol 2019; 597:2651-2672. [PMID: 30908648 DOI: 10.1113/jp277592] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 03/07/2019] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS Reduced computational models are used to test effects of loss of inhibition to the Kölliker-Fuse nucleus (KFn). Three reduced computational models that simulate eupnoeic and vagotomized respiratory rhythms are considered. All models exhibit the emergence of respiratory perturbations associated with Rett syndrome as inhibition to the KFn is diminished. Simulations suggest that application of 5-HT1A agonists can mitigate the respiratory pathology. The three models can be distinguished and tested based on their predictions about connections and dynamics within the respiratory circuit and about effects of perturbations on certain respiratory neuron populations. ABSTRACT Rett syndrome (RTT) is a developmental disorder that can lead to respiratory disturbances featuring prolonged apnoeas of variable durations. Determining the mechanisms underlying these effects at the level of respiratory neural circuits would have significant implications for treatment efforts and would also enhance our understanding of respiratory rhythm generation and control. While experimental studies have suggested possible factors contributing to the respiratory patterns of RTT, we take a novel computational approach to the investigation of RTT, which allows for direct manipulation of selected system parameters and testing of specific hypotheses. Specifically, we present three reduced computational models, developed using an established framework, all of which successfully simulate respiratory outputs across eupnoeic and vagotomized conditions. All three models show that loss of inhibition to the Kölliker-Fuse nucleus reproduces the key respiratory alterations associated with RTT and, as suggested experimentally, that effects of 5-HT1A agonists on the respiratory neural circuit suffice to alleviate this respiratory pathology. Each of the models makes distinct predictions regarding the neuronal populations and interactions underlying these effects, suggesting natural directions for future experimental testing.
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Affiliation(s)
- Samuel Wittman
- Department of Mathematics, University of Pittsburgh, 301 Thackeray Hall, Pittsburgh, PA, 15260, USA
| | - Ana Paula Abdala
- School of Physiology, Pharmacology & Neuroscience, Faculty of Life Sciences, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Jonathan E Rubin
- Department of Mathematics, University of Pittsburgh, 301 Thackeray Hall, Pittsburgh, PA, 15260, USA.,Center for the Neural Basis of Cognition, University of Pittsburgh, 4400 Fifth Avenue, Pittsburgh, PA, 15213, USA
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26
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Treating Rett syndrome: from mouse models to human therapies. Mamm Genome 2019; 30:90-110. [PMID: 30820643 PMCID: PMC6606665 DOI: 10.1007/s00335-019-09793-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 02/09/2019] [Indexed: 02/06/2023]
Abstract
Rare diseases are very difficult to study mechanistically and to develop therapies for because of the scarcity of patients. Here, the rare neuro-metabolic disorder Rett syndrome (RTT) is discussed as a prototype for precision medicine, demonstrating how mouse models have led to an understanding of the development of symptoms. RTT is caused by mutations in the X-linked gene methyl-CpG-binding protein 2 (MECP2). Mecp2-mutant mice are being used in preclinical studies that target the MECP2 gene directly, or its downstream pathways. Importantly, this work may improve the health of RTT patients. Clinical presentation may vary widely among individuals based on their mutation, but also because of the degree of X chromosome inactivation and the presence of modifier genes. Because it is a complex disorder involving many organ systems, it is likely that recovery of RTT patients will involve a combination of treatments. Precision medicine is warranted to provide the best efficacy to individually treat RTT patients.
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Davis MR, Magnusson JL, Cummings KJ. Increased central cholinergic drive contributes to the apneas of serotonin-deficient rat pups during active sleep. J Appl Physiol (1985) 2019; 126:1175-1183. [PMID: 30763168 DOI: 10.1152/japplphysiol.00909.2018] [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] [Indexed: 12/13/2022] Open
Abstract
Infant rat pups lacking central nervous system (CNS) serotonin (5-hydroxytryptamine; 5-HT) have unstable breathing during prolonged periods of active sleep. Given that cholinergic neurons are drivers of active sleep and project to respiratory patterning regions in the brainstem, we hypothesized that 5-HT preserves respiratory stability in active sleep by dampening central cholinergic drive. We used whole-body plethysmography coupled with nuchal electromyography to monitor the breathing pattern of 2-wk-old tryptophan hydroxylase 2 (TPH2)+/+ and TPH2-deficient (TPH2-/-) pups in active sleep, before and after muscarinic blockade. For the group 1 experiment we injected methylatropine (Ap-M), a CNS-impermeant form of atropine, followed ~30 min later by an injection of atropine sulfate (Ap-S), the CNS-permeant form (both 1 mg/kg, 10 μl bolus iv); both injections occurred within an active sleep episode. We analyzed the effect of each drug on the coefficient of variation of the respiratory period (CV-P) during active sleep. For the group 2 experiment rats were cycled through several episodes of active and quiet sleep before administration of Ap-S (1 mg/kg, 200 μl ip) or vehicle. We assessed the effect of Ap-S on the apnea indices of both genotypes during quiet and active sleep. In group 1 Ap-S significantly reduced the CV-P of TPH2-/- pups (P = 0.03), an effect not observed in TPH2+/+ pups or following Ap-M. In group 2 the apnea index of TPH2-/- pups was significantly reduced following Ap-S injection (P = 0.04), whereas the apnea index of TPH2+/+ littermates was unaffected (P = 0.58). These findings suggest that central 5-HT reduces apnea and stabilizes breathing by reducing cholinergic signaling through muscarinic receptors. NEW & NOTEWORTHY Serotonin in the central nervous system (CNS) is necessary for maintaining the stability of breathing in the early postnatal period, particularly during active sleep. Here we show that the administration of atropine to the CNS selectively stabilizes the respiratory pattern of tryptophan hydroxylase 2-deficient rat pups and reduces their apneas. This suggests that CNS serotonin stabilizes breathing at least in part by reducing central cholinergic drive.
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Affiliation(s)
- Marina R Davis
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri , Columbia, Missouri
| | - Jennifer L Magnusson
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri , Columbia, Missouri
| | - Kevin J Cummings
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri , Columbia, Missouri
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28
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Abstract
Rhythmicity is a universal timing mechanism in the brain, and the rhythmogenic mechanisms are generally dynamic. This is illustrated for the neuronal control of breathing, a behavior that occurs as a one-, two-, or three-phase rhythm. Each breath is assembled stochastically, and increasing evidence suggests that each phase can be generated independently by a dedicated excitatory microcircuit. Within each microcircuit, rhythmicity emerges through three entangled mechanisms: ( a) glutamatergic transmission, which is amplified by ( b) intrinsic bursting and opposed by ( c) concurrent inhibition. This rhythmogenic triangle is dynamically tuned by neuromodulators and other network interactions. The ability of coupled oscillators to reconfigure and recombine may allow breathing to remain robust yet plastic enough to conform to nonventilatory behaviors such as vocalization, swallowing, and coughing. Lessons learned from the respiratory network may translate to other highly dynamic and integrated rhythmic systems, if approached one breath at a time.
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Affiliation(s)
- Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington 98101, USA;
| | - Nathan A Baertsch
- Center for Integrative Brain Research, Seattle Children's Research Institute, Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington 98101, USA;
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29
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Silva TM, Aranda LC, Paula-Ribeiro M, Oliveira DM, Medeiros WM, Vianna LC, Nery LE, Silva BM. Hyperadditive ventilatory response arising from interaction between the carotid chemoreflex and the muscle mechanoreflex in healthy humans. J Appl Physiol (1985) 2018; 125:215-225. [PMID: 29565769 DOI: 10.1152/japplphysiol.00009.2018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Physical exercise potentiates the carotid chemoreflex control of ventilation (VE). Hyperadditive neural interactions may partially mediate the potentiation. However, some neural interactions remain incompletely explored. As the potentiation occurs even during low-intensity exercise, we tested the hypothesis that the carotid chemoreflex and the muscle mechanoreflex could interact in a hyperadditive fashion. Fourteen young healthy subjects inhaled randomly, in separate visits, 12% O2 to stimulate the carotid chemoreflex and 21% O2 as control. A rebreathing circuit maintained isocapnia. During gases administration, subjects either remained at rest (i.e., normoxic and hypoxic rest) or the muscle mechanoreflex was stimulated via passive knee movement (i.e., normoxic and hypoxic movement). Surface muscle electrical activity did not increase during the passive movement, confirming the absence of active contractions. Hypoxic rest and normoxic movement similarly increased VE [change (mean ± SE) = 1.24 ± 0.72 vs. 0.73 ± 0.43 l/min, respectively; P = 0.46], but hypoxic rest only increased tidal volume (Vt), and normoxic movement only increased breathing frequency (BF). Hypoxic movement induced greater VE and mean inspiratory flow (Vt/Ti) increase than the sum of hypoxic rest and normoxic movement isolated responses (VE change: hypoxic movement = 3.72 ± 0.81 l/min vs. sum = 1.96 ± 0.83 l/min, P = 0.01; Vt/Ti change: hypoxic movement = 0.13 ± 0.03 l/s vs. sum = 0.06 ± 0.03 l/s, P = 0.02). Moreover, hypoxic movement increased both Vt and BF. Collectively, the results indicate that the carotid chemoreflex and the muscle mechanoreflex interacted, mediating a hyperadditive ventilatory response in healthy humans. NEW & NOTEWORTHY The main finding of this study was that concomitant carotid chemoreflex and muscle mechanoreflex stimulation provoked greater ventilation increase than the sum of ventilation increase induced by stimulation of each reflex in isolation, which, consequently, supports that the carotid chemoreflex and the muscle mechanoreflex interacted, mediating a hyperadditive ventilatory response in healthy humans.
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Affiliation(s)
- Talita M Silva
- Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Postgraduate Program in Pulmonary Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Division of Exercise Physiology, Department of Physiology, Federal University of São Paulo , Brazil
| | - Liliane C Aranda
- Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Postgraduate Program in Pulmonary Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Division of Exercise Physiology, Department of Physiology, Federal University of São Paulo , Brazil
| | - Marcelle Paula-Ribeiro
- Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Division of Exercise Physiology, Department of Physiology, Federal University of São Paulo , Brazil.,Postgraduate Program in Translational Medicine, Department of Medicine, Federal University of São Paulo , Brazil
| | - Diogo M Oliveira
- Division of Exercise Physiology, Department of Physiology, Federal University of São Paulo , Brazil.,Postgraduate Program in Translational Medicine, Department of Medicine, Federal University of São Paulo , Brazil
| | - Wladimir M Medeiros
- Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Postgraduate Program in Pulmonary Medicine, Department of Medicine, Federal University of São Paulo , Brazil
| | - Lauro C Vianna
- Faculty of Physical Education, University of Brasilia, Federal District, Brazil
| | - Luiz E Nery
- Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Postgraduate Program in Pulmonary Medicine, Department of Medicine, Federal University of São Paulo , Brazil
| | - Bruno M Silva
- Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Postgraduate Program in Pulmonary Medicine, Department of Medicine, Federal University of São Paulo , Brazil.,Division of Exercise Physiology, Department of Physiology, Federal University of São Paulo , Brazil.,Postgraduate Program in Translational Medicine, Department of Medicine, Federal University of São Paulo , Brazil
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30
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Jiang C, Cui N, Zhong W, Johnson CM, Wu Y. Breathing abnormalities in animal models of Rett syndrome a female neurogenetic disorder. Respir Physiol Neurobiol 2017; 245:45-52. [PMID: 27884797 PMCID: PMC5438903 DOI: 10.1016/j.resp.2016.11.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 11/17/2016] [Accepted: 11/20/2016] [Indexed: 02/08/2023]
Abstract
A characteristic feature of Rett syndrome (RTT) is abnormal breathing accompanied by several other neurological and cognitive disorders. Since RTT rodent models became available, studies have begun shedding insight into the breathing abnormalities at behavioral, cellular and molecular levels. Defects are found in several groups of brainstem neurons involved in respiratory control, and potential neural mechanisms have been suggested. The findings in animal models are helpful in therapeutic strategies for people with RTT with respect to lowering sudden and unexpected death, preventing secondary developmental consequences, and improving the quality of lives.
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Affiliation(s)
- Chun Jiang
- Department of Biology, Georgia State University, Atlanta, USA.
| | - Ningren Cui
- Department of Biology, Georgia State University, Atlanta, USA
| | - Weiwei Zhong
- Department of Biology, Georgia State University, Atlanta, USA
| | | | - Yang Wu
- Department of Biology, Georgia State University, Atlanta, USA
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31
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Howell CJ, Sceniak MP, Lang M, Krakowiecki W, Abouelsoud FE, Lad SU, Yu H, Katz DM. Activation of the Medial Prefrontal Cortex Reverses Cognitive and Respiratory Symptoms in a Mouse Model of Rett Syndrome. eNeuro 2017; 4:ENEURO.0277-17.2017. [PMID: 29333487 PMCID: PMC5762598 DOI: 10.1523/eneuro.0277-17.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 11/27/2017] [Accepted: 12/01/2017] [Indexed: 12/30/2022] Open
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder caused by loss-of-function mutations in the gene encoding methyl-CpG-binding protein 2 (MeCP2; Amir et al., 1999), a transcriptional regulatory protein (Klose et al., 2005). Mouse models of RTT (Mecp2 mutants) exhibit excitatory hypoconnectivity in the medial prefrontal cortex (mPFC; Sceniak et al., 2015), a region critical for functions that are abnormal in RTT patients, ranging from learning and memory to regulation of visceral homeostasis (Riga et al., 2014). The present study was designed to test the hypothesis that increasing the activity of mPFC pyramidal neurons in heterozygous female Mecp2 mutants (Hets) would ameliorate RTT-like symptoms, including deficits in respiratory control and long-term retrieval of auditory conditioned fear. Selective activation of mPFC pyramidal neurons in adult animals was achieved by bilateral infection with an AAV8 vector expressing excitatory hm3D(Gq) DREADD (Designer Receptors Exclusively Activated by Designer Drugs) (Armbruster et al., 2007) under the control of the CamKIIa promoter. DREADD activation in Mecp2 Hets completely restored long-term retrieval of auditory conditioned fear, eliminated respiratory apneas, and reduced respiratory frequency variability to wild-type (Wt) levels. Reversal of respiratory symptoms following mPFC activation was associated with normalization of Fos protein levels, a marker of neuronal activity, in a subset of brainstem respiratory neurons. Thus, despite reduced levels of MeCP2 and severe neurological deficits, mPFC circuits in Het mice are sufficiently intact to generate normal behavioral output when pyramidal cell activity is increased. These findings highlight the contribution of mPFC hypofunction to the pathophysiology of RTT and raise the possibility that selective activation of cortical regions such as the mPFC could provide therapeutic benefit to RTT patients.
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Affiliation(s)
- C James Howell
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Michael P Sceniak
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Min Lang
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Wenceslas Krakowiecki
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Fatimah E Abouelsoud
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Saloni U Lad
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Heping Yu
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - David M Katz
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106
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32
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Barnett WH, Jenkin SEM, Milsom WK, Paton JFR, Abdala AP, Molkov YI, Zoccal DB. The Kölliker-Fuse nucleus orchestrates the timing of expiratory abdominal nerve bursting. J Neurophysiol 2017; 119:401-412. [PMID: 29070631 DOI: 10.1152/jn.00499.2017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Coordination of respiratory pump and valve muscle activity is essential for normal breathing. A hallmark respiratory response to hypercapnia and hypoxia is the emergence of active exhalation, characterized by abdominal muscle pumping during the late one-third of expiration (late-E phase). Late-E abdominal activity during hypercapnia has been attributed to the activation of expiratory neurons located within the parafacial respiratory group (pFRG). However, the mechanisms that control emergence of active exhalation, and its silencing in restful breathing, are not completely understood. We hypothesized that inputs from the Kölliker-Fuse nucleus (KF) control the emergence of late-E activity during hypercapnia. Previously, we reported that reversible inhibition of the KF reduced postinspiratory (post-I) motor output to laryngeal adductor muscles and brought forward the onset of hypercapnia-induced late-E abdominal activity. Here we explored the contribution of the KF for late-E abdominal recruitment during hypercapnia by pharmacologically disinhibiting the KF in in situ decerebrate arterially perfused rat preparations. These data were combined with previous results and incorporated into a computational model of the respiratory central pattern generator. Disinhibition of the KF through local parenchymal microinjections of gabazine (GABAA receptor antagonist) prolonged vagal post-I activity and inhibited late-E abdominal output during hypercapnia. In silico, we reproduced this behavior and predicted a mechanism in which the KF provides excitatory drive to post-I inhibitory neurons, which in turn inhibit late-E neurons of the pFRG. Although the exact mechanism proposed by the model requires testing, our data confirm that the KF modulates the formation of late-E abdominal activity during hypercapnia. NEW & NOTEWORTHY The pons is essential for the formation of the three-phase respiratory pattern, controlling the inspiratory-expiratory phase transition. We provide functional evidence of a novel role for the Kölliker-Fuse nucleus (KF) controlling the emergence of abdominal expiratory bursts during active expiration. A computational model of the respiratory central pattern generator predicts a possible mechanism by which the KF interacts indirectly with the parafacial respiratory group and exerts an inhibitory effect on the expiratory conditional oscillator.
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Affiliation(s)
- William H Barnett
- Department of Mathematics and Statistics, Georgia State University , Atlanta, Georgia
| | - Sarah E M Jenkin
- Department of Zoology, University of British Columbia , Vancouver, British Columbia , Canada
| | - William K Milsom
- Department of Zoology, University of British Columbia , Vancouver, British Columbia , Canada
| | - Julian F R Paton
- School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol , Bristol , United Kingdom.,Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland , Auckland , New Zealand
| | - Ana P Abdala
- School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol , Bristol , United Kingdom
| | - Yaroslav I Molkov
- Department of Mathematics and Statistics, Georgia State University , Atlanta, Georgia.,Neuroscience Institute, Georgia State University , Atlanta, Georgia
| | - Daniel B Zoccal
- Department of Physiology and Pathology, São Paulo State University , Araraquara , Brazil
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33
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Chen CY, Di Lucente J, Lin YC, Lien CC, Rogawski MA, Maezawa I, Jin LW. Defective GABAergic neurotransmission in the nucleus tractus solitarius in Mecp2-null mice, a model of Rett syndrome. Neurobiol Dis 2017; 109:25-32. [PMID: 28927958 DOI: 10.1016/j.nbd.2017.09.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 08/14/2017] [Accepted: 09/14/2017] [Indexed: 01/12/2023] Open
Abstract
Rett syndrome (RTT) is a devastating neurodevelopmental disorder caused by loss-of-function mutations in the X-linked methyl-CpG binding protein 2 (Mecp2) gene. GABAergic dysfunction has been implicated contributing to the respiratory dysfunction, one major clinical feature of RTT. The nucleus tractus solitarius (NTS) is the first central site integrating respiratory sensory information that can change the nature of the reflex output. We hypothesized that deficiency in Mecp2 gene reduces GABAergic neurotransmission in the NTS. Using whole-cell patch-clamp recordings in NTS slices, we measured spontaneous inhibitory postsynaptic currents (sIPSCs), miniature IPSCs (mIPSCs), NTS-evoked IPSCs (eIPSCs), and GABAA receptor (GABAA-R) agonist-induced responses. Compared to those from wild-type mice, NTS neurons from Mecp2-null mice had significantly (p<0.05) reduced sIPSC amplitude, sIPSC frequency, and mIPSC amplitude but not mIPSC frequency. Mecp2-null mice also had decreased eIPSC amplitude with no change in paired-pulse ratio. The data suggest reduced synaptic receptor-mediated phasic GABA transmission in Mecp2-null mice. In contrast, muscimol (GABAA-R agonist, 0.3-100μM) and THIP (selective extrasynaptic GABAA-R agonist, 5μM) induced significantly greater current response in Mecp2-null mice, suggesting increased extrasynaptic receptors. Using qPCR, we found a 2.5 fold increase in the delta subunit of the GABAA-Rs in the NTS in Mecp2-null mice, consistent with increased extrasynaptic receptors. As the NTS was recently found required for respiratory pathology in RTT, our results provide a mechanism for NTS dysfunction which involves shifting the balance of synaptic/extrasynaptic receptors in favor of extrasynaptic site, providing a target for boosting GABAergic inhibition in RTT.
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Affiliation(s)
- Chao-Yin Chen
- Department of Pharmacology, University of California Davis, One Shields Avenue, Davis, CA 95616, United States.
| | - Jacopo Di Lucente
- Department of Pathology and Laboratory Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Yen-Chu Lin
- Department of Pathology and Laboratory Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Cheng-Chang Lien
- Institute of Neuroscience, National Yang-Ming University, Taipei 112, Taiwan
| | - Michael A Rogawski
- Department of Neurology, University of California Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Izumi Maezawa
- Department of Pathology and Laboratory Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, United States; M.I.N.D. (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Lee-Way Jin
- Department of Pathology and Laboratory Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, United States; M.I.N.D. (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California Davis, One Shields Avenue, Davis, CA 95616, United States.
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34
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Tipton MJ, Harper A, Paton JFR, Costello JT. The human ventilatory response to stress: rate or depth? J Physiol 2017. [PMID: 28650070 DOI: 10.1113/jp274596] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Many stressors cause an increase in ventilation in humans. This is predominantly reported as an increase in minute ventilation (V̇E). But, the same V̇E can be achieved by a wide variety of changes in the depth (tidal volume, VT ) and number of breaths (respiratory frequency, ƒR ). This review investigates the impact of stressors including: cold, heat, hypoxia, pain and panic on the contributions of ƒR and VT to V̇E to see if they differ with different stressors. Where possible we also consider the potential mechanisms that underpin the responses identified, and propose mechanisms by which differences in ƒR and VT are mediated. Our aim being to consider if there is an overall differential control of ƒR and VT that applies in a wide range of conditions. We consider moderating factors, including exercise, sex, intensity and duration of stimuli. For the stressors reviewed, as the stress becomes extreme V̇E generally becomes increased more by ƒR than VT . We also present some tentative evidence that the pattern of ƒR and VT could provide some useful diagnostic information for a variety of clinical conditions. In The Physiological Society's year of 'Making Sense of Stress', this review has wide-ranging implications that are not limited to one discipline, but are integrative and relevant for physiology, psychophysiology, neuroscience and pathophysiology.
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Affiliation(s)
- Michael J Tipton
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, PO1 2ER, UK
| | - Abbi Harper
- Clinical Fellow in Intensive Care Medicine, Southmead Hospital, Bristol, BS10 5NB, UK
| | - Julian F R Paton
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences, University Walk, University of Bristol, Bristol, BS8 1TD, UK
| | - Joseph T Costello
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, PO1 2ER, UK
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35
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Peng J. [MECP2 gene and MECP2-related diseases]. ZHONGGUO DANG DAI ER KE ZA ZHI = CHINESE JOURNAL OF CONTEMPORARY PEDIATRICS 2017; 19:494-497. [PMID: 28506335 PMCID: PMC7389123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 03/10/2017] [Indexed: 08/01/2024]
Affiliation(s)
- Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha 410008, China
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Peng J. [MECP2 gene and MECP2-related diseases]. ZHONGGUO DANG DAI ER KE ZA ZHI = CHINESE JOURNAL OF CONTEMPORARY PEDIATRICS 2017; 19:494-497. [PMID: 28506335 PMCID: PMC7389123 DOI: 10.7499/j.issn.1008-8830.2017.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 03/10/2017] [Indexed: 06/07/2023]
Affiliation(s)
- Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha 410008, China
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Mackay J, Downs J, Wong K, Heyworth J, Epstein A, Leonard H. Autonomic breathing abnormalities in Rett syndrome: caregiver perspectives in an international database study. J Neurodev Disord 2017; 9:15. [PMID: 28465761 PMCID: PMC5410057 DOI: 10.1186/s11689-017-9196-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 04/21/2017] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Rett syndrome is a severe neurodevelopmental disorder associated with mutations in the MECP2 gene. Irregular breathing patterns and abdominal bloating are prominent but poorly understood features. Our aims were to characterize the abnormal breathing patterns and abdominal bloating, investigate the distribution of these by age and mutation type and examine their impact and management from a caregiver perspective. METHODS We invited previously recruited families from the International Rett Syndrome Study to complete a web-based questionnaire concerning their family member with Rett syndrome aged between 2 and 57 years. We used logistic regression to investigate presence, frequency and impact of breath-holding, hyperventilation, or abdominal bloating by age group and mutation type. Age of onset for both breathing abnormalities was investigated using time-to-onset analysis, and the Kaplan-Meier method was used to estimate the failure function for the study sample. Descriptive statistics were used to characterize the management of irregular breathing. RESULTS Questionnaires were returned by 413/482 (85.7%) families. Breath-holding was reported for 68.8%, hyperventilation for 46.4% and abdominal bloating for 42.4%. Hyperventilation was more prevalent and frequent in those younger than 7 years of age and abdominal bloating in those aged over 20 years. Onset of breathing irregularities usually occurred during early childhood. Caregivers perceived that daily life was considerably impacted for almost half (44.1%) of those with abdominal bloating and in just over than a third of those with breath-holding (35.8%) or hyperventilation (35.1%). Although perceived impact was broadly comparable between age and mutation groups for breath-holding, hyperventilation and abdominal bloating, girls and women with a p.Arg294* mutation were considered to be more affected by all three conditions. Only 31 individuals had received medically prescribed treatments including 12 different medications, added oxygen, rebreathing apparatus or non-invasive ventilation. CONCLUSIONS Autonomic disturbances are prevalent and burdensome in Rett syndrome. This information may guide the design of inclusion criteria and outcome measures for clinical intervention trials targeting autonomic abnormalities. Further investigation of available treatments is necessary to delineate evidence-based management pathways.
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Affiliation(s)
- Jessica Mackay
- Telethon Kids Institute, The University of Western Australia, PO Box 855, West Perth, WA 6872 Australia
- School of Population Health, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 Australia
| | - Jenny Downs
- Telethon Kids Institute, The University of Western Australia, PO Box 855, West Perth, WA 6872 Australia
- School of Physiotherapy and Exercise Science, Curtin University, GPO Box U1987, Perth, WA 6845 Australia
| | - Kingsley Wong
- Telethon Kids Institute, The University of Western Australia, PO Box 855, West Perth, WA 6872 Australia
| | - Jane Heyworth
- School of Population Health, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 Australia
| | - Amy Epstein
- Telethon Kids Institute, The University of Western Australia, PO Box 855, West Perth, WA 6872 Australia
| | - Helen Leonard
- Telethon Kids Institute, The University of Western Australia, PO Box 855, West Perth, WA 6872 Australia
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Effects of chronic exposure to low dose THIP on brainstem neuronal excitability in mouse models of Rett syndrome: Evidence from symptomatic females. Neuropharmacology 2017; 116:288-299. [PMID: 28069353 DOI: 10.1016/j.neuropharm.2017.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 12/10/2016] [Accepted: 01/04/2017] [Indexed: 01/17/2023]
Abstract
Rett Syndrome (RTT) is a neurodevelopmental disorder caused by mutations of the MECP2 gene, affecting predominantly females. One of the characteristic features of the disease is defective brainstem autonomic function. In Mecp2-/Y mice, several groups of brainstem neurons are overly excitable, which causes destabilization of neuronal networks for the autonomic control. We have previously shown that the extrasynaptic GABAA receptor agonist THIP relieves many RTT-like symptoms in Mecp2-/Y mice. Although neuronal activity is inhibited by acute THIP exposure, how a chronic treatment affects neuronal excitability remains elusive. Thus, we performed studies to address whether increased excitability occurs in brainstem neurons of female Mecp2+/- mice, how the MeCP expression affects the neuronal excitability, and whether chronic THIP exposure improves the neuronal hyperexcitability. Symptomatic Mecp2+/- (sMecp2+/-) female mice were identified with a two-step screening system. Whole-cell recording was performed in brain slices after a prior exposure of the sMecp2+/- mice to a 5-week low-dose THIP. Neurons in the locus coeruleus (LC) and the mesencephalic trigeminal nucleus (Me5) showed excessive firing activity in the sMecp2+/- mice. THIP pretreatment reduced the hyperexcitability of both LC and Me5 neurons in the sMecp2+/- mice, to a similar level as their counterparts in Mecp2-/Y mice. In identified LC neurons, the hyperexcitability appeared to be determined by not only the MeCP2 expression, but also their environmental cues. The alleviation of LC neuronal hyperexcitability seems to benefit brainstem autonomic function as THIP also improved breathing abnormalities of these sMecp2+/- mice.
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Dhingra RR, Dutschmann M, Galán RF, Dick TE. Kölliker-Fuse nuclei regulate respiratory rhythm variability via a gain-control mechanism. Am J Physiol Regul Integr Comp Physiol 2016; 312:R172-R188. [PMID: 27974314 DOI: 10.1152/ajpregu.00238.2016] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 11/14/2016] [Accepted: 12/11/2016] [Indexed: 11/22/2022]
Abstract
Respiration varies from breath to breath. On the millisecond timescale of spiking, neuronal circuits exhibit variability due to the stochastic properties of ion channels and synapses. Does this fast, microscopic source of variability contribute to the slower, macroscopic variability of the respiratory period? To address this question, we modeled a stochastic oscillator with forcing; then, we tested its predictions experimentally for the respiratory rhythm generated by the in situ perfused preparation during vagal nerve stimulation (VNS). Our simulations identified a relationship among the gain of the input, entrainment strength, and rhythm variability. Specifically, at high gain, the periodic input entrained the oscillator and reduced variability, whereas at low gain, the noise interacted with the input, causing events known as "phase slips", which increased variability on a slow timescale. Experimentally, the in situ preparation behaved like the low-gain model: VNS entrained respiration but exhibited phase slips that increased rhythm variability. Next, we used bilateral muscimol microinjections in discrete respiratory compartments to identify areas involved in VNS gain control. Suppression of activity in the nucleus tractus solitarii occluded both entrainment and amplification of rhythm variability by VNS, confirming that these effects were due to the activation of the Hering-Breuer reflex. Suppressing activity of the Kölliker-Fuse nuclei (KFn) enhanced entrainment and reduced rhythm variability during VNS, consistent with the predictions of the high-gain model. Together, the model and experiments suggest that the KFn regulates respiratory rhythm variability via a gain control mechanism.
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Affiliation(s)
- Rishi R Dhingra
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio.,Division of Pulmonary, Critical Care & Sleep, Department of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Mathias Dutschmann
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia; and
| | - Roberto F Galán
- Department of Electrical Engineering and Computer Science, School of Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Thomas E Dick
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio; .,Division of Pulmonary, Critical Care & Sleep, Department of Medicine, Case Western Reserve University, Cleveland, Ohio
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Gillombardo CB, Darrah R, Dick TE, Moore M, Kong N, Decker MJ, Han F, Yamauchi M, Dutschmann M, Azzam S, Strohl KP. C57BL/6J mouse apolipoprotein A2 gene is deterministic for apnea. Respir Physiol Neurobiol 2016; 235:88-94. [PMID: 27756649 DOI: 10.1016/j.resp.2016.10.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Revised: 09/30/2016] [Accepted: 10/11/2016] [Indexed: 11/16/2022]
Abstract
RATIONALE Brainstem apolipoprotein AII (apoa2) mRNA expression correlates with apnea in breathing present in the adult C57Bl/6J (B6) sleep apnea model. OBJECTIVES To test the hypothesis that the B6 apoa2 gene contributes to the trait, we performed plethysmographic testing in apoa2 knock out (KO: -/-) mice, an in situ brainstem-spinal cord preparation comparing KO to WT (+/+) mice, and B6xDBA recombinant inbred strains (RISs). MEASUREMENTS AND MAIN RESULTS Apoa2 WT do, but KO and heterozygote (+/-) mice do not exhibit apnea during post-hypoxic breathing, measured in vivo. In the in situ model, pauses and instability in fictive phrenic bursting are substantially reduced in KO vs. WT preparations. In 24 RISs, apnea number in vivo was higher in strains with B6 apoa2 than with DBA apoa2 alleles. CONCLUSIONS The B6 apoa2 polymorphism is directly involved in breath production, and its identification suggests a novel pathway influencing risk for adult sleep apnea.
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Affiliation(s)
- Carl B Gillombardo
- Department of Medicine, Cleveland Clinic Foundation, Cleveland, OH, United States
| | - Rebecca Darrah
- Department of Genetics and Genome Science, Case Western Reserve University, Cleveland, OH, United States
| | - Thomas E Dick
- Department of Medicine, University Hospitals Case Medical Center, Cleveland, OH, United States; School of Medicine, Case Western Reserve University, Cleveland, OH, United States
| | - Michael Moore
- Department of Medicine, University Hospitals Case Medical Center, Cleveland, OH, United States
| | - Nathan Kong
- Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Michael J Decker
- Francis Payne Bolton School of Nursing, Case Western Reserve University, Cleveland, OH, United States
| | - Fang Han
- People's Hospital, Beijing Medical University, Beijing, China
| | | | - Mathias Dutschmann
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Australia
| | - Sausan Azzam
- Department of Nutrition, Case School of Medicine, Cleveland, OH, United States
| | - Kingman P Strohl
- Department of Medicine, University Hospitals Case Medical Center, Cleveland, OH, United States; School of Medicine, Case Western Reserve University, Cleveland, OH, United States.
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Hülsmann S, Mesuret G, Dannenberg J, Arnoldt M, Niebert M. GlyT2-Dependent Preservation of MECP2-Expression in Inhibitory Neurons Improves Early Respiratory Symptoms but Does Not Rescue Survival in a Mouse Model of Rett Syndrome. Front Physiol 2016; 7:385. [PMID: 27672368 PMCID: PMC5018520 DOI: 10.3389/fphys.2016.00385] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 08/22/2016] [Indexed: 11/25/2022] Open
Abstract
Mutations in methyl-CpG-binding protein 2 (MECP2) gene have been shown to manifest in a neurodevelopmental disorder that is called Rett syndrome. A typical problem that occurs during development is a disturbance of breathing. To address the role of inhibitory neurons, we generated a mouse line that restores MECP2 in inhibitory neurons in the brainstem by crossbreeding a mouse line that expresses the Cre-recombinase (Cre) in inhibitory neurons under the control of the glycine transporter 2 (GlyT2, slc6a5) promotor (GlyT2-Cre) with a mouse line that has a floxed-stop mutation of the Mecp2 gene (Mecp2stop/y). Unrestrained whole-body-plethysmography at postnatal day P60 revealed a low respiratory rate and prolonged respiratory pauses in Mecp2stop/y mice. In contrast, GlyT2-Cre positive Mecp2stop/y mice (Cre+; Mecp2stop/y) showed greatly improved respiration and were indistinguishable from wild type littermates. These data support the concept that alterations in inhibitory neurons are important for the development of the respiratory phenotype in Rett syndrome.
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Affiliation(s)
- Swen Hülsmann
- Clinic for Anesthesiology, University Medical CenterGöttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the BrainGöttingen, Germany
| | - Guillaume Mesuret
- Clinic for Anesthesiology, University Medical CenterGöttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the BrainGöttingen, Germany
| | - Julia Dannenberg
- Clinic for Anesthesiology, University Medical Center Göttingen, Germany
| | - Mauricio Arnoldt
- Clinic for Anesthesiology, University Medical Center Göttingen, Germany
| | - Marcus Niebert
- Center for Nanoscale Microscopy and Molecular Physiology of the BrainGöttingen, Germany; Institute of Neuro- and Sensory Physiology, University Medical Center GöttingenGöttingen, Germany
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Kaufmann WE, Stallworth JL, Everman DB, Skinner SA. Neurobiologically-based treatments in Rett syndrome: opportunities and challenges. Expert Opin Orphan Drugs 2016; 4:1043-1055. [PMID: 28163986 PMCID: PMC5214376 DOI: 10.1080/21678707.2016.1229181] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 08/23/2016] [Indexed: 12/14/2022]
Abstract
Introduction: Rett syndrome (RTT) is an X-linked neurodevelopmental disorder that primarily affects females, typically resulting in a period of developmental regression in early childhood followed by stabilization and severe chronic cognitive, behavioral, and physical disability. No known treatment exists beyond symptomatic management, and while insights into the genetic cause, pathophysiology, neurobiology, and natural history of RTT have been gained, many challenges remain. Areas covered: Based on a comprehensive survey of the primary literature on RTT, this article describes and comments upon the general and unique features of the disorder, genetic and neurobiological bases of drug development, and the history of clinical trials in RTT, with an emphasis on drug trial design, outcome measures, and implementation. Expert opinion: Neurobiologically based drug trials are the ultimate goal in RTT, and due to the complexity and global nature of the disorder, drugs targeting both general mechanisms (e.g., growth factors) and specific systems (e.g., glutamate modulators) could be effective. Trial design should optimize data on safety and efficacy, but selection of outcome measures with adequate measurement properties, as well as innovative strategies, such as those enhancing synaptic plasticity and use of biomarkers, are essential for progress in RTT and other neurodevelopmental disorders.
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Affiliation(s)
- Walter E Kaufmann
- Center for Translational Research, Greenwood Genetic Center, Greenwood, SC, USA; Department of Neurology, Boston Children's Hospital, Boston, MA, USA
| | | | - David B Everman
- Center for Translational Research, Greenwood Genetic Center , Greenwood , SC , USA
| | - Steven A Skinner
- Center for Translational Research, Greenwood Genetic Center , Greenwood , SC , USA
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Silva JN, Lucena EV, Silva TM, Damasceno RS, Takakura AC, Moreira TS. Inhibition of the pontine Kölliker-Fuse nucleus reduces genioglossal activity elicited by stimulation of the retrotrapezoid chemoreceptor neurons. Neuroscience 2016; 328:9-21. [PMID: 27126558 DOI: 10.1016/j.neuroscience.2016.04.028] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 04/16/2016] [Accepted: 04/18/2016] [Indexed: 01/06/2023]
Abstract
The Kölliker-Fuse (KF) region, located in the dorsolateral pons, projects to several brainstem areas involved in respiratory regulation, including the chemoreceptor neurons within the retrotrapezoid nucleus (RTN). Several lines of evidence indicate that the pontine KF region plays an important role in the control of the upper airways for the maintenance of appropriate airflow to and from the lungs. Specifically, we hypothesized that the KF region is involved in mediating the response of the hypoglossal motor activity to central respiratory chemoreflex activation and to stimulation of the chemoreceptor neurons within the RTN region. To test this hypothesis, we combined immunohistochemistry and physiological experiments. We found that in the KF, the majority of biotinylated dextran amine (BDA)-labeled axonal varicosities contained detectable levels of vesicular glutamate transporter-2 (VGLUT2), but few contained glutamic acid decarboxylase-67 (GAD67). The majority of the RTN neurons that were FluorGold (FG)-immunoreactive (i.e., projected to the KF) contained hypercapnia-induced Fos, but did not express tyrosine hydroxylase. In urethane-anesthetized sino-aortic denervated and vagotomized male Wistar rats, hypercapnia (10% CO2) or N-methyl-d-aspartate (NMDA) injection (0.1mM) in the RTN increased diaphragm (DiaEMG) and genioglossus muscle (GGEMG) activities and elicited abdominal (AbdEMG) activity. Bilateral injection of muscimol (GABA-A agonist; 2mM) into the KF region reduced the increase in DiaEMG and GGEMG produced by hypercapnia or NMDA into the RTN. Our data suggest that activation of chemoreceptor neurons in the RTN produces a significant increase in the genioglossus muscle activity and the excitatory pathway is dependent on the neurons located in the dorsolateral pontine KF region.
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Affiliation(s)
- Josiane N Silva
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo (USP), 05508-000 São Paulo/SP, Brazil
| | - Elvis V Lucena
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo (USP), 05508-000 São Paulo/SP, Brazil
| | - Talita M Silva
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo (USP), 05508-000 São Paulo/SP, Brazil
| | - Rosélia S Damasceno
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo (USP), 05508-000 São Paulo/SP, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo (USP), 05508-000 São Paulo/SP, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo (USP), 05508-000 São Paulo/SP, Brazil.
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Excitatory synapses are stronger in the hippocampus of Rett syndrome mice due to altered synaptic trafficking of AMPA-type glutamate receptors. Proc Natl Acad Sci U S A 2016; 113:E1575-84. [PMID: 26929363 DOI: 10.1073/pnas.1517244113] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Deficits in long-term potentiation (LTP) at central excitatory synapses are thought to contribute to cognitive impairments in neurodevelopmental disorders associated with intellectual disability and autism. Using the methyl-CpG-binding protein 2 (Mecp2) knockout (KO) mouse model of Rett syndrome, we show that naïve excitatory synapses onto hippocampal pyramidal neurons of symptomatic mice have all of the hallmarks of potentiated synapses. Stronger Mecp2 KO synapses failed to undergo LTP after either theta-burst afferent stimulation or pairing afferent stimulation with postsynaptic depolarization. On the other hand, basal synaptic strength and LTP were not affected in slices from younger presymptomatic Mecp2 KO mice. Furthermore, spine synapses in pyramidal neurons from symptomatic Mecp2 KO are larger and do not grow in size or incorporate GluA1 subunits after electrical or chemical LTP. Our data suggest that LTP is occluded in Mecp2 KO mice by already potentiated synapses. The higher surface levels of GluA1-containing receptors are consistent with altered expression levels of proteins involved in AMPA receptor trafficking, suggesting previously unidentified targets for therapeutic intervention for Rett syndrome and other MECP2-related disorders.
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Blockade of dorsolateral pontine 5HT1A receptors destabilizes the respiratory rhythm in C57BL6/J wild-type mice. Respir Physiol Neurobiol 2016; 226:110-4. [PMID: 26840837 DOI: 10.1016/j.resp.2016.01.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 01/28/2016] [Accepted: 01/28/2016] [Indexed: 11/23/2022]
Abstract
The neurotransmitter serotonin (5HT) acting via 5HT1a receptors (5HT1aR) is a potent determinant of respiratory rhythm variability. Here, we address the 5HT1aR-dependent control of respiratory rhythm variability in C57BL6/J mice. Using the in situ perfused preparation, we compared the effects of systemic versus focal blockade of 5HT1aRs. Blocking 5HT1aRs in the Kölliker-Fuse nucleus (KFn) increased the occurrence of spontaneous apneas and accounted for the systemic effects of 5HT1aR antagonists. Further, 5HT1aRs of the KFn stabilized the respiratory rhythm's response to arterial chemoreflex perturbations; reducing the recovering time, e.g., the latency to return to the baseline pattern. Together, these results suggest that the KFn regulates both intrinsic and sensory determinants of respiratory rhythm variability.
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