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Toor RUAS, Sun QJ, Kumar NN, Le S, Hildreth CM, Phillips JK, McMullan S. Neurons in the Intermediate Reticular Nucleus Coordinate Postinspiratory Activity, Swallowing, and Respiratory-Sympathetic Coupling in the Rat. J Neurosci 2019; 39:9757-9766. [PMID: 31666354 PMCID: PMC6891060 DOI: 10.1523/jneurosci.0502-19.2019] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 10/04/2019] [Accepted: 10/15/2019] [Indexed: 11/21/2022] Open
Abstract
Breathing results from sequential recruitment of muscles in the expiratory, inspiratory, and postinspiratory (post-I) phases of the respiratory cycle. Here we investigate whether neurons in the medullary intermediate reticular nucleus (IRt) are components of a central pattern generator (CPG) that generates post-I activity in laryngeal adductors and vasomotor sympathetic nerves and interacts with other members of the central respiratory network to terminate inspiration. We first identified the region of the (male) rat IRt that contains the highest density of lightly cholinergic neurons, many of which are glutamatergic, which aligns well with the putative postinspiratory complex in the mouse (Anderson et al., 2016). Acute bilateral inhibition of this region reduced the amplitudes of post-I vagal and sympathetic nerve activities. However, although associated with reduced expiratory duration and increased respiratory frequency, IRt inhibition did not affect inspiratory duration or abolish the recruitment of post-I activity during acute hypoxemia as predicted. Rather than representing an independent CPG for post-I activity, we hypothesized that IRt neurons may instead function as a relay that distributes post-I activity generated elsewhere, and wondered whether they could be a site of integration for para-respiratory CPGs that drive the same outputs. Consistent with this idea, IRt inhibition blocked rhythmic motor and autonomic components of fictive swallow but not swallow-related apnea. Our data support a role for IRt neurons in the transmission of post-I and swallowing activity to motor and sympathetic outputs, but suggest that other mechanisms also contribute to the generation of post-I activity.SIGNIFICANCE STATEMENT Interactions between multiple coupled oscillators underlie a three-part respiratory cycle composed from inspiratory, postinspiratory (post-I), and late-expiratory phases. Central post-I activity terminates inspiration and activates laryngeal motoneurons. We investigate whether neurons in the intermediate reticular nucleus (IRt) form the central pattern generator (CPG) responsible for post-I activity. We confirm that IRt activity contributes to post-I motor and autonomic outputs, and find that IRt neurons are necessary for activation of the same outputs during swallow, but that they are not required for termination of inspiration or recruitment of post-I activity during hypoxemia. We conclude that this population may not represent a distinct CPG, but instead may function as a premotor relay that integrates activity generated by diverse respiratory and nonrespiratory CPGs.
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Affiliation(s)
- Rahat Ul Ain Summan Toor
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, 2109 New South Wales, Australia, and
| | - Qi-Jian Sun
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, 2109 New South Wales, Australia, and
| | - Natasha N Kumar
- Department of Pharmacology, School of Medical Science, University of New South Wales, 2052 New South Wales, Australia
| | - Sheng Le
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, 2109 New South Wales, Australia, and
| | - Cara M Hildreth
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, 2109 New South Wales, Australia, and
| | - Jacqueline K Phillips
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, 2109 New South Wales, Australia, and
| | - Simon McMullan
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, 2109 New South Wales, Australia, and
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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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The relationship between partial upper-airway obstruction and inter-breath transition period during sleep. Respir Physiol Neurobiol 2017; 244:32-40. [PMID: 28676331 DOI: 10.1016/j.resp.2017.06.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 06/16/2017] [Accepted: 06/21/2017] [Indexed: 11/27/2022]
Abstract
Short pauses or "transition-periods" at the end of expiration and prior to subsequent inspiration are commonly observed during sleep in humans. However, the role of transition periods in regulating ventilation during physiological challenges such as partial airway obstruction (PAO) has not been investigated. Twenty-nine obstructive sleep apnea patients and eight controls underwent overnight polysomnography with an epiglottic catheter. Sustained-PAO segments (increased epiglottic pressure over ≥5 breaths without increased peak inspiratory flow) and unobstructed reference segments were manually scored during apnea-free non-REM sleep. Nasal pressure data was computationally segmented into inspiratory (TI, shortest period achieving 95% inspiratory volume), expiratory (TE, shortest period achieving 95% expiratory volume), and inter-breath transition period (TTrans, period between TE and subsequent TI). Compared with reference segments, sustained-PAO segments had a mean relative reduction in TTrans (-24.7±17.6%, P<0.001), elevated TI (11.8±10.5%, P<0.001), and a small reduction in TE (-3.9±8.0, P≤0.05). Compensatory increases in inspiratory period during PAO are primarily explained by reduced transition period and not by reduced expiratory period.
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Jenkin SEM, Milsom WK, Zoccal DB. The Kölliker-Fuse nucleus acts as a timekeeper for late-expiratory abdominal activity. Neuroscience 2017; 348:63-72. [PMID: 28188852 PMCID: PMC5759332 DOI: 10.1016/j.neuroscience.2017.01.050] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 01/27/2017] [Accepted: 01/31/2017] [Indexed: 10/20/2022]
Abstract
While the transition from the inspiratory to the post-inspiratory (post-I) phase is dependent on the pons, little attention has been paid to understanding the role of the pontine respiratory nuclei, specifically the Kölliker-Fuse nucleus (KF), in transitioning from post-I to the late expiratory (late-E) activity seen with elevated respiratory drive. To elucidate this, we used the in situ working heart-brainstem preparation of juvenile male Holtzman rats and recorded from the vagus (cVN), phrenic (PN) and abdominal nerves (AbN) during baseline conditions and during chemoreflex activation [with potassium cyanide (KCN; n=13) or hypercapnia (8% CO2; n=10)] to recruit active expiration. Chemoreflex activation with KCN increased PN frequency and cVN post-I and AbN activities. The inhibition of KF with isoguvacine microinjections (10mM) attenuated the typical increase in PN frequency and cVN post-I activity, and amplified the AbN response. During hypercapnia, AbN late-E activity emerged in association with a significant reduction in expiratory time. KF inhibition during hypercapnia significantly decreased PN frequency and reduced the duration and amplitude of post-I cVN activity, while the onset of the AbN late-E bursts occurred significantly earlier. Our data reveal a negative relationship between KF-induced post-I and AbN late-E activities, suggesting that the KF coordinates the transition between post-I to late-E activity during conditions of elevated respiratory drive.
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Affiliation(s)
- Sarah E M Jenkin
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
| | - William K Milsom
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Daniel B Zoccal
- School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil
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Tachikawa S, Nakayama K, Nakamura S, Mochizuki A, Iijima T, Inoue T. Coordinated Respiratory Motor Activity in Nerves Innervating the Upper Airway Muscles in Rats. PLoS One 2016; 11:e0166436. [PMID: 27832132 PMCID: PMC5104329 DOI: 10.1371/journal.pone.0166436] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 10/28/2016] [Indexed: 12/02/2022] Open
Abstract
Maintaining the patency of the upper airway during breathing is of vital importance. The activity of various muscles is related to the patency of the upper airway. In the present study, we examined the respiratory motor activity in the efferent nerves innervating the upper airway muscles to determine the movements of the upper airway during respiration under normocapnic conditions (pH = 7.4) and in hypercapnic acidosis (pH = 7.2). Experiments were performed on arterially perfused decerebrate rats aged between postnatal days 21–35. We recorded the efferent nerve activity in a branch of the cervical spinal nerve innervating the infrahyoid muscles (CN), the hypoglossal nerve (HGN), the external branch of the superior laryngeal nerve (SLN), and the recurrent laryngeal nerve (RLN) with the phrenic nerve (PN). Inspiratory nerve discharges were observed in all these nerves under normocapnic conditions. The onset of inspiratory discharges in the CN and HGN was slightly prior to those in the SLN and RLN. When the CO2 concentration in the perfusate was increased from 5% to 8% to prepare for hypercapnic acidosis, the peak amplitudes of the inspiratory discharges in all the recorded nerves were increased. Moreover, hypercapnic acidosis induced pre-inspiratory discharges in the CN, HGN, SLN, and RLN. The onset of pre-inspiratory discharges in the CN, HGN, and SLN was prior to that of discharges in the RLN. These results suggest that the securing of the airway that occurs a certain time before dilation of the glottis may facilitate ventilation and improve hypercapnic acidosis.
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Affiliation(s)
- Satoshi Tachikawa
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
- Department of Perioperative Medicine, Division of Anesthesiology, Showa University School of Dentistry, Oota-ku, Tokyo 145–8515, Japan
| | - Kiyomi Nakayama
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
- * E-mail:
| | - Shiro Nakamura
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
| | - Ayako Mochizuki
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
| | - Takehiko Iijima
- Department of Perioperative Medicine, Division of Anesthesiology, Showa University School of Dentistry, Oota-ku, Tokyo 145–8515, Japan
| | - Tomio Inoue
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
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Pilowsky PM. Foreword. Respir Physiol Neurobiol 2016; 226:1-2. [PMID: 27305188 DOI: 10.1016/j.resp.2016.03.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Paul M Pilowsky
- University of Sydney, 7 Eliza St, Newtown, Sydney, NSW 2042, Australia.
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Jones SE, Dutschmann M. Testing the hypothesis of neurodegeneracy in respiratory network function with a priori transected arterially perfused brain stem preparation of rat. J Neurophysiol 2016; 115:2593-607. [PMID: 26888109 DOI: 10.1152/jn.01073.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/12/2016] [Indexed: 11/22/2022] Open
Abstract
Degeneracy of respiratory network function would imply that anatomically discrete aspects of the brain stem are capable of producing respiratory rhythm. To test this theory we a priori transected brain stem preparations before reperfusion and reoxygenation at 4 rostrocaudal levels: 1.5 mm caudal to obex (n = 5), at obex (n = 5), and 1.5 (n = 7) and 3 mm (n = 6) rostral to obex. The respiratory activity of these preparations was assessed via recordings of phrenic and vagal nerves and lumbar spinal expiratory motor output. Preparations with a priori transection at level of the caudal brain stem did not produce stable rhythmic respiratory bursting, even when the arterial chemoreceptors were stimulated with sodium cyanide (NaCN). Reperfusion of brain stems that preserved the pre-Bötzinger complex (pre-BötC) showed spontaneous and sustained rhythmic respiratory bursting at low phrenic nerve activity (PNA) amplitude that occurred simultaneously in all respiratory motor outputs. We refer to this rhythm as the pre-BötC burstlet-type rhythm. Conserving circuitry up to the pontomedullary junction consistently produced robust high-amplitude PNA at lower burst rates, whereas sequential motor patterning across the respiratory motor outputs remained absent. Some of the rostrally transected preparations expressed both burstlet-type and regular PNA amplitude rhythms. Further analysis showed that the burstlet-type rhythm and high-amplitude PNA had 1:2 quantal relation, with burstlets appearing to trigger high-amplitude bursts. We conclude that no degenerate rhythmogenic circuits are located in the caudal medulla oblongata and confirm the pre-BötC as the primary rhythmogenic kernel. The absence of sequential motor patterning in a priori transected preparations suggests that pontine circuits govern respiratory pattern formation.
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Affiliation(s)
- Sarah E Jones
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Mathias Dutschmann
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
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Dorsal and ventral aspects of the most caudal medullary reticular formation have differential roles in modulation and formation of the respiratory motor pattern in rat. Brain Struct Funct 2015; 221:4353-4368. [DOI: 10.1007/s00429-015-1165-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 11/26/2015] [Indexed: 11/24/2022]
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