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Guo X, Akanda N, Fiorino G, Nimbalkar S, Long CJ, Colón A, Patel A, Tighe PJ, Hickman JJ. Human IPSC-Derived PreBötC-Like Neurons and Development of an Opiate Overdose and Recovery Model. Adv Biol (Weinh) 2024; 8:e2300276. [PMID: 37675827 PMCID: PMC10921423 DOI: 10.1002/adbi.202300276] [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: 08/04/2023] [Indexed: 09/08/2023]
Abstract
Opioid overdose is the leading cause of drug overdose lethality, posing an urgent need for investigation. The key brain region for inspiratory rhythm regulation and opioid-induced respiratory depression (OIRD) is the preBötzinger Complex (preBötC) and current knowledge has mainly been obtained from animal systems. This study aims to establish a protocol to generate human preBötC neurons from induced pluripotent cells (iPSCs) and develop an opioid overdose and recovery model utilizing these iPSC-preBötC neurons. A de novo protocol to differentiate preBötC-like neurons from human iPSCs is established. These neurons express essential preBötC markers analyzed by immunocytochemistry and demonstrate expected electrophysiological responses to preBötC modulators analyzed by patch clamp electrophysiology. The correlation of the specific biomarkers and function analysis strongly suggests a preBötC-like phenotype. Moreover, the dose-dependent inhibition of these neurons' activity is demonstrated for four different opioids with identified IC50's comparable to the literature. Inhibition is rescued by naloxone in a concentration-dependent manner. This iPSC-preBötC mimic is crucial for investigating OIRD and combating the overdose crisis and a first step for the integration of a functional overdose model into microphysiological systems.
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Affiliation(s)
- Xiufang Guo
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826, USA
| | - Nesar Akanda
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826, USA
| | - Gabriella Fiorino
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826, USA
| | - Siddharth Nimbalkar
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826, USA
| | - Christopher J Long
- Hesperos Inc, 12501 Research Parkway, Suite 100, Orlando, FL, 32826, USA
| | - Alisha Colón
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826, USA
| | - Aakash Patel
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826, USA
| | - Patrick J Tighe
- College of Medicine, Department of Anesthesiology, University of Florida, 1600 SW Archer Road, Gainesville, FL, 32610, USA
| | - James J Hickman
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826, USA
- Hesperos Inc, 12501 Research Parkway, Suite 100, Orlando, FL, 32826, USA
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Khalilpour J, Soltani Zangbar H, Alipour MR, Shahabi P. The hypoxic respiratory response of the pre-Bötzinger complex. Heliyon 2024; 10:e34491. [PMID: 39114066 PMCID: PMC11305331 DOI: 10.1016/j.heliyon.2024.e34491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 06/18/2024] [Accepted: 07/10/2024] [Indexed: 08/10/2024] Open
Abstract
Since the discovery of the pre-Bötzinger Complex (preBötC) as a crucial region for generating the main respiratory rhythm, our understanding of its cellular and molecular aspects has rapidly increased within the last few decades. It is now apparent that preBötC is a highly flexible neuronal network that reconfigures state-dependently to produce the most appropriate respiratory output in response to various metabolic challenges, such as hypoxia. However, the responses of the preBötC to hypoxic conditions can be varied based on the intensity, pattern, and duration of the hypoxic challenge. This review discusses the preBötC response to hypoxic challenges at the cellular and network level. Particularly, the involvement of preBötC in the classical biphasic response of the respiratory network to acute hypoxia is illuminated. Furthermore, the article discusses the functional and structural changes of preBötC neurons following intermittent and sustained hypoxic challenges. Accumulating evidence shows that the preBötC neural circuits undergo substantial changes following hypoxia and contribute to several types of the respiratory system's hypoxic ventilatory responses.
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Affiliation(s)
- Jamal Khalilpour
- Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Hamid Soltani Zangbar
- Department of Neuroscience, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
| | | | - Parviz Shahabi
- Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
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Furdui A, da Silveira Scarpellini C, Montandon G. Anatomical distribution of µ-opioid receptors, neurokinin-1 receptors, and vesicular glutamate transporter 2 in the mouse brainstem respiratory network. J Neurophysiol 2024; 132:108-129. [PMID: 38748514 DOI: 10.1152/jn.00478.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 05/08/2024] [Accepted: 05/12/2024] [Indexed: 07/03/2024] Open
Abstract
µ-Opioid receptors (MORs) are responsible for mediating both the analgesic and respiratory effects of opioid drugs. By binding to MORs in brainstem regions involved in controlling breathing, opioids produce respiratory depressive effects characterized by slow and shallow breathing, with potential cardiorespiratory arrest and death during overdose. To better understand the mechanisms underlying opioid-induced respiratory depression, thorough knowledge of the regions and cellular subpopulations that may be vulnerable to modulation by opioid drugs is needed. Using in situ hybridization, we determined the distribution and coexpression of Oprm1 (gene encoding MORs) mRNA with glutamatergic (Vglut2) and neurokinin-1 receptor (Tacr1) mRNA in medullary and pontine regions involved in breathing control and modulation. We found that >50% of cells expressed Oprm1 mRNA in the preBötzinger complex (preBötC), nucleus tractus solitarius (NTS), nucleus ambiguus (NA), postinspiratory complex (PiCo), locus coeruleus (LC), Kölliker-Fuse nucleus (KF), and the lateral and medial parabrachial nuclei (LBPN and MPBN, respectively). Among Tacr1 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, Bötzinger complex (BötC), PiCo, LC, raphe magnus nucleus, KF, LPBN, and MPBN, whereas among Vglut2 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, BötC, PiCo, LC, KF, LPBN, and MPBN. Taken together, our study provides a comprehensive map of the distribution and coexpression of Oprm1, Tacr1, and Vglut2 mRNA in brainstem regions that control and modulate breathing and identifies Tacr1 and Vglut2 mRNA-expressing cells as subpopulations with potential vulnerability to modulation by opioid drugs.NEW & NOTEWORTHY Opioid drugs can cause serious respiratory side-effects by binding to µ-opioid receptors (MORs) in brainstem regions that control breathing. To better understand the regions and their cellular subpopulations that may be vulnerable to modulation by opioids, we provide a comprehensive map of Oprm1 (gene encoding MORs) mRNA expression throughout brainstem regions that control and modulate breathing. Notably, we identify glutamatergic and neurokinin-1 receptor-expressing cells as potentially vulnerable to modulation by opioid drugs and worthy of further investigation using targeted approaches.
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Affiliation(s)
- Andreea Furdui
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | | | - Gaspard Montandon
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Division of Respirology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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4
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Chang Z, Skach J, Kam K. Inhibitory Subpopulations in preBötzinger Complex Play Distinct Roles in Modulating Inspiratory Rhythm and Pattern. J Neurosci 2024; 44:e1928232024. [PMID: 38729762 PMCID: PMC11209648 DOI: 10.1523/jneurosci.1928-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 04/19/2024] [Accepted: 05/06/2024] [Indexed: 05/12/2024] Open
Abstract
Inhibitory neurons embedded within mammalian neural circuits shape breathing, walking, and other rhythmic motor behaviors. At the core of the neural circuit controlling breathing is the preBötzinger Complex (preBötC), where GABAergic (GAD1/2+) and glycinergic (GlyT2+) neurons are functionally and anatomically intercalated among glutamatergic Dbx1-derived (Dbx1+) neurons that generate rhythmic inspiratory drive. The roles of these preBötC inhibitory neurons in breathing remain unclear. We first characterized the spatial distribution of molecularly defined preBötC inhibitory subpopulations in male and female neonatal double reporter mice expressing either tdTomato or EGFP in GlyT2+, GAD1+, or GAD2+ neurons. We found that the majority of preBötC inhibitory neurons expressed both GlyT2 and GAD2 while a much smaller subpopulation also expressed GAD1. To determine the functional role of these subpopulations, we used holographic photostimulation, a patterned illumination technique, in rhythmically active medullary slices from neonatal Dbx1tdTomato;GlyT2EGFP and Dbx1tdTomato;GAD1EGFP double reporter mice of either sex. Stimulation of 4 or 8 preBötC GlyT2+ neurons during endogenous rhythm prolonged the interburst interval in a phase-dependent manner and increased the latency to burst initiation when bursts were evoked by stimulation of Dbx1+ neurons. In contrast, stimulation of 4 or 8 preBötC GAD1+ neurons did not affect interburst interval or latency to burst initiation. Instead, photoactivation of GAD1+ neurons during the inspiratory burst prolonged endogenous and evoked burst duration and decreased evoked burst amplitude. We conclude that GlyT2+/GAD2+ neurons modulate breathing rhythm by delaying burst initiation while a smaller GAD1+ subpopulation shapes inspiratory patterning by altering burst duration and amplitude.
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Affiliation(s)
- Zheng Chang
- Stanson Toshok Center for Brain Function and Repair, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064
| | - Jordan Skach
- Stanson Toshok Center for Brain Function and Repair, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064
| | - Kaiwen Kam
- Stanson Toshok Center for Brain Function and Repair, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064
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Karlen-Amarante M, Glovak ZT, Huff A, Oliveira LM, Ramirez JM. Postinspiratory and preBötzinger complexes contribute to respiratory-sympathetic coupling in mice before and after chronic intermittent hypoxia. Front Neurosci 2024; 18:1386737. [PMID: 38774786 PMCID: PMC11107097 DOI: 10.3389/fnins.2024.1386737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 04/16/2024] [Indexed: 05/24/2024] Open
Abstract
The sympathetic nervous system modulates arterial blood pressure. Individuals with obstructive sleep apnea (OSA) experience numerous nightly hypoxic episodes and exhibit elevated sympathetic activity to the cardiovascular system leading to hypertension. This suggests that OSA disrupts normal respiratory-sympathetic coupling. This study investigates the role of the postinspiratory complex (PiCo) and preBötzinger complex (preBötC) in respiratory-sympathetic coupling under control conditions and following exposure to chronic intermittent hypoxia (CIH) for 21 days (5% O2-80 bouts/day). The surface of the ventral brainstem was exposed in urethane (1.5 g/kg) anesthetized, spontaneously breathing adult mice. Cholinergic (ChAT), glutamatergic (Vglut2), and neurons that co-express ChAT and Vglut2 at PiCo, as well as Dbx1 and Vglut2 neurons at preBötC, were optogenetically stimulated while recording activity from the diaphragm (DIA), vagus nerve (cVN), and cervical sympathetic nerve (cSN). Following CIH exposure, baseline cSN activity increased, breathing frequency increased, and expiratory time decreased. In control mice, stimulating PiCo specific cholinergic-glutamatergic neurons caused a sympathetic burst during all phases of the respiratory cycle, whereas optogenetic activation of cholinergic-glutamatergic PiCo neurons in CIH mice increased sympathetic activity only during postinspiration and late expiration. Stimulation of glutamatergic PiCo neurons increased cSN activity during the postinspiratory phase in control and CIH mice. Optogenetic stimulation of ChAT containing neurons in the PiCo area did not affect sympathetic activity under control or CIH conditions. Stimulating Dbx1 or Vglut2 neurons in preBötC evoked an inspiration and a concomitant cSN burst under control and CIH conditions. Taken together, these results suggest that PiCo and preBötC contribute to respiratory-sympathetic coupling, which is altered by CIH, and may contribute to the hypertension observed in patients with OSA.
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Affiliation(s)
- Marlusa Karlen-Amarante
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA, United States
| | - Zachary T. Glovak
- 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
| | - Luiz M. Oliveira
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA, United States
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA, United States
- Department of Neurological Surgery, University of Washington, Seattle, WA, United States
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Borrus DS, Stettler MK, Grover CJ, Kalajian EJ, Gu J, Conradi Smith GD, Del Negro CA. Inspiratory and sigh breathing rhythms depend on distinct cellular signalling mechanisms in the preBötzinger complex. J Physiol 2024; 602:809-834. [PMID: 38353596 PMCID: PMC10940220 DOI: 10.1113/jp285582] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 12/21/2023] [Indexed: 02/21/2024] Open
Abstract
Breathing behaviour involves the generation of normal breaths (eupnoea) on a timescale of seconds and sigh breaths on the order of minutes. Both rhythms emerge in tandem from a single brainstem site, but whether and how a single cell population can generate two disparate rhythms remains unclear. We posit that recurrent synaptic excitation in concert with synaptic depression and cellular refractoriness gives rise to the eupnoea rhythm, whereas an intracellular calcium oscillation that is slower by orders of magnitude gives rise to the sigh rhythm. A mathematical model capturing these dynamics simultaneously generates eupnoea and sigh rhythms with disparate frequencies, which can be separately regulated by physiological parameters. We experimentally validated key model predictions regarding intracellular calcium signalling. All vertebrate brains feature a network oscillator that drives the breathing pump for regular respiration. However, in air-breathing mammals with compliant lungs susceptible to collapse, the breathing rhythmogenic network may have refashioned ubiquitous intracellular signalling systems to produce a second slower rhythm (for sighs) that prevents atelectasis without impeding eupnoea. KEY POINTS: A simplified activity-based model of the preBötC generates inspiratory and sigh rhythms from a single neuron population. Inspiration is attributable to a canonical excitatory network oscillator mechanism. Sigh emerges from intracellular calcium signalling. The model predicts that perturbations of calcium uptake and release across the endoplasmic reticulum counterintuitively accelerate and decelerate sigh rhythmicity, respectively, which was experimentally validated. Vertebrate evolution may have adapted existing intracellular signalling mechanisms to produce slow oscillations needed to optimize pulmonary function in mammals.
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Affiliation(s)
- Daniel S. Borrus
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Marco K. Stettler
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Cameron J. Grover
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Eva J. Kalajian
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Jeffrey Gu
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Gregory D. Conradi Smith
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
- Conradi Smith and Del Negro contributed equally
| | - Christopher A. Del Negro
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
- Conradi Smith and Del Negro contributed equally
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7
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Olmos-Pastoresa CA, Vázquez-Mendoza E, López-Meraz ML, Pérez-Estudillo CA, Beltran-Parrazal L, Morgado-Valle C. Transgenic rodents as dynamic models for the study of respiratory rhythm generation and modulation: a scoping review and a bibliometric analysis. Front Physiol 2023; 14:1295632. [PMID: 38179140 PMCID: PMC10764557 DOI: 10.3389/fphys.2023.1295632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 11/20/2023] [Indexed: 01/06/2024] Open
Abstract
The pre-Bötzinger complex, situated in the ventrolateral medulla, serves as the central generator for the inspiratory phase of the respiratory rhythm. Evidence strongly supports its pivotal role in generating, and, in conjunction with the post-inspiratory complex and the lateral parafacial nucleus, in shaping the respiratory rhythm. While there remains an ongoing debate concerning the mechanisms underlying these nuclei's ability to generate and modulate breathing, transgenic rodent models have significantly contributed to our understanding of these processes. However, there is a significant knowledge gap regarding the spectrum of transgenic rodent lines developed for studying respiratory rhythm, and the methodologies employed in these models. In this study, we conducted a scoping review to identify commonly used transgenic rodent lines and techniques for studying respiratory rhythm generation and modulation. Following PRISMA guidelines, we identified relevant papers in PubMed and EBSCO on 29 March 2023, and transgenic lines in Mouse Genome Informatics and the International Mouse Phenotyping Consortium. With strict inclusion and exclusion criteria, we identified 80 publications spanning 1997-2022 using 107 rodent lines. Our findings revealed 30 lines focusing on rhythm generation, 61 on modulation, and 16 on both. The primary in vivo method was whole-body plethysmography. The main in vitro method was hypoglossal/phrenic nerve recordings using the en bloc preparation. Additionally, we identified 119 transgenic lines with the potential for investigating the intricate mechanisms underlying respiratory rhythm. Through this review, we provide insights needed to design more effective experiments with transgenic animals to unravel the mechanisms governing respiratory rhythm. The identified transgenic rodent lines and methodological approaches compile current knowledge and guide future research towards filling knowledge gaps in respiratory rhythm generation and modulation.
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Affiliation(s)
| | | | | | | | - Luis Beltran-Parrazal
- Laboratorio de Neurofisiología, Instituto de Investigaciones Cerebrales, Universidad Veracruzana, Xalapa, Veracruz, Mexico
| | - Consuelo Morgado-Valle
- Laboratorio de Neurofisiología, Instituto de Investigaciones Cerebrales, Universidad Veracruzana, Xalapa, Veracruz, Mexico
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Oliveira LM, Severs L, Moreira TS, Ramirez JM, Takakura AC. Ampakine CX614 increases respiratory rate in a mouse model of Parkinson's disease. Brain Res 2023; 1815:148448. [PMID: 37301422 DOI: 10.1016/j.brainres.2023.148448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 05/11/2023] [Accepted: 06/05/2023] [Indexed: 06/12/2023]
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive loss of dopaminergic neurons in the substantia nigra compacta (SNpc). In a mouse model of PD induced by the injection of 6-hydroxydopamine (6-OHDA) into the caudate putamen (CPu) dyspnea events are very common. Neuroanatomical and functional studies show that the number of glutamatergic neurons in the pre-Bötzinger Complex (preBötC) are reduced. We hypothesize that the neuronal loss, and consequently loss of glutamatergic connections in the respiratory network previously investigated, are responsible for the breathing impairment in PD. Here, we tested whether ampakines (CX614), a subgroup of AMPA receptor positive allosteric modulators, could stimulate the respiratory activity in PD-induced animals. CX614 (50 µM) injected intraperitoneally or directly into the preBötC region reduced the irregularity pattern and increased the respiratory rate by 37% or 82%, respectively, in PD-induced animals. CX614 also increased the respiratory frequency in healthy animals. These data suggest that ampakine CX614 could become a tool to restore breathing in PD.
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Affiliation(s)
- Luiz M Oliveira
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, SP 05508, Brazil; Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 9th Avenue, JMB10, Seattle, WA 98101, USA
| | - Liza Severs
- Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 9th Avenue, JMB10, Seattle, WA 98101, USA
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, SP, 05508, Brazil
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 9th Avenue, JMB10, Seattle, WA 98101, USA; Department of Neurological Surgery, University of Washington, 1900 9th Avenue, JMB10, Seattle, WA 98101, USA; Department of Pediatrics, University of Washington, 1900 9th Avenue, JMB10, Seattle, WA 98101, USA
| | - Ana C Takakura
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, SP 05508, Brazil.
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Chang Z, Skach J, Kam K. Inhibitory subpopulations in preBötzinger Complex play distinct roles in modulating inspiratory rhythm and pattern. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.07.552303. [PMID: 37609332 PMCID: PMC10441369 DOI: 10.1101/2023.08.07.552303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Inhibitory neurons embedded within mammalian neural circuits shape breathing, walking, chewing, and other rhythmic motor behaviors. At the core of the neural circuit controlling breathing is the preBötzinger Complex (preBötC), a nucleus in the ventrolateral medulla necessary for generation of inspiratory rhythm. In the preBötC, a recurrently connected network of glutamatergic Dbx1-derived (Dbx1 + ) neurons generates rhythmic inspiratory drive. Functionally and anatomically intercalated among Dbx1 + preBötC neurons are GABAergic (GAD1/2 + ) and glycinergic (GlyT2 + ) neurons, whose roles in breathing remain unclear. To elucidate the inhibitory microcircuits within preBötC, we first characterized the spatial distribution of molecularly-defined inhibitory preBötC subpopulations in double reporter mice expressing either the red fluorescent protein tdTomato or EGFP in GlyT2 + , GAD1 + , or GAD2 + neurons. We found that, in postnatal mice, the majority of inhibitory preBötC neurons expressed a combination of GlyT2 and GAD2 while a much smaller subpopulation also expressed GAD1. To determine the functional role of these subpopulations, we used holographic photostimulation, a patterned illumination technique with high spatiotemporal resolution, in rhythmically active medullary slices from neonatal Dbx1 tdTomato ;GlyT2 EGFP and Dbx1 tdTomato ;GAD1 EGFP double reporter mice. Stimulation of 4 or 8 preBötC GlyT2 + neurons during endogenous rhythm prolonged the interburst interval in a phase-dependent manner and increased the latency to burst initiation when bursts were evoked by stimulation of Dbx1 + neurons. In contrast, stimulation of 4 or 8 preBötC GAD1 + neurons did not affect interburst interval or latency to burst initiation. Instead, photoactivation of GAD1 + neurons during the inspiratory burst prolonged endogenous and evoked burst duration and decreased evoked burst amplitude. We conclude that the majority of preBötC inhibitory neurons express both GlyT2 and GAD2 and modulate breathing rhythm by delaying burst initiation while a smaller GAD1 + subpopulation shapes inspiratory patterning by altering burst duration and amplitude.
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10
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da Silva CA, Grover CJ, Picardo MCD, Del Negro CA. Role of Na V1.6-mediated persistent sodium current and bursting-pacemaker properties in breathing rhythm generation. Cell Rep 2023; 42:113000. [PMID: 37590134 PMCID: PMC10528911 DOI: 10.1016/j.celrep.2023.113000] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 06/16/2023] [Accepted: 08/01/2023] [Indexed: 08/19/2023] Open
Abstract
Inspiration is the inexorable active phase of breathing. The brainstem pre-Bötzinger complex (preBötC) gives rise to inspiratory neural rhythm, but its underlying cellular and ionic bases remain unclear. The long-standing "pacemaker hypothesis" posits that the persistent Na+ current (INaP) that gives rise to bursting-pacemaker properties in preBötC interneurons is essential for rhythmogenesis. We tested the pacemaker hypothesis by conditionally knocking out and knocking down the Scn8a (Nav1.6 [voltage-gated sodium channel 1.6]) gene in core rhythmogenic preBötC neurons. Deleting Scn8a substantially decreases the INaP and abolishes bursting-pacemaker activity, which slows inspiratory rhythm in vitro and negatively impacts the postnatal development of ventilation. Diminishing Scn8a via genetic interference has no impact on breathing in adult mice. We argue that the Scn8a-mediated INaP is not obligatory but that it influences the development and rhythmic function of the preBötC. The ubiquity of the INaP in respiratory brainstem interneurons could underlie breathing-related behaviors such as neonatal phonation or rhythmogenesis in different physiological conditions.
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Affiliation(s)
- Carlos A da Silva
- Department of Applied Science, William & Mary, Williamsburg, VA 23185, USA
| | - Cameron J Grover
- Department of Applied Science, William & Mary, Williamsburg, VA 23185, USA
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11
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Kang J, Lu N, Yang S, Guo B, Zhu Y, Wu S, Huang X, Wong-Riley MTT, Liu YY. Alterations in synapses and mitochondria induced by acute or chronic intermittent hypoxia in the pre-Bötzinger complex of rats: an ultrastructural triple-labeling study with immunocytochemistry and histochemistry. Front Cell Neurosci 2023; 17:1132241. [PMID: 37396926 PMCID: PMC10312010 DOI: 10.3389/fncel.2023.1132241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 06/05/2023] [Indexed: 07/04/2023] Open
Abstract
Introduction The pre-Bötzinger complex (pre-BötC), a kernel of inspiratory rhythmogenesis, is a heterogeneous network with excitatory glutamatergic and inhibitory GABAergic and glycinergic neurons. Inspiratory rhythm generation relies on synchronous activation of glutamatergic neuron, whilst inhibitory neurons play a critical role in shaping the breathing pattern, endowing the rhythm with flexibility in adapting to environmental, metabolic, and behavioral needs. Here we report ultrastructural alterations in excitatory, asymmetric synapses (AS) and inhibitory, symmetric synapses (SS), especially perforated synapses with discontinuous postsynaptic densities (PSDs) in the pre-BötC in rats exposed to daily acute intermittent hypoxia (dAIH) or chronic (C) IH. Methods We utilized for the first time a combination of somatostatin (SST) and neurokinin 1 receptor (NK1R) double immunocytochemistry with cytochrome oxidase histochemistry, to reveal synaptic characteristics and mitochondrial dynamic in the pre-BötC. Results We found perforated synapses with synaptic vesicles accumulated in distinct pools in apposition to each discrete PSD segments. dAIH induced significant increases in the PSD size of macular AS, and the proportion of perforated synapses. AS were predominant in the dAIH group, whereas SS were in a high proportion in the CIH group. dAIH significantly increased SST and NK1R expressions, whereas CIH led to a decrease. Desmosome-like contacts (DLC) were characterized for the first time in the pre-BötC. They were distributed alongside of synapses, especially SS. Mitochondria appeared in more proximity to DLC than synapses, suggestive of a higher energy demand of the DLC. Findings of single spines with dual AS and SS innervation provide morphological evidence of excitation-inhibition interplay within a single spine in the pre-BötC. In particular, we characterized spine-shaft microdomains of concentrated synapses coupled with mitochondrial positioning that could serve as a structural basis for synchrony of spine-shaft communication. Mitochondria were found within spines and ultrastructural features of mitochondrial fusion and fission were depicted for the first time in the pre-BötC. Conclusion We provide ultrastructural evidence of excitation-inhibition synapses in shafts and spines, and DLC in association with synapses that coincide with mitochondrial dynamic in their contribution to respiratory plasticity in the pre-BötC.
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Affiliation(s)
- Junjun Kang
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Naining Lu
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Shoujing Yang
- Department of Pathology, The Fourth Military Medical University, Xi’an, China
| | - Baolin Guo
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Yuanyuan Zhu
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Shengxi Wu
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Xiaofeng Huang
- Department of Pathology, Xi’an Gaoxin Hospital, Xi’an, China
| | - Margaret T. T. Wong-Riley
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Ying-Ying Liu
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
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12
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Tran HN, Nguyen QH, Jeong JE, Loi DL, Nam YH, Kang TH, Yoon J, Baek K, Jeong Y. The embryonic patterning gene Dbx1 governs the survival of the auditory midbrain via Tcf7l2-Ap2δ transcriptional cascade. Cell Death Differ 2023; 30:1563-1574. [PMID: 37081114 PMCID: PMC10244374 DOI: 10.1038/s41418-023-01165-6] [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: 08/16/2022] [Revised: 04/03/2023] [Accepted: 04/05/2023] [Indexed: 04/22/2023] Open
Abstract
At the top of the midbrain is the inferior colliculus (IC), which functions as the major hub for processing auditory information. Despite the functional significance of neurons in the IC, our understanding of their formation is limited. In this study, we identify the embryonic patterning gene Dbx1 as a key molecular player that governs genetic programs for IC survival. We find that Dbx1 plays a critical role in preventing apoptotic cell death in postnatal IC by transcriptionally repressing c-Jun and pro-apoptotic BH3 only factors. Furthermore, by employing combined approaches, we uncover that Tcf7l2 functions downstream of Dbx1. Loss of Tcf7l2 function causes IC phenotypes with striking similarity to those of Dbx1 mutant mice, which include defective embryonic maturation and postnatal deletion of the IC. Finally, we demonstrate that the Dbx1-Tcf7l2 cascade functions upstream of Ap-2δ, which is essential for IC development and survival. Together, these results unravel a novel molecular mechanism for IC maintenance, which is indispensable for normal brain development.
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Affiliation(s)
- Hong-Nhung Tran
- Department of Genetics and Biotechnology, College of Life Sciences, Graduate School of Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea
| | - Quy-Hoai Nguyen
- Department of Genetics and Biotechnology, College of Life Sciences, Graduate School of Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea
| | - Ji-Eun Jeong
- Department of Genetics and Biotechnology, College of Life Sciences, Graduate School of Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea
| | - Duc-Linh Loi
- Department of Genetics and Biotechnology, College of Life Sciences, Graduate School of Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea
| | - Youn Hee Nam
- Department of Oriental Medicine Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea
| | - Tong Ho Kang
- Department of Oriental Medicine Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea
| | - Jaeseung Yoon
- Department of Genetics and Biotechnology, College of Life Sciences, Graduate School of Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea
| | - Kwanghee Baek
- Department of Genetics and Biotechnology, College of Life Sciences, Graduate School of Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea
| | - Yongsu Jeong
- Department of Genetics and Biotechnology, College of Life Sciences, Graduate School of Biotechnology, Kyung Hee University, Yongin, Gyeonggi, Republic of Korea.
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13
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Ma HT, Zhang HC, Zuo ZF, Liu YX. Heterogeneous organization of Locus coeruleus: An intrinsic mechanism for functional complexity. Physiol Behav 2023; 268:114231. [PMID: 37172640 DOI: 10.1016/j.physbeh.2023.114231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 04/06/2023] [Accepted: 05/09/2023] [Indexed: 05/15/2023]
Abstract
Locus coeruleus (LC) is a small nucleus located deep in the brainstem that contains the majority of central noradrenergic neurons, which provide the primary source of noradrenaline (NA) throughout the entire central nervous system (CNS).The release of neurotransmitter NA is considered to modulate arousal, sensory processing, attention, aversive and adaptive stress responses as well as high-order cognitive function and memory, with the highly ramified axonal arborizations of LC-NA neurons sending wide projections to the targeted brain areas. For over 30 years, LC was thought to be a homogeneous nucleus in structure and function due to the widespread uniform release of NA by LC-NA neurons and simultaneous action in several CNS regions, such as the prefrontal cortex, hippocampus, cerebellum, and spinal cord. However, recent advances in neuroscience tools have revealed that LC is probably not so homogeneous as we previous thought and exhibits heterogeneity in various aspects. Accumulating studies have shown that the functional complexity of LC may be attributed to its heterogeneity in developmental origin, projection patterns, topography distribution, morphology and molecular organization, electrophysiological properties and sex differences. This review will highlight the heterogeneity of LC and its critical role in modulating diverse behavioral outcomes.
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Affiliation(s)
- Hai-Tao Ma
- Department of Neurobiology, School of Basic Medicine, Jinzhou Medical University, Jinzhou, Liaoning, 121000, China; Department of Neurobiology, School of Basic Medicine, Capital Medical University, Beijing, 100069, China.
| | - Hao-Chen Zhang
- Department of Neurobiology, School of Basic Medicine, Capital Medical University, Beijing, 100069, China
| | - Zhong-Fu Zuo
- Department of Human Anatomy, Histology and Embryology, Jinzhou Medical University, Jinzhou, 121000, China
| | - Ying-Xue Liu
- Department of Human Anatomy, Histology and Embryology, Jinzhou Medical University, Jinzhou, 121000, China.
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14
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Gourévitch B, Pitts T, Iceman K, Reed M, Cai J, Chu T, Zeng W, Morgado-Valle C, Mellen N. Synchronization of inspiratory burst onset along the ventral respiratory column in the neonate mouse is mediated by electrotonic coupling. BMC Biol 2023; 21:83. [PMID: 37061721 PMCID: PMC10105963 DOI: 10.1186/s12915-023-01575-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 03/20/2023] [Indexed: 04/17/2023] Open
Abstract
Breathing is a singularly robust behavior, yet this motor pattern is continuously modulated at slow and fast timescales to maintain blood-gas homeostasis, while intercalating orofacial behaviors. This functional multiplexing goes beyond the rhythmogenic function that is typically ascribed to medullary respiration-modulated networks and may explain lack of progress in identifying the mechanism and constituents of the respiratory rhythm generator. By recording optically along the ventral respiratory column in medulla, we found convergent evidence that rhythmogenic function is distributed over a dispersed and heterogeneous network that is synchronized by electrotonic coupling across a neuronal syncytium. First, high-speed recordings revealed that inspiratory onset occurred synchronously along the column and did not emanate from a rhythmogenic core. Second, following synaptic isolation, synchronized stationary rhythmic activity was detected along the column. This activity was attenuated following gap junction blockade and was silenced by tetrodotoxin. The layering of syncytial and synaptic coupling complicates identification of rhythmogenic mechanism, while enabling functional multiplexing.
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Affiliation(s)
- Boris Gourévitch
- Unité de Génétique Et Physiologie de L'Audition, INSERM, Institut Pasteur, Sorbonne Université, 75015, Paris, France
| | - Teresa Pitts
- Department of Neurological Surgery, University of Louisville, Louisville, KY, USA
| | - Kimberly Iceman
- Department of Neurological Surgery, University of Louisville, Louisville, KY, USA
| | - Mitchell Reed
- Department of Neurological Surgery, University of Louisville, Louisville, KY, USA
| | - Jun Cai
- Department of Pediatrics, University of Louisville, Louisville, KY, USA
| | - Tianci Chu
- Department of Pediatrics, University of Louisville, Louisville, KY, USA
| | - Wenxin Zeng
- Department of Pediatrics, University of Louisville, Louisville, KY, USA
| | - Consuelo Morgado-Valle
- Instituto de Investigaciones Cerebrales, Universidad Veracruzana, Xalapa, Veracruz, México
| | - Nicholas Mellen
- Department of Neurology, University of Louisville, Louisville, KY, USA.
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15
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Danaf J, da Silveira Scarpellini C, Montandon G. βγ G-proteins, but not regulators of G-protein signaling 4, modulate opioid-induced respiratory rate depression. Front Physiol 2023; 14:1043581. [PMID: 37089428 PMCID: PMC10117644 DOI: 10.3389/fphys.2023.1043581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 03/24/2023] [Indexed: 04/09/2023] Open
Abstract
Opioid medications are the mainstay of pain management but present substantial side-effects such as respiratory depression which can be lethal with overdose. Most opioid drugs, such as fentanyl, act on opioid receptors such as the G-protein-coupled µ-opioid receptors (MOR). G-protein-coupled receptors activate pertussis toxin-sensitive G-proteins to inhibit neuronal activity. Binding of opioid ligands to MOR and subsequent activation G proteins βγ is modulated by regulator of G-protein signaling (RGS). The roles of G-proteins βγ and RGS in MOR-mediated inhibition of the respiratory network are not known. Using rodent models to pharmacologically modulate G-protein signaling, we aim to determine the roles of βγ G-proteins and RGS4. We showed that inhibition of βγ G-proteins using gallein perfused in the brainstem circuits regulating respiratory depression by opioid drugs results in complete reversal of respiratory depression. Blocking of RGS4 using CCG55014 did not change the respiratory depression induced by MOR activation despite co-expression of RGS4 and MORs in the brainstem. Our results suggest that neuronal inhibition by opioid drugs is mediated by G-proteins, but not by RGS4, which supports the concept that βγ G-proteins could be molecular targets to develop opioid overdose antidotes without the risks of re-narcotization often found with highly potent opioid drugs. On the other hand, RGS4 mediates opioid analgesia, but not respiratory depression, and RGS4 may be molecular targets to develop pain therapies without respiratory liability.
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Affiliation(s)
- Jamil Danaf
- St. Michael’s Hospital, Unity Health Toronto, Toronto, ON, Canada
| | | | - Gaspard Montandon
- St. Michael’s Hospital, Unity Health Toronto, Toronto, ON, Canada
- Department of Medicine, University of Toronto, Toronto, ON, Canada
- *Correspondence: Gaspard Montandon,
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16
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Beyeler SA, Naidoo R, Morrison NR, McDonald EA, Albarrán D, Huxtable AG. Maternal opioids age-dependently impair neonatal respiratory control networks. Front Physiol 2023; 14:1109754. [PMID: 37008014 PMCID: PMC10060555 DOI: 10.3389/fphys.2023.1109754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 02/28/2023] [Indexed: 03/18/2023] Open
Abstract
Infants exposed to opioids in utero are an increasing clinical population and these infants are often diagnosed with Neonatal Abstinence Syndrome (NAS). Infants with NAS have diverse negative health consequences, including respiratory distress. However, many factors contribute to NAS, confounding the ability to understand how maternal opioids directly impact the neonatal respiratory system. Breathing is controlled centrally by respiratory networks in the brainstem and spinal cord, but the impact of maternal opioids on developing perinatal respiratory networks has not been studied. Using progressively more isolated respiratory network circuitry, we tested the hypothesis that maternal opioids directly impair neonatal central respiratory control networks. Fictive respiratory-related motor activity from isolated central respiratory networks was age-dependently impaired in neonates after maternal opioids within more complete respiratory networks (brainstem and spinal cords), but unaffected in more isolated networks (medullary slices containing the preBötzinger Complex). These deficits were due, in part, to lingering opioids within neonatal respiratory control networks immediately after birth and involved lasting impairments to respiratory pattern. Since opioids are routinely given to infants with NAS to curb withdrawal symptoms and our previous work demonstrated acute blunting of opioid-induced respiratory depression in neonatal breathing, we further tested the responses of isolated networks to exogenous opioids. Isolated respiratory control networks also demonstrated age-dependent blunted responses to exogenous opioids that correlated with changes in opioid receptor expression within a primary respiratory rhythm generating region, the preBötzinger Complex. Thus, maternal opioids age-dependently impair neonatal central respiratory control and responses to exogenous opioids, suggesting central respiratory impairments contribute to neonatal breathing destabilization after maternal opioids and likely contribute to respiratory distress in infants with NAS. These studies represent a significant advancement of our understanding of the complex effects of maternal opioids, even late in gestation, contributing to neonatal breathing deficits, necessary first steps in developing novel therapeutics to support breathing in infants with NAS.
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Affiliation(s)
- Sarah A. Beyeler
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
| | - Robyn Naidoo
- Department of Human Physiology, University of Oregon, Eugene, OR, United States
| | - Nina R. Morrison
- Department of Human Physiology, University of Oregon, Eugene, OR, United States
| | - Emilee A. McDonald
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
| | - David Albarrán
- Department of Human Physiology, University of Oregon, Eugene, OR, United States
| | - Adrianne G. Huxtable
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
- Department of Human Physiology, University of Oregon, Eugene, OR, United States
- *Correspondence: Adrianne G. Huxtable,
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17
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Yackle K. Transformation of Our Understanding of Breathing Control by Molecular Tools. Annu Rev Physiol 2023; 85:93-113. [PMID: 36323001 PMCID: PMC9918693 DOI: 10.1146/annurev-physiol-021522-094142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The rhythmicity of breath is vital for normal physiology. Even so, breathing is enriched with multifunctionality. External signals constantly change breathing, stopping it when under water or deepening it during exertion. Internal cues utilize breath to express emotions such as sighs of frustration and yawns of boredom. Breathing harmonizes with other actions that use our mouth and throat, including speech, chewing, and swallowing. In addition, our perception of breathing intensity can dictate how we feel, such as during the slow breathing of calming meditation and anxiety-inducing hyperventilation. Heartbeat originates from a peripheral pacemaker in the heart, but the automation of breathing arises from neural clusters within the brainstem, enabling interaction with other brain areas and thus multifunctionality. Here, we document how the recent transformation of cellular and molecular tools has contributed to our appreciation of the diversity of neuronal types in the breathing control circuit and how they confer the multifunctionality of breathing.
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Affiliation(s)
- Kevin Yackle
- Department of Physiology, University of California, San Francisco, California, USA;
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18
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Vagnozzi AN, Moore MT, Lin M, Brozost EM, KC R, Agarwal A, Schwarz LA, Duan X, Zampieri N, Landmesser LT, Philippidou P. Coordinated cadherin functions sculpt respiratory motor circuit connectivity. eLife 2022; 11:e82116. [PMID: 36583530 PMCID: PMC9910829 DOI: 10.7554/elife.82116] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 12/29/2022] [Indexed: 12/31/2022] Open
Abstract
Breathing, and the motor circuits that control it, is essential for life. At the core of respiratory circuits are Dbx1-derived interneurons, which generate the rhythm and pattern of breathing, and phrenic motor neurons (MNs), which provide the final motor output that drives diaphragm muscle contractions during inspiration. Despite their critical function, the principles that dictate how respiratory circuits assemble are unknown. Here, we show that coordinated activity of a type I cadherin (N-cadherin) and type II cadherins (Cadherin-6, -9, and -10) is required in both MNs and Dbx1-derived neurons to generate robust respiratory motor output. Both MN- and Dbx1-specific cadherin inactivation in mice during a critical developmental window results in perinatal lethality due to respiratory failure and a striking reduction in phrenic MN bursting activity. This combinatorial cadherin code is required to establish phrenic MN cell body and dendritic topography; surprisingly, however, cell body position appears to be dispensable for the targeting of phrenic MNs by descending respiratory inputs. Our findings demonstrate that type I and II cadherins function cooperatively throughout the respiratory circuit to generate a robust breathing output and reveal novel strategies that drive the assembly of motor circuits.
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Affiliation(s)
- Alicia N Vagnozzi
- Department of Neurosciences, Case Western Reserve UniversityClevelandUnited States
| | - Matthew T Moore
- Department of Neurosciences, Case Western Reserve UniversityClevelandUnited States
| | - Minshan Lin
- Department of Neurosciences, Case Western Reserve UniversityClevelandUnited States
| | - Elyse M Brozost
- Department of Neurosciences, Case Western Reserve UniversityClevelandUnited States
| | - Ritesh KC
- Department of Neurosciences, Case Western Reserve UniversityClevelandUnited States
| | - Aambar Agarwal
- Department of Neurosciences, Case Western Reserve UniversityClevelandUnited States
| | - Lindsay A Schwarz
- Department of Developmental Neurobiology, St. Jude Children's Research HospitalMemphisUnited States
| | - Xin Duan
- Department of Ophthalmology, University of California, San FranciscoSan FranciscoUnited States
| | - Niccolò Zampieri
- Max Delbrück Center for Molecular Medicine in the Helmholtz AssociationBerlinGermany
| | - Lynn T Landmesser
- Department of Neurosciences, Case Western Reserve UniversityClevelandUnited States
| | - Polyxeni Philippidou
- Department of Neurosciences, Case Western Reserve UniversityClevelandUnited States
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19
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Xia Y, Cui K, Alonso A, Lowenstein ED, Hernandez-Miranda LR. Transcription factors regulating the specification of brainstem respiratory neurons. Front Mol Neurosci 2022; 15:1072475. [PMID: 36523603 PMCID: PMC9745097 DOI: 10.3389/fnmol.2022.1072475] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 11/14/2022] [Indexed: 11/12/2023] Open
Abstract
Breathing (or respiration) is an unconscious and complex motor behavior which neuronal drive emerges from the brainstem. In simplistic terms, respiratory motor activity comprises two phases, inspiration (uptake of oxygen, O2) and expiration (release of carbon dioxide, CO2). Breathing is not rigid, but instead highly adaptable to external and internal physiological demands of the organism. The neurons that generate, monitor, and adjust breathing patterns locate to two major brainstem structures, the pons and medulla oblongata. Extensive research over the last three decades has begun to identify the developmental origins of most brainstem neurons that control different aspects of breathing. This research has also elucidated the transcriptional control that secures the specification of brainstem respiratory neurons. In this review, we aim to summarize our current knowledge on the transcriptional regulation that operates during the specification of respiratory neurons, and we will highlight the cell lineages that contribute to the central respiratory circuit. Lastly, we will discuss on genetic disturbances altering transcription factor regulation and their impact in hypoventilation disorders in humans.
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Affiliation(s)
- Yiling Xia
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ke Cui
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Antonia Alonso
- Functional Genoarchitecture and Neurobiology Groups, Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain
- Department of Human Anatomy and Psychobiology, Faculty of Medicine, University of Murcia, Murcia, Spain
| | - Elijah D. Lowenstein
- Developmental Biology/Signal Transduction, Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Luis R. Hernandez-Miranda
- The Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
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20
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Cabirol MJ, Cardoit L, Courtand G, Mayeur ME, Simmers J, Pascual O, Thoby-Brisson M. Microglia shape the embryonic development of mammalian respiratory networks. eLife 2022; 11:80352. [PMID: 36321865 PMCID: PMC9629827 DOI: 10.7554/elife.80352] [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] [Received: 05/18/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022] Open
Abstract
Microglia, brain-resident macrophages, play key roles during prenatal development in defining neural circuitry function, including ensuring proper synaptic wiring and maintaining homeostasis. Mammalian breathing rhythmogenesis arises from interacting brainstem neural networks that are assembled during embryonic development, but the specific role of microglia in this process remains unknown. Here, we investigated the anatomical and functional consequences of respiratory circuit formation in the absence of microglia. We first established the normal distribution of microglia within the wild-type (WT, Spi1+/+ (Pu.1 WT)) mouse (Mus musculus) brainstem at embryonic ages when the respiratory networks are known to emerge (embryonic day (E) 14.5 for the parafacial respiratory group (epF) and E16.5 for the preBötzinger complex (preBötC)). In transgenic mice depleted of microglia (Spi1−/− (Pu.1 KO) mutant), we performed anatomical staining, calcium imaging, and electrophysiological recordings of neuronal activities in vitro to assess the status of these circuits at their respective times of functional emergence. Spontaneous respiratory-related activity recorded from reduced in vitro preparations showed an abnormally slow rhythm frequency expressed by the epF at E14.5, the preBötC at E16.5, and in the phrenic motor nerves from E16.5 onwards. These deficits were associated with a reduced number of active epF neurons, defects in commissural projections that couple the bilateral preBötC half-centers, and an accompanying decrease in their functional coordination. These abnormalities probably contribute to eventual neonatal death, since plethysmography revealed that E18.5 Spi1−/− embryos are unable to sustain breathing activity ex utero. Our results thus point to a crucial contribution of microglia in the proper establishment of the central respiratory command during embryonic development.
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Affiliation(s)
- Marie-Jeanne Cabirol
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, CNRS, Université de Bordeaux, Bordeaux, France
| | - Laura Cardoit
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, CNRS, Université de Bordeaux, Bordeaux, France
| | - Gilles Courtand
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, CNRS, Université de Bordeaux, Bordeaux, France
| | - Marie-Eve Mayeur
- MeLis INSERM U1314-CNRS UMR 5284, Faculté Rockefeller, Lyon, France
| | - John Simmers
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, CNRS, Université de Bordeaux, Bordeaux, France
| | - Olivier Pascual
- MeLis INSERM U1314-CNRS UMR 5284, Faculté Rockefeller, Lyon, France
| | - Muriel Thoby-Brisson
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, CNRS, Université de Bordeaux, Bordeaux, France
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21
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David CK, Sugimura YK, Kallurkar PS, Picardo MCD, Saha MS, Conradi Smith GD, Del Negro CA. Single cell transcriptome sequencing of inspiratory neurons of the preBötzinger complex in neonatal mice. Sci Data 2022; 9:457. [PMID: 35907922 PMCID: PMC9338969 DOI: 10.1038/s41597-022-01569-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 07/19/2022] [Indexed: 02/06/2023] Open
Abstract
Neurons in the brainstem preBötzinger complex (preBötC) generate the rhythm and rudimentary motor pattern for inspiratory breathing movements. We performed whole-cell patch-clamp recordings from inspiratory neurons in the preBötC of neonatal mouse slices that retain breathing-related rhythmicity in vitro. We classified neurons based on their electrophysiological properties and genetic background, and then aspirated their cellular contents for single-cell RNA sequencing (scRNA-seq). This data set provides the raw nucleotide sequences (FASTQ files) and annotated files of nucleotide sequences mapped to the mouse genome (mm10 from Ensembl), which includes the fragment counts, gene lengths, and fragments per kilobase of transcript per million mapped reads (FPKM). These data reflect the transcriptomes of the neurons that generate the rhythm and pattern for inspiratory breathing movements.
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Affiliation(s)
- Caroline K David
- Department of Applied Science, William & Mary, 540 Landrum Drive, Williamsburg, Virginia, 23185, USA
| | - Yae K Sugimura
- Department of Neuroscience, Jikei University School of Medicine, 3-25-8 Nishi-shimbashi, Minato, Tokyo, 105-8461, Japan
| | - Prajkta S Kallurkar
- Department of Applied Science, William & Mary, 540 Landrum Drive, Williamsburg, Virginia, 23185, USA
| | - Maria Cristina D Picardo
- Department of Applied Science, William & Mary, 540 Landrum Drive, Williamsburg, Virginia, 23185, USA
| | - Margaret S Saha
- Department of Biology, William & Mary, 540 Landrum Drive, Williamsburg, Virginia, 23185, USA
| | - Gregory D Conradi Smith
- Department of Applied Science, William & Mary, 540 Landrum Drive, Williamsburg, Virginia, 23185, USA
| | - Christopher A Del Negro
- Department of Applied Science, William & Mary, 540 Landrum Drive, Williamsburg, Virginia, 23185, USA.
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22
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Huff A, Karlen-Amarante M, Pitts T, Ramirez JM. Optogenetic stimulation of pre-Bötzinger complex reveals novel circuit interactions in swallowing-breathing coordination. Proc Natl Acad Sci U S A 2022; 119:e2121095119. [PMID: 35858334 PMCID: PMC9304034 DOI: 10.1073/pnas.2121095119] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 05/31/2022] [Indexed: 02/02/2023] Open
Abstract
The coordination of swallowing with breathing, in particular inspiration, is essential for homeostasis in most organisms. While much has been learned about the neuronal network critical for inspiration in mammals, the pre-Bötzinger complex (preBötC), little is known about how this network interacts with swallowing. Here we activate within the preBötC excitatory neurons (defined as Vglut2 and Sst neurons) and inhibitory neurons (defined as Vgat neurons) and inhibit and activate neurons defined by the transcription factor Dbx1 to gain an understanding of the coordination between the preBötC and swallow behavior. We found that stimulating inhibitory preBötC neurons did not mimic the premature shutdown of inspiratory activity caused by water swallows, suggesting that swallow-induced suppression of inspiratory activity is not directly mediated by the inhibitory neurons in the preBötC. By contrast, stimulation of preBötC Dbx1 neurons delayed laryngeal closure of the swallow sequence. Inhibition of Dbx1 neurons increased laryngeal closure duration and stimulation of Sst neurons pushed swallow occurrence to later in the respiratory cycle, suggesting that excitatory neurons from the preBötC connect to the laryngeal motoneurons and contribute to the timing of swallowing. Interestingly, the delayed swallow sequence was also caused by chronic intermittent hypoxia (CIH), a model for sleep apnea, which is 1) known to destabilize inspiratory activity and 2) associated with dysphagia. This delay was not present when inhibiting Dbx1 neurons. We propose that a stable preBötC is essential for normal swallow pattern generation and disruption may contribute to the dysphagia seen in obstructive sleep apnea.
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Affiliation(s)
- Alyssa Huff
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101
| | - Marlusa Karlen-Amarante
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101
| | - Teresa Pitts
- Department of Neurological Surgery, School of Medicine, University of Louisville, Louisville, KY 40202
| | - Jan Marino Ramirez
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101
- Department of Neurological Surgery, School of Medicine, University of Washington, Seattle, WA 98108
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23
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Abstract
Breathing is a vital rhythmic motor behavior with a surprisingly broad influence on the brain and body. The apparent simplicity of breathing belies a complex neural control system, the breathing central pattern generator (bCPG), that exhibits diverse operational modes to regulate gas exchange and coordinate breathing with an array of behaviors. In this review, we focus on selected advances in our understanding of the bCPG. At the core of the bCPG is the preBötzinger complex (preBötC), which drives inspiratory rhythm via an unexpectedly sophisticated emergent mechanism. Synchronization dynamics underlying preBötC rhythmogenesis imbue the system with robustness and lability. These dynamics are modulated by inputs from throughout the brain and generate rhythmic, patterned activity that is widely distributed. The connectivity and an emerging literature support a link between breathing, emotion, and cognition that is becoming experimentally tractable. These advances bring great potential for elucidating function and dysfunction in breathing and other mammalian neural circuits.
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Affiliation(s)
- Sufyan Ashhad
- Department of Neurobiology, University of California at Los Angeles, Los Angeles, California, USA;
| | - Kaiwen Kam
- Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | | | - Jack L Feldman
- Department of Neurobiology, University of California at Los Angeles, Los Angeles, California, USA;
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Burgraff NJ, Phillips RS, Severs LJ, Bush NE, Baertsch NA, Ramirez JM. Inspiratory rhythm generation is stabilized by Ih. J Neurophysiol 2022; 128:181-196. [PMID: 35675444 PMCID: PMC9291429 DOI: 10.1152/jn.00150.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Cellular and network properties must be capable of generating rhythmic activity that is both flexible and stable. This is particularly important for breathing, a rhythmic behavior that dynamically adapts to environmental, behavioral, and metabolic changes from the first to the last breath. The pre-Bötzinger complex (preBötC), located within the ventral medulla, is responsible for producing rhythmic inspiration. Its cellular properties must be tunable, flexible as well as stabilizing. Here, we explore the role of the hyperpolarization-activated, nonselective cation current (Ih) for stabilizing PreBötC activity during opioid exposure and reduced excitatory synaptic transmission. Introducing Ih into an in silico preBötC network predicts that loss of this depolarizing current should significantly slow the inspiratory rhythm. By contrast, in vitro and in vivo experiments revealed that the loss of Ih minimally affected breathing frequency, but destabilized rhythmogenesis through the generation of incompletely synchronized bursts (burstlets). Associated with the loss of Ih was an increased susceptibility of breathing to opioid-induced respiratory depression or weakened excitatory synaptic interactions, a paradoxical depolarization at the cellular level, and the suppression of tonic spiking. Tonic spiking activity is generated by nonrhythmic excitatory and inhibitory preBötC neurons, of which a large percentage express Ih. Together, our results suggest that Ih is important for maintaining tonic spiking, stabilizing inspiratory rhythmogenesis, and protecting breathing against perturbations or changes in network state.NEW & NOTEWORTHY The Ih current plays multiple roles within the preBötC. This current is important for promoting intrinsic tonic spiking activity in excitatory and inhibitory neurons and for preserving rhythmic function during conditions that dampen network excitability, such as in the context of opioid-induced respiratory depression. We therefore propose that the Ih current expands the dynamic range of rhythmogenesis, buffers the preBötC against network perturbations, and stabilizes rhythmogenesis by preventing the generation of unsynchronized bursts.
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Affiliation(s)
- Nicholas J. Burgraff
- 1Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington
| | - Ryan S. Phillips
- 1Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington
| | - Liza J. Severs
- 1Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington
| | - Nicholas E. Bush
- 1Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington
| | - Nathan A. Baertsch
- 1Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington,2Department of Pediatrics, University of Washington, Seattle, Washington
| | - Jan-Marino Ramirez
- 1Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington,2Department of Pediatrics, University of Washington, Seattle, Washington,3Department of Neurological Surgery, University of Washington, Seattle, Washington
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Baldo BA. Current research in pathophysiology of opioid-induced respiratory depression, neonatal opioid withdrawal syndrome, and neonatal antidepressant exposure syndrome. Curr Res Toxicol 2022; 3:100078. [PMID: 35734228 PMCID: PMC9207297 DOI: 10.1016/j.crtox.2022.100078] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/20/2022] [Accepted: 06/01/2022] [Indexed: 01/29/2023] Open
Abstract
Respiratory depression (RD) is the primary cause of death due to opioids. Opioids bind to mu (µ)-opioid receptors (MORs) encoded by the MOR gene Oprm1, widely expressed in the central and peripheral nervous systems including centers that modulate breathing. Respiratory centers are located throughout the brainstem. Experiments with Oprm1-deleted knockout (KO) mice undertaken to determine which sites are necessary for the induction of opioid-induced respiratory depression (OIRD) showed that the pre-Bötzinger complex (preBötC) and the pontine Kölliker-Fuse nucleus (KF) contribute equally to OIRD but RD was not totally eliminated. Morphine showed a differential influence on preBötC and KF neurons - low doses attenuated RD following deletion of MORs from preBötC neurons and an increase in apneas after high doses whereas deletion of MORs from KF neurons but not the preBötC attenuated RD at both high and low doses. In other KO mice studies, morphine administration after deletion of Oprm1 from both the preBötC and the KF/PBN neurons, led to the conclusion that both respiratory centres contribute to OIRD but the preBötC predominates. MOR-mediated post-synaptic activation of GIRK potassium channels has been implicated as a cause of OIRD. A complementary mechanism in the preBötC involving KCNQ potassium channels independent of MOR signaling has been described. Recent experiments in rats showing that morphine depresses normal, but not gasping breathing, cast doubt on the belief that eupnea, sighs, and gasps, are under the control of preBötC neurons. Methadone, administered to alleviate symptoms of neonatal opioid withdrawal syndrome (NOWES), desensitized rats to OIRD. Protection lost between postnatal days 1 and 2 coincides with the preBötC becoming the dominant generator of respiratory rhythm. Neonatal antidepressant exposure syndrome (NADES) and serotonin toxicity (ST) show similarities including RD. Enzyme CYP2D6 involved in opioid detoxification is polymorphic. Individuals of different CYP2D6 genotype may show increased, decreased, or no enzyme activity, contributing to the variability of patient responses to different opioids and OIRD.
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Key Words
- AAV, adeno-associated virus
- CDC, Centers for Disease control and prevention
- CTAP, MOR agonist (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2)
- DAMGO, synthetic specific MOR agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin
- DRG, dorsal respiratory group
- FDA, Food and Drug Administration
- GIRK, G protein-gated inwardly-rectifying potassium (K+)
- GPCR, G protein-coupled receptor
- KCNQ, voltage-gated potassium (Kv) channels in the KCNQ (Kv7) family
- KF, Kölliker-Fuse nucleus
- Kölliker-Fuse nucleus and opioid-induced respiratory depression
- MOR, mu opioid receptor
- NADES, neonatal antidepressant exposure syndrome
- NAS, neonatal abstinence syndrome
- NIH, National Institutes of Health
- NK-1R, neurokinin-1 receptor
- NOWES, neonatal opioid withdrawal syndrome
- Neonatal opioid withdrawal syndrome
- Neural mediation of opioid-induced respiratory depression
- OAD, opioid analgesic drug
- OIRD, opioid-induced respiratory depression
- PBL, lateral parabrachial
- PBN, parabrachial nucleus
- PRG, pontine respiratory group
- Pathophysiology of opioid-induced respiratory depression
- Pre-Bötzinger complex and opioid-induced respiratory depression
- RD, respiratory depression
- TACR1, tachykinin receptor 1
- VRG, ventral respiratory group
- preBötC, pre-Bötzinger complex
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Affiliation(s)
- Brian A. Baldo
- Kolling Institute of Medical Research, Royal North Shore Hospital of Sydney and Department of Medicine, University of Sydney, Sydney, NSW, Australia
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Reising JP, Phillips WS, Ramadan N, Herlenius E. Prostaglandin E2 Exerts Biphasic Dose Response on the PreBötzinger Complex Respiratory-Related Rhythm. Front Neural Circuits 2022; 16:826497. [PMID: 35669453 PMCID: PMC9163299 DOI: 10.3389/fncir.2022.826497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 03/28/2022] [Indexed: 11/19/2022] Open
Abstract
Inflammation in infants can cause respiratory dysfunction and is potentially life-threatening. Prostaglandin E2 (PGE2) is released during inflammatory events and perturbs breathing behavior in vivo. Here we study the effects of PGE2 on inspiratory motor rhythm generated by the preBötzinger complex (preBötC). We measured the concentration dependence of PGE2 (1 nM-1 μM) on inspiratory-related motor output in rhythmic medullary slice preparations. Low concentrations (1–10 nM) of PGE2 increased the duration of the inspiratory burst period, while higher concentrations (1 μM) decreased the burst period duration. Using specific pharmacology for prostanoid receptors (EP1-4R, FPR, and DP2R), we determined that coactivation of both EP2R and EP3R is necessary for PGE2 to modulate the inspiratory burst period. Additionally, biased activation of EP3 receptors lengthened the duration of the inspiratory burst period, while biased activation of EP2 receptors shortened the burst period. To help delineate which cell populations are affected by exposure to PGE2, we analyzed single-cell RNA-Seq data derived from preBötC cells. Transcripts encoding for EP2R (Ptger2) were differentially expressed in a cluster of excitatory neurons putatively located in the preBötC. A separate cluster of mixed inhibitory neurons differentially expressed EP3R (Ptger3). Our data provide evidence that EP2 and EP3 receptors increase the duration of the inspiratory burst period at 1–10 nM PGE2 and decrease the burst period duration at 1 μM. Further, the biphasic dose response likely results from differences in receptor binding affinity among prostanoid receptors.
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Affiliation(s)
- Jan Philipp Reising
- Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden
- Astrid Lindgren Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden
| | - Wiktor S. Phillips
- Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden
- Astrid Lindgren Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden
| | - Naify Ramadan
- Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden
- Astrid Lindgren Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden
| | - Eric Herlenius
- Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden
- Astrid Lindgren Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden
- *Correspondence: Eric Herlenius,
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27
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Mechanisms of opioid-induced respiratory depression. Arch Toxicol 2022; 96:2247-2260. [PMID: 35471232 DOI: 10.1007/s00204-022-03300-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 04/06/2022] [Indexed: 11/02/2022]
Abstract
Opioid-induced respiratory depression (OIRD), the primary cause of opioid-induced death, is the neural depression of respiratory drive which, together with a decreased level of consciousness and obstructive sleep apnea, cause ventilatory insufficiency. Variability of responses to opioids and individual differences in physiological and neurological states (e.g., anesthesia, sleep-disordered breathing, concurrent drug administration) add to the risk. Multiple sites can independently exert a depressive effect on breathing, making it unclear which sites are necessary for the induction of OIRD. The generator of inspiratory rhythm is the preBötzinger complex (preBötC) in the ventrolateral medulla. Other important brainstem respiratory centres include the pontine Kölliker-Fuse and adjacent parabrachial nuclei (KF/PBN) in the dorsal lateral pons, and the dorsal respiratory group in the medulla. Deletion of μ opioid receptors from neurons showed that the preBötC and KF/PBN contribute to OIRD with the KF as a respiratory modulator and the preBötC as inspiratory rhythm generator. Glutamatergic neurons expressing NK-1R and somatostatin involved in the autonomic function of breathing, and modulatory signal pathways involving GIRK and KCNQ potassium channels, remain poorly understood. Reversal of OIRD has relied heavily on naloxone which also reverses analgesia but mismatches between the half-lives of naloxone and opioids can make it difficult to clinically safely avoid OIRD. Maternal opioid use, which is rising, increases apneas and destabilizes neonatal breathing but opioid effects on maternal and neonatal respiratory circuits in neonatal abstinence syndrome (NAS) are not well understood. Methadone, administered to alleviate symptoms of NAS in humans, desensitizes rats to RD.
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Kallurkar PS, Picardo MCD, Sugimura YK, Saha MS, Conradi Smith GD, Del Negro CA. Transcriptomes of electrophysiologically recorded Dbx1-derived respiratory neurons of the preBötzinger complex in neonatal mice. Sci Rep 2022; 12:2923. [PMID: 35190626 PMCID: PMC8861066 DOI: 10.1038/s41598-022-06834-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 02/04/2022] [Indexed: 12/26/2022] Open
Abstract
Breathing depends on interneurons in the preBötzinger complex (preBötC) derived from Dbx1-expressing precursors. Here we investigate whether rhythm- and pattern-generating functions reside in discrete classes of Dbx1 preBötC neurons. In a slice model of breathing with ~ 5 s cycle period, putatively rhythmogenic Type-1 Dbx1 preBötC neurons activate 100-300 ms prior to Type-2 neurons, putatively specialized for output pattern, and 300-500 ms prior to the inspiratory motor output. We sequenced Type-1 and Type-2 transcriptomes and identified differential expression of 123 genes including ionotropic receptors (Gria3, Gabra1) that may explain their preinspiratory activation profiles and Ca2+ signaling (Cracr2a, Sgk1) involved in inspiratory and sigh bursts. Surprisingly, neuropeptide receptors that influence breathing (e.g., µ-opioid and bombesin-like peptide receptors) were only sparsely expressed, which suggests that cognate peptides and opioid drugs exert their profound effects on a small fraction of the preBötC core. These data in the public domain help explain the neural origins of breathing.
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Affiliation(s)
| | | | - Yae K Sugimura
- Department of Neuroscience, Jikei University School of Medicine, Tokyo, Japan
| | - Margaret S Saha
- Department of Biology, William & Mary, Williamsburg, VA, USA
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Palkovic B, Cook-Snyder D, Callison JJ, Langer TM, Nugent R, Stuth EA, Zuperku EJ, Stucke AG. Contribution of the caudal medullary raphe to opioid induced respiratory depression. Respir Physiol Neurobiol 2022; 299:103855. [PMID: 35124284 PMCID: PMC8897277 DOI: 10.1016/j.resp.2022.103855] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 01/10/2022] [Accepted: 01/30/2022] [Indexed: 01/31/2023]
Abstract
BACKGROUND Opioid-induced respiratory depression can be partially antagonized in the preBötzinger Complex and Parabrachial Nucleus/Kölliker-Fuse Complex. We hypothesized that additional opioid antagonism in the caudal medullary raphe completely reverses the opioid effect. METHODS In adult ventilated, vagotomized, decerebrate rabbits, we administrated remifentanil intravenously at "analgesic", "apneic", and "very high" doses and determined the reversal with sequential naloxone microinjections into the bilateral Parabrachial Nucleus/Kölliker-Fuse Complex, preBötzinger Complex, and caudal medullary raphe. In separate animals, we injected opioid antagonists into the raphe without intravenous remifentanil. RESULTS Sequential naloxone microinjections completely reversed respiratory rate depression from "analgesic" and "apneic" remifentanil, but not "very high" remifentanil concentrations. Antagonist injection into the caudal medullary raphe without remifentanil independently increased respiratory rate. CONCLUSIONS Opioid-induced respiratory depression results from a combined effect on the respiratory rhythm generator and respiratory drive. The effect in the caudal medullary raphe is complex as we also observed local antagonism of endogenous opioid receptor activation, which has not been described before.
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30
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Smith JC. Respiratory rhythm and pattern generation: Brainstem cellular and circuit mechanisms. HANDBOOK OF CLINICAL NEUROLOGY 2022; 188:1-35. [PMID: 35965022 DOI: 10.1016/b978-0-323-91534-2.00004-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Breathing movements in mammals are driven by rhythmic neural activity automatically generated within spatially and functionally organized brainstem neural circuits comprising the respiratory central pattern generator (CPG). This chapter reviews up-to-date experimental information and theoretical studies of the cellular and circuit mechanisms of respiratory rhythm and pattern generation operating within critical components of this CPG in the lower brainstem. Over the past several decades, there have been substantial advances in delineating the spatial architecture of essential medullary regions and their regional cellular and circuit properties required to understand rhythm and pattern generation mechanisms. A fundamental concept is that the circuits in these regions have rhythm-generating capabilities at multiple cellular and circuit organization levels. The regional cellular properties, circuit organization, and control mechanisms allow flexible expression of neural activity patterns for a repertoire of respiratory behaviors under various physiologic conditions that are dictated by requirements for homeostatic regulation and behavioral integration. Many mechanistic insights have been provided by computational modeling studies driven by experimental results and have advanced understanding in the field. These conceptual and theoretical developments are discussed.
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Affiliation(s)
- Jeffrey C Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States.
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31
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Abstract
Breathing (or respiration) is a complex motor behavior that originates in the brainstem. In minimalistic terms, breathing can be divided into two phases: inspiration (uptake of oxygen, O2) and expiration (release of carbon dioxide, CO2). The neurons that discharge in synchrony with these phases are arranged in three major groups along the brainstem: (i) pontine, (ii) dorsal medullary, and (iii) ventral medullary. These groups are formed by diverse neuron types that coalesce into heterogeneous nuclei or complexes, among which the preBötzinger complex in the ventral medullary group contains cells that generate the respiratory rhythm (Chapter 1). The respiratory rhythm is not rigid, but instead highly adaptable to the physic demands of the organism. In order to generate the appropriate respiratory rhythm, the preBötzinger complex receives direct and indirect chemosensory information from other brainstem respiratory nuclei (Chapter 2) and peripheral organs (Chapter 3). Even though breathing is a hard-wired unconscious behavior, it can be temporarily altered at will by other higher-order brain structures (Chapter 6), and by emotional states (Chapter 7). In this chapter, we focus on the development of brainstem respiratory groups and highlight the cell lineages that contribute to central and peripheral chemoreflexes.
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Affiliation(s)
- Eser Göksu Isik
- Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Luis R Hernandez-Miranda
- Brainstem Group, Institute for Cell Biology and Neurobiology, Charité Universitätsmedizin Berlin, Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.
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32
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Milsom WK, Kinkead R, Hedrick MS, Gilmour K, Perry S, Gargaglioni L, Wang T. Evolution of vertebrate respiratory central rhythm generators. Respir Physiol Neurobiol 2021; 295:103781. [PMID: 34481078 DOI: 10.1016/j.resp.2021.103781] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/03/2021] [Accepted: 08/29/2021] [Indexed: 12/01/2022]
Abstract
Tracing the evolution of the central rhythm generators associated with ventilation in vertebrates is hindered by a lack of information surrounding key transitions. To begin with, central rhythm generation has been studied in detail in only a few species from four vertebrate groups, lamprey, anuran amphibians, turtles, and mammals (primarily rodents). Secondly, there is a lack of information regarding the transition from water breathing fish to air breathing amniotes (reptiles, birds, and mammals). Specifically, the respiratory rhythm generators of fish appear to be single oscillators capable of generating both phases of the respiratory cycle (expansion and compression) and projecting to motoneurons in cranial nerves innervating bucco-pharyngeal muscles. In the amniotes we find oscillators capable of independently generating separate phases of the respiratory cycle (expiration and inspiration) and projecting to pre-motoneurons in the ventrolateral medulla that in turn project to spinal motoneurons innervating thoracic and abdominal muscles (reptiles, birds, and mammals). Studies of the one group of amphibians that lie at this transition (the anurans), raise intriguing possibilities but, for a variety of reasons that we explore, also raise unanswered questions. In this review we summarize what is known about the rhythm generating circuits associated with breathing that arise from the different rhombomeric segments in each of the different vertebrate classes. Assuming oscillating circuits form in every pair of rhombomeres in every vertebrate during development, we trace what appears to be the evolutionary fate of each and highlight the questions that remain to be answered to properly understand the evolutionary transitions in vertebrate central respiratory rhythm generation.
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Affiliation(s)
- W K Milsom
- Department of Zoology, University of British Columbia, Canada.
| | - R Kinkead
- Département de Pédiatrie, Université Laval, Canada
| | - M S Hedrick
- Department of Biological Sciences, California State University, Hayward, CA, USA
| | - K Gilmour
- Department of Biology, University of Ottawa, Canada
| | - S Perry
- Department of Biology, University of Ottawa, Canada
| | - L Gargaglioni
- Departamento de Morfologia e Fisiologia Animal, UNESP, Jaboticabal, Brazil
| | - T Wang
- Department of Zoophysiology, Aarhus University, Denmark
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Astrocytic contribution to glutamate-related central respiratory chemoreception in vertebrates. Respir Physiol Neurobiol 2021; 294:103744. [PMID: 34302992 DOI: 10.1016/j.resp.2021.103744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/01/2021] [Accepted: 07/18/2021] [Indexed: 12/24/2022]
Abstract
Central respiratory chemoreceptors play a key role in the respiratory homeostasis by sensing CO2 and H+ in brain and activating the respiratory neural network. This ability of specific brain regions to respond to acidosis and hypercapnia is based on neuronal and glial mechanisms. Several decades ago, glutamatergic transmission was proposed to be involved as a main mechanism in central chemoreception. However, a complete identification of mechanism has been elusive. At the rostral medulla, chemosensitive neurons of the retrotrapezoid nucleus (RTN) are glutamatergic and they are stimulated by ATP released by RTN astrocytes in response to hypercapnia. In addition, recent findings show that caudal medullary astrocytes in brainstem can also contribute as CO2 and H+ sensors that release D-serine and glutamate, both gliotransmitters able to activate the respiratory neural network. In this review, we describe the mammalian astrocytic glutamatergic contribution to the central respiratory chemoreception trying to trace in vertebrates the emergence of several components involved in this process.
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34
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Cinelli E, Mutolo D, Pantaleo T, Bongianni F. Neural mechanisms underlying respiratory regulation within the preBötzinger complex of the rabbit. Respir Physiol Neurobiol 2021; 293:103736. [PMID: 34224867 DOI: 10.1016/j.resp.2021.103736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 07/01/2021] [Accepted: 07/01/2021] [Indexed: 11/29/2022]
Abstract
The preBötzinger complex (preBötC) is a medullary area essential for normal breathing and widely recognized as necessary and sufficient to generate the inspiratory phase of respiration. It has been studied mainly in rodents. Here we report the main results of our studies revealing the characteristics of the rabbit preBötC identified by means of neuronal recordings, D,L-homocysteic acid microinjections and histological controls. A crucial role in the respiratory rhythmogenesis within this neural substrate is played by excitatory amino acids, but also GABA and glycine display important contributions. Increases in respiratory frequency are induced by microinjections of neurokinins, somatostatin as well by serotonin (5-HT) through an action on 5-HT1A and 5-HT3 receptors or the disinhibition of a GABAergic circuit. Respiratory depression is observed in response to microinjections of the μ-opioid receptor agonist DAMGO. Our results show similarities and differences with the rodent preBötC and emphasize the importance of comparative studies on the mechanisms underlying respiratory rhythmogenesis in different animal species.
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Affiliation(s)
- Elenia Cinelli
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Donatella Mutolo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Tito Pantaleo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Fulvia Bongianni
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy.
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35
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Oliveira LM, Baertsch NA, Moreira TS, Ramirez JM, Takakura AC. Unraveling the Mechanisms Underlying Irregularities in Inspiratory Rhythm Generation in a Mouse Model of Parkinson's Disease. J Neurosci 2021; 41:4732-4747. [PMID: 33863785 PMCID: PMC8260248 DOI: 10.1523/jneurosci.2114-20.2021] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 03/03/2021] [Accepted: 03/09/2021] [Indexed: 12/15/2022] Open
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder anatomically characterized by a progressive loss of dopaminergic neurons in the substantia nigra compacta (SNpc). Much less known, yet clinically very important, are the detrimental effects on breathing associated with this disease. Consistent with the human pathophysiology, the 6-hydroxydopamine hydrochloride (6-OHDA) rodent model of PD shows reduced respiratory frequency (fR) and NK1r-immunoreactivity in the pre-Bötzinger complex (preBötC) and PHOX2B+ neurons in the retrotrapezoid nucleus (RTN). To unravel mechanisms that underlie bradypnea in PD, we employed a transgenic approach to label or stimulate specific neuron populations in various respiratory-related brainstem regions. PD mice were characterized by a pronounced decreased number of putatively rhythmically active excitatory neurons in the preBötC and adjacent ventral respiratory column (VRC). Specifically, the number of Dbx1 and Vglut2 neurons was reduced by 47.6% and 17.3%, respectively. By contrast, inhibitory Vgat+ neurons in the VRC, as well as neurons in other respiratory-related brainstem regions, showed relatively minimal or no signs of neuronal loss. Consistent with these anatomic observations, optogenetic experiments identified deficits in respiratory function that were specific to manipulations of excitatory (Dbx1/Vglut2) neurons in the preBötC. We conclude that the decreased number of this critical population of respiratory neurons is an important contributor to the development of irregularities in inspiratory rhythm generation in this mouse model of PD.SIGNIFICANCE STATEMENT We found a decreased number of a specific population of medullary neurons which contributes to breathing abnormalities in a mouse model of Parkinson's disease (PD).
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Affiliation(s)
- Luiz M Oliveira
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de São Paulo, São Paulo 05508, Brazil
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington 98101
| | - Nathan A Baertsch
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington 98101
- Department of Pediatrics, University of Washington, Seattle, Washington 98101
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de São Paulo, São Paulo 05508, Brazil
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington 98101
- Department of Neurological Surgery, University of Washington, Seattle, Washington 98101
- Department of Pediatrics, University of Washington, Seattle, Washington 98101
| | - Ana C Takakura
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de São Paulo, São Paulo 05508, Brazil
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36
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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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37
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Abstract
The development of the control of breathing begins in utero and continues postnatally. Fetal breathing movements are needed for establishing connectivity between the lungs and central mechanisms controlling breathing. Maturation of the control of breathing, including the increase of hypoxia chemosensitivity, continues postnatally. Insufficient oxygenation, or hypoxia, is a major stressor that can manifest for different reasons in the fetus and neonate. Though the fetus and neonate have different hypoxia sensing mechanisms and respond differently to acute hypoxia, both responses prevent deviations to respiratory and other developmental processes. Intermittent and chronic hypoxia pose much greater threats to the normal developmental respiratory processes. Gestational intermittent hypoxia, due to maternal sleep-disordered breathing and sleep apnea, increases eupneic breathing and decreases the hypoxic ventilatory response associated with impaired gasping and autoresuscitation postnatally. Chronic fetal hypoxia, due to biologic or environmental (i.e. high-altitude) factors, is implicated in fetal growth restriction and preterm birth causing a decrease in the postnatal hypoxic ventilatory responses with increases in irregular eupneic breathing. Mechanisms driving these changes include delayed chemoreceptor development, catecholaminergic activity, abnormal myelination, increased astrocyte proliferation in the dorsal respiratory group, among others. Long-term high-altitude residents demonstrate favorable adaptations to chronic hypoxia as do their offspring. Neonatal intermittent hypoxia is common among preterm infants due to immature respiratory systems and thus, display a reduced drive to breathe and apneas due to insufficient hypoxic sensitivity. However, ongoing intermittent hypoxia can enhance hypoxic sensitivity causing ventilatory overshoots followed by apnea; the number of apneas is positively correlated with degree of hypoxic sensitivity in preterm infants. Chronic neonatal hypoxia may arise from fetal complications like maternal smoking or from postnatal cardiovascular problems, causing blunting of the hypoxic ventilatory responses throughout at least adolescence due to attenuation of carotid body fibers responses to hypoxia with potential roles of brainstem serotonin, microglia, and inflammation, though these effects depend on the age in which chronic hypoxia initiates. Fetal and neonatal intermittent and chronic hypoxia are implicated in preterm birth and complicate the respiratory system through their direct effects on hypoxia sensing mechanisms and interruptions to the normal developmental processes. Thus, precise regulation of oxygen homeostasis is crucial for normal development of the respiratory control network. © 2021 American Physiological Society. Compr Physiol 11:1653-1677, 2021.
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Affiliation(s)
- Gary C. Mouradian
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Satyan Lakshminrusimha
- Department of Pediatrics, UC Davis Children’s Hospital, UC Davis Health, UC Davis, Davis, California, USA
| | - Girija G. Konduri
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
- Children’s Research Institute, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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38
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Schnerwitzki D, Hayn C, Perner B, Englert C. Wt1 Positive dB4 Neurons in the Hindbrain Are Crucial for Respiration. Front Neurosci 2020; 14:529487. [PMID: 33328840 PMCID: PMC7734174 DOI: 10.3389/fnins.2020.529487] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 11/10/2020] [Indexed: 02/02/2023] Open
Abstract
Central pattern generator (CPG) networks coordinate the generation of rhythmic activity such as locomotion and respiration. Their development is driven by various transcription factors, one of which is the Wilms tumor protein (Wt1). It is present in dI6 neurons of the mouse spinal cord, and involved in the coordination of locomotion. Here we report about the presence of Wt1 in neurons of the caudoventral medulla oblongata and their impact on respiration. By employing immunohistofluorescence staining, we were able to characterize these Wt1 positive (+) cells as dB4 neurons. The temporal occurrence of Wt1 suggests a role for this transcription factor in the differentiation of dB4 neurons during embryonic and postnatal development. Conditional knockout of Wt1 in these cells caused an altered population size of V0 neurons already in the developing hindbrain, leading to a decline in the respiration rate in the adults. Thereby, we confirmed and extended the previously proposed similarity between dB4 neurons in the hindbrain and dI6 neurons of the spinal cord, in terms of development and function. Ablation of Wt1+ dB4 neurons resulted in the death of neonates due to the inability to initiate respiration, suggesting a vital role for Wt1+ dB4 neurons in breathing. These results expand the role of Wt1 in the CNS and show that, in addition to its function in differentiation of dI6 neurons, it also contributes to the development of dB4 neurons in the hindbrain that are critically involved in the regulation of respiration.
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Affiliation(s)
- Danny Schnerwitzki
- Molecular Genetics Laboratory, Leibniz Institute on Aging-Fritz Lipmann Institute (FLI), Jena, Germany
| | - Christian Hayn
- Molecular Genetics Laboratory, Leibniz Institute on Aging-Fritz Lipmann Institute (FLI), Jena, Germany
| | - Birgit Perner
- Molecular Genetics Laboratory, Leibniz Institute on Aging-Fritz Lipmann Institute (FLI), Jena, Germany.,Core Facility Imaging, Leibniz Institute on Aging-Fritz Lipmann Institute (FLI), Jena, Germany
| | - Christoph Englert
- Molecular Genetics Laboratory, Leibniz Institute on Aging-Fritz Lipmann Institute (FLI), Jena, Germany.,Institute of Biochemistry and Biophysics, Friedrich-Schiller-University Jena, Jena, Germany
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39
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Kang JJ, Fung ML, Zhang K, Lam CS, Wu SX, Huang XF, Yang SJ, Wong-Riley MTT, Liu YY. Chronic intermittent hypoxia alters the dendritic mitochondrial structure and activity in the pre-Bötzinger complex of rats. FASEB J 2020; 34:14588-14601. [PMID: 32910512 DOI: 10.1096/fj.201902141r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 07/21/2020] [Accepted: 08/17/2020] [Indexed: 11/11/2022]
Abstract
Mitochondrial bioenergetics is dynamically coupled with neuronal activities, which are altered by hypoxia-induced respiratory neuroplasticity. Here we report structural features of postsynaptic mitochondria in the pre-Bötzinger complex (pre-BötC) of rats treated with chronic intermittent hypoxia (CIH) simulating a severe condition of obstructive sleep apnea. The subcellular changes in dendritic mitochondria and histochemistry of cytochrome c oxidase (CO) activity were examined in pre-BötC neurons localized by immunoreactivity of neurokinin 1 receptors. Assays of mitochondrial electron transport chain (ETC) complex I, IV, V activities, and membrane potential were performed in the ventrolateral medulla containing the pre-BötC region. We found significant decreases in the mean length and area of dendritic mitochondria in the pre-BötC of CIH rats, when compared to the normoxic control and hypoxic group with daily acute intermittent hypoxia (dAIH) that evokes robust synaptic plasticity. Notably, these morphological alterations were mainly observed in the mitochondria in close proximity to the synapses. In addition, the proportion of mitochondria presented with enlarged compartments and filamentous cytoskeletal elements in the CIH group was less than the control and dAIH groups. Intriguingly, these distinct characteristics of structural adaptability were observed in the mitochondria within spatially restricted dendritic spines. Furthermore, the proportion of moderately to darkly CO-reactive mitochondria was reduced in the CIH group, indicating reduced mitochondrial activity. Consistently, mitochondrial ETC enzyme activities and membrane potential were lowered in the CIH group. These findings suggest that hypoxia-induced respiratory plasticity was characterized by spatially confined mitochondrial alterations within postsynaptic spines in the pre-BötC neurons. In contrast to the robust plasticity evoked by dAIH preconditioning, a severe CIH challenge may weaken the local mitochondrial bioenergetics that the fuel postsynaptic activities of the respiratory motor drive.
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Affiliation(s)
- Jun-Jun Kang
- Department of Neurobiology, The Fourth Military Medical University, Xi'an, China
| | - Man-Lung Fung
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China
| | - Kun Zhang
- Department of Neurobiology, The Fourth Military Medical University, Xi'an, China
| | - Chun-Sing Lam
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China
| | - Sheng-Xi Wu
- Department of Neurobiology, The Fourth Military Medical University, Xi'an, China
| | - Xiao-Feng Huang
- Department of Pathology and Pathophysiology, The Fourth Military Medical University, Xi'an, China
| | - Shou-Jing Yang
- Department of Pathology and Pathophysiology, The Fourth Military Medical University, Xi'an, China
| | - Margaret T T Wong-Riley
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Ying-Ying Liu
- Department of Neurobiology, The Fourth Military Medical University, Xi'an, China
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40
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Biancardi V, Saini J, Pageni A, Prashaad M. H, Funk GD, Pagliardini S. Mapping of the excitatory, inhibitory, and modulatory afferent projections to the anatomically defined active expiratory oscillator in adult male rats. J Comp Neurol 2020; 529:853-884. [DOI: 10.1002/cne.24984] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/29/2020] [Accepted: 07/05/2020] [Indexed: 01/21/2023]
Affiliation(s)
- Vivian Biancardi
- Department of Physiology University of Alberta Edmonton Canada
- Women and Children's Health Research Institute, Faculty of Medicine and Dentistry University of Alberta Edmonton Canada
| | - Jashan Saini
- Department of Physiology University of Alberta Edmonton Canada
| | - Anileen Pageni
- Department of Physiology University of Alberta Edmonton Canada
| | | | - Gregory D. Funk
- Department of Physiology University of Alberta Edmonton Canada
- Women and Children's Health Research Institute, Faculty of Medicine and Dentistry University of Alberta Edmonton Canada
- Neuroscience and Mental Health Institute University of Alberta Edmonton Canada
| | - Silvia Pagliardini
- Department of Physiology University of Alberta Edmonton Canada
- Women and Children's Health Research Institute, Faculty of Medicine and Dentistry University of Alberta Edmonton Canada
- Neuroscience and Mental Health Institute University of Alberta Edmonton Canada
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41
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Borrus DS, Grover CJ, Conradi Smith GD, Del Negro CA. Role of Synaptic Inhibition in the Coupling of the Respiratory Rhythms that Underlie Eupnea and Sigh Behaviors. eNeuro 2020; 7:ENEURO.0302-19.2020. [PMID: 32393585 PMCID: PMC7363481 DOI: 10.1523/eneuro.0302-19.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 04/14/2020] [Accepted: 05/01/2020] [Indexed: 11/21/2022] Open
Abstract
The preBötzinger complex (preBötC) gives rise to two types of breathing behavior under normal physiological conditions: eupnea and sighing. Here, we examine the neural mechanisms that couple their underlying rhythms. We measured breathing in awake intact adult mice and recorded inspiratory rhythms from the preBötC in neonatal mouse brainstem slice preparations. We show previously undocumented variability in the temporal relationship between sigh breaths or bursts and their preceding eupneic breaths or inspiratory bursts. Investigating the synaptic mechanisms for this variability in vitro, we further show that pharmacological blockade of chloride-mediated synaptic inhibition strengthens inspiratory-to-sigh temporal coupling. These findings contrast with previous literature, which suggested glycinergic inhibition linked sigh bursts to their preceding inspiratory bursts with minimal time intervals. Furthermore, we verify that pharmacological disinhibition did not alter the duration of the prolonged interval that follows a sigh burst before resumption of the inspiratory rhythm. These results demonstrate that synaptic inhibition does not enhance coupling between sighs and preceding inspiratory events or contribute to post-sigh apneas. Instead, we conclude that excitatory synaptic mechanisms coordinate inspiratory (eupnea) and sigh rhythms.
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Affiliation(s)
- Daniel S Borrus
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, VA 23185
| | - Cameron J Grover
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, VA 23185
| | - Gregory D Conradi Smith
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, VA 23185
| | - Christopher A Del Negro
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, VA 23185
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42
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Ashhad S, Feldman JL. Emergent Elements of Inspiratory Rhythmogenesis: Network Synchronization and Synchrony Propagation. Neuron 2020; 106:482-497.e4. [PMID: 32130872 PMCID: PMC11221628 DOI: 10.1016/j.neuron.2020.02.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 01/15/2020] [Accepted: 02/07/2020] [Indexed: 12/22/2022]
Abstract
We assessed the mechanism of mammalian breathing rhythmogenesis in the preBötzinger complex (preBötC) in vitro, where experimental tests remain inconsistent with hypotheses of canonical rhythmogenic cellular or synaptic mechanisms, i.e., pacemaker neurons or inhibition. Under rhythmic conditions, in each cycle, an inspiratory burst emerges as (presumptive) preBötC rhythmogenic neurons transition from aperiodic uncorrelated population spike activity to become increasingly synchronized during preinspiration (for ∼50-500 ms), which can trigger inspiratory bursts that propagate to motoneurons. In nonrhythmic conditions, antagonizing GABAA receptors can initiate this synchronization while inducing a higher conductance state in nonrhythmogenic preBötC output neurons. Our analyses uncover salient features of preBötC network dynamics where inspiratory bursts arise when and only when the preBötC rhythmogenic subpopulation strongly synchronizes to drive output neurons. Furthermore, downstream propagation of preBötC network activity, ultimately to motoneurons, is dependent on the strength of input synchrony onto preBötC output neurons exemplifying synchronous propagation of network activity.
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Affiliation(s)
- Sufyan Ashhad
- Department of Neurobiology, University of California, Los Angeles, Box 951763, Los Angeles, CA 90095-1763, USA
| | - Jack L Feldman
- Department of Neurobiology, University of California, Los Angeles, Box 951763, Los Angeles, CA 90095-1763, USA.
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43
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Bachmutsky I, Wei XP, Kish E, Yackle K. Opioids depress breathing through two small brainstem sites. eLife 2020; 9:52694. [PMID: 32073401 PMCID: PMC7077984 DOI: 10.7554/elife.52694] [Citation(s) in RCA: 81] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Accepted: 02/17/2020] [Indexed: 12/24/2022] Open
Abstract
The rates of opioid overdose in the United States quadrupled between 1999 and 2017, reaching a staggering 130 deaths per day. This health epidemic demands innovative solutions that require uncovering the key brain areas and cell types mediating the cause of overdose— opioid-induced respiratory depression. Here, we identify two primary changes to murine breathing after administering opioids. These changes implicate the brainstem’s breathing circuitry which we confirm by locally eliminating the µ-Opioid receptor. We find the critical brain site is the preBötzinger Complex, where the breathing rhythm originates, and use genetic tools to reveal that just 70–140 neurons in this region are responsible for its sensitivity to opioids. Future characterization of these neurons may lead to novel therapies that prevent respiratory depression while sparing analgesia. Opioids such as morphine or fentanyl are powerful substances used to relieve pain in medical settings. However, taken in too high a dose they can depress breathing – in other words, they can lead to slow, shallow breaths that cannot sustain life. In the United States, where the misuse of these drugs has been soaring in the past decades, about 130 people die each day from opioid overdose. Pinpointing the exact brain areas and neurons that opioids act on to depress breathing could help to create safer painkillers that do not have this deadly effect. While previous studies have proposed several brain regions that could be involved, they have not been able to confirm these results, or determine which area plays the biggest role. Opioids influence the brain of animals (including humans) by attaching to proteins known as opioid receptors that are present at the surface of neurons. Here, Bachmutsky et al. genetically engineered mice that lack these receptors in specific brain regions that control breathing. The animals were then exposed to opioids, and their breathing was closely monitored. The experiments showed that two small brain areas were responsible for breathing becoming depressed under the influence of opioids. The region with the most critical impact also happens to be where the breathing rhythms originate. There, a small group of 50 to 140 neurons were used by opioids to depress breathing. Crucially, these cells were not necessary for the drugs’ ability to relieve pain. Overall, the work by Bachmutsky et al. highlights a group of neurons whose role in creating breathing rhythms deserves further attention. It also opens the possibility that targeting these neurons would help to create safer painkillers.
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Affiliation(s)
- Iris Bachmutsky
- Department of Physiology, University of California-San Francisco, San Francisco, United States.,Neuroscience Graduate Program, University of California-San Francisco, San Francisco, United States
| | - Xin Paul Wei
- Department of Physiology, University of California-San Francisco, San Francisco, United States.,Biomedical Sciences Graduate Program, University of California-San Francisco, San Francisco, United States
| | - Eszter Kish
- Department of Physiology, University of California-San Francisco, San Francisco, United States.,Neuroscience Graduate Program, University of California-San Francisco, San Francisco, United States
| | - Kevin Yackle
- Department of Physiology, University of California-San Francisco, San Francisco, United States
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44
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Evaluating the Burstlet Theory of Inspiratory Rhythm and Pattern Generation. eNeuro 2020; 7:ENEURO.0314-19.2019. [PMID: 31888961 PMCID: PMC6964920 DOI: 10.1523/eneuro.0314-19.2019] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 12/17/2019] [Accepted: 12/17/2019] [Indexed: 12/12/2022] Open
Abstract
The preBötzinger complex (preBötC) generates the rhythm and rudimentary motor pattern for inspiratory breathing movements. Here, we test “burstlet” theory (Kam et al., 2013a), which posits that low amplitude burstlets, subthreshold from the standpoint of inspiratory bursts, reflect the fundamental oscillator of the preBötC. In turn, a discrete suprathreshold process transforms burstlets into full amplitude inspiratory bursts that drive motor output, measurable via hypoglossal nerve (XII) discharge in vitro. We recap observations by Kam and Feldman in neonatal mouse slice preparations: field recordings from preBötC demonstrate bursts and concurrent XII motor output intermingled with lower amplitude burstlets that do not produce XII motor output. Manipulations of excitability affect the relative prevalence of bursts and burstlets and modulate their frequency. Whole-cell and photonic recordings of preBötC neurons suggest that burstlets involve inconstant subsets of rhythmogenic interneurons. We conclude that discrete rhythm- and pattern-generating mechanisms coexist in the preBötC and that burstlets reflect its fundamental rhythmogenic nature.
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45
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Sun X, Thörn Pérez C, Halemani D N, Shao XM, Greenwood M, Heath S, Feldman JL, Kam K. Opioids modulate an emergent rhythmogenic process to depress breathing. eLife 2019; 8:e50613. [PMID: 31841107 PMCID: PMC6938398 DOI: 10.7554/elife.50613] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Accepted: 12/11/2019] [Indexed: 12/13/2022] Open
Abstract
How mammalian neural circuits generate rhythmic activity in motor behaviors, such as breathing, walking, and chewing, remains elusive. For breathing, rhythm generation is localized to a brainstem nucleus, the preBötzinger Complex (preBötC). Rhythmic preBötC population activity consists of strong inspiratory bursts, which drive motoneuronal activity, and weaker burstlets, which we hypothesize reflect an emergent rhythmogenic process. If burstlets underlie inspiratory rhythmogenesis, respiratory depressants, such as opioids, should reduce burstlet frequency. Indeed, in medullary slices from neonatal mice, the μ-opioid receptor (μOR) agonist DAMGO slowed burstlet generation. Genetic deletion of μORs in a glutamatergic preBötC subpopulation abolished opioid-mediated depression, and the neuropeptide Substance P, but not blockade of inhibitory synaptic transmission, reduced opioidergic effects. We conclude that inspiratory rhythmogenesis is an emergent process, modulated by opioids, that does not rely on strong bursts of activity associated with motor output. These findings also point to strategies for ameliorating opioid-induced depression of breathing.
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Affiliation(s)
- Xiaolu Sun
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Carolina Thörn Pérez
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Nagaraj Halemani D
- Department of Cell Biology and AnatomyChicago Medical School, Rosalind Franklin University of Medicine and ScienceNorth ChicagoUnited States
| | - Xuesi M Shao
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Morgan Greenwood
- RFUMS/DePaul Research Internship ProgramRosalind Franklin University of Medicine and ScienceNorth ChicagoUnited States
| | - Sarah Heath
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Jack L Feldman
- Department of NeurobiologyDavid Geffen School of Medicine at UCLALos AngelesUnited States
| | - Kaiwen Kam
- Department of Cell Biology and AnatomyChicago Medical School, Rosalind Franklin University of Medicine and ScienceNorth ChicagoUnited States
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46
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Lee D, Kume M, Holy TE. Sensory coding mechanisms revealed by optical tagging of physiologically defined neuronal types. Science 2019; 366:1384-1389. [PMID: 31831669 PMCID: PMC7591936 DOI: 10.1126/science.aax8055] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 10/25/2019] [Indexed: 01/27/2023]
Abstract
Neural circuit analysis relies on having molecular markers for specific cell types. However, for a cell type identified only by its circuit function, the process of identifying markers remains laborious. We developed physiological optical tagging sequencing (PhOTseq), a technique for tagging and expression profiling of cells on the basis of their functional properties. PhOTseq was capable of selecting rare cell types and enriching them by nearly 100-fold. We applied PhOTseq to the challenge of mapping receptor-ligand pairings among pheromone-sensing neurons in mice. Together with in vivo ectopic expression of vomeronasal chemoreceptors, PhOTseq identified the complete combinatorial receptor code for a specific set of ligands.
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Affiliation(s)
- Donghoon Lee
- Department of Neuroscience, Washington University School of Medicine in St. Louis, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
| | - Maiko Kume
- Department of Neuroscience, Washington University School of Medicine in St. Louis, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
| | - Timothy E Holy
- Department of Neuroscience, Washington University School of Medicine in St. Louis, 660 S. Euclid Avenue, St. Louis, MO 63110, USA.,Correspondence to
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47
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van der Heijden ME, Zoghbi HY. Development of the brainstem respiratory circuit. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2019; 9:e366. [PMID: 31816185 DOI: 10.1002/wdev.366] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 02/01/2023]
Abstract
The respiratory circuit is comprised of over a dozen functionally and anatomically segregated brainstem nuclei that work together to control respiratory rhythms. These respiratory rhythms emerge prenatally but only acquire vital importance at birth, which is the first time the respiratory circuit faces the sole responsibility for O2 /CO2 homeostasis. Hence, the respiratory circuit has little room for trial-and-error-dependent fine tuning and relies on a detailed genetic blueprint for development. This blueprint is provided by transcription factors that have specific spatiotemporal expression patterns along the rostral-caudal or dorsal-ventral axis of the developing brainstem, in proliferating precursor cells and postmitotic neurons. Studying these transcription factors in mice has provided key insights into the functional segregation of respiratory control and the vital importance of specific respiratory nuclei. Many studies converge on just two respiratory nuclei that each have rhythmogenic properties during the prenatal period: the preBötzinger complex (preBötC) and retrotrapezoid nucleus/parafacial nucleus (RTN/pF). Here, we discuss the transcriptional regulation that guides the development of these nuclei. We also summarize evidence showing that normal preBötC development is necessary for neonatal survival, and that neither the preBötC nor the RTN/pF alone is sufficient to sustain normal postnatal respiratory rhythms. Last, we highlight several studies that use intersectional genetics to assess the necessity of transcription factors only in subregions of their expression domain. These studies independently demonstrate that lack of RTN/pF neurons weakens the respiratory circuit, yet these neurons are not necessary for neonatal survival because developmentally related populations can compensate for abnormal RTN/pF function at birth. This article is categorized under: Nervous System Development > Vertebrates: Regional Development.
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Affiliation(s)
- Meike E van der Heijden
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas.,Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas
| | - Huda Y Zoghbi
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas.,Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas.,Department of Pediatrics, Baylor College of Medicine, Houston, Texas.,Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas
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48
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Baertsch NA, Ramirez JM. Insights into the dynamic control of breathing revealed through cell-type-specific responses to substance P. eLife 2019; 8:51350. [PMID: 31804180 PMCID: PMC6957314 DOI: 10.7554/elife.51350] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 12/04/2019] [Indexed: 12/23/2022] Open
Abstract
The rhythm generating network for breathing must continuously adjust to changing metabolic and behavioral demands. Here, we examined network-based mechanisms in the mouse preBötzinger complex using substance P, a potent excitatory modulator of breathing frequency and stability, as a tool to dissect network properties that underlie dynamic breathing. We find that substance P does not alter the balance of excitation and inhibition during breaths or the duration of the resulting refractory period. Instead, mechanisms of recurrent excitation between breaths are enhanced such that the rate that excitation percolates through the network is increased. We propose a conceptual framework in which three distinct phases of inspiration, the burst phase, refractory phase, and percolation phase, can be differentially modulated to control breathing dynamics and stability. Unraveling mechanisms that support this dynamic control may improve our understanding of nervous system disorders that destabilize breathing, many of which involve changes in brainstem neuromodulatory systems.
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Affiliation(s)
- Nathan A Baertsch
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, United States
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, United States.,Department of Neurological Surgery, University of Washington School of Medicine, Seattle, United States
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Wei AD, Ramirez JM. Presynaptic Mechanisms and KCNQ Potassium Channels Modulate Opioid Depression of Respiratory Drive. Front Physiol 2019; 10:1407. [PMID: 31824331 PMCID: PMC6882777 DOI: 10.3389/fphys.2019.01407] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Accepted: 10/31/2019] [Indexed: 01/02/2023] Open
Abstract
Opioid-induced respiratory depression (OIRD) is the major cause of death associated with opioid analgesics and drugs of abuse, but the underlying cellular and molecular mechanisms remain poorly understood. We investigated opioid action in vivo in unanesthetized mice and in in vitro medullary slices containing the preBötzinger Complex (preBötC), a locus critical for breathing and inspiratory rhythm generation. Although hypothesized as a primary mechanism, we found that mu-opioid receptor (MOR1)-mediated GIRK activation contributed only modestly to OIRD. Instead, mEPSC recordings from genetically identified Dbx1-derived interneurons, essential for rhythmogenesis, revealed a prevalent presynaptic mode of action for OIRD. Consistent with MOR1-mediated suppression of presynaptic release as a major component of OIRD, Cacna1a KO slices lacking P/Q-type Ca2+ channels enhanced OIRD. Furthermore, OIRD was mimicked and reversed by KCNQ potassium channel activators and blockers, respectively. In vivo whole-body plethysmography combined with systemic delivery of GIRK- and KCNQ-specific potassium channel drugs largely recapitulated these in vitro results, and revealed state-dependent modulation of OIRD. We propose that respiratory failure from OIRD results from a general reduction of synaptic efficacy, leading to a state-dependent collapse of rhythmic network activity.
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Affiliation(s)
- Aguan D. Wei
- Seattle Children’s Research Institute, Center for Integrative Brain Research, Seattle, WA, United States
- Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA, United States
| | - Jan-Marino Ramirez
- Seattle Children’s Research Institute, Center for Integrative Brain Research, Seattle, WA, United States
- Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA, United States
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The pre-Bötzinger complex: Generation and modulation of respiratory rhythm. NEUROLOGÍA (ENGLISH EDITION) 2019. [DOI: 10.1016/j.nrleng.2018.05.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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