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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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Bhagavan H, Wei AD, Oliveira LM, Aldinger KA, Ramirez JM. Chronic intermittent hypoxia elicits distinct transcriptomic responses among neurons and oligodendrocytes within the brainstem of mice. Am J Physiol Lung Cell Mol Physiol 2024; 326:L698-L712. [PMID: 38591125 DOI: 10.1152/ajplung.00320.2023] [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: 10/13/2023] [Revised: 01/22/2024] [Accepted: 03/26/2024] [Indexed: 04/10/2024] Open
Abstract
Chronic intermittent hypoxia (CIH) is a prevalent condition characterized by recurrent episodes of oxygen deprivation, linked to respiratory and neurological disorders. Prolonged CIH is known to have adverse effects, including endothelial dysfunction, chronic inflammation, oxidative stress, and impaired neuronal function. These factors can contribute to serious comorbidities, including metabolic disorders and cardiovascular diseases. To investigate the molecular impact of CIH, we examined male C57BL/6J mice exposed to CIH for 21 days, comparing with normoxic controls. We used single-nucleus RNA sequencing to comprehensively examine the transcriptomic impact of CIH on key cell classes within the brainstem, specifically excitatory neurons, inhibitory neurons, and oligodendrocytes. These cell classes regulate essential physiological functions, including autonomic tone, cardiovascular control, and respiration. Through analysis of 10,995 nuclei isolated from pontine-medullary tissue, we identified seven major cell classes, further subdivided into 24 clusters. Our findings among these cell classes, revealed significant differential gene expression, underscoring their distinct responses to CIH. Notably, neurons exhibited transcriptional dysregulation of genes associated with synaptic transmission, and structural remodeling. In addition, we found dysregulated genes encoding ion channels and inflammatory response. Concurrently, oligodendrocytes exhibited dysregulated genes associated with oxidative phosphorylation and oxidative stress. Utilizing CellChat network analysis, we uncovered CIH-dependent altered patterns of diffusible intercellular signaling. These insights offer a comprehensive transcriptomic cellular atlas of the pons-medulla and provide a fundamental resource for the analysis of molecular adaptations triggered by CIH.NEW & NOTEWORTHY This study on chronic intermittent hypoxia (CIH) from pons-medulla provides initial insights into the molecular effects on excitatory neurons, inhibitory neurons, and oligodendrocytes, highlighting our unbiased approach, in comparison with earlier studies focusing on single target genes. Our findings reveal that CIH affects cell classes distinctly, and the dysregulated genes in distinct cell classes are associated with synaptic transmission, ion channels, inflammation, oxidative stress, and intercellular signaling, advancing our understanding of CIH-induced molecular responses.
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Affiliation(s)
- Hemalatha Bhagavan
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
| | - Aguan D Wei
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
| | - Luiz M Oliveira
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
| | - Kimberly A Aldinger
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
- Department of Pediatrics, University of Washington, Seattle, Washington, United States
- Department of Neurology, University of Washington, Seattle, Washington, United States
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
- Department of Pediatrics, University of Washington, Seattle, Washington, United States
- Department of Neurological Surgery, University of Washington, Seattle, Washington, United States
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Filchenko I, Korostovtseva L, Bochkarev M, Tsoy U, Sviryaev Y. Cardiovascular remodeling in active and controlled acromegaly: association with sleep-disordered breathing. Sleep Breath 2023; 27:2305-2314. [PMID: 37148385 DOI: 10.1007/s11325-023-02838-9] [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: 12/25/2022] [Revised: 04/20/2023] [Accepted: 04/24/2023] [Indexed: 05/08/2023]
Abstract
PURPOSE We hypothesized that an unfavorable cardiovascular profile in acromegaly is associated with sleep-disordered breathing (SDB), while acromegaly control improves both respiratory sleep characteristics and the cardiovascular profile. METHODS The patients underwent the assessment of breathing during sleep and cardiovascular profile assessment at the start of the study including arterial stiffness, blood pressure, echocardiography, nocturnal heart rate variability (HRV). The assessment was repeated in patients with acromegaly at 1 year after transsphenoidal adenectomy (TSA). RESULTS A total of 47 patients with acromegaly and 55 control subjects were enrolled. At one year after TSA, 22 patients with acromegaly were reassessed. Multiple linear regression analysis with adjustment for age, sex and body mass index (BMI) showed the associations of insulin growth-like factor 1 (IGF-1) with obstructive apnea index (OAI: β=0.035/h, p<0.001), but not with cardiovascular parameters, in patients with acromegaly. The analysis of combined acromegaly and control dataset with adjustment for age, sex and BMI showed the association the presence of acromegaly with diastolic blood pressure (DBP; β=17.99 mmHg, p<0.001), ejection fraction (EF; β=6.23%, p=0.009), left heart remodeling (left ventricle posterior wall: β=0.81 mm, p=0.045) and the association of the presence of SDB (apnea-hypopnea index≥15/h) with left ventricular function (EF: -4.12%, p=0.040; end systolic volume: 10.12 ml, p=0.004). Control of acromegaly was accompanied by the decrease in OAI (5.9 [0.8, 14.5]/h and 1.7 [0.2, 5.1]/h, p=0.004) and nocturnal heart rate (66.1 [59.2, 69.8] bpm and 61.7 [54.0, 67.2] bpm, p=0.025) and by the increase in blood pressure (DBP: 78.0 [70.3, 86.0] mm Hg and 80.0 [80.0, 90.0] mm Hg, p=0.012). CONCLUSION The comorbidities of acromegaly, including sleep-disordered breathing, appear to have a long-term effect on cardiovascular remodeling in active acromegaly. Future studies should investigate the applicability of the treatment of SDB for the reduction of cardiovascular risk in acromegaly.
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Affiliation(s)
- Irina Filchenko
- Almazov National Medical Research Center, Laboratory of Somnology, Ulitsa Akkuratova, 2, St Petersburg, Russia, 197341.
| | - Lyudmila Korostovtseva
- Almazov National Medical Research Center, Laboratory of Somnology, Ulitsa Akkuratova, 2, St Petersburg, Russia, 197341
| | - Mikhail Bochkarev
- Almazov National Medical Research Center, Laboratory of Somnology, Ulitsa Akkuratova, 2, St Petersburg, Russia, 197341
| | - Uliana Tsoy
- Almazov National Medical Research Center, Laboratory of Endocrinology, Ulitsa Akkuratova, 2, St Petersburg, Russia, 197341
| | - Yuri Sviryaev
- Almazov National Medical Research Center, Laboratory of Somnology, Ulitsa Akkuratova, 2, St Petersburg, Russia, 197341
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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) 2023: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] [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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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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Kelly E, Sutcliffe K, Cavallo D, Ramos-Gonzalez N, Alhosan N, Henderson G. The anomalous pharmacology of fentanyl. Br J Pharmacol 2023; 180:797-812. [PMID: 34030211 DOI: 10.1111/bph.15573] [Citation(s) in RCA: 36] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 04/27/2021] [Accepted: 05/12/2021] [Indexed: 11/26/2022] Open
Abstract
Fentanyl is a key therapeutic, used in anaesthesia and pain management. It is also increasingly used illicitly and is responsible for a large and growing number of opioid overdose deaths, especially in North America. A number of factors have been suggested to contribute to fentanyl's lethality, including rapid onset of action, in vivo potency, ligand bias, induction of muscle rigidity and reduced sensitivity to reversal by naloxone. Some of these factors can be considered to represent 'anomalous' pharmacological properties of fentanyl when compared with prototypical opioid agonists such as morphine. In this review, we examine the nature of fentanyl's 'anomalous' properties, to determine whether there is really a pharmacological basis to support the existence of such properties, and also discuss whether such properties are likely to contribute to overdose deaths involving fentanyls. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.
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Affiliation(s)
- Eamonn Kelly
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Katy Sutcliffe
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Damiana Cavallo
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | | | - Norah Alhosan
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Graeme Henderson
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
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Morgado-Valle C, Smith JC, Fernandez-Ruiz J, Lopez-Meraz L, Beltran-Parrazal L. Modulation of inspiratory burst duration and frequency by bombesin in vitro. Pflugers Arch 2023; 475:101-117. [PMID: 35066612 DOI: 10.1007/s00424-022-02663-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 12/19/2021] [Accepted: 01/04/2022] [Indexed: 01/31/2023]
Abstract
Mammalian respiratory rhythm-generating circuits in the brainstem are subject to neuromodulation by multiple peptidergic afferent inputs controlling circuit behavior and outputs. Although functionally important, actions of neuropeptide modulators have not been fully characterized. We analyzed at cellular and circuit levels two inspiratory patterns intrinsically generated by the preBötzinger complex (preBötC) and their modulation by the neuropeptides bombesin and substance P (SP) in neonatal rat medullary slices in vitro. We found that, in recordings of hypoglossal nerve and preBötC neuron inspiratory activity, some inspiratory bursts occurring spontaneously under basal conditions have a biphasic shape with longer duration than normal inspiratory bursts and occur at a lower frequency. This biphasic burst pattern has been proposed to represent inspiratory activity underling periodic sighs. Bath-applied bombesin or SP decreased the period and increased the duration of both normal inspiratory and biphasic bursts and their underlying synaptic drives. The ratio of the biphasic long-duration burst period to the normal inspiratory burst period and the ratio of their burst durations remained the same before and after peptidergic modulation. Bombesin increased the frequency of the inspiratory rhythm in a Ca2+-independent manner and the frequency of long-duration bursts in a Ca2+-dependent manner. This finding suggests that period and burst duration coupling are due to intrinsic mechanisms controlling simultaneously timing and burst termination within the inspiratory rhythm-generating network. We propose a model in which signaling cascades activated by bombesin and SP modulate mechanisms controlling inspiratory burst frequency and duration to coordinate preBötC circuit behavioral outputs.
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Affiliation(s)
- Consuelo Morgado-Valle
- Instituto de Investigaciones Cerebrales, Dirección General de Investigaciones, Universidad Veracruzana, Xalapa Veracruz, México, 91190. .,Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke (NINDS). National Institutes of Health (NIH), Bethesda, MD, 20892, USA.
| | - Jeffrey C Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke (NINDS). National Institutes of Health (NIH), Bethesda, MD, 20892, USA
| | - Juan Fernandez-Ruiz
- Facultad de Medicina, Universidad Nacional Autónoma de México. Ciudad de México, México City, 04510, México
| | - Leonor Lopez-Meraz
- Instituto de Investigaciones Cerebrales, Dirección General de Investigaciones, Universidad Veracruzana, Xalapa Veracruz, México, 91190
| | - Luis Beltran-Parrazal
- Instituto de Investigaciones Cerebrales, Dirección General de Investigaciones, Universidad Veracruzana, Xalapa Veracruz, México, 91190.
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Current research in pathophysiology of opioid induced respiratory depression. 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] [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
In Oprm1-deleted KO mice, both the preBötC and the KF/PBN are major contributors to OIRD but RD is not totally eliminated. PreBötC neurons expressing NK-1R are necessary for breathing. Their deletion results in ataxic breathing and/or apnoea. GIRK channels are involved in inhibiting respiration by mu opioid receptors. KCNQ channels modulate OIRD independent of mu signaling. Morphine depresses normal but not gasping breathing in rats indicating distinct mechanisms for these 2 forms of breathing. Methadone, given to alleviate symptoms of neonatal opioid withdrawal syndrome, desensitizes rats to respiratory depression.
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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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: 13] [Impact Index Per Article: 6.5] [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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Pre-treatment with Tandospirone attenuates fentanyl-induced respiratory depression without affecting the analgesic effects of fentanyl in rodents. Neurosci Lett 2022; 771:136459. [PMID: 35041907 DOI: 10.1016/j.neulet.2022.136459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 12/13/2022]
Abstract
Opioid analgesics are widely used to treat acute, postoperative, and chronic pain. However, opioid receptor activation can result in severe respiratory depression. In this study, we demonstrated that Tandospirone (TS), a selective serotonin-1A receptor partial agonist, is effective against opioid-induced respiratory depression. Fentanyl was used to establish a respiratory depression model in rodents. We observed the effects of TS on respiratory depression in rats by using plethysmographic recordings and arterial oxygen saturation. In addition, we evaluated the effects of TS on fentanyl-induced sedation and analgesia by using the loss of righting reflex (LORR) and hot-plate tests, respectively. Rats (n = 5) were treated with TS or saline 5 min prior to fentanyl administration. TS [2 mg/kg, intravenous (i.v.)] dose-dependently attenuated fentanyl-induced respiratory depression versus saline + fentanyl group. Furthermore, pre-treatment with TS (2 mg/kg, i.v.) increased arterial oxygen saturation to 76.5 ± 2.0% at 5 min after fentanyl injection, compared with 35.9 ± 2.5% in saline pre-treated rats (P < 0.001), whereas the time to induction of LORR (P > 0.99) and duration of LORR (P = 0.95) did not differ between the "TS + fentanyl" and "saline + fentanyl" group. The antinociceptive effect of fentanyl was not affected by the administration of TS (P = 0.99) in mice (n = 10). In conclusion, we found that TS, a novel non-benzodiazepine anxiolytic/antidepressant drug, could attenuate severe fentanyl-induced respiratory depression and did not affect the analgesic/sedative effect of fentanyl. The clinical application of TS could significantly improve pain management.
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Abstract
Opiates, such as morphine, and synthetic opioids, such as fentanyl, constitute a class of drugs acting on opioid receptors which have been used therapeutically and recreationally for centuries. Opioid drugs have strong analgesic properties and are used to treat moderate to severe pain, but also present side effects including opioid dependence, tolerance, addiction, and respiratory depression, which can lead to lethal overdose if not treated. This chapter explores the pathophysiology, the neural circuits, and the cellular mechanisms underlying opioid-induced respiratory depression and provides a translational perspective of the most recent research. The pathophysiology discussed includes the effects of opioid drugs on the respiratory system in patients, as well as the animal models used to identify underlying mechanisms. Using a combination of gene editing and pharmacology, the neural circuits and molecular pathways mediating neuronal inhibition by opioids are examined. By using pharmacology and neuroscience approaches, new therapies to prevent or reverse respiratory depression by opioid drugs have been identified and are currently being developed. Considering the health and economic burden associated with the current opioid epidemic, innovative research is needed to better understand the side effects of opioid drugs and to discover new therapeutic solutions to reduce the incidence of lethal overdoses.
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Baldo BA. Toxicities of opioid analgesics: respiratory depression, histamine release, hemodynamic changes, hypersensitivity, serotonin toxicity. Arch Toxicol 2021; 95:2627-2642. [PMID: 33974096 DOI: 10.1007/s00204-021-03068-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 04/29/2021] [Indexed: 11/30/2022]
Abstract
Opioid-induced respiratory depression is potentially life-threatening and often regarded as the main hazard of opioid use. Main cause of death is cardiorespiratory arrest with hypoxia and hypercapnia. Respiratory depression is mediated by opioid μ receptors expressed on respiratory neurons in the CNS. Studies on the major sites in the brainstem mediating respiratory rate suppression, the pre-Bӧtzinger complex and parabrachial complex (including the Kӧlliker Fuse nucleus), have yielded conflicting findings and interpretations but recent investigations involving deletion of μ receptors from neurons have led to greater consensus. Some opioid analgesic drugs are histamine releasers. The range of clinical effects of released histamine include increased cardiac output due to an increase in heart rate, increased force of myocardial contraction, and a dilatatory effect on small blood vessels leading to flushing, decreased vascular resistance and hypotension. Resultant hemodynamic changes do not necessarily relate directly to the concentration of histamine in plasma due to a range of variables including functional differences between mast cells and histamine-induced anaphylactoid reactions may occur less often than commonly believed. Opioid-induced histamine release rarely if ever provokes bronchospasm and histamine released by opioids in normal doses does not lead to anaphylactoid reactions or result in IgE-mediated reactions in normal patients. Hypersensitivities to opioids, mainly some skin reactions and occasional type I hypersensitivities, chiefly anaphylaxis and urticaria, are uncommon. Hypersensitivities to morphine, codeine, heroin, methadone, meperidine, fentanyl, remifentanil, buprenorphine, tramadol, and dextromethorphan are summarized. In 2016, the FDA issued a Drug Safety Communication concerning the association of opioids with serotonin syndrome, a toxicity associated with raised intra-synaptic concentrations of serotonin in the CNS, inhibition of serotonin reuptake, and activation of 5-HT receptors. Opioids may provoke serotonin toxicity especially if administered in conjunction with other serotonergic medications. The increasing use of opioid analgesics and widespread prescribing of antidepressants and psychiatric medicines, indicates the likelihood of an increased incidence of serotonin toxicity in opioid-treated patients.
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Affiliation(s)
- Brian A Baldo
- Molecular Immunology Unit, Kolling Institute of Medical Research, Royal North Shore Hospital of Sydney, Sydney, NSW, 2070, Australia.
- Department of Medicine, University of Sydney, Sydney, NSW, Australia.
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13
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The lamprey respiratory network: Some evolutionary aspects. Respir Physiol Neurobiol 2021; 294:103766. [PMID: 34329767 DOI: 10.1016/j.resp.2021.103766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/19/2021] [Accepted: 07/25/2021] [Indexed: 01/25/2023]
Abstract
Breathing is a complex behaviour that involves rhythm generating networks. In this review, we examine the main characteristics of respiratory rhythm generation in vertebrates and, in particular, we describe the main results of our studies on the role of neural mechanisms involved in the neuromodulation of the lamprey respiration. The lamprey respiratory rhythm generator is located in the paratrigeminal respiratory group (pTRG) and shows similarities with the mammalian preBötzinger complex. In fact, within the pTRG a major role is played by glutamate, but also GABA and glycine display important contributions. In addition, neuromodulatory influences are exerted by opioids, substance P, acetylcholine and serotonin. Both structures respond to exogenous ATP with a biphasic response and astrocytes there located strongly contribute to the modulation of the respiratory pattern. The results emphasize that some important characteristics of the respiratory rhythm generating network are, to a great extent, maintained throughout evolution.
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14
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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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15
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Ramirez JM, Burgraff NJ, Wei AD, Baertsch NA, Varga AG, Baghdoyan HA, Lydic R, Morris KF, Bolser DC, Levitt ES. Neuronal mechanisms underlying opioid-induced respiratory depression: our current understanding. J Neurophysiol 2021; 125:1899-1919. [PMID: 33826874 DOI: 10.1152/jn.00017.2021] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [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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Abstract
Opioids such as morphine and oxycodone are analgesics frequently prescribed for the treatment of moderate or severe pain. Unfortunately, these medications are associated with exceptionally high abuse potentials and often cause fatal side effects, mainly through the μ-opioid receptor (MOR). Efforts to discover novel, safer, and more efficacious analgesics targeting MOR have encountered challenges. In this review, we summarize alternative strategies and targets that could be used to develop safer nonopioid analgesics. A molecular understanding of G protein-coupled receptor activation and signaling has illuminated not only the complexities of receptor pharmacology but also the potential for pathway-selective agonists and allosteric modulators as safer medications. The availability of structures of pain-related receptors, in combination with high-throughput computational tools, has accelerated the discovery of multitarget ligands with promising pharmacological profiles. Emerging clinical evidence also supports the notion that drugs targeting peripheral opioid receptors have potential as improved analgesic agents.
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Affiliation(s)
- Tao Che
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA; .,Center for Clinical Pharmacology, University of Health Sciences and Pharmacy and Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Bryan L Roth
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA;
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17
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Cinelli E, Bongianni F, Pantaleo T, Mutolo D. Activation of μ-opioid receptors differentially affects the preBötzinger Complex and neighbouring regions of the respiratory network in the adult rabbit. Respir Physiol Neurobiol 2020; 280:103482. [DOI: 10.1016/j.resp.2020.103482] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 06/05/2020] [Accepted: 06/12/2020] [Indexed: 11/25/2022]
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18
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Busserolles J, Lolignier S, Kerckhove N, Bertin C, Authier N, Eschalier A. Replacement of current opioid drugs focusing on MOR-related strategies. Pharmacol Ther 2020; 210:107519. [PMID: 32165137 DOI: 10.1016/j.pharmthera.2020.107519] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 02/24/2020] [Indexed: 12/12/2022]
Abstract
The scarcity and limited risk/benefit ratio of painkillers available on the market, in addition to the opioid crisis, warrant reflection on new innovation strategies. The pharmacopoeia of analgesics is based on products that are often old and derived from clinical empiricism, with limited efficacy or spectrum of action, or resulting in an unsatisfactory tolerability profile. Although they are reference analgesics for nociceptive pain, opioids are subject to the same criticism. The use of opium as an analgesic is historical. Morphine was synthesized at the beginning of the 19th century. The efficacy of opioids is limited in certain painful contexts and these drugs can induce potentially serious and fatal adverse effects. The current North American opioid crisis, with an ever-rising number of deaths by opioid overdose, is a tragic illustration of this. It is therefore legitimate to develop research into molecules likely to maintain or increase opioid efficacy while improving their tolerability. Several avenues are being explored including targeting of the mu opioid receptor (MOR) splice variants, developing biased agonists or targeting of other receptors such as heteromers with MOR. Ion channels acting as MOR effectors, are also targeted in order to offer compounds without MOR-dependent adverse effects. Another route is to develop opioid analgesics with peripheral action or limited central nervous system (CNS) access. Finally, endogenous opioids used as drugs or compounds that modify the metabolism of endogenous opioids (Dual ENKephalinase Inhibitors) are being developed. The aim of the present review is to present these various targets/strategies with reference to current indications for opioids, concerns about their widespread use, particularly in chronic non-cancer pains, and ways of limiting the risk of opioid abuse and misuse.
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Affiliation(s)
- Jérôme Busserolles
- Université Clermont Auvergne, INSERM, CHU, NEURO-DOL Pharmacologie Fondamentale et Clinique de la douleur, F-63000 Clermont-Ferrand, France; Institut ANALGESIA, Faculté de Médecine, F-63000 Clermont-Ferrand, France
| | - Stéphane Lolignier
- Université Clermont Auvergne, INSERM, CHU, NEURO-DOL Pharmacologie Fondamentale et Clinique de la douleur, F-63000 Clermont-Ferrand, France; Institut ANALGESIA, Faculté de Médecine, F-63000 Clermont-Ferrand, France
| | - Nicolas Kerckhove
- Université Clermont Auvergne, INSERM, CHU, NEURO-DOL Pharmacologie Fondamentale et Clinique de la douleur, F-63000 Clermont-Ferrand, France; Institut ANALGESIA, Faculté de Médecine, F-63000 Clermont-Ferrand, France; Observatoire Français des Médicaments Antalgiques (OFMA), French monitoring centre for analgesic drugs, CHU, F-63000 Clermont-Ferrand, France
| | - Célian Bertin
- Université Clermont Auvergne, INSERM, CHU, NEURO-DOL Pharmacologie Fondamentale et Clinique de la douleur, F-63000 Clermont-Ferrand, France; Institut ANALGESIA, Faculté de Médecine, F-63000 Clermont-Ferrand, France; Observatoire Français des Médicaments Antalgiques (OFMA), French monitoring centre for analgesic drugs, CHU, F-63000 Clermont-Ferrand, France
| | - Nicolas Authier
- Université Clermont Auvergne, INSERM, CHU, NEURO-DOL Pharmacologie Fondamentale et Clinique de la douleur, F-63000 Clermont-Ferrand, France; Institut ANALGESIA, Faculté de Médecine, F-63000 Clermont-Ferrand, France; Observatoire Français des Médicaments Antalgiques (OFMA), French monitoring centre for analgesic drugs, CHU, F-63000 Clermont-Ferrand, France
| | - Alain Eschalier
- Université Clermont Auvergne, INSERM, CHU, NEURO-DOL Pharmacologie Fondamentale et Clinique de la douleur, F-63000 Clermont-Ferrand, France; Institut ANALGESIA, Faculté de Médecine, F-63000 Clermont-Ferrand, France.
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19
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Measurement and State-Dependent Modulation of Hypoglossal Motor Excitability and Responsivity In-Vivo. Sci Rep 2020; 10:550. [PMID: 31953471 PMCID: PMC6969049 DOI: 10.1038/s41598-019-57328-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 12/19/2019] [Indexed: 12/17/2022] Open
Abstract
Motoneurons are the final output pathway for the brain’s influence on behavior. Here we identify properties of hypoglossal motor output to the tongue musculature. Tongue motor control is critical to the pathogenesis of obstructive sleep apnea, a common and serious sleep-related breathing disorder. Studies were performed on mice expressing a light sensitive cation channel exclusively on cholinergic neurons (ChAT-ChR2(H134R)-EYFP). Discrete photostimulations under isoflurane-induced anesthesia from an optical probe positioned above the medullary surface and hypoglossal motor nucleus elicited discrete increases in tongue motor output, with the magnitude of responses dependent on stimulation power (P < 0.001, n = 7) and frequency (P = 0.002, n = 8, with responses to 10 Hz stimulation greater than for 15–25 Hz, P < 0.022). Stimulations during REM sleep elicited significantly reduced responses at powers 3–20 mW compared to non-rapid eye movement (non-REM) sleep and wakefulness (each P < 0.05, n = 7). Response thresholds were also greater in REM sleep (10 mW) compared to non-REM and waking (3 to 5 mW, P < 0.05), and the slopes of the regressions between input photostimulation powers and output motor responses were specifically reduced in REM sleep (P < 0.001). This study identifies that variations in photostimulation input produce tunable changes in hypoglossal motor output in-vivo and identifies REM sleep specific suppression of net motor excitability and responsivity.
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Varga AG, Reid BT, Kieffer BL, Levitt ES. Differential impact of two critical respiratory centres in opioid-induced respiratory depression in awake mice. J Physiol 2020; 598:189-205. [PMID: 31589332 PMCID: PMC6938533 DOI: 10.1113/jp278612] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 10/03/2019] [Indexed: 12/29/2022] Open
Abstract
KEY POINTS The main cause of death from opioid overdose is respiratory depression due to the activation of µ-opioid receptors (MORs). We conditionally deleted MORs from neurons in two key areas of the brainstem respiratory circuitry (the Kölliker-Fuse nucleus (KF) and pre-Bötzinger complex (preBötC)) to determine their role in opioid-induced respiratory disturbances in adult, awake mice. Deletion of MORs from KF neurons attenuated respiratory rate depression at all doses of morphine. Deletion of MORs from preBötC neurons attenuated rate depression at the low dose, but had no effect on rate following high doses of morphine. Instead, high doses of morphine increased the occurrence of apnoeas. The results indicate that opioids affect distributed key areas of the respiratory network in a dose-dependent manner and countering the respiratory effects of high dose opioids via the KF may be an effective approach to combat overdose. ABSTRACT The primary cause of death from opioid overdose is respiratory failure. High doses of opioids cause severe rate depression and increased risk of fatal apnoea, which correlate with increasing irregularities in breathing pattern. µ-Opioid receptors (MORs) are widely distributed throughout the brainstem respiratory network, but the mechanisms underlying respiratory depression are poorly understood. The medullary pre-Bötzinger complex (preBötC) and the pontine Kölliker-Fuse nucleus (KF) are considered critical for inducing opioid-related respiratory disturbances. We used a conditional knockout approach to investigate the roles and relative contribution of MORs in KF and preBötC neurons in opioid-induced respiratory depression in awake adult mice. The results revealed dose-dependent and region-specific opioid effects on the control of both respiratory rate and pattern. Respiratory depression induced by an anti-nociceptive dose of morphine was significantly attenuated following deletion of MORs from either the KF or the preBötC, suggesting cumulative network effects on respiratory rate control at low opioid doses. Deletion of MORs from KF neurons also relieved rate depression at near-maximal respiratory depressant doses of morphine. Meanwhile, deletion of MORs from the preBötC had no effect on rate following administration of high doses of morphine. Instead, a severe ataxic breathing pattern emerged with many apnoeas. We conclude that opioids affect distributed areas of the respiratory network and opioid-induced respiratory depression cannot be attributed to only one area in isolation. However, countering the effects of near maximal respiratory depressant doses of opioids in the KF may be a powerful approach to combat opioid overdose.
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Affiliation(s)
- Adrienn G. Varga
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy, University of Florida, Gainesville, FL 32610
| | - Brandon T. Reid
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610
| | | | - Erica S. Levitt
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy, University of Florida, Gainesville, FL 32610
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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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δ-Subunit Containing GABA A Receptors Modulate Respiratory Networks. Sci Rep 2017; 7:18105. [PMID: 29273726 PMCID: PMC5741762 DOI: 10.1038/s41598-017-17379-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 11/13/2017] [Indexed: 12/20/2022] Open
Abstract
Persistent and stable respiratory activity across behavioral states is key to homeostasis. Extrasynaptic δ-subunit containing GABAA receptors (δGABAARs) mediate tonic inhibition and regulate network activity. However, the influence of δGABAARs on respiratory rhythm and motor outputs is unknown. We manipulated extra-synaptic GABAA receptor function in the preBötzinger Complex (preBötC), a site central to the generation of inspiratory motor activity in mammals. Activation of preBötC δGABAARs in anesthetized rats and wild-type mice decreased breathing rate. In δGABAAR knockout (Gabrd -/-) mice, however, δGABAARs activation had no effect on breathing rate. We then found that during active wakefulness associated with behaviors and movements, diaphragm activation was higher in the Gabrd -/- compared to wild-type mice, but not in other states. These findings identify that δGABAARs modulate the respiratory network, which is critical to understand how δGABAARs change breathing in pathological conditions affecting extra-synaptic GABAA receptor function such as exposure to anesthetics and neurosteroids.
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