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Herlihy R, Frasson Dos Reis L, Gvritishvili A, Kvizhinadze M, Dybas E, Malhotra A, Fenik VB, Rukhadze I. Chronic intermittent hypoxia attenuates noradrenergic innervation of hypoglossal motor nucleus. Respir Physiol Neurobiol 2024; 321:104206. [PMID: 38142024 PMCID: PMC10872249 DOI: 10.1016/j.resp.2023.104206] [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: 10/10/2023] [Revised: 12/11/2023] [Accepted: 12/19/2023] [Indexed: 12/25/2023]
Abstract
The state-dependent noradrenergic activation of hypoglossal motoneurons plays an important role in the maintenance of upper airway patency and pathophysiology of obstructive sleep apnea (OSA). Chronic intermittent hypoxia (CIH), a major pathogenic factor of OSA, contributes to the risk for developing neurodegenerative disorders in OSA patients. Using anterograde tracer, channelrhodopsin-2, we mapped axonal projections from noradrenergic A7 and SubCoeruleus neurons to hypoglossal nucleus in DBH-cre mice and assessed the effect of CIH on these projections. We found that CIH significantly reduced the number of axonal projections from SubCoeruleus neurons to both dorsal (by 68%) and to ventral (by73%) subregions of the hypoglossal motor nucleus compared to sham-treated animals. The animals' body weight was also negatively affected by CIH. Both effects, the decrease in axonal projections and body weight, were more pronounced in male than female mice, which was likely caused by less sensitivity of female mice to CIH as compared to males. The A7 neurons appeared to have limited projections to the hypoglossal nucleus. Our findings suggest that CIH-induced reduction of noradrenergic innervation of hypoglossal motoneurons may exacerbate progression of OSA, especially in men.
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Affiliation(s)
- Rachael Herlihy
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Leonardo Frasson Dos Reis
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Anzor Gvritishvili
- VA West Los Angeles Medical Center, VAGLAHS, West Los Angeles, CA 90073, USA
| | - Maya Kvizhinadze
- VA West Los Angeles Medical Center, VAGLAHS, West Los Angeles, CA 90073, USA
| | - Elizabeth Dybas
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Atul Malhotra
- University of California San Diego, San Diego, CA 92093, USA
| | - Victor B Fenik
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA; VA West Los Angeles Medical Center, VAGLAHS, West Los Angeles, CA 90073, USA.
| | - Irma Rukhadze
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA; VA West Los Angeles Medical Center, VAGLAHS, West Los Angeles, CA 90073, USA; Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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Mo H, Zhao J, Wu X, Liu W, Hu K. The combination of intermittent electrical stimulation with acute intermittent hypoxia strengthens genioglossus muscle discharge in chronic intermittent hypoxia-pretreated rats. Respir Physiol Neurobiol 2021; 291:103680. [PMID: 33971311 DOI: 10.1016/j.resp.2021.103680] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 04/24/2021] [Accepted: 04/30/2021] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Exploring whether the genioglossus discharge in chronic intermittent hypoxia(CIH) - pretreated rats could be enhanced by intermittent electrical stimulation combined with acute intermittent hypoxia(AIH). METHODS Rats were pretreated with CIH for 4 weeks and then were randomly divided into 6 groups: time control, intermittent electric stimulation, AIH, intermittent electric stimulation + AIH, continuous electric stimulation and continuous hypoxia exposure. The genioglossus discharges were recorded and compared before and after stimulation. Normoxic-treated rats were grouped and treated with the same stimulation protocols. RESULTS Intermittent electrical stimulation or AIH temporarily increased the activity of the genioglossus discharge, in which the degree of the increase was significantly higher in CIH-pretreated rats than in normoxic rats.After intermittent electrical stimulation, AIH evoked a sustained elevation of genioglossus discharge activities in CIH-pretreated rats, in which the degree of the increase was significantly higher than in rats induced by a single intermittent electric stimulation. CONCLUSION Intermittent electrical stimulation combined with AIH strengthens the genioglossus plasticity in CIH-pretreated rats.
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Affiliation(s)
- Huaheng Mo
- Department of Respiratory and Critical Care Medicine, Renmin Hospital of Wuhan University, Wuhan 430060, China.
| | - JingJing Zhao
- Department of Respiratory and Critical Care Medicine, Zhumadian Central Hospital, Zhumadian 463000, China.
| | - Xiaofeng Wu
- Department of Respiratory and Critical Care Medicine, Renmin Hospital of Wuhan University, Wuhan 430060, China.
| | - Wei Liu
- Department of Respiratory and Critical Care Medicine, Renmin Hospital of Wuhan University, Wuhan 430060, China.
| | - Ke Hu
- Department of Respiratory and Critical Care Medicine, Renmin Hospital of Wuhan University, Wuhan 430060, China.
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da Silva MP, Magalhães KS, de Souza DP, Moraes DJA. Chronic intermittent hypoxia increases excitability and synaptic excitation of protrudor and retractor hypoglossal motoneurones. J Physiol 2021; 599:1917-1932. [PMID: 33507557 DOI: 10.1113/jp280788] [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: 09/15/2020] [Accepted: 01/11/2021] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS Dysfunctions in the hypoglossal control of tongue extrinsic muscles are implicated in obstructive sleep apnoea (OSA) syndrome. Chronic intermittent hypoxia (CIH), an important feature of OSA syndrome, produces deleterious effects on the motor control of oropharyngeal resistance, but whether the hypoglossal motoneurones innervating the tongue extrinsic muscles are affected by CIH is unknown. We show that CIH enhanced the respiratory-related activity of rat hypoglossal nerve innervating the protrudor and retractor tongue extrinsic muscles. Intracellular recordings revealed increases in respiratory-related firing frequency and synaptic excitation of inspiratory protrudor and retractor hypoglossal motoneurones after CIH. CIH also increased their intrinsic excitability, depolarised resting membrane potential and reduced K+ -dominated leak conductance. CIH affected the breathing-related synaptic control and intrinsic electrophysiological properties of protrudor and retractor hypoglossal motoneurones to optimise the neural control of oropharyngeal function. ABSTRACT Inspiratory-related tongue movements and oropharyngeal motor actions are controlled mainly by the protrudor and retractor extrinsic tongue muscles, which are innervated by the hypoglossal motoneurones. Chronic intermittent hypoxia (CIH), an important feature of obstructive sleep apnoea syndrome, produces detrimental effects on the contractile function of the tongue extrinsic muscles and the medullary inspiratory network of rodents. However, the impact of the CIH on the electrophysiological properties of protrudor and retractor hypoglossal motoneurones has not been described before. Using nerves and intracellular recordings in in situ preparation of rats (5 weeks old), we tested the hypothesis that CIH (FiO2 of 0.06, SaO2 74%, during 30-40 s, every 9 min, 8 h/day for 10 days) increases the intrinsic excitability of protrudor and retractor motoneurones from the hypoglossal motor nucleus of rats. Recordings of hypoglossal nerve, before its bifurcation to innervate the tongue protrudor and retractor muscles, revealed that CIH enhances its pre-inspiratory, simultaneously with the presence of active expiration, and inspiratory activities. These changes were mediated by increases in the respiratory-related firing frequency and synaptic excitation of inspiratory protrudor and retractor hypoglossal motoneurones. Besides, CIH increases their intrinsic excitability and depolarises resting membrane potential by reducing a K+ -dominated leak conductance. In conclusion, CIH enhances the respiratory-related neural control of oropharyngeal function of rats by increasing the synaptic excitation, intrinsic excitability, and reducing leak conductance in both protrudor and retractor hypoglossal motoneurones. We propose that these network and cellular changes are important to optimise the oropharyngeal resistance in conditions related to intermittent hypoxia.
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Affiliation(s)
- Melina P da Silva
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Karolyne S Magalhães
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Daniel P de Souza
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
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Chang HS, Lee KZ. Modulation of the extrinsic tongue muscle activity in response to bronchopulmonary C-fiber activation following midcervical contusion in the rat. J Appl Physiol (1985) 2020; 128:1130-1145. [DOI: 10.1152/japplphysiol.00857.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Tongue muscle activity plays an important role in the regulation of upper airway patency. This study aimed to investigate the respiratory activity of the extrinsic tongue muscle in response to capsaicin-induced bronchopulmonary C-fiber activation following cervical spinal cord contusion. Midcervical spinal-contused animals exhibited a greater baseline preinspiratory burst amplitude of the extrinsic tongue muscle and were resistant to inhaled capsaicin-induced reduction of respiratory tongue muscle activity at the acute injured stage. However, inhalation of capsaicin caused a more severe attenuation of preinspiratory activity of the extrinsic tongue muscle at the chronic injured stage. These results suggest that the upper airway may be predisposed to collapse in response to bronchopulmonary C-fiber activation following chronic cervical spinal cord injury.
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Affiliation(s)
- Hsiao-Sen Chang
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan
- Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University, Kaohsiung, Taiwan
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan
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Li WY, Wang A, Jin H, Zou Y, Wang Z, Wang W, Kang J. Transient upregulation of TASK-1 expression in the hypoglossal nucleus during chronic intermittent hypoxia is reduced by serotonin 2A receptor antagonist. J Cell Physiol 2019; 234:17886-17895. [PMID: 30864194 DOI: 10.1002/jcp.28419] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 02/10/2019] [Accepted: 02/14/2019] [Indexed: 11/11/2022]
Abstract
Hypoglossal motoneurons innervate genioglossus muscle, the contraction of which is critical in the maintenance of upper airway patency in patients with obstructive sleep apnea. As a potassium channel distributed in hypoglossal motoneurons, TWIK-related acid-sensitive K+ channel-1 (TASK-1) could be inhibited by 5-HT. This study aimed to investigate if TASK-1 expression in hypoglossal nucleus could be influenced by chronic intermittent hypoxia (CIH) and 5-HT2A receptors antagonist. Two hundred twenty-eight rats were exposed to CIH or normoxia (NO) in the presence and absence of 5-HT 2A receptor antagonist (MDL-100907) microinjected into the hypoglossal nucleus. The expression of 5-HT and TASK-1 in the hypoglossal nucleus were detected by immunohistochemistry and reverse transcription quantitative polymerase chain reaction on the 1st, 3rd, 7th, 14th and 21st day of CIH exposure. The mean optical density (MOD) of 5-HT in the XII nucleus was significantly increased in the CIH and CIH + MDL group than the NO group on the 7th and 21st day ( p < 0.05). Compared with the NO group, the MOD and gene expression of TASK-1 in the CIH group was significantly increased on the 7th and 14th day ( p < 0.05), then normalized on the 21st day. The TASK-1 expression in the CIH + MDL group was significantly lower than the CIH + PBS and CIH group on the 7th and 14th day ( p < 0.05). The CIH-induced transiently upregulation of the TASK-1 expression in the hypoglossal nucleus could be reversed by 5-HT 2A receptor antagonist, indicating that the modulation of the TASK-1 expression in response to CIH involves 5-HT and 5-HT 2A receptors, and this CIH effect might be 5-HT 2A receptor-dependent.
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Affiliation(s)
- Wen-Yang Li
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Aidi Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Hongyu Jin
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Ying Zou
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Zanfeng Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Wei Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Jian Kang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
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Nie X, Zhou L, Wang A, Jin H, Qin Z, Pang J, Wang W, Kang J. Noradrenergic Activation of Hypoglossal Nucleus Modulates the Central Regulation of Genioglossus in Chronic Intermittent Hypoxic Rats. Front Neurol 2017; 8:171. [PMID: 28507531 PMCID: PMC5410562 DOI: 10.3389/fneur.2017.00171] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 04/12/2017] [Indexed: 11/13/2022] Open
Abstract
Neuromuscular compensation of the genioglossus muscle can be induced by chronic intermittent hypoxia (CIH) in obstructive sleep apnea to maintain upper airway stability. Noradrenergic activation of hypoglossal nucleus plays a critical role in the central control of the genioglossus. However, it remains unknown whether norepinephrine takes part in the central regulation of the genioglossus during CIH. Adult male Wistar rats (n = 32) were studied to explore the influence of noradrenergic activation of hypoglossal nucleus on the central control of the genioglossus at different stages of CIH. The rats were divided into four groups: normal control or normoxic (NO) group, CIH group, CIH + normal saline (NS) group, and CIH + prazosin (PZ, α1-adrenergic antagonist) group. PZ (0.2 mM, 60 nl) and NS (0.9%, 60 nl) were microinjected into the hypoglossal nucleus. The responses of the genioglossus corticomotor area to transcranial magnetic stimulation (TMS) were recorded on the 1st, 7th, 14th, and 21st day of CIH. The CIH group showed significantly shorter TMS latencies on days 1, 7, and 14 (3.85 ± 0.37 vs. 4.58 ± 0.42, 3.93 ± 0.17 vs. 4.49 ± 0.55, 3.79 ± 0.38 vs. 4.39 ± 0.30 ms, P < 0.05), and higher TMS amplitudes on day 1 (2.74 ± 0.87 vs. 1.60 ± 0.52 mV, P < 0.05) of CIH than the NO group. Compared to the CIH + NS group, the CIH + PZ group showed decreased TMS responses (longer latencies and lower amplitudes) only on the 14th day of CIH (3.99 ± 0.28 vs. 4.61 ± 0.48 ms, 2.51 ± 0.67 vs. 1.18 ± 0.62 mV, P < 0.05). These results indicated that noradrenergic activation of the hypoglossal nucleus played a role in the central compensation of genioglossus through α1-adrenoceptor on the 14th day of CIH.
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Affiliation(s)
- Xinshi Nie
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, China
| | - Ling Zhou
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, China
| | - Aidi Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, China
| | - Hongyu Jin
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, China
| | - Zheng Qin
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, China
| | - Jian Pang
- The 463rd Hospital of the Chinese PLA, Shenyang, China
| | - Wei Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, China
| | - Jian Kang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, China
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Wu X, Lu H, Hu L, Gong W, Wang J, Fu C, Liu Z, Li S. Chronic intermittent hypoxia affects endogenous serotonergic inputs and expression of synaptic proteins in rat hypoglossal nucleus. Am J Transl Res 2017; 9:546-557. [PMID: 28337282 PMCID: PMC5340689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 01/22/2017] [Indexed: 06/06/2023]
Abstract
Evidence has shown that hypoxic episodes elicit hypoglossal neuroplasticity which depends on elevated serotonin (5-HT), in contrast to the rationale of obstructive sleep apnea (OSA) that deficient serotonergic input to HMs fails to keep airway patency. Therefore, understanding of the 5-HT dynamic changes at hypoglossal nucleus (HN) during chronic intermittent hypoxia (CIH) will be essential to central pathogenic mechanism and pharmacological therapy of OSA. Moreover, the effect of CIH on BDNF-TrkB signaling proteins was quantified in an attempt to elucidate cellular cascades/synaptic mechanisms following 5-HT alteration. Male rats were randomly exposed to normal air (control), intermittent hypoxia of 3 weeks (IH3) and 5 weeks (IH5) groups. Through electrical stimulation of dorsal raphe nuclei (DRN), we conducted amperometric technique with carbon fiber electrode in vivo to measure the real time release of 5-HT at XII nucleus. 5-HT2A receptors immunostaining measured by intensity and c-Fos quantified visually were both determined by immunohistochemistry. CIH significantly reduced endogenous serotonergic inputs from DRN to XII nucleus, shown as decreased peak value of 5-HT signals both in IH3 and IH5groups, whereas time to peak and half-life period of 5-HT were unaffected. Neither 5-HT2A receptors nor c-Fos expression in HN were significantly altered by CIH. Except for marked increase in phosphorylation of ERK in IH5 rats, BDNF-TrkB signaling and synaptophys consistently demonstrated downregulated levels. These results suggest that the deficiency of 5-HT and BDNF-dependent synaptic proteins in our CIH protocol contribute to the decompensated mechanism of OSA.
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Affiliation(s)
- Xu Wu
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan UniversityShanghai, China
- Clinical Center for Sleep Breathing Disorder and Snoring, Zhongshan Hospital, Fudan UniversityShanghai 200032, China
| | - Huan Lu
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan UniversityShanghai, China
- Clinical Center for Sleep Breathing Disorder and Snoring, Zhongshan Hospital, Fudan UniversityShanghai 200032, China
| | - Lijuan Hu
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan UniversityShanghai, China
| | - Wankun Gong
- Department of Pharmacology, State Key Laboratory of Medical Neurobiology, Institutes of Brain Research, Shanghai Medical College of Fudan UniversityShanghai 200032, China
| | - Juan Wang
- Department of Pharmacology, State Key Laboratory of Medical Neurobiology, Institutes of Brain Research, Shanghai Medical College of Fudan UniversityShanghai 200032, China
| | - Cuiping Fu
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan UniversityShanghai, China
- Clinical Center for Sleep Breathing Disorder and Snoring, Zhongshan Hospital, Fudan UniversityShanghai 200032, China
| | - Zilong Liu
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan UniversityShanghai, China
- Clinical Center for Sleep Breathing Disorder and Snoring, Zhongshan Hospital, Fudan UniversityShanghai 200032, China
| | - Shanqun Li
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan UniversityShanghai, China
- Clinical Center for Sleep Breathing Disorder and Snoring, Zhongshan Hospital, Fudan UniversityShanghai 200032, China
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Kubin L. Neural Control of the Upper Airway: Respiratory and State-Dependent Mechanisms. Compr Physiol 2016; 6:1801-1850. [PMID: 27783860 DOI: 10.1002/cphy.c160002] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Upper airway muscles subserve many essential for survival orofacial behaviors, including their important role as accessory respiratory muscles. In the face of certain predisposition of craniofacial anatomy, both tonic and phasic inspiratory activation of upper airway muscles is necessary to protect the upper airway against collapse. This protective action is adequate during wakefulness, but fails during sleep which results in recurrent episodes of hypopneas and apneas, a condition known as the obstructive sleep apnea syndrome (OSA). Although OSA is almost exclusively a human disorder, animal models help unveil the basic principles governing the impact of sleep on breathing and upper airway muscle activity. This article discusses the neuroanatomy, neurochemistry, and neurophysiology of the different neuronal systems whose activity changes with sleep-wake states, such as the noradrenergic, serotonergic, cholinergic, orexinergic, histaminergic, GABAergic and glycinergic, and their impact on central respiratory neurons and upper airway motoneurons. Observations of the interactions between sleep-wake states and upper airway muscles in healthy humans and OSA patients are related to findings from animal models with normal upper airway, and various animal models of OSA, including the chronic-intermittent hypoxia model. Using a framework of upper airway motoneurons being under concurrent influence of central respiratory, reflex and state-dependent inputs, different neurotransmitters, and neuropeptides are considered as either causing a sleep-dependent withdrawal of excitation from motoneurons or mediating an active, sleep-related inhibition of motoneurons. Information about the neurochemistry of state-dependent control of upper airway muscles accumulated to date reveals fundamental principles and may help understand and treat OSA. © 2016 American Physiological Society. Compr Physiol 6:1801-1850, 2016.
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Affiliation(s)
- Leszek Kubin
- Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Ge D, Yan X, Guo Y, Chen X, Guan R, Chen Y, Qiu D, Wang J. Activation of α1-adrenoceptors facilitates excitatory inputs to medullary airway vagal preganglionic neurons. J Appl Physiol (1985) 2015. [PMID: 26205539 DOI: 10.1152/japplphysiol.00045.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In mammals, the neural control of airway smooth muscle is dominated by a subset of airway vagal preganglionic neurons in the ventrolateral medulla. These neurons are physiologically modulated by adrenergic/noradrenergic projections, and weakened α₂-adrenergic inhibition of them is indicated to participate in the pathogenesis and exacerbation of asthma. This study tests whether these neurons are modulated by α₁-adrenoceptors, and if so, how. In anesthetized adult rats, microinjection of the α₁A-adrenoceptor agonist A61603 (1 pmol) unilaterally into the medullary region containing these neurons caused a significant increase in airway resistance, which was prevented by intraperitoneal atropine (0.5 mg/kg). In rhythmically firing medullary slices of newborn rats, A61603 (10 nM) caused depolarization in both the inspiratory-activated and inspiratory-inhibited airway vagal preganglionic neurons that were retrogradely labeled, and a significant increase in the spontaneous firing rate. Under voltage clamp, A61603 significantly enhanced the spontaneous excitatory inputs to both types of neurons and caused a tonic inward current in the inspiratory-activated neurons along with significantly increased peak amplitude of the inspiratory inward currents. The responses in vitro were prevented by α₁A-adrenoceptor antagonist RS100329 (1 μM), which alone significantly inhibited the spontaneous excitatory inputs to both types of the neurons. After pretreatment with tetrodotoxin (1 μM), A61603 (10 or 100 nM) had no effect on either type of neuron. We conclude that in rats, activation of α₁-adrenoceptors in the medullary region containing airway vagal preganglionic neurons increases airway vagal tone, and that this effect is primarily mediated by facilitation of the excitatory inputs to the preganglionic neurons.
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Affiliation(s)
- Dengyun Ge
- Department of Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Xianxia Yan
- Department of Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Yuhong Guo
- Department of Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Xingxin Chen
- Department of Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Ruijuan Guan
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Fudan University, Shanghai, China; and
| | - Yonghua Chen
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Fudan University, Shanghai, China; and
| | - Dongying Qiu
- Department of Gerontology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Jijiang Wang
- Department of Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Fudan University, Shanghai, China; and
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Kubin L. Sleep-wake control of the upper airway by noradrenergic neurons, with and without intermittent hypoxia. PROGRESS IN BRAIN RESEARCH 2014; 209:255-74. [PMID: 24746052 PMCID: PMC4498577 DOI: 10.1016/b978-0-444-63274-6.00013-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Hypoglossal (XII) motoneurons innervate muscles of the tongue whose tonic and inspiratory modulated activity protects the upper airway from collapse in patients affected by the obstructive sleep apnea (OSA) syndrome. Both norepinephrine and serotonin provide wakefulness-related excitatory drives that maintain activity in XII motoneurons, with the noradrenergic system playing a particularly prominent role in rats. When noradrenergic and serotonergic drives are antagonized, no further decline of XII nerve activity occurs during pharmacologically induced rapid eye movement (REM) sleep-like state. This is the best evidence to date that, at least in this model, the entire REM sleep-related decline of upper airway muscle tone results from withdrawal of these two excitatory inputs. A major component of noradrenergic input to XII motoneurons originates from pontine noradrenergic neurons that have state-dependent patterns of activity, maximal during wakefulness, and minimal, or absent during REM sleep. Our data suggest that not all ventrolateral medullary catecholaminergic neurons follow this pattern, with adrenergic C1 neurons probably increasing their activity during REM sleep. When rats are subjected to chronic-intermittent hypoxia, noradrenergic drive to XII motoneurons is increased by mechanisms that include sprouting of noradrenergic terminals in the XII nucleus, and increased expression of α1-adrenoceptors; an outcome that may underlie the elevated baseline activity of upper airway muscles during wakefulness in OSA patients.
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Affiliation(s)
- Leszek Kubin
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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Edge D, McDonald FB, Jones JFX, Bradford A, O'Halloran KD. Effect of chronic intermittent hypoxia on the reflex recruitment of the genioglossus during airway obstruction in the anesthetized rat. PROGRESS IN BRAIN RESEARCH 2014; 209:147-68. [PMID: 24746047 DOI: 10.1016/b978-0-444-63274-6.00008-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We sought to test the hypothesis that chronic intermittent hypoxia (CIH)-a feature of sleep-disordered breathing in humans-impairs reflex recruitment of the genioglossus (GG, pharyngeal dilator) during obstructive airway events. Adult male Wistar rats were exposed to 20 cycles of normoxia and hypoxia (5% O2 at nadir) per hour, 8h a day for 7 days (CIH, N=7). The sham group (N=7) were exposed to normoxia in parallel. Following gas treatments, rats were anesthetized with an i.p. injection of urethane (1.5g/kg; 20%, w/v). Fine concentric needle electrodes were inserted into the GG and the costal diaphragm. Discriminated GG motor unit potentials and whole electromyograph (EMG), together with arterial blood pressure and arterial O2 saturation, were recorded during quiet basal breathing and during nasal airway occlusion. Airway occlusion significantly increased GG EMG activity in all animals; but there was no difference in the reflex response to airway occlusion between sham and CIH-treated animals (+105±22% vs. +105±17%, mean±SEM for area under the curve of integrated GG EMG, % increase from baseline, p=0.99). Occluded breaths were characterized by a significant increase in the firing frequency of phasically active units and the recruitment of large motor units that were quiescent under basal conditions. Though there are reports of impaired control of the upper airway following CIH in the rat, we conclude that reflexly evoked motor discharge to the GG is not affected by 7 days of CIH, a paradigm that we have shown increases apnea index in sleeping rats.
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Affiliation(s)
- Deirdre Edge
- UCD School of Medicine and Medical Science, University College Dublin, Dublin, Ireland.
| | - Fiona B McDonald
- UCD School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
| | - James F X Jones
- UCD School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
| | - Aidan Bradford
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Ken D O'Halloran
- Department of Physiology, Western Gateway Building, University College Cork, Cork, Ireland
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Stettner GM, Rukhadze I, Mann GL, Lei Y, Kubin L. Respiratory modulation of lingual muscle activity across sleep-wake states in rats. Respir Physiol Neurobiol 2013; 188:308-17. [PMID: 23732510 DOI: 10.1016/j.resp.2013.05.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 05/22/2013] [Accepted: 05/23/2013] [Indexed: 11/26/2022]
Abstract
In obstructive sleep apnea (OSA) patients, inspiratory activation (IA) of lingual muscles protects the upper airway from collapse. We aimed to determine when rats' lingual muscles exhibit IA. In 5 Sprague-Dawley and 3 Wistar rats, we monitored cortical EEG and lingual, diaphragmatic and nuchal electromyograms (EMGs), and identified segments of records when lingual EMG exhibited IA. Individual segments lasted 2.4-269 s (median: 14.5 s), most (89%) occurred during slow-wave sleep (SWS), and they collectively occupied 0.3-6.1% of the total recording time. IA usually started to increase with a delay after SWS onset and ended with an arousal, or declined prior to rapid eye movement sleep. IA of lingual EMG was not accompanied by increased diaphragmatic activity or respiratory rate changes, but occurred when cortical EEG power was particularly low in a low beta-1 frequency range (12.5-16.4 Hz). A deep SWS-related activation of upper airway muscles may be an endogenous phenomenon designed to protect the upper airway against collapse.
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Affiliation(s)
- Georg M Stettner
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104-6046, USA
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Mateika JH, Syed Z. Intermittent hypoxia, respiratory plasticity and sleep apnea in humans: present knowledge and future investigations. Respir Physiol Neurobiol 2013; 188:289-300. [PMID: 23587570 DOI: 10.1016/j.resp.2013.04.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 03/28/2013] [Accepted: 04/06/2013] [Indexed: 11/18/2022]
Abstract
This review examines the role that respiratory plasticity has in the maintenance of breathing stability during sleep in individuals with sleep apnea. The initial portion of the review considers the manner in which repetitive breathing events may be initiated in individuals with sleep apnea. Thereafter, the role that two forms of respiratory plasticity, progressive augmentation of the hypoxic ventilatory response and long-term facilitation of upper airway and respiratory muscle activity, might have in modifying breathing events in humans is examined. In this context, present knowledge regarding the initiation of respiratory plasticity in humans during wakefulness and sleep is addressed. Also, published findings which reveal that exposure to intermittent hypoxia promotes breathing instability, at least in part, because of progressive augmentation of the hypoxic ventilatory response and the absence of long-term facilitation, are considered. Next, future directions are presented and are focused on the manner in which forms of plasticity that stabilize breathing might be promoted while diminishing destabilizing forms, concurrently. These future directions will consider the potential role of circadian rhythms in the promotion of respiratory plasticity and the role of respiratory plasticity in enhancing established treatments for sleep apnea.
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Affiliation(s)
- Jason H Mateika
- John D. Dingell Veterans Affairs Medical Center, Detroit, MI 48201, United States; Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, United States; Department of Internal Medicine, Wayne State University School of Medicine, Detroit, MI 48201, United States.
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Herr KB, Stettner GM, Kubin L. Reduced c-Fos expression in medullary catecholaminergic neurons in rats 20 h after exposure to chronic intermittent hypoxia. Am J Physiol Regul Integr Comp Physiol 2013; 304:R514-22. [PMID: 23364524 DOI: 10.1152/ajpregu.00542.2012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Persons affected by obstructive sleep apnea (OSA) have increased arterial blood pressure and elevated activity in upper airway muscles. Many cardiorespiratory features of OSA have been reproduced in rodents subjected to chronic-intermittent hypoxia (CIH). We previously reported that, following exposure to CIH, rats have increased noradrenergic terminal density in brain stem sensory and motor nuclei and upregulated expression of the excitatory α(1)-adrenergic receptors in the hypoglossal motor nucleus. This suggested that CIH may enhance central catecholaminergic transmission. We now quantified c-Fos expression in different groups of pontomedullary catecholaminergic neurons as an indirect way of assessing their baseline activity in rats subjected to CIH or sham treatment (7 AM-5 PM daily for 35 days). One day after the last CIH exposure, the rats were gently kept awake for 2.5 h and then were anesthetized and perfused, and their pontomedullary brain sections were subjected to dopamine β-hydroxylase (DBH) and c-Fos immunohistochemistry. DBH-positive cells were counted in the A1/C1, A2/C2, A5, subcoeruleus (sub-C) and A7 groups of catecholaminergic neurons, and the percentages of those expressing c-Fos were determined. We found that fewer DBH cells expressed c-Fos in CIH- than in sham-treated rats in the medulla (significant in the A1 group). In the pons (rostral A5, sub-C, and A7), c-Fos expression did not differ between the CIH- and sham-treated animals. We suggest that, when measured 20 h after the last CIH exposure, catecholaminergic transmission is enhanced through terminal sprouting and receptor upregulation rather than through increased baseline activity in pontomedullary catecholaminergic neurons.
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Affiliation(s)
- Kate Benincasa Herr
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Stettner GM, Kubin L. Antagonism of orexin receptors in the posterior hypothalamus reduces hypoglossal and cardiorespiratory excitation from the perifornical hypothalamus. J Appl Physiol (1985) 2012; 114:119-30. [PMID: 23104701 DOI: 10.1152/japplphysiol.00965.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The perifornical (PF) region of the posterior hypothalamus promotes wakefulness and facilitates motor activity. In anesthetized rats, local disinhibition of PF neurons by GABA(A) receptor antagonists activates orexin (OX) neurons and elicits a systemic response, including increases of hypoglossal nerve activity (XIIa), respiratory rate, heart rate, and blood pressure. The increase of XIIa is mediated to hypoglossal (XII) motoneurons by pathways that do not require noradrenergic or serotonergic projections. We hypothesized that the pathway might include OX-dependent activation locally within the PF region or direct projections of OX neurons to the XII nucleus. Adult, male Sprague-Dawley rats were urethane anesthetized, vagotomized, paralyzed, and ventilated. Gabazine (GABA(A) receptor antagonist, 0.18 mM, 20 nl) was injected into the PF region, and ~2 h later, a second gabazine injection was performed preceded by injection of a dual OX1/2 receptor antagonist (almorexant; 90 mM) either into the XII nucleus (40-60 nl at 2-3 rostrocaudal levels; n = 6 rats), or into the PF region (40-60 nl; n = 6 rats). XIIa, respiratory rate, heart rate, and arterial blood pressure were analyzed for 70 min after each gabazine injection. The excitatory effects of PF gabazine on XIIa, respiratory, and heart rates were significantly reduced by up to 44-82% when gabazine injections were preceded by PF almorexant injections, but not when almorexant was injected into the XII nucleus. These data suggest that a significant portion of XII motoneuronal and cardiorespiratory activation evoked by disinhibition of PF neurons is mediated by local OX-dependent mechanisms within the posterior hypothalamus.
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Affiliation(s)
- Georg M Stettner
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6046, USA.
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Fenik VB, Singletary T, Branconi JL, Davies RO, Kubin L. Glucoregulatory consequences and cardiorespiratory parameters in rats exposed to chronic-intermittent hypoxia: effects of the duration of exposure and losartan. Front Neurol 2012; 3:51. [PMID: 22509173 PMCID: PMC3321439 DOI: 10.3389/fneur.2012.00051] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 03/20/2012] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Obstructive sleep apnea (OSA) is associated with glucose intolerance. Both chronic sleep disruption and recurrent blood oxygen desaturations (chronic-intermittent hypoxia, CIH) may cause, or exacerbate, metabolic derangements. METHODS To assess the impact of CIH alone, without accompanying upper airway obstructions, on the counter-regulatory response to glucose load and cardiorespiratory parameters, we exposed adult male Sprague-Dawley rats to CIH or sham room air exchanges for 10 h/day for 7, 21, or 35 days and then, 1 day after conclusion of CIH exposure, conducted intravenous glucose-tolerance tests (ivgtt) under urethane anesthesia. Additional rats underwent 35 days of CIH followed by 35 days of regular housing, or had 35 day-long CIH exposure combined with daily administration of the type 1 angiotensin II receptor antagonist, losartan (15 mg/kg, p.o.), and then were also subjected to ivgtt. RESULTS Compared with the corresponding control groups, CIH rats had progressively reduced glucose-stimulated insulin release and impaired glucose clearance, only mildly elevated heart rate and/or arterial blood pressure and slightly reduced respiratory rate. The differences in insulin release between the CIH and sham-treated rats disappeared in the rats normally housed for 35 days after 35 days of CIH/sham exposure. The losartan-treated rats had improved insulin sensitivity, with no evidence of suppressed insulin release in the CIH group. CONCLUSION In adult rats, the glucose-stimulated insulin release is gradually suppressed with the duration of exposure to CIH, but the effect is reversible. Elimination of the detrimental effect of CIH on insulin release by losartan suggests that CIH disrupts glucoregulation through angiotensin/catecholaminergic pathways. Accordingly, treatment with continuous positive airway pressure may ameliorate pre-diabetic conditions in OSA patients, in part, by reducing sympathoexcitatory effects of recurrent nocturnal hypoxia.
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Affiliation(s)
- Victor B Fenik
- Department of Animal Biology 209E/VET, School of Veterinary Medicine, University of Pennsylvania Philadelphia, PA, USA
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