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MacDonald EA, Rose RA, Quinn TA. Neurohumoral Control of Sinoatrial Node Activity and Heart Rate: Insight From Experimental Models and Findings From Humans. Front Physiol 2020; 11:170. [PMID: 32194439 PMCID: PMC7063087 DOI: 10.3389/fphys.2020.00170] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 02/13/2020] [Indexed: 12/22/2022] Open
Abstract
The sinoatrial node is perhaps one of the most important tissues in the entire body: it is the natural pacemaker of the heart, making it responsible for initiating each-and-every normal heartbeat. As such, its activity is heavily controlled, allowing heart rate to rapidly adapt to changes in physiological demand. Control of sinoatrial node activity, however, is complex, occurring through the autonomic nervous system and various circulating and locally released factors. In this review we discuss the coupled-clock pacemaker system and how its manipulation by neurohumoral signaling alters heart rate, considering the multitude of canonical and non-canonical agents that are known to modulate sinoatrial node activity. For each, we discuss the principal receptors involved and known intracellular signaling and protein targets, highlighting gaps in our knowledge and understanding from experimental models and human studies that represent areas for future research.
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Affiliation(s)
- Eilidh A MacDonald
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada
| | - Robert A Rose
- Cumming School of Medicine, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - T Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada.,School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada
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Siebenmann C, Rasmussen P, Sørensen H, Bonne TC, Zaar M, Aachmann-Andersen NJ, Nordsborg NB, Secher NH, Lundby C. Hypoxia increases exercise heart rate despite combined inhibition of β-adrenergic and muscarinic receptors. Am J Physiol Heart Circ Physiol 2015; 308:H1540-6. [DOI: 10.1152/ajpheart.00861.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 04/15/2015] [Indexed: 11/22/2022]
Abstract
Hypoxia increases the heart rate response to exercise, but the mechanism(s) remains unclear. We tested the hypothesis that the tachycardic effect of hypoxia persists during separate, but not combined, inhibition of β-adrenergic and muscarinic receptors. Nine subjects performed incremental exercise to exhaustion in normoxia and hypoxia (fraction of inspired O2 = 12%) after intravenous administration of 1) no drugs (Cont), 2) propranolol (Prop), 3) glycopyrrolate (Glyc), or 4) Prop + Glyc. HR increased with exercise in all drug conditions ( P < 0.001) but was always higher at a given workload in hypoxia than normoxia ( P < 0.001). Averaged over all workloads, the difference between hypoxia and normoxia was 19.8 ± 13.8 beats/min during Cont and similar (17.2 ± 7.7 beats/min, P = 0.95) during Prop but smaller ( P < 0.001) during Glyc and Prop + Glyc (9.8 ± 9.6 and 8.1 ± 7.6 beats/min, respectively). Cardiac output was enhanced by hypoxia ( P < 0.002) to an extent that was similar between Cont, Glyc, and Prop + Glyc (2.3 ± 1.9, 1.7 ± 1.8, and 2.3 ± 1.2 l/min, respectively, P > 0.4) but larger during Prop (3.4 ± 1.6 l/min, P = 0.004). Our results demonstrate that the tachycardic effect of hypoxia during exercise partially relies on vagal withdrawal. Conversely, sympathoexcitation either does not contribute or increases heart rate through mechanisms other than β-adrenergic transmission. A potential candidate is α-adrenergic transmission, which could also explain why a tachycardic effect of hypoxia persists during combined β-adrenergic and muscarinic receptor inhibition.
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Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
- Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - P. Rasmussen
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - H. Sørensen
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - T. C. Bonne
- Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, Denmark; and
| | - M. Zaar
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | - N. B. Nordsborg
- Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, Denmark; and
| | - N. H. Secher
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - C. Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
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Affiliation(s)
- James P. Fisher
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
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Kolettis TM, Vilaeti AD, Tsalikakis DG, Zoga A, Valenti M, Tzallas AT, Papalois A, Iliodromitis EK. Effects of Pre- and Postconditioning on Arrhythmogenesis in the In Vivo Rat Model. J Cardiovasc Pharmacol Ther 2013; 18:376-85. [DOI: 10.1177/1074248413482183] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The antiarrhythmic potential of postconditioning in in vivo models remains poorly defined. We compared the effects of pre- and postconditioning on ventricular arrhythmogenesis against controls with and without reperfusion. Wistar rats (n = 40, 269 ± 3 g) subjected to ischemia (30 minutes)–reperfusion (24 hours) were assigned to the following groups: (1) preconditioning (2 cycles), (2) postconditioning (6 cycles), or (3) no intervention and were compared with (4) nonreperfused infarcts and (5) sham-operated animals. Infarct size was measured, and arrhythmogenesis was evaluated with continuous telemetric electrocardiographic recording, heart rate variability indices, and monophasic action potentials (MAPs). During a 24-hour observation period, no differences in mortality were observed. Reperfusion decreased infarct size and ameliorated sympathetic activation during the late reperfusion phase. Preconditioning decreased infarct size by a further 35% ( P = .0017), but only a marginal decrease (by 18%, P = .075) was noted after postconditioning. Preconditioning decreased arrhythmias during ischemia and early reperfusion, whereas postconditioning almost abolished them during the entire reperfusion period. No differences were noted in MAPs or in the magnitude of sympathetic activation between the 2 interventions. Compared to postconditioning, preconditioning affords more powerful cytoprotection, but both interventions exert antiarrhythmic actions. In the latter, these are mainly evident during the ischemic phase and continue during early reperfusion. Postconditioning markedly decreases reperfusion arrhythmias during a prolonged observation period. The mechanisms underlying the antiarrhythmic effects of pre- and postconditioning are likely different but remain elusive.
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Affiliation(s)
- Theofilos M. Kolettis
- Medical School, University of Ioannina, Ioannina, Greece
- Cardiovascular Research Institute, Ioannina and Athens, Greece
| | - Agapi D. Vilaeti
- Cardiovascular Research Institute, Ioannina and Athens, Greece
- Department of Cardiology, Medical School, University of Ioannina, Ioannina, Greece
| | - Dimitrios G. Tsalikakis
- Department of Engineering Informatics and Telecommunications, Computational Cardiology and Modeling, University of Western Macedonia, Kozani, Greece
| | - Anastasia Zoga
- Second Department of Cardiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Mesele Valenti
- Cardiovascular Research Institute, Ioannina and Athens, Greece
| | - Alexandros T. Tzallas
- Department of Informatics & Telecommunications Technology, Technological Educational Institute of Epirus, Arta, Greece
| | - Apostolos Papalois
- Cardiovascular Research Institute, Ioannina and Athens, Greece
- ELPEN Research Laboratory, Pikermi, Athens, Greece
| | - Efstathios K. Iliodromitis
- Second Department of Cardiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
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Giusti MF, Sato MA, Cardoso LM, Braga VA, Colombari E. Central antioxidant therapy inhibits parasympathetic baroreflex control in conscious rats. Neurosci Lett 2011; 489:115-8. [DOI: 10.1016/j.neulet.2010.11.077] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 11/30/2010] [Accepted: 11/30/2010] [Indexed: 02/07/2023]
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Kwatra SG, Goldsmith LE, White WD, Lin SS, Kwatra MM. LOW EXPRESSION OF α 1-ADRENERGIC RECEPTORS IN THE AGING HUMAN HEART. J Am Geriatr Soc 2010; 58:210-2. [DOI: 10.1111/j.1532-5415.2009.02659.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Haramaki N, Ikeda H, Takenaka K, Katoh A, Sugano R, Yamagishi SI, Matsuoka H, Imaizumi T. Fluvastatin Alters Platelet Aggregability in Patients With Hypercholesterolemia. Arterioscler Thromb Vasc Biol 2007; 27:1471-7. [PMID: 17379842 DOI: 10.1161/atvbaha.106.128793] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Hypercholesterolemia enhances platelet aggregability. Statins have beneficial effects on cardiovascular events. The purpose of this study is to investigate whether statins inhibit platelet aggregation and, if so, the mechanisms. METHODS AND RESULTS Twelve patients with hypercholesterolemia were prospectively randomized in a crossover design to receive either fluvastatin (20 mg/d) or colestimide (3000 mg/d) for 12 weeks. The subjects were switched to the opposite arm for additional 12 weeks. Before and after first and second treatments, experiments were performed. Eleven age-matched volunteers with normal lipid profiles served as controls. ADP-induced platelet aggregation, platelet-derive nitric oxide (PDNO) release, intraplatelet levels of GSH and GSSG, and intraplatelet nitrotyrosine production during platelet aggregation were measured. Fluvastatin and colestimide equally lowered total and low density lipoprotein cholesterol levels in hypercholesterolemia. Platelet aggregation was greater in hypercholesterolemia than in normocholesterolemia before treatment and was altered by fluvastatin. PDNO release, intraplatelet glutathione level, and GSH/GSSG ratio were lower in hypercholesterolemia than in normocholesterolemia before treatment and were increased by fluvastatin. Intraplatelet nitrotyrosine formation was greater in hypercholesterolemia than in normocholesterolemia, and decreased by fluvastatin. Colestimide did not have such effects. In vitro application of fluvastatin dose-dependently inhibited platelet aggregation. Furthermore, in vitro application of fluvastatin dose-dependently inhibited platelet nitrotyrosine expressions and the inhibitory effects by fluvastatin were reversed by preincubation with geranylgeranylpyrophosphate. CONCLUSIONS Fluvastatin altered platelet aggregability in hypercholesterolemic patients in a cholesterol-lowering independent manner, which was partly mediated by the improvement of intraplatelet redox imbalance.
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Affiliation(s)
- Nobuya Haramaki
- Division of Cardiovascular Medicine, Department of Medicine, Kurume University School of Medicine, 67 Asahi-machi, Kurume, 830-0011, Japan
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Hopkins SR, Bogaard HJ, Niizeki K, Yamaya Y, Ziegler MG, Wagner PD. Beta-adrenergic or parasympathetic inhibition, heart rate and cardiac output during normoxic and acute hypoxic exercise in humans. J Physiol 2003; 550:605-16. [PMID: 12766243 PMCID: PMC2343040 DOI: 10.1113/jphysiol.2003.040568] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Acute hypoxia increases heart rate (HR) and cardiac output (Qt) at a given oxygen consumption (VO2) during submaximal exercise. It is widely believed that the underlying mechanism involves increased sympathetic activation and circulating catecholamines acting on cardiac beta receptors. Recent evidence indicating a continued role for parasympathetic modulation of HR during moderate exercise suggests that increased parasympathetic withdrawal plays a part in the increase in HR and Qt during hypoxic exercise. To test this, we separately blocked the beta-sympathetic and parasympathetic arms of the autonomic nervous system (ANS) in six healthy subjects (five male, one female; mean +/- S.E.M. age = 31.7+/-1.6 years, normoxic maximal VO2 (VO2,max)=3.1+/-0.3 l min(-1)) during exercise in conditions of normoxia and acute hypoxia (inspired oxygen fraction=0.125) to VO2,max. Data were collected on different days under the following conditions: (1)control, (2) after 8.0 mg propranolol i.v. and (3) after 0.8 mg glycopyrrolate i.v. Qt was measured using open-circuit acetylene uptake. Hypoxia increased venous [adrenaline] and [noradrenaline] but not [dopamine] at a given VO2 (P<0.05, P<0.01 and P=0.2, respectively). HR/VO2 and Qt/VO2 increased during hypoxia in all three conditions (P<0.05). Unexpectedly, the effects of hypoxia on HR and Qt were not significantly different from control with either beta-sympathetic or parasympathetic inhibition. These data suggest that although acute exposure to hypoxia increases circulating [catecholamines], the effects of hypoxia on HR and Qt do not necessarily require intact cardiac muscarinic and beta receptors. It may be that cardiac alpha receptors play a primary role in elevating HR and Qt during hypoxic exercise, or perhaps offer an alternative mechanism when other ANS pathways are blocked.
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Affiliation(s)
- Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
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Affiliation(s)
- John Longhurst
- College of Medicine, Med Sci I, Room C240, Irvine, CA 92697-4075, USA.
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Madden KM, Levy WC, Jacobson A, Stratton JR. The effect of aging on phenylephrine response in normal subjects. J Am Aging Assoc 2003; 26:3-9. [PMID: 23604913 PMCID: PMC3456817 DOI: 10.1007/s11357-003-0001-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
INTRODUCTION With aging, cardiac responses to β-adrenergic stimulation decline but the responses to α1-stimulation are less clear. Moreover, whether aging, in the absence of disease, influences the left ventricular response to an increase in afterload is unclear. This study examined the effect of aging on heart rate (HR), blood pressure (BP), cardiac index (CI) and several left ventricular contractility measurements during α 1-stimulation with a phenylephrine infusion. METHODS Subjects were rigorously screened to be normal by history, physical, blood tests, ECG, ETT and echocardiogram. Twelve young (mean 26 years, all male) and 15 aged (69 years, 11 males) subjects were studied during 10 minute infusions of phenylephrine at 0.5 and 1.0 mcg/ kg/min. HR, BP and radionuclide ventriculographic cardiac volumes were measured. RESULTS Systolic BP increased more in the aged than in the young (22 vs. 13%, p=0.003), while heart rate (16 vs. 21%, p=0.05) fell less. Contractile responses to phenylephrine, including EF, stroke volume index (SVI), stroke work index and left ventricular contractility index were not altered with aging. Systemic vascular resistance (SVR) was higher at baseline and at each infusion rate, but there was no age-associate change in the response to PE. CONCLUSIONS In a healthy normal aged population, a preserved SVI response in the setting of a higher baseline SVR results in an increased SBP response to α1-stimulation. Contractile responses to increased afterload are not altered with aging. Age-associated differences in the response to α1-stimulation are small and are explained by altered baroreflex sensitivity and a stiffer vasculature.
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Affiliation(s)
- Kenneth M. Madden
- />Division of Cardiology, Department of Medicine, Seattle Veterans Affairs Medical Center and University of Washington, Seattle, Washington
- />Division of Nuclear Medicine, Department of Radiology, Seattle Veterans Affairs Medical Center and University of Washington, Seattle, Washington
- />Department of Geriatric Medicine, Vancouver Hospital and Health Science Center, S124-2211 Westbrook Mall, Vancouver, BC Canada V6T 2B5
| | - Wayne C. Levy
- />Division of Cardiology, Department of Medicine, Seattle Veterans Affairs Medical Center and University of Washington, Seattle, Washington
- />Division of Nuclear Medicine, Department of Radiology, Seattle Veterans Affairs Medical Center and University of Washington, Seattle, Washington
| | - Arnold Jacobson
- />Division of Cardiology, Department of Medicine, Seattle Veterans Affairs Medical Center and University of Washington, Seattle, Washington
- />Division of Nuclear Medicine, Department of Radiology, Seattle Veterans Affairs Medical Center and University of Washington, Seattle, Washington
| | - John R. Stratton
- />Division of Cardiology, Department of Medicine, Seattle Veterans Affairs Medical Center and University of Washington, Seattle, Washington
- />Division of Nuclear Medicine, Department of Radiology, Seattle Veterans Affairs Medical Center and University of Washington, Seattle, Washington
- />Cardiology (SIIIc), VAPSHCS, 1600 South Columbian Way, Seattle, WA 98108
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Ono T, Saitoh H, Atarashi H, Hayakawa H. Abnormality of alpha-adrenergic vascular response in patients with neurally mediated syncope. Am J Cardiol 1998; 82:438-43. [PMID: 9723630 DOI: 10.1016/s0002-9149(98)00358-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Although diagnosis of neurally mediated syncope (NMS) using the head-up tilt (HUT) test has been established, the precise etiologic mechanism of NMS is still obscure. Previously, we reported the contribution of impaired alpha-adrenergic vascular response to syncope in patients with various arrhythmias. This study evaluates alpha-adrenergic vascular response in 21 NMS patients with syncope and a positive HUT test (80 degrees, 30 minutes, and low-dose isoproterenol, NMS group, mean age 31 +/- 14 years) and 21 control subjects (C group, 33 +/- 14 years) who had no evidence of syncope and no structural heart disease. After 30 minutes in a recumbent position, pharmacologic total autonomic blockade was attained using atropine and propranolol. Thereafter, increased systolic blood pressure with 0.4 microg/kg/min phenylephrine (designated as deltaBPphenyl) and decreased systolic blood pressure with 0.5 microg/kg/30 seconds of phentolamine (designated as deltaBPphent) were measured as indexes of alpha-adrenergic vascular sensitivity and activity, respectively. DeltaBPphenyl in the NMS group (70.0 +/- 37) was significantly less than that in C group (107 +/- 38, p <0.005). DeltaBPphent was significantly greater in the NMS group than in the C group (33.5 +/- 10 vs 21.0 +/- 14, p <0.005). Thus, decreased alpha-adrenergic vascular sensitivity and elevated alpha-adrenergic vascular tone were observed in patients with NMS. Although it is not known whether the mechanism causing NMS can be attributed to this abnormal alpha-adrenergic vascular response, the abnormality could at least contribute to augmenting the symptoms of NMS.
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Affiliation(s)
- T Ono
- 1st Department of Internal Medicine, Nippon Medical School, Tokyo, Japan
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