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Miranda CM, da Silva RMFL, Peruhybe-Magalhães V, Brugada J. Vasoactive Biomarkers in Patients With Vasovagal Syncope During Head-Up Tilt Test: A Case-Control Study. CLINICAL MEDICINE INSIGHTS-CARDIOLOGY 2022; 16:11795468221116848. [PMID: 36046183 PMCID: PMC9421056 DOI: 10.1177/11795468221116848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 06/15/2022] [Indexed: 11/25/2022]
Abstract
Background: Vasovagal syncope (VVS) is the most common cause of syncope. Some stages of its pathophysiological mechanisms remain unclear. Vasoactive substances such as nitric oxide metabolites (NOx) and endothelin (ET) may be involved during acute orthostatic stress. Objective: To analyze plasma changes in NOx and ET and heart rate variability (HRV) in the supine positions (T1) and during the head-up tilt test (HUTT) (T2), in patients with VVS (case group) and control group. Methods: Thirty-seven patients (17 in the case group and 20 in the control group), matched for age and sex (mean aged 31.8 years) underwent HUTT with simultaneous HRV recording and venipuncture. Blood samples were collected during phases T1 and T2 and the analysis was performed without knowledge of the HUTT result. Results: In the total sample, there was an increase in NOx values (P = .014), however there was no increase in ET values from phase T1 to phase T2. Patients with VVS tended to increase plasma NOx values (P = .057) and had significantly higher plasma values compared to ET (P = .033) between phases T1 to T2. In the control group, there was no significant change in the values of these vasoactive substances. Regarding HRV, there were a decrease in the component HF (high frequency) and increased of the LF (low frequency)/HF ratio during HUTT. Conclusions: There was an increase in ET during HUTT occurred only in the case group. These patients are more likely to have an imbalance between antagonistic vasoactive biomarkers during orthostatic stress.
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Affiliation(s)
- Cláudia Madeira Miranda
- Faculty of Medicine, Federal University of Minas Gerais, Brazil.,Madre Teresa Hospital, Minas Gerais, Brazil
| | | | | | - Josep Brugada
- Institut Clínic Cardiovascular, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain
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2
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Turner D, Kang C, Mesirca P, Hong J, Mangoni ME, Glukhov AV, Sah R. Electrophysiological and Molecular Mechanisms of Sinoatrial Node Mechanosensitivity. Front Cardiovasc Med 2021; 8:662410. [PMID: 34434970 PMCID: PMC8382116 DOI: 10.3389/fcvm.2021.662410] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 06/24/2021] [Indexed: 01/01/2023] Open
Abstract
The understanding of the electrophysiological mechanisms that underlie mechanosensitivity of the sinoatrial node (SAN), the primary pacemaker of the heart, has been evolving over the past century. The heart is constantly exposed to a dynamic mechanical environment; as such, the SAN has numerous canonical and emerging mechanosensitive ion channels and signaling pathways that govern its ability to respond to both fast (within second or on beat-to-beat manner) and slow (minutes) timescales. This review summarizes the effects of mechanical loading on the SAN activity and reviews putative candidates, including fast mechanoactivated channels (Piezo, TREK, and BK) and slow mechanoresponsive ion channels [including volume-regulated chloride channels and transient receptor potential (TRP)], as well as the components of mechanochemical signal transduction, which may contribute to SAN mechanosensitivity. Furthermore, we examine the structural foundation for both mechano-electrical and mechanochemical signal transduction and discuss the role of specialized membrane nanodomains, namely, caveolae, in mechanical regulation of both membrane and calcium clock components of the so-called coupled-clock pacemaker system responsible for SAN automaticity. Finally, we emphasize how these mechanically activated changes contribute to the pathophysiology of SAN dysfunction and discuss controversial areas necessitating future investigations. Though the exact mechanisms of SAN mechanosensitivity are currently unknown, identification of such components, their impact into SAN pacemaking, and pathological remodeling may provide new therapeutic targets for the treatment of SAN dysfunction and associated rhythm abnormalities.
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Affiliation(s)
- Daniel Turner
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States
| | - Chen Kang
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Pietro Mesirca
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Juan Hong
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Matteo E Mangoni
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Alexey V Glukhov
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States
| | - Rajan Sah
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
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3
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O'Gallagher K, Shabeeh H, Munir S, Roomi A, Jiang B, Guilcher A, Brett S, Chowienczyk P. Effects of Inhibition of Nitric Oxide Synthase on Muscular Arteries During Exercise: Nitric Oxide Does Not Contribute to Vasodilation During Exercise or in Recovery. J Am Heart Assoc 2020; 9:e013849. [PMID: 32781940 PMCID: PMC7660814 DOI: 10.1161/jaha.119.013849] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Background Basal release of nitric oxide (NO) from the vascular endothelium regulates the tone of muscular arteries and resistance vasculature. Effects of NO on muscular arteries could be particularly important during exercise when shear stress may stimulate increased NO synthesis. Methods and Results We investigated acute effects of NO synthase inhibition on exercise hemodynamics using NG‐monomethyl‐l‐arginine (l‐NMMA), a nonselective NO synthase ‐inhibitor. Healthy volunteers (n=10, 5 female, 19–33 years) participated in a 2‐phase randomized crossover study, receiving l‐NMMA (6 mg/kg, iv over 5 minutes) or placebo before bicycle exercise (25–150 W for 12 minutes). Blood pressure, cardiac output (measured by dilution of soluble and inert tracers) and femoral artery diameter were measured before, during, and after exercise. At rest, l‐NMMA reduced heart rate (by 16.2±4.3 bpm relative to placebo, P<0.01), increased peripheral vascular resistance (by 7.0±1.4 mmHg per L/min, P<0.001), mean arterial blood pressure (by 8.9±3.5 mmHg, P<0.05), and blunted an increase in femoral artery diameter that occurred immediately before exercise (change in diameter: 0.14±0.04 versus 0.32±0.06 mm after l‐NMMA and placebo, P<0.01). During/after exercise l‐NMMA had no significant effect on peripheral resistance, cardiac output, or on femoral artery diameter. Conclusions These results suggest that NO plays little role in modulating muscular artery function during exercise but that it may mediate changes in muscular artery tone immediately before exercise.
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Affiliation(s)
- Kevin O'Gallagher
- Cardiovascular Division Department of Clinical Pharmacology King's College London School of Medicine St Thomas' Hospital London United Kingdom
| | - Husain Shabeeh
- Cardiovascular Division Department of Clinical Pharmacology King's College London School of Medicine St Thomas' Hospital London United Kingdom
| | - Shahzad Munir
- Cardiovascular Division Department of Clinical Pharmacology King's College London School of Medicine St Thomas' Hospital London United Kingdom
| | - Ali Roomi
- Cardiovascular Division Department of Clinical Pharmacology King's College London School of Medicine St Thomas' Hospital London United Kingdom
| | - Benyu Jiang
- Cardiovascular Division Department of Clinical Pharmacology King's College London School of Medicine St Thomas' Hospital London United Kingdom
| | - Antoine Guilcher
- Cardiovascular Division Department of Clinical Pharmacology King's College London School of Medicine St Thomas' Hospital London United Kingdom
| | - Sally Brett
- Cardiovascular Division Department of Clinical Pharmacology King's College London School of Medicine St Thomas' Hospital London United Kingdom
| | - Philip Chowienczyk
- Cardiovascular Division Department of Clinical Pharmacology King's College London School of Medicine St Thomas' Hospital London United Kingdom
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4
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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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5
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Carll AP, Hazari MS, Perez CM, Krantz QT, King CJ, Haykal-Coates N, Cascio WE, Costa DL, Farraj AK. An autonomic link between inhaled diesel exhaust and impaired cardiac performance: insight from treadmill and dobutamine challenges in heart failure-prone rats. Toxicol Sci 2013; 135:425-36. [PMID: 23872579 DOI: 10.1093/toxsci/kft155] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cardiac disease exacerbation is associated with short-term exposure to vehicular emissions. Diesel exhaust (DE) might impair cardiac performance in part through perturbing efferent sympathetic and parasympathetic autonomic nervous system (ANS) input to the heart. We hypothesized that acute changes in ANS balance mediate decreased cardiac performance upon DE inhalation. Young adult heart failure-prone rats were implanted with radiotelemeters to measure heart rate (HR), HR variability (HRV), blood pressure (BP), core body temperature, and pre-ejection period (PEP, a contractility index). Animals pretreated with sympathetic antagonist (atenolol), parasympathetic antagonist (atropine), or saline were exposed to DE (500 µg/m(3) fine particulate matter, 4h) or filtered air and then treadmill exercise challenged. At 1 day postexposure, separate rats were catheterized for left ventricular pressure (LVP), contractility, and lusitropy and assessed for autonomic influence using the sympathoagonist dobutamine and surgical vagotomy. During DE exposure, atenolol inhibited increases in HR, BP, and contractility, but not body temperature, suggesting a role for sympathetic dominance. During treadmill recovery at 4h post-DE exposure, HR and HRV indicated parasympathetic dominance in saline- and atenolol-pretreated groups that atropine inhibited. Conversely, at treadmill recovery 21h post-DE exposure, HRV and PEP indicated sympathetic dominance and subsequently diminished contractility that only atenolol inhibited. LVP at 1 day postexposure indicated that DE impaired contractility and lusitropy while abolishing parasympathetic-regulated cardiac responses to dobutamine. This is the first evidence that air pollutant inhalation both causes time-dependent oscillations between sympathetic and parasympathetic dominance and decreases cardiac performance via aberrant sympathetic dominance.
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Affiliation(s)
- Alex P Carll
- * Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, North Carolina 27599
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6
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Gamboa A, Okamoto LE, Raj SR, Diedrich A, Shibao CA, Robertson D, Biaggioni I. Nitric oxide and regulation of heart rate in patients with postural tachycardia syndrome and healthy subjects. Hypertension 2013; 61:376-81. [PMID: 23283362 DOI: 10.1161/hypertensionaha.111.00203] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The objective is to study the role of nitric oxide (NO) on cardiovascular regulation in healthy subjects and postural tachycardia syndrome (POTS) patients. Reduced neuronal NO function, which could contribute to a hyperadrenergic state, and increased NO-induced vasodilation, which could contribute to orthostatic intolerance, have been reported in POTS. In protocol 1, 13 healthy volunteers (33 ± 3 years) underwent autonomic blockade with trimethaphan and were administered equipressor doses of Nω-monomethyl-L-arginine (L-NMMA, a NO synthase inhibitor) and phenylephrine to determine the direct chronotropic effects of NO (independent of baroreflex modulation). In protocol 2, we compared the effects of L-NMMA in 9 POTS patients (31 ± 3 years) and 14 healthy (32 ± 2 years) volunteers, during autonomic blockade. During autonomic blockade, L-NMMA and phenylephrine produced similar increases in systolic blood pressure (27 ± 2 versus 27 ± 3 mm Hg). Phenylephrine produced only minimal heart rate changes, whereas L-NMMA produced a modest, but significant, bradycardia (-0.8 ± 0.4 versus -4.8 ± 1.2 bpm; P=0.011). There were no differences between POTS and healthy volunteers in the systolic blood pressure increase (22 ± 2 and 28 ± 5 mm Hg) or heart rate decrease (-6 ± 2 and -4 ± 1 bpm for POTS and controls, respectively) produced by L-NMMA. In the absence of baroreflex buffering, inhibition of endogenous NO synthesis results in a significant bradycardia, reflecting direct tonic modulation of heart rate by NO in healthy individuals. We found no evidence of a primary alteration in NO function in POTS. If NO dysfunction plays a role in POTS, it is through its interaction with the autonomic nervous system.
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Affiliation(s)
- Alfredo Gamboa
- Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN, USA
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7
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Kaumann AJ. Phosphodiesterases reduce spontaneous sinoatrial beating but not the 'fight or flight' tachycardia elicited by agonists through Gs-protein-coupled receptors. Trends Pharmacol Sci 2011; 32:377-83. [PMID: 21481950 DOI: 10.1016/j.tips.2011.03.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 03/07/2011] [Accepted: 03/09/2011] [Indexed: 01/01/2023]
Abstract
Cyclic AMP (cAMP) steers the generation of basal heart beat in the sinoatrial node. It also induces sinoatrial tachycardia and increased cardiac force, elicited through activation of Gs-protein-coupled receptors (GsPCRs). Phosphodiesterases (PDEs) hydrolyse cAMP. In the heart mainly PDE3 and PDE4 would be expected to limit those functions, and the PDE isoenzymes do indeed reduce basal sinoatrial beating rate and blunt the positive inotropic effects of agonists, mediated by GsPCRs. By contrast, recent evidence shows that GsPCR-mediated sinoatrial tachycardia is not controlled by PDE1-5. A PDE-resistant cAMP pool in sinoatrial cells, generated through activation of GsPCRs, including β(1)- and β(2)-adrenoceptors, appears to guarantee unrestrained tachycardia during fight or flight stress.
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Affiliation(s)
- Alberto J Kaumann
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
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8
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Mendes-Ribeiro AC, Mann GE, de Meirelles LR, Moss MB, Matsuura C, Brunini TMC. The role of exercise on L-arginine nitric oxide pathway in chronic heart failure. Open Biochem J 2009; 3:55-65. [PMID: 19911071 PMCID: PMC2775128 DOI: 10.2174/1874091x00903010055] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 07/24/2009] [Accepted: 08/20/2009] [Indexed: 01/14/2023] Open
Abstract
Chronic heart failure (CHF) is a pathological state with high morbidity and mortality and the full understanding of its genesis remain to be elucidated. In this syndrome, a cascade of neurohormonal and hemodynamic mechanisms, as well as inflammatory mediators, are activated to improve the impaired cardiac function. Clinical and experimental observations have shown that CHF is associated with a generalized disturbance in endothelium-dependent vasodilation, which may contribute to the progression of ventricular and vascular remodelling in this syndrome. There is also accumulating evidence that disturbances in nitric oxide (NO) availability is involved in the development of heart failure at the systemic and cardiac levels. NO is a ubiquitous signalling molecule which causes potent vasodilation, inhibits platelet activation and regulates the contractile properties of cardiac myocytes. It is generated from the amino acid L-arginine via constitutive and inducible isoforms of the enzyme NO synthase (NOS). There is evidence that exercise, a nonpharmacological tool, improves symptoms, fitness (VO2peak), quality of life and NO bioavailability in CHF population. This review examines different aspects of the L-arginine-NO pathway and inflammation in the physiopathology of CHF and highlights the important beneficial effects of exercise in this disease.
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Affiliation(s)
- A C Mendes-Ribeiro
- Departamento de Farmacologia e Psicobiologia, Instituto de Biologia, Av. 28 de Setembro 87 CEP 20551-030, Rio de Janeiro, Brazil
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9
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Jaja S, Kehinde M, Ogungbemi S. Cardiac and autonomic responses to change in posture or vitamin C supplementation in sickle cell anemia subjects. PATHOPHYSIOLOGY 2008; 15:25-30. [DOI: 10.1016/j.pathophys.2007.12.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2007] [Revised: 12/07/2007] [Accepted: 12/08/2007] [Indexed: 10/22/2022] Open
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10
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Pieper GM, Roza AM. The complex role of iNOS in acutely rejecting cardiac transplants. Free Radic Biol Med 2008; 44:1536-52. [PMID: 18291116 PMCID: PMC2443548 DOI: 10.1016/j.freeradbiomed.2008.01.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 01/17/2008] [Accepted: 01/18/2008] [Indexed: 12/13/2022]
Abstract
This review summarizes the evidence for a detrimental role of nitric oxide (NO) derived from inducible NO synthase (iNOS) and/or reactive nitrogen species such as peroxynitrite in acutely rejecting cardiac transplants. In chronic cardiac transplant rejection, iNOS may have an opposing beneficial component. The purpose of this review is primarily to address issues related to acute rejection, which is a recognized risk factor for chronic rejection. The evidence for a detrimental role is based upon strategies involving nonselective NOS inhibitors, NO neutralizers, selective iNOS inhibitors, and iNOS gene deletion in rodent models of cardiac rejection. The review is presented in the context of the impact on various components, including graft survival, histological rejection, and cardiac function, which may contribute to the process of graft rejection in toto. Possible limitations of each strategy are discussed in order to understand better the variance in published findings, including issues related to the potential importance of cell localization of iNOS expression. Finally, the concept of a dual role for NO and its downstream product, peroxynitrite, in rejection vs immune regulation is discussed.
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Affiliation(s)
- Galen M Pieper
- Division of Transplant Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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11
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González DR, Fernández IC, Ordenes PP, Treuer AV, Eller G, Boric MP. Differential role of S-nitrosylation and the NO-cGMP-PKG pathway in cardiac contractility. Nitric Oxide 2007; 18:157-67. [PMID: 18023373 DOI: 10.1016/j.niox.2007.09.086] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 09/05/2007] [Accepted: 09/19/2007] [Indexed: 10/22/2022]
Abstract
The role of nitric oxide (NO) in cardiac contractility is complex and controversial. Several NO donors have been reported to cause positive or negative inotropism. NO can bind to guanylate cyclase, increasing cGMP production and activating PKG. NO may also directly S-nitrosylate cysteine residues of specific proteins. We used the isolated rat heart preparation to test the hypothesis that the differential inotropic effects depend on the degree of NO production and the signaling recruited. SNAP (S-nitroso-N-acetylpenicillamine), a NO donor, increased contractility at 0.1, 1 and 10 microM. This effect was independent of phospholamban phosphorylation, was not affected by PKA inhibition with H-89 (N-[2((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide), but it was abolished by the radical scavenger Tempol (4-hydroxy-[2,2,4,4]-tetramethyl-piperidine-1-oxyl). However, at 100 microM SNAP reduced contractility, effect reversed to positive inotropism by guanylyl cyclase blockade with ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one), and abolished by PKG inhibition with KT5823, but not affected by Tempol. SNAP increased tissue cGMP at 100 microM, but not at lower concentrations. Consistently, a cGMP analog also reduced cardiac contractility. Finally, SNAP at 1 microM increased the level of S-nitrosylation of various cardiac proteins, including the ryanodine receptor. This study demonstrates the biphasic role for NO in cardiac contractility in a given preparation; furthermore, the differential effect is clearly ascribed to the signaling pathways involved. We conclude that although NO is highly diffusible, its output determines the fate of the messenger: low NO concentrations activate redox processes (S-nitrosylation), increasing contractility; while the cGMP-PKG pathway is activated at high NO concentrations, reducing contractility.
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Affiliation(s)
- Daniel R González
- Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Alameda 340, PO Box 114D, Santiago, Chile
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12
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Abstract
The physiological mechanisms responsible for determining heart rate during exercise are complex, and further research into "chronotropic incompetence" is clearly required.
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13
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O'Leary DD, Steinback CD, Cechetto AD, Foell BT, Topolovec JC, Gelb AW, Cechetto DF, Shoemaker JK. Relating drug-induced changes in carotid artery mechanics to cardiovagal and sympathetic baroreflex control. Can J Physiol Pharmacol 2005; 83:439-46. [PMID: 15897926 DOI: 10.1139/y05-030] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous evidence indicates that sensitivity of the baroreflex cardiovagal and sympathetic arms is dissociated. In addition, pharmacologic assessment of baroreflex sensitivity (BRS) has revealed that cardiovagal, but not sympathetic, BRS is greater when blood pressure is increasing versus falling. The origin of this hysteresis is unknown. In this study, carotid artery distensibility and absolute distension (diameter) were assessed to test the hypothesis that vessel mechanics in barosensitive regions affect the BRS of cardiovagal, but not sympathetic, outflow. R-R interval (i.e. time between successive R waves), finger arterial blood pressure, muscle sympathetic nerve activity, and carotid artery dimensions (B-mode imaging) were measured during sequential infusions of sodium nitroprusside (SNP) and phenylephrine (PHE). Systolic and diastolic common carotid artery diameters and pulse pressure were recorded to calculate distensibility of this vessel under each drug condition. Cardiovagal BRS was greater when blood pressure was increasing versus decreasing (p < 0.01). Sympathetic BRS was not affected by direction of pressure change. Distensibility did not differ between SNP and PHE injections. However, compared with SNP, infusion of PHE resulted in larger absolute systolic and diastolic carotid diameters (p < 0.001). Therefore, cardiovagal reflex hysteresis was related to drug-induced changes in common carotid artery diameter but not distensibility. The lack of sympathetic hysteresis in this model suggests a relative insensitivity of this baroreflex component to carotid artery dimensions and provides a possible mechanism for the dissociation between cardiovagal and sympathetic BRS.
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Affiliation(s)
- Deborah D O'Leary
- Department of Community Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada.
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14
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Foley CM, Mueller PJ, Hasser EM, Heesch CM. Hindlimb unloading and female gender attenuate baroreflex-mediated sympathoexcitation. Am J Physiol Regul Integr Comp Physiol 2005; 289:R1440-7. [PMID: 16051718 DOI: 10.1152/ajpregu.00356.2005] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exposure to a period of microgravity or bed rest produces several physiological adaptations. These changes, which include an increased incidence of orthostatic intolerance, have an impact when people return to a 1G environment or resume an upright posture. Compared with males, females appear more susceptible to orthostatic intolerance after exposure to real or simulated microgravity. Decreased arterial baroreflex compensation may contribute to orthostatic intolerance. We hypothesized that female rats would exhibit a greater reduction in arterial baroreflex function after hindlimb unloading (HU) compared with male rats. Mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded in conscious animals after 13–15 days of HU. Baseline HR was elevated in female rats, and HU increased HR in both genders. Consistent with previous results in males, baroreflex-mediated activation of RSNA was blunted by HU in both genders. Maximum RSNA in response to decreases in MAP was reduced by HU (male control 513 ± 42%, n = 11; male HU 346 ± 38%, n = 13; female control 359 ± 44%, n = 10; female HU 260 ± 43%, n = 10). Maximum baroreflex increase in RSNA was lower in females compared with males in both control and HU rats. Both female gender and HU attenuated baroreflex-mediated increases in sympathetic activity. The combined effects of HU and gender resulted in reduced baroreflex sympathetic reserve in females compared with males and could contribute to the greater incidence of orthostatic intolerance in females after exposure to spaceflight or bed rest.
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Affiliation(s)
- C Michael Foley
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri-Columbia, 134 Research Park Drive, Columbia, Missouri 65211, USA.
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15
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Gardiner SM, March JE, Kemp PA, Bennett T. Bolus injection of human UII in conscious rats evokes a biphasic haemodynamic response. Br J Pharmacol 2004; 143:422-30. [PMID: 15339862 PMCID: PMC1575352 DOI: 10.1038/sj.bjp.0705954] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2004] [Revised: 06/10/2004] [Accepted: 07/14/2004] [Indexed: 01/22/2023] Open
Abstract
A biphasic cardiovascular response to bolus i.v. injection of human urotensin II (hUII, 3 nmol kg(-1)) in conscious, male, Sprague-Dawley (SD) rats was identified and underlying mechanisms were explored. Initially (0-5 min) there was tachycardia, hypotension and mesenteric and hindquarters vasodilatation; later (30-120 min), tachycardia, hindquarters vasodilatation and a modest rise in blood pressure occurred. Pretreatment with indomethacin or N(G) nitro-l-arginine methylester (l-NAME) reduced the mesenteric vasodilator response to hUII, and abolished the late tachycardia and hindquarters vasodilatation. Indomethacin also abolished the hypotension and early hindquarters vasodilatation, and substantially reduced the initial tachycardia. Indomethacin and l-NAME together prevented all haemodynamic responses to hUII. Inhibition of inducible NOS had no effect on responses to hUII, whereas inhibition of neuronal NOS reduced the delayed tachycardic response to hUII but did not significantly affect the vasodilatation. Only the initial tachycardic response to hUII was antagonised by propranolol. In spontaneously hypertensive rats (SHR), the initial haemodynamic responses to hUII were qualitatively similar to those in SD rats, although there was also a modest renal vasodilatation. The secondary response comprised a smaller tachycardia and a small rise in blood pressure, with no significant hindquarters vasodilatation. Haemodynamic responses to hUII were not enhanced by endothelin and angiotensin receptor antagonism in either SD rats or in SHRs. One interpretation of these results is that the primary response to bolus injection of hUII is prostanoid- or prostanoid- and NO-mediated (mesenteric vasodilatation) and that this triggers secondary events, which are dependent on eNOS (hindquarters vasodilatation) and neuronal NOS (tachycardia).
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Affiliation(s)
- Sheila M Gardiner
- Centre for Integrated Systems Biology & Medicine, School of Biomedical Sciences, University of Nottingham, Nottingham.
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16
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Guimarães GV, d'Avila VM, Chizzola PR, Bacal F, Stolf N, Bocchi EA. Reabilitação física no transplante de coração. REV BRAS MED ESPORTE 2004. [DOI: 10.1590/s1517-86922004000500008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Após o transplante cardíaco os pacientes melhoram a qualidade de vida. Porém, freqüentemente apresentam problemas clínicos pós-operatórios, como descondicionamento físico, atrofia e fraqueza muscular e menor capacidade aeróbia máxima, decorrentes em parte da inatividade pré-operatória e de fatores como diferença de superfície corpórea doador/receptor, denervação do coração, entre outros. A atividade física regular tem papel importante na terapêutica dos transplantados, devendo ser iniciada precocemente, se possível ainda na fase hospitalar, dando prosseguimento pós-alta hospitalar, para que possam retornar a um estilo de vida normal, próximo do que tinham antes da doença, permitindo um convívio social satisfatório, com retorno a uma vida ativa e produtiva.
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17
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Sears CE, Ashley EA, Casadei B. Nitric oxide control of cardiac function: is neuronal nitric oxide synthase a key component? Philos Trans R Soc Lond B Biol Sci 2004; 359:1021-44. [PMID: 15306414 PMCID: PMC1693378 DOI: 10.1098/rstb.2004.1477] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Nitric oxide (NO) has been shown to regulate cardiac function, both in physiological conditions and in disease states. However, several aspects of NO signalling in the myocardium remain poorly understood. It is becoming increasingly apparent that the disparate functions ascribed to NO result from its generation by different isoforms of the NO synthase (NOS) enzyme, the varying subcellular localization and regulation of NOS isoforms and their effector proteins. Some apparently contrasting findings may have arisen from the use of non-isoform-specific inhibitors of NOS, and from the assumption that NO donors may be able to mimic the actions of endogenously produced NO. In recent years an at least partial explanation for some of the disagreements, although by no means all, may be found from studies that have focused on the role of the neuronal NOS (nNOS) isoform. These data have shown a key role for nNOS in the control of basal and adrenergically stimulated cardiac contractility and in the autonomic control of heart rate. Whether or not the role of nNOS carries implications for cardiovascular disease remains an intriguing possibility requiring future study.
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Affiliation(s)
- Claire E Sears
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
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18
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Kaufmann PA, Rimoldi O, Gnecchi-Ruscone T, Bonser RS, Lüscher TF, Camici PG. Systemic inhibition of nitric oxide synthase unmasks neural constraint of maximal myocardial blood flow in humans. Circulation 2004; 110:1431-6. [PMID: 15353503 DOI: 10.1161/01.cir.0000141294.25130.54] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Nitric oxide (NO) is an endothelial mediator that regulates vascular smooth muscle tone, but it may exert its cardiovascular action also by modulating the autonomic control of vasomotor tone. We assessed the effect of simultaneous inhibition of both endothelial (eNOS) and neuronal (nNOS) NO synthase isoforms on myocardial blood flow (MBF) and coronary flow reserve (CFR) in volunteers and in (denervated) transplant recipients. METHODS AND RESULTS MBF (mL x min(-1) x g(-1)) was measured at rest and during adenosine-induced hyperemia with positron emission tomography and 15O-labeled water. CFR was calculated as adenosine/resting MBF. Measurements were repeated during one of the following intravenous infusions: group 1 (n=12), saline; group 2 (n=9), 3 mg/kg N(G)-monomethyl-L-arginine (L-NMMA), which crosses the blood-brain barrier and inhibits both eNOS and nNOS; group 3 (n=13), 10 mg/kg L-NMMA; group 4 (n=8), phenylephrine titrated to simulate the hemodynamic changes in group 3; and group 5 (n=6), 10 mg/kg L-NMMA infused into the heart transplant recipients. After intervention, hyperemic MBF and CFR were unchanged in groups 1, 2, and 4. By contrast, both hyperemic MBF (+53%, P<0.0001 versus baseline) and CFR (+52%, P<0.0001 versus baseline) increased in group 3, whereas they remained unchanged in group 5, which suggests that an intact cardiac innervation was required for the increase in MBF and CFR observed in group 3. CONCLUSIONS The results of the present study suggest that maximal adenosine-induced hyperemia and CFR in humans are constrained by neurally mediated vasoconstriction, which can be relieved by systemic NOS inhibition with L-NMMA.
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Affiliation(s)
- Philipp A Kaufmann
- MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College of Science, Technology and Medicine, Hammersmith Hospital, London, UK
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19
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Wang S, Dusting GJ, Woodman OL, May CN. Selective vasodilator and chronotropic actions of 3′,4′-dihydroxyflavonol in conscious sheep. Eur J Pharmacol 2004; 491:43-51. [PMID: 15102532 DOI: 10.1016/j.ejphar.2004.03.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2003] [Revised: 02/26/2004] [Accepted: 03/03/2004] [Indexed: 11/24/2022]
Abstract
Flavonoids are known to relax isolated large arteries, but the cardiovascular actions of flavonoids are not well studied in vivo. Hence, we determined the systemic and regional haemodynamic responses to a novel synthetic flavonol, 3',4'-dihydroxyflavonol (DiOHF), in conscious sheep previously instrumented with flow probes on the aorta and coronary, mesenteric, renal, and iliac arteries. Intravenous injection of DiOHF (1.0 mg/kg) caused a delayed but prolonged vasodilatation in the coronary and renal vascular beds, with no changes in the mesenteric or iliac vascular beds. DiOHF induced prolonged increases in heart rate and cardiac output without altering arterial pressure. Pretreatment with Nomega-nitro-L-arginine, a nonspecific inhibitor of nitric oxide synthase, abolished all the cardiovascular effects of DiOHF. The results indicate that DiOHF caused a nitric oxide-dependent vasodilatation of the coronary and renal vasculature and an increase in cardiac output due to its chronotropic action.
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Affiliation(s)
- Sheng Wang
- Howard Florey Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
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20
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Mohan RM, Golding S, Heaton DA, Danson EJ, Paterson DJ. Targeting neuronal nitric oxide synthase with gene transfer to modulate cardiac autonomic function. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2004; 84:321-44. [PMID: 14769442 DOI: 10.1016/j.pbiomolbio.2003.11.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Microdomains of neuronal nitric oxide synthase (nNOS) are spatially localised within both autonomic neurons innervating the heart and post-junctional myocytes. This review examines the use of gene transfer to investigate the role of nNOS in cardiac autonomic control. Furthermore, it explores techniques that may be used to improve upon gene delivery to the cardiac autonomic nervous system, potentially allowing more specific delivery of genes to the target neurons/myocytes. This may involve modification of the tropism of the adenoviral vector, or the use of alternative viral and non-viral gene delivery mechanisms to minimise potential immune responses in the host. Here we show that adenoviral vectors provide an efficient method of gene delivery to cardiac-neural tissue. Functionally, adenovirus-nNOS can increase cardiac vagal responsiveness by facilitating cholinergic neurotransmission and decrease beta-adrenergic excitability. Whether gene transfer remains the preferred strategy for targeting cardiac autonomic impairment will depend on site-specific promoters eliciting sustained gene expression that results in restoration of physiological function.
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Affiliation(s)
- R M Mohan
- University Laboratory of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK
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21
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Ramchandra R, Barrett CJ, Malpas SC. Chronic blockade of nitric oxide does not produce hypertension in baroreceptor denervated rabbits. Hypertension 2003; 42:974-7. [PMID: 14504256 DOI: 10.1161/01.hyp.0000094556.83257.8c] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Although the vascular action of endothelium-derived nitric oxide in modulating arterial pressure is well established, nitric oxide can also act as a neurotransmitter in the central nervous system. In addition, there is evidence for an interaction between nitric oxide and baroreceptor afferent processing; thus, nitric oxide may regulate blood pressure through central modulation of arterial baroreflexes. To test this possible interaction of nitric oxide and baroreflexes in the long-term regulation of blood pressure, we measured arterial pressure and heart rate responses to nitric oxide blockade by using L-NAME (50 mg/kg per day in drinking water) over 7 days in baroreceptor intact and sinoaortic denervated conscious rabbits. In the baroreceptor intact animals, blockade of nitric oxide leads to a significant increase in mean arterial pressure (from 75+/-2 to 84+/-3 mm Hg) and decrease in heart rate (from 233+/-8 to 195+/-8 bpm) that was sustained over the 7 days of nitric oxide blockade. In the sinoaortic denervated animals, blockade of nitric oxide initially led to a similar increase in arterial pressure (82+/-3 mm Hg on the second day), but in all sinoaortic denervated animals this increase was not sustained and recovered back to pre-L-NAME levels. This finding indicates that baroreflexes play an important role in the long-term control of blood pressure, and, second, that one mediator of this control is nitric oxide.
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Affiliation(s)
- Rohit Ramchandra
- Circulatory Control Laboratory, Department of Physiology, University of Auckland Medical School, Private Bag 92019, Auckland, New Zealand
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22
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Hjorth Lassen L, Klingenberg Iversen H, Olesen J. A dose-response study of nitric oxide synthase inhibition in different vascular beds in man. Eur J Clin Pharmacol 2003; 59:499-505. [PMID: 13680036 DOI: 10.1007/s00228-003-0662-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2003] [Accepted: 07/11/2003] [Indexed: 12/21/2022]
Abstract
BACKGROUND AND OBJECTIVE Nitric oxide (NO) is an almost ubiquitous messenger molecule and is implicated in several disorders. NG monomethyl L-arginine ( L-NMMA:546C88) is an inhibitor of all three NO synthases (NOS), the enzymes that catalyse the production of NO. The present study was performed to evaluate the dose-response relation of L-NMMA to improve the design and interpretation of studies in migraine sufferers and other diseases. METHODS In a double-blind, placebo-controlled, cross-over design, six healthy volunteers were randomised to receive three different doses of L-NMMA (0.3 mg/kg, 1 mg/kg, 3 mg/kg) or placebo (5% dextrose) intravenously (iv) over 5 min on four different days. On a fifth study day, in an open design, the same subjects received L-NMMA in the dose 6 mg/kg iv over 15 min. The effect of L-NMMA on the maximal mean blood velocity (Vmean) in the middle cerebral artery (MCA) (transcranial Doppler), the luminal diameter of the radial artery (high-frequency ultrasound), mean arterial blood pressure (MAP), heart rate and electrocardiogram were repeatedly followed every 5 min until 60 min after start of the infusion, then every 15 min during the following hour, and at 3 h and 4 h. RESULTS Inhibition of NOS had no effect on Vmean in MCA or on the diameter of the radial artery, but MAP increased and heart rate decreased dose dependently. With a dose of 6-mg/kg L-NMMA infused over a 15-min period, the maximum MAP increase was 20% 20 min after the start of L-NMMA infusion. The maximum decrease of heart rate was 24% 15 min after start of the L-NMMA infusion. CONCLUSION L-NMMA in a dose that caused marked changes in systemic blood pressure and heart rate had no effect on cerebral and radial arteries in man.
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Affiliation(s)
- Lisbeth Hjorth Lassen
- Danish Headache Center, Department of neurology, Glostrup University Hospital, 2600 Glostrup, Denmark.
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23
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Paton JFR, Kasparov S, Paterson DJ. Nitric oxide and autonomic control of heart rate: a question of specificity. Trends Neurosci 2002; 25:626-31. [PMID: 12446130 DOI: 10.1016/s0166-2236(02)02261-0] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Despite its highly diffusible nature, the gaseous signalling molecule nitric oxide (NO) can exert specific effects within the CNS and PNS. To date, the specificity of the actions of NO remains an unsolved puzzle. There are several plausible mechanisms that might account for this specificity in the context of autonomic regulation of heart rate. NO acts at distinct levels within the autonomic nervous system to control cardiac rate, with opposing effects at different sites. We discuss factors that might contribute to this diversity of action, and conclude that the isoform of enzyme involved in producing NO, the spatial proximity of the NO source to the target, and differences in the intracellular coupling within the target cell are all crucial for encoding the functional action of NO.
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Affiliation(s)
- Julian F R Paton
- Dept of Physiology, School of Medical Sciences, University of Bristol, UK.
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