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Simpson LL, Stembridge M, Siebenmann C, Moore JP, Lawley JS. Mechanisms underpinning sympathoexcitation in hypoxia. J Physiol 2024. [PMID: 38533641 DOI: 10.1113/jp284579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/28/2024] [Indexed: 03/28/2024] Open
Abstract
Sympathoexcitation is a hallmark of hypoxic exposure, occurring acutely, as well as persisting in acclimatised lowland populations and with generational exposure in highland native populations of the Andean and Tibetan plateaus. The mechanisms mediating altitude sympathoexcitation are multifactorial, involving alterations in both peripheral autonomic reflexes and central neural pathways, and are dependent on the duration of exposure. Initially, hypoxia-induced sympathoexcitation appears to be an adaptive response, primarily mediated by regulatory reflex mechanisms concerned with preserving systemic and cerebral tissue O2 delivery and maintaining arterial blood pressure. However, as exposure continues, sympathoexcitation is further augmented above that observed with acute exposure, despite acclimatisation processes that restore arterial oxygen content (C a O 2 ${C_{{\mathrm{a}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ). Under these conditions, sympathoexcitation may become maladaptive, giving rise to reduced vascular reactivity and mildly elevated blood pressure. Importantly, current evidence indicates the peripheral chemoreflex does not play a significant role in the augmentation of sympathoexcitation during altitude acclimatisation, although methodological limitations may underestimate its true contribution. Instead, processes that provide no obvious survival benefit in hypoxia appear to contribute, including elevated pulmonary arterial pressure. Nocturnal periodic breathing is also a potential mechanism contributing to altitude sympathoexcitation, although experimental studies are required. Despite recent advancements within the field, several areas remain unexplored, including the mechanisms responsible for the apparent normalisation of muscle sympathetic nerve activity during intermediate hypoxic exposures, the mechanisms accounting for persistent sympathoexcitation following descent from altitude and consideration of whether there are sex-based differences in sympathetic regulation at altitude.
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Affiliation(s)
- Lydia L Simpson
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | | | - Jonathan P Moore
- School of Psychology and Sport Science, Institute of Applied Human Physiology, Bangor University, Bangor, UK
| | - Justin S Lawley
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
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2
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D'Souza AW, Hissen SL, Manabe K, Takeda R, Washio T, Coombs GB, Sanchez B, Fu Q, Shoemaker JK. Age- and sex-related differences in sympathetic vascular transduction and neurohemodynamic balance in humans. Am J Physiol Heart Circ Physiol 2023; 325:H917-H932. [PMID: 37594483 DOI: 10.1152/ajpheart.00301.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 08/14/2023] [Accepted: 08/15/2023] [Indexed: 08/19/2023]
Abstract
Bursts of muscle sympathetic nerve activity (MSNA) and the ensuing vasoconstriction are pivotal determinants of beat-by-beat blood pressure regulation. Although age and sex impact blood pressure regulation, how these factors affect the central and peripheral arcs of the baroreflex remains unclear. In 27 young [25 (SD 3) yr] males (YM; n = 14) and females (YF; n = 13) and 23 older [71 (SD 5) yr] males (OM; n = 11) and females (OF; n = 12), femoral artery blood flow, blood pressure, and MSNA were recorded for 10 min of supine rest. Sympathetic baroreflex sensitivity (i.e., central arc) was quantified as the relationship between diastolic blood pressure and MSNA burst incidence. Signal averaging was used to determine sympathetic vascular transduction into leg vascular conductance (LVC) for 12 cardiac cycles following MSNA bursts (i.e., peripheral arc). Older adults demonstrated attenuated sympathetic transduction into LVC (both P < 0.001) following MSNA bursts, and smaller increases in sympathetic transduction as a function of MSNA burst size and firing pattern compared with young adults (range, P = 0.004-0.032). YM (r2 = 0.36; P = 0.032) and OM (r2 = 0.51; P = 0.014) exhibited an inverse relationship between the central and peripheral arcs of the baroreflex, whereas females did not (YF, r2 = 0.03, P = 0.621; OF, r2 = 0.06, P = 0.445). MSNA burst incidence was inversely related to sympathetic transduction in YM and OF (range, P = 0.03-0.046) but not in YF or OM (range, P = 0.360-0.603). These data indicate that age is associated with attenuated sympathetic vascular transduction, whereas age- and sex-specific changes are present in the relationship between the central and peripheral arcs of the baroreflex regulation of blood pressure.NEW & NOTEWORTHY Sympathetic vascular transduction is attenuated in older compared with young adults, regardless of biological sex. Males, but not females (regardless of age), demonstrate an inverse relationship between central (sympathetic baroreflex sensitivity) and peripheral (sympathetic vascular transduction) components of the baroreflex arc. Young males and older females exhibit an inverse relationship between resting sympathetic outflow and sympathetic vascular transduction. Our results indicate that age and sex exert independent and interactive effects on sympathetic vascular transduction and sympathetic neurohemodynamic balance in humans.
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Affiliation(s)
- Andrew W D'Souza
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Sarah L Hissen
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Kazumasa Manabe
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Ryosuke Takeda
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan
| | - Takuro Washio
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Geoff B Coombs
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Belinda Sanchez
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Qi Fu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - J Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
- Department of Physiology and Pharmacology, Western University, London, Ontario, Canada
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3
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Hotta H, Iimura K, Watanabe N, Suzuki H, Sugie M, Shigemoto K. Sympathetic modulation of hindlimb muscle contractility is altered in aged rats. Sci Rep 2023; 13:7504. [PMID: 37193678 DOI: 10.1038/s41598-023-33821-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 04/19/2023] [Indexed: 05/18/2023] Open
Abstract
It has recently been demonstrated that reflex excitation of muscle sympathetic nerves triggered by muscle contraction contributes to the maintenance of tetanic force (TF) in rat hindlimb muscles. We hypothesized that this feedback mechanism between the contraction of hindlimb muscles and the lumbar sympathetic nerves declines during aging. In this study, we examined the contribution of sympathetic nerves on skeletal muscle contractility in young adult (4-9 months old, n = 11) and aged (32-36 months old, n = 11) male and female rats. The tibial nerve was electrically stimulated to measure the TF of the triceps surae muscles resulting from motor nerve activation before and after cutting or stimulating (at 5-20 Hz) the lumbar sympathetic trunk (LST). The TF amplitude decreased by cutting the LST in the young and aged groups; however, the magnitude of the decrease in TF following transection of the LST in the aged rats (6.2%) was significantly (P = 0.02) smaller compared with that in the young rats (12.9%). The TF amplitude was increased by LST stimulation at ≥ 5 Hz in the young and ≥ 10 Hz in the aged groups. The overall TF response to LST stimulation was not significantly different between the two groups; however, an increase in muscle tonus resulting from LST stimulation, independent of motor nerve stimulation, was significantly (P = 0.03) greater in aged compared with young rats. The sympathetic contribution to support motor nerve-induced muscle contraction declined, whereas sympathetic-mediated muscle tonus, independent of motor nerve activity, was augmented in aged rats. These changes in sympathetic modulation of hindlimb muscle contractility may underlie the reduction of skeletal muscle strength during voluntary contraction and rigidity of motion during senescence.
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Affiliation(s)
- Harumi Hotta
- Department of Autonomic Neuroscience, Tokyo Metropolitan Institute for Geriatrics and Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan.
| | - Kaori Iimura
- Department of Autonomic Neuroscience, Tokyo Metropolitan Institute for Geriatrics and Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Nobuhiro Watanabe
- Department of Autonomic Neuroscience, Tokyo Metropolitan Institute for Geriatrics and Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Harue Suzuki
- Department of Autonomic Neuroscience, Tokyo Metropolitan Institute for Geriatrics and Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Masamitsu Sugie
- Health Promotion Management Office, Tokyo Metropolitan Institute for Geriatrics and Gerontology, Tokyo, Japan
| | - Kazuhiro Shigemoto
- Department of Geriatric Medicine, Tokyo Metropolitan Institute for Geriatrics and Gerontology, Tokyo, Japan
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4
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Jiang Y, Yabluchanskiy A, Deng J, Amil FA, Po SS, Dasari TW. The role of age-associated autonomic dysfunction in inflammation and endothelial dysfunction. GeroScience 2022; 44:2655-2670. [PMID: 35773441 PMCID: PMC9768093 DOI: 10.1007/s11357-022-00616-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 06/22/2022] [Indexed: 01/23/2023] Open
Abstract
Aging of the cardiovascular regulatory function manifests as an imbalance between the sympathetic and parasympathetic (vagal) components of the autonomic nervous system (ANS). The most characteristic change is sympathetic overdrive, which is manifested by an increase in the muscle sympathetic nerve activity (MSNA) burst frequency with age. Age-related changes that occur in vagal nerve activity is less clear. The resting tonic parasympathetic activity can be estimated noninvasively by measuring the increase in heart rate occurring in response to muscarinic cholinergic receptor blockade; animal study models have shown this to diminish with age. Humoral, cellular, and neural mechanisms work together to prevent non-resolving inflammation. This review focuses on the mechanisms underlying age-related alternations in the ANS and how an imbalance in the ANS, evaluated by MSNA and heart rate variability (HRV), potentially facilitates inflammation when the homeostatic mechanisms between reflex neural circuits and the immune system are compromised, particularly the dysfunction of the cholinergic anti-inflammatory reflex. Physiologically, the efferent arm of this reflex acts via the [Formula: see text] 7 nicotinic acetylcholine receptors expressed in macrophages, monocytes, dendritic cells, T cells, and endothelial cells to curb the release of inflammatory cytokines, in which inhibition of NF‑κB nuclear translocation and activation of a JAK/STAT-mediated signaling cascade in macrophages and other immune cells are implicated. This reflex is likely to become less adequate with advanced age. Consequently, a pro-inflammatory state induced by reduced vagus output with age is associated with endothelial dysfunction and may significantly contribute to the development and propagation of atherosclerosis, heart failure, and hypertension. The aim of this review is to summarize the relationship between ANS dysfunction, inflammation, and endothelial dysfunction in the context of aging. Meanwhile, this review also attempts to describe the role of HRV measures as a predictor of the level of inflammation and endothelial dysfunction in the aged population and explore the possible therapeutical effects of vagus nerve stimulation.
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Affiliation(s)
- Yunqiu Jiang
- Cardiovascular Section, Department of Internal Medicine, University of Oklahoma Health Sciences Center, 800 SL Young Blvd, COM 5400, Oklahoma City, OK, 73104, USA
| | - Andriy Yabluchanskiy
- Center for Geroscience and Healthy Brain Aging, Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Jielin Deng
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
- Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, China
- Hubei Key Laboratory of Cardiology, Wuhan, 430060, China
| | - Faris A Amil
- Cardiovascular Section, Department of Internal Medicine, University of Oklahoma Health Sciences Center, 800 SL Young Blvd, COM 5400, Oklahoma City, OK, 73104, USA
| | - Sunny S Po
- Cardiovascular Section, Department of Internal Medicine, University of Oklahoma Health Sciences Center, 800 SL Young Blvd, COM 5400, Oklahoma City, OK, 73104, USA
- Heart Rhythm Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Tarun W Dasari
- Cardiovascular Section, Department of Internal Medicine, University of Oklahoma Health Sciences Center, 800 SL Young Blvd, COM 5400, Oklahoma City, OK, 73104, USA.
- Heart Rhythm Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
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5
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Greenlund IM, Carter JR. Sympathetic neural responses to sleep disorders and insufficiencies. Am J Physiol Heart Circ Physiol 2022; 322:H337-H349. [PMID: 34995163 PMCID: PMC8836729 DOI: 10.1152/ajpheart.00590.2021] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Short sleep duration and poor sleep quality are associated with cardiovascular risk, and sympathetic nervous system (SNS) dysfunction appears to be a key contributor. The present review will characterize sympathetic function across several sleep disorders and insufficiencies in humans, including sleep deprivation, insomnia, narcolepsy, and obstructive sleep apnea (OSA). We will focus on direct assessments of sympathetic activation, e.g., plasma norepinephrine and muscle sympathetic nerve activity, but include heart rate variability (HRV) when direct assessments are lacking. The review also highlights sex as a key biological variable. Experimental models of total sleep deprivation and sleep restriction are converging to support several epidemiological studies reporting an association between short sleep duration and hypertension, especially in women. A systemic increase of SNS activity via plasma norepinephrine is present with insomnia and has also been confirmed with direct, regionally specific evidence from microneurographic studies. Narcolepsy is characterized by autonomic dysfunction via both HRV and microneurographic studies but with opposing conclusions regarding SNS activation. Robust sympathoexcitation is well documented in OSA and is related to baroreflex and chemoreflex dysfunction. Treatment of OSA with continuous positive airway pressure results in sympathoinhibition. In summary, sleep disorders and insufficiencies are often characterized by sympathoexcitation and/or sympathetic/baroreflex dysfunction, with several studies suggesting women may be at heightened risk.
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Affiliation(s)
- Ian M. Greenlund
- 1Department of Health and Human Development, Montana State University, Bozeman, Montana,2Department of Psychology, Montana State University, Bozeman, Montana
| | - Jason R. Carter
- 1Department of Health and Human Development, Montana State University, Bozeman, Montana,2Department of Psychology, Montana State University, Bozeman, Montana
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6
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Klassen SA, Joyner MJ, Baker SE. The impact of ageing and sex on sympathetic neurocirculatory regulation. Semin Cell Dev Biol 2021; 116:72-81. [PMID: 33468420 PMCID: PMC8282778 DOI: 10.1016/j.semcdb.2021.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 12/30/2020] [Accepted: 01/04/2021] [Indexed: 02/07/2023]
Abstract
The sympathetic nervous system represents a critical mechanism for homoeostatic blood pressure regulation in humans. This review focuses on age-related alterations in neurocirculatory regulation in men and women by highlighting human studies that examined the relationship between muscle sympathetic nerve activity (MSNA) acquired by microneurography and circulatory variables (e.g., blood pressure, vascular resistance). We frame this review with epidemiological evidence highlighting sex-specific patterns in age-related blood pressure increases in developed nations. Indeed, young women exhibit lower blood pressure than men, but women demonstrate larger blood pressure increases with age, such that by about age 60 years, blood pressure is greater in women. Sympathetic neurocirculatory mechanisms contribute to sex differences in blood pressure rises with age. Muscle sympathetic nerve activity increases with age in both sexes, but women demonstrate greater age-related increases. The circulatory adjustments imposed by MSNA - referred to as neurovascular transduction or autonomic (sympathetic) support of blood pressure - differ in men and women. For example, whereas young men demonstrate a positive relationship between resting MSNA and vascular resistance, this relationship is absent in young women due to beta-2 adrenergic vasodilation, which offsets alpha-adrenergic vasoconstriction. However, post-menopausal women demonstrate a positive relationship between MSNA and vascular resistance due to a decline in beta-2 adrenergic vasodilatory mechanisms. Emerging data suggest that greater aerobic fitness appears to modulate neurocirculatory regulation, at least in young, healthy men and women. This review also highlights recent advances in microneurographic recordings of sympathetic action potential discharge, which may nuance our understanding of age-related alterations in sympathetic neurocirculatory regulation in humans.
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Affiliation(s)
- Stephen A Klassen
- Human and Integrative Physiology and Clinical Pharmacology Laboratory, Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Michael J Joyner
- Human and Integrative Physiology and Clinical Pharmacology Laboratory, Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Sarah E Baker
- Human and Integrative Physiology and Clinical Pharmacology Laboratory, Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA.
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7
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Balasubramanian P, Branen L, Sivasubramanian MK, Monteiro R, Subramanian M. Aging is associated with glial senescence in the brainstem - implications for age-related sympathetic overactivity. Aging (Albany NY) 2021; 13:13460-13473. [PMID: 34038388 PMCID: PMC8202881 DOI: 10.18632/aging.203111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Accepted: 04/28/2021] [Indexed: 12/11/2022]
Abstract
Accumulating evidence suggests that the sympathetic nervous system (SNS) overactivity plays a crucial role in age-related increase in the risk for cardiovascular diseases such as hypertension, myocardial infarction, stroke and heart diseases. Previous studies indicate that neuroinflammation in key brainstem regions that regulate sympathetic outflow plays a pathogenic role in aging-mediated sympathoexcitation. However, the molecular mechanisms underlying this phenomenon are not clear. While senescent cells and their secretory phenotype (SASP) have been implicated in the pathogenesis of several age-related diseases, their role in age-related neuroinflammation in the brainstem and SNS overactivity has not been investigated. To test this, we isolated brainstems from young (2-4 months) and aged (24 months) male C57BL/6J mice and assessed senescence using a combination of RNA-in situ hybridization, PCR analysis, multiplex assay and SA-β gal staining. Our results show significant increases in p16Ink4a expression, increased activity of SA-β gal and increases in SASP levels in the aged brainstem, suggesting age-induced senescence in the brainstem. Further, analysis of senescence markers in glial cells enriched fraction from fresh brainstem samples demonstrated that glial cells are more susceptible to senesce with age in the brainstem. In conclusion, our study suggests that aging induces glial senescence in the brainstem which likely causes inflammation and SNS overactivity.
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Affiliation(s)
- Priya Balasubramanian
- Oklahoma Center for Geroscience and Healthy Brain Aging, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Lyndee Branen
- Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078, USA
| | - Mahesh Kumar Sivasubramanian
- Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078, USA
| | - Raisa Monteiro
- Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078, USA
| | - Madhan Subramanian
- Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078, USA
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8
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Colditz IG. Adrenergic Tone as an Intermediary in the Temperament Syndrome Associated With Flight Speed in Beef Cattle. FRONTIERS IN ANIMAL SCIENCE 2021. [DOI: 10.3389/fanim.2021.652306] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The temperament of farm animals can influence their resilience to everyday variations within the managed production environment and has been under strong direct and indirect selection during the course of domestication. A prominent objective measure used for assessing temperament in beef cattle is the behavioral flight response to release from confinement in a crush or chute. This behavioral measure, termed flight speed (also known as escape velocity) is associated with physiological processes including body temperature, feeding behavior, growth rate, carcass composition, immune function, and health outcomes. This review examines the functional links between this suite of traits and adrenergic activity of the sympathetic nervous system and the adrenomedullary hormonal system. It is suggested that flight speed is the behavioral aspect of an underlying “flightiness” temperament syndrome, and that elevated adrenergic tone in animals with a high level of flightiness (i.e., flighty animals) tunes physiological activities toward a sustained “fight or flight” defense profile that reduces productivity and the capacity to flourish within the production environment. Nonetheless, despite a common influence of adrenergic tone on this suite of traits, variation in each trait is also influenced by other regulatory pathways and by the capacity of tissues to respond to a range of modulators in addition to adrenergic stimuli. It is suggested that tuning by adrenergic tone is an example of homeorhetic regulation that can help account for the persistent expression of behavioral and somatic traits associated with the flight speed temperament syndrome across the life of the animal. At a population level, temperament may modulate ecological fit within and across generations in the face of environmental variability and change. Associations of flight speed with the psychological affective state of the animal, and implications for welfare are also considered. The review will help advance understanding of the developmental biology and physiological regulation of temperament syndromes.
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9
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Meusel M, Herrmann M, Machleidt F, Franzen K, Vonthein R, Sayk F. Intranasal oxytocin has sympathoexcitatory effects on vascular tone in healthy males. Am J Physiol Regul Integr Comp Physiol 2020; 320:R162-R172. [PMID: 33296278 DOI: 10.1152/ajpregu.00062.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Oxytocin appears to be involved in the neuroendocrine regulation of sympathetic blood pressure (BP) homeostasis. In animals, intracerebral administration of oxytocin induces BP-relevant sympathetic activation. In humans, central nervous effects of oxytocin on BP regulation remain unclear. Intranasal administration supposedly delivers oligopeptides such as oxytocin directly to the brain. We investigated the effects of intranasal oxytocin on sympathetic vascular baroreflex function in humans using microneurographic techniques. In a balanced, double-blind crossover design, oxytocin or placebo was administered intranasally to 12 lean, healthy males (age 25 ± 4 yr). Muscle sympathetic nerve activity (MSNA) was assessed microneurographically before (presubstance), 30-45 min (postsubstance I), and 105-120 min (postsubstance II) after oxytocin administration. Baroreflex was challenged via graded infusions of vasoactive drugs, and correlation of BP with MSNA and heart rate (HR) defined baroreflex function. Experiments were conducted in the afternoon after a 5-h fasting period. After oxytocin, resting MSNA (burst rate and total activity) showed significant net increases from pre to postsubstance II compared with placebo [Δincrease = +4.3 ± 1.2 (oxytocin) vs. +2.2 ± 1.4 bursts/min (placebo), ANOVA; P < 0.05; total activity = 184 ± 11.5% (oxytocin) vs. 121 ± 14.3% (placebo), ANOVA; P = 0.01). This was combined with a small but significant net increase in resting diastolic BP, whereas systolic and mean arterial BP or HR as well as baroreflex sensitivity at vasoactive drug challenge were not altered. Intranasally administered oxytocin induced vasoconstrictory sympathoactivation in healthy male humans. The concomitant increase of diastolic BP was most likely attributable to increased vascular tone. This suggests oxytocin-mediated upward resetting of the vascular baroreflex set point at centers superordinate to the mere baroreflex-feedback loop.
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Affiliation(s)
- M Meusel
- Department of Internal Medicine II, University Heart Center Luebeck, University Hospital Schleswig-Holstein, Luebeck, Germany
| | - M Herrmann
- Department of Internal Medicine II, University Heart Center Luebeck, University Hospital Schleswig-Holstein, Luebeck, Germany
| | - F Machleidt
- Department of Internal Medicine I, University Hospital of Schleswig-Holstein, Luebeck, Germany
| | - K Franzen
- Department of Internal Medicine III, University Hospital of Schleswig-Holstein, Luebeck, Germany
| | - R Vonthein
- Institute for Medical Biometry and Statistics, University of Luebeck, Luebeck, Germany
| | - F Sayk
- Department of Internal Medicine I, University Hospital of Schleswig-Holstein, Luebeck, Germany
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10
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Venkataraman S, Vungarala S, Covassin N, Somers VK. Sleep Apnea, Hypertension and the Sympathetic Nervous System in the Adult Population. J Clin Med 2020; 9:jcm9020591. [PMID: 32098169 PMCID: PMC7073618 DOI: 10.3390/jcm9020591] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 02/16/2020] [Accepted: 02/19/2020] [Indexed: 02/06/2023] Open
Abstract
Sleep apnea is very common in patients with cardiovascular disease, especially in patients with hypertension. Over the last few decades a number of discoveries have helped support a causal relationship between the two and even resistant hypertension. The role neurogenic mechanisms play has gathered more attention in the recent past due to their immediate bedside utility. Several innovative discoveries in pathogenesis including those exploring the role of baroreflex gain, cardiovascular variability, chemoreceptor reflex activation and the sympathetic nervous system have emerged. In this review, we discuss the epidemiology of sleep apnea and hypertension and the pathogenic mechanisms contributing to neurogenic hypertension. Furthermore, recent management strategies in addition to continuous positive airway pressure (CPAP), such as upper airway stimulation and renal denervation that target these pathogenic mechanisms, are also discussed.
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11
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Lambert GW, Schlaich MP, Eikelis N, Lambert EA. Sympathetic activity in obesity: a brief review of methods and supportive data. Ann N Y Acad Sci 2019; 1454:56-67. [PMID: 31268175 DOI: 10.1111/nyas.14140] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 05/11/2019] [Accepted: 05/23/2019] [Indexed: 12/12/2022]
Abstract
The increase in the prevalence of obesity and the concomitant rise in obesity-related illness have led to substantial pressure on health care systems throughout the world. While the combination of reduced exercise, increased sedentary time, poor diet, and genetic predisposition is undoubtedly pivotal in generating obesity and increasing disease risk, a large body of work indicates that the sympathetic nervous system (SNS) contributes to obesity-related disease development and progression. In obesity, sympathetic nervous activity is regionalized, with activity in some outflows being particularly sensitive to the obese state, whereas other outflows, or responses to stimuli, may be blunted, thereby making the assessment of sympathetic nervous activation in the clinical setting difficult. Isotope dilution methods and direct nerve recording techniques have been developed and utilized in clinical research, demonstrating that in obesity there is preferential activation of the muscle vasoconstrictor and renal sympathetic outflows. With weight loss, sympathetic activity is reduced. Importantly, sympathetic nervous activity is associated with end-organ dysfunction and changes in sympathetic activation that accompany weight loss are often reflected in an improvement of end-organ function. Whether targeting the SNS directly improves obesity-related illness remains unknown, but merits further attention.
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Affiliation(s)
- Gavin W Lambert
- The Iverson Health Innovation Research Institute, Swinburne University of Technology, Hawthorn, Victoria, Australia.,The School of Health Sciences, Swinburne University of Technology, Hawthorn, Victoria, Australia
| | - Markus P Schlaich
- Dobney Hypertension Centre, School of Medicine, Royal Perth Hospital Unit, University of Western Australia, Perth, Western Australia, Australia
| | - Nina Eikelis
- The Iverson Health Innovation Research Institute, Swinburne University of Technology, Hawthorn, Victoria, Australia.,The School of Health Sciences, Swinburne University of Technology, Hawthorn, Victoria, Australia
| | - Elisabeth A Lambert
- The Iverson Health Innovation Research Institute, Swinburne University of Technology, Hawthorn, Victoria, Australia.,The School of Health Sciences, Swinburne University of Technology, Hawthorn, Victoria, Australia
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12
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Carter JR. Microneurography and sympathetic nerve activity: a decade-by-decade journey across 50 years. J Neurophysiol 2019; 121:1183-1194. [PMID: 30673363 DOI: 10.1152/jn.00570.2018] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The technique of microneurography has advanced the field of neuroscience for the past 50 years. While there have been a number of reviews on microneurography, this paper takes an objective approach to exploring the impact of microneurography studies. Briefly, Web of Science (Thomson Reuters) was used to identify the highest citation articles over the past 50 years, and key findings are presented in a decade-by-decade highlight. This includes the establishment of microneurography in the 1960s, the acceleration of the technique by Gunnar Wallin in the 1970s, the international collaborations of the 1980s and 1990s, and finally the highest impact studies from 2000 to present. This journey through 50 years of microneurographic research related to peripheral sympathetic nerve activity includes a historical context for several of the laboratory interventions commonly used today (e.g., cold pressor test, mental stress, lower body negative pressure, isometric handgrip, etc.) and how these interventions and experimental approaches have advanced our knowledge of cardiovascular, cardiometabolic, and other human diseases and conditions.
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Affiliation(s)
- Jason R Carter
- Department of Kinesiology and Integrative Physiology, Michigan Technological University , Houghton, Michigan
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Wenner MM, Paul EP, Robinson AT, Rose WC, Farquhar WB. Acute NaCl Loading Reveals a Higher Blood Pressure for a Given Serum Sodium Level in African American Compared to Caucasian Adults. Front Physiol 2018; 9:1354. [PMID: 30327611 PMCID: PMC6174209 DOI: 10.3389/fphys.2018.01354] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 09/07/2018] [Indexed: 01/13/2023] Open
Abstract
Purpose: African American individuals are more prone to salt-sensitive hypertension than Caucasian individuals. Small changes in serum sodium (Na+) result in increased blood pressure (BP). However, it remains unclear if there are racial differences in BP responsiveness to increases in serum Na+. Therefore, the purpose of this investigation was to determine if African American adults have altered BP responsiveness to acute changes in serum Na+ compared to Caucasian adults. Methods: We measured beat-by-beat BP, serum Na+, plasma renin activity (PRA), angiotensin II (Ang II), and aldosterone (Aldo) during a 60-min 3% NaCl infusion (hypertonic saline infusion, HSI) in 39 participants (19 African Americans, age: 23 ± 1, 20 Caucasians, age: 25 ± 1). Data reported as African American vs. Caucasian cohort, mean ± SEM. Results: Baseline BP and serum Na+ were similar between groups and increased during HSI in both African American and Caucasian participants (p < 0.01). However, the peak change in serum Na+ was greater in African American participants (Δ5.8 ± 0.34 vs. Δ4.85 ± 0.38 mmol/L, p = 0.03). There was a significant group effect (p = 0.02) and an interaction between race and serum Na+ on systolic BP (p = 0.02). Larger categorical changes in serum Na+ corresponded to changes in systolic BP (p < 0.01) and African American participants demonstrated greater systolic BP responses for a given categorical serum Na+ increase (p < 0.01). Baseline Aldo was lower in African American adults (7.2 ± 0.6 vs. 12.0 ± 1.9 ng/dL, p = 0.03), there was a trend for lower baseline PRA (0.59 ± 0.9 vs. 1.28 ± 0.34 ng/mL/h, p = 0.07), and baseline Ang II was not different (14.2 ± 1.8 vs. 18.5 ± 1.4 pg/mL, p = 0.17). PRA and Aldo decreased during the HSI (p ≤ 0.01), with a greater decline in PRA (Δ–0.31 ± 0.07 vs. Δ–0.85 ± 0.25 ng/mL/h, p < 0.01) and Aldo (Δ–2.5 ± 0.5 vs. Δ–5.0 ± 1.1 ng/dL, p < 0.01) in Caucasian participants. However, the racial difference in PRA (p = 0.57) and Aldo (p = 0.59) reduction were no longer significant following baseline covariate analysis. Conclusion: African American individuals demonstrate augmented serum Na+ to an acute hypertonic saline load and greater systolic BP responsiveness to a given serum Na+. The altered BP response may be attributable to lower basal PRA and Aldo and a subsequently blunted RAAS response during the HSI.
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Affiliation(s)
- Megan M Wenner
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States
| | - Erin P Paul
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States
| | - Austin T Robinson
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States
| | - William C Rose
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States
| | - William B Farquhar
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States
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Reyes LM, Usselman CW, Davenport MH, Steinback CD. Sympathetic Nervous System Regulation in Human Normotensive and Hypertensive Pregnancies. Hypertension 2018. [DOI: 10.1161/hypertensionaha.117.10766] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Laura M. Reyes
- From the Program for Pregnancy and Postpartum Health, Faculty of Kinesiology, Sport and Recreation, Women and Children’s Health Research Institute (L.M.R., C.W.U., M.H.D., C.D.S.) and Alberta Diabetes Institute (M.H.D.), University of Alberta, Edmonton, Canada
| | - Charlotte W. Usselman
- From the Program for Pregnancy and Postpartum Health, Faculty of Kinesiology, Sport and Recreation, Women and Children’s Health Research Institute (L.M.R., C.W.U., M.H.D., C.D.S.) and Alberta Diabetes Institute (M.H.D.), University of Alberta, Edmonton, Canada
| | - Margie H. Davenport
- From the Program for Pregnancy and Postpartum Health, Faculty of Kinesiology, Sport and Recreation, Women and Children’s Health Research Institute (L.M.R., C.W.U., M.H.D., C.D.S.) and Alberta Diabetes Institute (M.H.D.), University of Alberta, Edmonton, Canada
| | - Craig D. Steinback
- From the Program for Pregnancy and Postpartum Health, Faculty of Kinesiology, Sport and Recreation, Women and Children’s Health Research Institute (L.M.R., C.W.U., M.H.D., C.D.S.) and Alberta Diabetes Institute (M.H.D.), University of Alberta, Edmonton, Canada
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15
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Hagbarth KE. Microelectrode Exploration of Human Nerves: Physiological and Clinical Implications. J R Soc Med 2018; 76:7-15. [PMID: 6298417 PMCID: PMC1438572 DOI: 10.1177/014107688307600104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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16
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Shoemaker JK, Klassen SA, Badrov MB, Fadel PJ. Fifty years of microneurography: learning the language of the peripheral sympathetic nervous system in humans. J Neurophysiol 2018; 119:1731-1744. [PMID: 29412776 DOI: 10.1152/jn.00841.2017] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
As a primary component of homeostasis, the sympathetic nervous system enables rapid adjustments to stress through its ability to communicate messages among organs and cause targeted and graded end organ responses. Key in this communication model is the pattern of neural signals emanating from the central to peripheral components of the sympathetic nervous system. But what is the communication strategy employed in peripheral sympathetic nerve activity (SNA)? Can we develop and interpret the system of coding in SNA that improves our understanding of the neural control of the circulation? In 1968, Hagbarth and Vallbo (Hagbarth KE, Vallbo AB. Acta Physiol Scand 74: 96-108, 1968) reported the first use of microneurographic methods to record sympathetic discharges in peripheral nerves of conscious humans, allowing quantification of SNA at rest and sympathetic responsiveness to physiological stressors in health and disease. This technique also has enabled a growing investigation into the coding patterns within, and cardiovascular outcomes associated with, postganglionic SNA. This review outlines how results obtained by microneurographic means have improved our understanding of SNA outflow patterns at the action potential level, focusing on SNA directed toward skeletal muscle in conscious humans.
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Affiliation(s)
- J Kevin Shoemaker
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Stephen A Klassen
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Mark B Badrov
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Paul J Fadel
- Department of Kinesiology, University of Texas at Arlington , Arlington, Texas
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17
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Imai D, Takeda R, Suzuki A, Naghavi N, Yamashina Y, Ota A, Matsumura S, Yokoyama H, Miyagawa T, Okazaki K. Effects of skin surface cooling before exercise on lactate accumulation in cool environment. Eur J Appl Physiol 2018; 118:551-562. [PMID: 29299665 DOI: 10.1007/s00421-017-3797-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 12/28/2017] [Indexed: 10/18/2022]
Abstract
PURPOSE We assessed whether plasma lactate accumulation increased and the lactate threshold (LT) declined when the skin temperature was lowered by whole body skin surface cooling before exercise in cool, but not temperate, conditions, and whether the lowered LT was associated with sympathetic activation or lowered plasma volume (PV) by cold-induced diuresis. METHODS Ten healthy subjects performed a graded maximal cycling exercise after pre-conditioning under three different conditions for 60 min. Ambient temperature (using an artificial climatic chamber) and water temperature in a water-perfusion suit controlled at 25 and 34 °C in temperate-neutral (Temp-Neut); 25 and 10 °C in temperate-cool (Temp-Cool); and at 10 and 10 °C in cool-cool (Cool-Cool) conditions, respectively. Esophageal (Tes) and skin temperatures were measured; plasma lactate ([Lac]p) and noradrenaline concentrations ([Norad]p), and relative change in PV (%ΔPV) were determined before and after pre-conditioning and during exercise, and LT was determined. RESULTS After pre-conditioning, Tes was not different among trials, whereas the mean skin temperature was lower in Cool-Cool and Temp-Cool than in Temp-Neut (P < 0.001). During exercise, [Lac]p and [Norad]p were higher (P = 0.009 and P < 0.001, respectively) and LT was lower (P = 0.013) in Cool-Cool than in the other trials. The %ΔPV was not different among trials. LT was correlated with [Norad]p during exercise (R = 0.50, P = 0.005). CONCLUSIONS Whole body skin surface cooling before exercise increases lactate accumulation and decreases LT with sympathetic activation when exercise is performed in a cool, but not in a temperate, environment.
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Affiliation(s)
- Daiki Imai
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan.,Department of Environmental Physiology for Exercise, Osaka City University Graduate School of Medicine, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan
| | - Ryosuke Takeda
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan
| | - Akina Suzuki
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan
| | - Nooshin Naghavi
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan
| | - Yoshihiro Yamashina
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan
| | - Akemi Ota
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan
| | - Shinya Matsumura
- Research Area of Sports Physiology, Osaka University of Health and Sport Sciences, Osaka, Japan
| | - Hisayo Yokoyama
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan.,Department of Environmental Physiology for Exercise, Osaka City University Graduate School of Medicine, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan
| | - Toshiaki Miyagawa
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan.,Department of Environmental Physiology for Exercise, Osaka City University Graduate School of Medicine, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan
| | - Kazunobu Okazaki
- Research Center for Urban Health and Sports, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan. .,Department of Environmental Physiology for Exercise, Osaka City University Graduate School of Medicine, 3-3-138 Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan.
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18
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Does sympathetic dysfunction occur before denervation in pure autonomic failure? Clin Sci (Lond) 2018; 132:1-16. [PMID: 29162745 DOI: 10.1042/cs20170240] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 11/03/2017] [Accepted: 11/17/2017] [Indexed: 01/08/2023]
Abstract
Pure autonomic failure (PAF) is a rare sporadic disorder characterized by autonomic failure in the absence of a movement disorder or dementia and is associated with very low plasma norepinephrine (NE) levels-suggesting widespread sympathetic denervation, however due to its rarity the pathology remains poorly elucidated. We sought to correlate clinical and neurochemical findings with sympathetic nerve protein abundances, accessed by way of a forearm vein biopsy, in patients with PAF and in healthy controls and patients with multiple systems atrophy (MSA) in whom sympathetic nerves are considered intact. The abundance of sympathetic nerve proteins, extracted from forearm vein biopsy specimens, in 11 patients with PAF, 8 patients with MSA and 9 age-matched healthy control participants was performed following a clinical evaluation and detailed evaluation of sympathetic nervous system function, which included head-up tilt (HUT) testing with measurement of plasma catecholamines and muscle sympathetic nerve activity (MSNA) in addition to haemodynamic assessment to confirm the clinical phenotype. PAF participants were found to have normal abundance of the NE transporter (NET) protein, together with very low levels of tyrosine hydroxylase (TH) (P<0.0001) and reduced vesicular monoamine transporter 2 (VMAT2) (P<0.05) protein expression compared with control and MSA participants. These findings were associated with a significantly higher ratio of plasma 3,4-dihydroxyphenylglycol (DHPG):NE in PAF participants when compared with controls (P<0.05). The finding of normal NET abundance in PAF suggests intact sympathetic nerves but with reduced NE synthesis. The finding of elevated plasma ratio of DHPG:NE and reduced VMAT2 in PAF indicates a shift towards intraneuronal NE metabolism over sequestration in sympathetic nerves and suggests that sympathetic dysfunction may occur ahead of denervation.
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La Rovere MT, Pinna GD. Beneficial effects of physical activity on baroreflex control in the elderly. Ann Noninvasive Electrocardiol 2014; 19:303-10. [PMID: 24844457 DOI: 10.1111/anec.12170] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The baroreflex mechanisms, by controlling autonomic outflow to the heart and circulation, contribute importantly to neural circulatory control. The main function of the baroreflex is to prevent wide fluctuations in arterial blood pressure and to maintain the physiological homeostasis under basal resting conditions and in response to acute stress. Baroreflex-mediated changes in autonomic outflow affect heart rate, myocardial contractility, and peripheral vascular resistance. The baroreflex control of heart rate is of particular interest in pathological conditions, since it has been associated with increased propensity for cardiac mortality and sudden death. Aging is associated with significant cardiovascular modifications. The changes in baroreflex function that occur with age have been systematically studied by several methodological approaches. The available evidence indicates a reduced arterial baroreflex control of heart rate favoring an increase in sympathetic and a decrease in parasympathetic drive to the heart as well as an impairment in the baroreceptor control of blood pressure. Both kinds of changes have resultant clinical implications. Exercise training can modulate the age-related decline in baroreflex function and the attending abnormalities in autonomic control, thus accounting for some of the beneficial effects of physical activity in reducing the risk of cardiovascular morbidity and mortality.
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Affiliation(s)
- Maria Teresa La Rovere
- Department of Cardiology and Biomedical Engineering, Fondazione "Salvatore Maugeri," IRCCS, Istituto Scientifico di Montescano (Pavia), Italy
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20
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Time course of the attenuation of sympathetic nervous activity during active heat acclimation. Auton Neurosci 2013; 177:101-3. [DOI: 10.1016/j.autneu.2013.02.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 02/16/2013] [Accepted: 02/19/2013] [Indexed: 11/18/2022]
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van Lien R, Schutte NM, Meijer JH, de Geus EJC. Estimated preejection period (PEP) based on the detection of the R-wave and dZ/dt-min peaks does not adequately reflect the actual PEP across a wide range of laboratory and ambulatory conditions. Int J Psychophysiol 2012; 87:60-9. [PMID: 23142412 DOI: 10.1016/j.ijpsycho.2012.11.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 10/31/2012] [Accepted: 11/01/2012] [Indexed: 11/16/2022]
Abstract
The current study evaluates the validity of the PEP computed from a fixed value for the Q-wave onset to R-wave peak (QR) interval and an R-wave peak to B-point (RB) interval that is estimated from the R-peak to dZ/dt-min peak (ISTI) interval. Ninety-one subjects participated in a 90min laboratory experiment in which a variety of often employed physical and mental stressors were presented and 31 further subjects participated in a structured 2hour ambulatory recording in which they partook in natural activities that induced large variation in posture and physical activity. PEP, QR interval, and ISTI were scored and rigorously checked by interactive inspection. Across the very diverse laboratory and ambulatory conditions the QR interval could be approximated by a fixed interval of 40ms but 95% confidence intervals were large (25.5 to 54.5ms). Multilevel analysis showed that 79% to 81% of the within and between-subject variation in the RB interval could be predicted by the ISTI with a simple linear regression equation. However, the optimal intercept and slope values in this equation varied significantly across subjects and study setting. Bland Altman plots revealed a large discrepancy between the estimated PEP using the R-wave peak and dZ/dt-min peak and the actual PEP based on the Q-wave onset and B-point. We conclude that the PEP estimated from a fixed QR interval and the ISTI could be a useful addition to the psychophysiologist's toolbox, but that it cannot replace the actual PEP to index cardiac sympathetic control.
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Affiliation(s)
- René van Lien
- Department of Biological Psychology, VU University, Amsterdam, The Netherlands.
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Okada Y, Galbreath MM, Jarvis SS, Bivens TB, Vongpatanasin W, Levine BD, Fu Q. Elderly blacks have a blunted sympathetic neural responsiveness but greater pressor response to orthostasis than elderly whites. Hypertension 2012; 60:842-8. [PMID: 22777937 DOI: 10.1161/hypertensionaha.112.195313] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Neural control of blood pressure (BP) has been reported to differ between young blacks and whites. We hypothesized that elderly blacks have enhanced sympathetic neural responses during orthostasis compared with elderly whites. Muscle sympathetic nerve activity, arm-cuff BP, and heart rate were recorded continuously, and cardiac output, stroke volume, and total peripheral resistance were measured intermittently during supine and 5-minute 60° upright tilt in 10 blacks (65 [SD, 4] years; 4 women) and 20 whites (68 [6] years; 8 women). We found that muscle sympathetic nerve activity burst frequency was similar between blacks and whites in the supine position (44 [10] versus 42 [7] bursts per minute) and during upright tilt (59 [11] versus 60 [9] bursts per minute; P=0.846 for race, P<0.001 for posture, and P=0.622 for interaction). However, upright total muscle sympathetic nerve activity was smaller in blacks than in whites (162 [39] versus 243 [112]%; P=0.003). Systolic BP, heart rate, cardiac output, and stroke volume were not different between groups. Diastolic BP was similar in the supine position, increased in all of the subjects during tilting; upright diastolic BP was greater in blacks than in whites (80 [10] versus 71 [7] mmHg; P=0.008). Total peripheral resistance did not differ between blacks and whites in the supine position or during upright tilt (P=0.354 for race, P<0.001 for posture, P=0.825 for interaction). Thus, elderly blacks have a blunted sympathetic neural responsiveness but enhanced pressor response to orthostasis compared with elderly whites, which may be attributable to an augmented sympathetic vascular transduction and/or nonadrenergic vasoconstrictor mechanisms (ie, angiotensin II or the venoarteriolar response).
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Affiliation(s)
- Yoshiyuki Okada
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA
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Sympathetic nerve activity in stress-induced cardiomyopathy. Clin Auton Res 2012; 22:259-64. [PMID: 22492095 PMCID: PMC3501184 DOI: 10.1007/s10286-012-0162-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 03/27/2012] [Indexed: 01/08/2023]
Abstract
Purpose To evaluate directly recorded efferent sympathetic nerve traffic in patients with stress-induced cardiomyopathy (SIC). Background SIC is a syndrome affecting mostly postmenopausal women following severe emotional stress. Though the precise pathophysiology is not well understood, a catecholamine overstimulation of the myocardium is thought to underlie the pathogenesis. Methods Direct recordings of multiunit efferent postganglionic muscle sympathetic nerve activity (MSNA) were obtained from 12 female patients, 5 in the acute (24–48 h) and 7 in the recovery phase (1–6 months), with apical ballooning pattern and 12 healthy matched controls. MSNA was expressed as burst frequency (BF), burst incidence (BI) and relative median burst amplitude (RMBA %). One of the twelve patients in this study was on beta blockade treatment due to a different illness, at time of onset of SIC. All patients were investigated with ongoing medication. Results MSNA was lower in patients with SIC as compared to matched controls, but did not differ between the acute and recovery phase of SIC. RMBA %, blood pressure and heart rate did not differ between the groups. Conclusion MSNA is shown to be lower in patients with SIC compared to healthy controls, suggesting that sympathetic neuronal outflow is rapidly reduced following the initial phase of SIC. A distension of the ventricular myocardium, due to excessive catecholamine release over the heart in the acute phase, may increase the firing rate of unmyelinated cardiac c-fibre afferents resulting in widespread sympathetic inhibition. Such a mechanism may underlie the lower MSNA reported in our patients.
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Puhl AA, Injeyan HS. Short-term effects of manipulation to the upper thoracic spine of asymptomatic subjects on plasma concentrations of epinephrine and norepinephrine-a randomized and controlled observational study. J Manipulative Physiol Ther 2012; 35:209-15. [PMID: 22343005 DOI: 10.1016/j.jmpt.2012.01.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 10/20/2011] [Accepted: 10/27/2011] [Indexed: 12/15/2022]
Abstract
OBJECTIVE The purpose of this study was to investigate the short-term effects of spinal manipulation applied to a hypomobile segment of the upper thoracic spine (T1-T6), on plasma concentrations of norepinephrine (NE) and epinephrine (E) in asymptomatic subjects, under strictly controlled conditions. METHODS Fifty-six asymptomatic subjects were randomly assigned to receive either a chiropractic manipulative intervention or a sham intervention in the upper thoracic spine. A 20-gauge catheter fitted with a saline lock was used to sample blood before, immediately after, and 15 minutes after intervention. Plasma NE and E concentrations were determined using an enzyme-linked immunosorbent assay. Changes in plasma catecholamine concentrations were analyzed within and between groups using 1- and 2-sample t tests, respectively. RESULTS The plasma samples of 36 subjects (18 treatment, 18 control) were used in the analysis. Mean plasma concentrations of NE and E did not significantly differ between the 2 groups at any time point and did not change significantly after either the manipulative or sham intervention. CONCLUSIONS The results of this study indicate that a manipulative thrust directed to a hypomobile segment in the upper thoracic spine of asymptomatic subjects does not have a measurable effect on the plasma concentrations of NE or E. These results provide a baseline measure of the sympathetic response to spinal manipulation.
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Affiliation(s)
- Aaron A Puhl
- Canadian Memorial Chiropractic College, Toronto, Ontario, Canada
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Nygren I, Fagius J. High resting level and weak response of baroreflex-governed sympathetic outflow in amyotrophic lateral sclerosis. Muscle Nerve 2011; 43:432-40. [PMID: 21305564 DOI: 10.1002/mus.21894] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2010] [Indexed: 11/10/2022]
Affiliation(s)
- Ingela Nygren
- Department of Neurology, University Hospital, Uppsala SE-751 85, Sweden
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Crimmins EM, Vasunilashorn S. Links Between Biomarkers and Mortality. INTERNATIONAL HANDBOOK OF ADULT MORTALITY 2011. [DOI: 10.1007/978-90-481-9996-9_18] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Hotta H, Uchida S. Aging of the autonomic nervous system and possible improvements in autonomic activity using somatic afferent stimulation. Geriatr Gerontol Int 2010; 10 Suppl 1:S127-36. [PMID: 20590828 DOI: 10.1111/j.1447-0594.2010.00592.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
There are significant age-related changes in autonomic nervous system function that are responsible for an impaired ability to adapt to environmental or intrinsic visceral stimuli in the elderly. We review data on changes in autonomic nervous system regulation of cardiovascular and urinary function, as well as data on strategies to improve function. There are data showing alterations in peripheral and central autonomic nerve activity, and decreases in neurotransmitter receptor action that lead to diminished autonomic reactivity (e.g. blood pressure and cerebral blood flow regulation) and poorly coordinated autonomic discharge (e.g. bladder function). Simple strategies for autonomic function improvement and increasing cortical blood flow include walking and somatic afferent stimulation (e.g. stroking skin or acupuncture) to increase sympathetic, parasympathetic and central cholinergic activity.
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Affiliation(s)
- Harumi Hotta
- Department of the Autonomic Nervous System, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo, Japan.
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Abstract
We hypothesized that orthostatic tolerance is higher in young, healthy black compared with white women. To determine orthostatic tolerance, 22 women (11 black and 11 white) underwent graded lower body negative pressure to presyncope. We measured blood pressure, heart rate, and R-R interval (ECG) continuously at baseline and through all of the levels of lower body negative pressure. Blood samples were taken at baseline along with presyncope for the measurement of plasma catecholamine concentrations, serum aldosterone concentration, and plasma renin activity. Cumulative stress index, the sum of the product of time and lower body negative pressure, was the indicator of orthostatic tolerance. Orthostatic tolerance in the black women was greater than in the white women [cumulative stress index: -1003 (375) versus -476 (197); P<0.05]. Although plasma concentrations of norepinephrine increased in both groups at presyncope, the increase was greater in black [Deltaplasma concentrations of norepinephrine: 167 (123)] versus white women [86 (64); P<0.05], as was the increase in PRA [DeltaPRA 2.6 (1.0) versus 0.6 (0.9) ng of angiotensin II x mL(-1) x h(-1); P<0.05, for black and white women, respectively). Although heart rate increased and R-R interval decreased to a greater extent during lower body negative pressure in black women compared with white women (ANOVA: P<0.05), baroreflex function (ie, slope R-R interval versus systolic blood pressure) was unaffected by race. These data indicate that orthostatic tolerance is greater in black compared with white women, which appears to be a function of greater sympathetic nervous system responses to orthostatic challenges.
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Affiliation(s)
- Kumba Hinds
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale School of Public Health, Yale University School of Medicine, New Haven, Conn, USA
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Hedrington MS, Farmerie S, Ertl AC, Wang Z, Tate DB, Davis SN. Effects of antecedent GABAA activation with alprazolam on counterregulatory responses to hypoglycemia in healthy humans. Diabetes 2010; 59:1074-81. [PMID: 20086227 PMCID: PMC2844816 DOI: 10.2337/db09-1520] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE To date, there are no data investigating the effects of GABA(A) activation on counterregulatory responses during repeated hypoglycemia in humans. The aim of this study was to determine the effects of prior GABA(A) activation using the benzodiazepine alprazolam on the neuroendocrine and autonomic nervous system (ANS) and metabolic counterregulatory responses during next-day hypoglycemia in healthy humans. RESEARCH DESIGN AND METHODS Twenty-eight healthy individuals (14 male and 14 female, age 27 +/- 6 years, BMI 24 +/- 3 kg/m(2), and A1C 5.2 +/- 0.1%) participated in four randomized, double-blind, 2-day studies. Day 1 consisted of either morning and afternoon 2-h hyperinsulinemic euglycemia or 2-h hyperinsulinemic hypoglycemia (2.9 mmol/l) with either 1 mg alprazolam or placebo administered 30 min before the start of each clamp. Day 2 consisted of a single-step hyperinsulinemic-hypoglycemic clamp of 2.9 mmol/l. RESULTS Despite similar hypoglycemia (2.9 +/- 1 mmol/l) and insulinemia (672 +/- 108 pmol/l) during day 2 studies, GABA(A) activation with alprazolam during day 1 euglycemia resulted in significant blunting (P < 0.05) of ANS (epinephrine, norepinephrine, muscle sympathetic nerve activity, and pancreatic polypeptide), neuroendocrine (glucagon and growth hormone), and metabolic (glucose kinetics, lipolysis, and glycogenolysis) counterregulatory responses. GABA(A) activation with alprazolam during prior hypoglycemia caused further significant (P < 0.05) decrements in subsequent glucagon, growth hormone, pancreatic polypeptide, and muscle sympathetic nerve activity counterregulatory responses. CONCLUSIONS Alprazolam activation of GABA(A) pathways during day 1 hypoglycemia can play an important role in regulating a spectrum of key physiologic responses during subsequent (day 2) hypoglycemia in healthy man.
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Affiliation(s)
| | | | - Andrew C. Ertl
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Zhihui Wang
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Donna B. Tate
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Stephen N. Davis
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
- Department of Medicine, Veterans Affairs, Nashville, Tennessee
- Corresponding author: Stephen N. Davis,
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Christensen NJ. Catecholamines and sympathetic nervous activity in the elderly. ACTA MEDICA SCANDINAVICA. SUPPLEMENTUM 2009; 676:52-63. [PMID: 6581693 DOI: 10.1111/j.0954-6820.1983.tb19333.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Katzman PL, Hulthén UL, Hökfelt B. Effects of the calcium antagonist felodipine on the sympathetic and renin-angiotensin-aldosterone systems in essential hypertension. ACTA MEDICA SCANDINAVICA 2009; 223:125-31. [PMID: 3279724 DOI: 10.1111/j.0954-6820.1988.tb15776.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Studies were performed in 10 male patients with untreated essential hypertension, WHO grade I-II, aged 25-62 years, to explore the acute (single dose) and long-term (8 weeks) effects of felodipine on sympathetic activity--evaluated by plasma and urinary catecholamines--as related to blood pressure, heart rate and the activity in the renin-angiotensin-aldosterone system. The patients were hospitalized for 8 (acute) and 6 (long-term) days and were maintained on a standardized daily intake of sodium (150 mmol), potassium (75 mmol) and water (2,500 ml). Acute felodipine administration (10 mg) significantly reduced blood pressure and increased heart rate. Plasma and urinary noradrenaline, plasma renin activity and angiotensin II increased, whereas plasma and urinary adrenaline, dopamine, aldosterone and plasma vasopressin were unaltered. Long-term felodipine treatment, 10 mg twice daily, reduced blood pressure to a similar extent as acute felodipine administration, but heart rate was not significantly changed. Plasma noradrenaline 3 and 12 hours after the last dose and urinary noradrenaline were increased, whereas plasma and urinary adrenaline and dopamine were unchanged. Plasma renin activity and angiotensin II were increased 3 hours, but unchanged 12 hours after the last dose. Plasma aldosterone was unchanged but urinary aldosterone increased. Plasma vasopressin was unchanged. The changes in plasma noradrenaline as related to blood pressure, heart rate, plasma renin activity and angiotensin II during long-term felodipine treatment may reflect decreased cardiac and renal beta-adrenoceptor-mediated responses. Increased renal clearance of aldosterone could partly explain the unaltered plasma aldosterone level in spite of increased plasma angiotensin II following long-term felodipine treatment.
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Affiliation(s)
- P L Katzman
- Department of Endocrinology, Lund University Clinics, General Hospital, Malmö, Sweden
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Frisk-Holmberg M, Essén B, Fredrikson M, Ström G, Wibell L. Muscle fibre composition in relation to blood pressure response to isometric exercise in normotensive and hypertensive subjects. ACTA MEDICA SCANDINAVICA 2009; 213:21-6. [PMID: 6829315 DOI: 10.1111/j.0954-6820.1983.tb03683.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A positive relationship was demonstrated between the blood pressure and the fibre composition of the vastus muscle at rest in 17 hypertensive and 17 age- and sex-matched normotensive subjects. The hypertensive group had a higher proportion of fast twitch (FT) fibres (p less than 0.1). The circulatory response was measured during isometric exercise (IE) and cold pressor test (CPT). During IE the blood pressure increase was positively related to the percentage of FT fibres. No such relationship was demonstrated during CPT. It was thus found, particularly in hypertensive subjects, that an individual's muscle fibre profile is of importance for the blood pressure response during IE.
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Andersson B, Wallin G, Hedner T, Ahlberg AC, Andersson OK. Acute effects of short-term fasting on blood pressure, circulating noradrenaline and efferent sympathetic nerve activity. ACTA MEDICA SCANDINAVICA 2009; 223:485-90. [PMID: 3389203 DOI: 10.1111/j.0954-6820.1988.tb17685.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Eleven moderately obese women, aged 46-62 years, with a body mass index of 29-34 and with borderline hypertension (repeated diastolic blood pressure greater than 90 mmHg) fasted for 48 hours. Before the fast and after 48 hours of fasting, plasma noradrenaline, urinary noradrenaline, urine potassium, urine sodium and weight were measured. In six of the patients muscle nerve sympathetic activity was recorded from the peroneal nerve by tungsten microelectrodes for 15 min each time. The efferent muscle sympathetic activity (MSA) was expressed as the number of bursts/min. The recordings were done before the fast and after 48 hours of fasting. We found significant decreases in body weight from 88.4 +/- 2.5 kg to 86.4 +/- 2.5 kg. Systolic blood pressure (BP) was reduced from 158 +/- 3 mmHg to 146 +/- 5 mmHg (p less than 0.001) and diastolic BP from 96 +/- 3 mmHg to 89 +/- 3 mmHg (p less than 0.01) during the fast. MSA was significantly increased from 42.0 +/- 5.5 bursts/min to 44.5 +/- 5.8 (n = 6), while plasma and urine noradrenaline concentrations (n = 11) showed a non-significant tendency to increase. We conclude that the hypotensive response during the first days of extensive caloric reduction is not due to a decreased sympathetic activity. If anything, there may be weak increase of efferent sympathetic nerve activity and venous plasma levels of circulating noradrenaline. The mechanisms behind the acute hypotensive response to negative caloric balance are thus still unclear, but obviously different from long-term adaptation of the blood pressure.
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Affiliation(s)
- B Andersson
- Department of Internal Medicine, Sahlgrenska Hospital, University of Göteborg, Sweden
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Hjemdahl P. Sympatho-adrenal mechanisms and the antihypertensive response to thiazide diuretics. ACTA PHARMACOLOGICA ET TOXICOLOGICA 2009; 54 Suppl 1:43-6. [PMID: 6711331 DOI: 10.1111/j.1600-0773.1984.tb03630.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Thiazide diuretics lower the blood pressure during long-term treatment by reducing the peripheral vascular resistance. This seems to be related to the natriuresis rather than to a direct vasodilating effect of the thiazides. There is evidence that the volume depletion caused by thiazide treatment initially triggers an increase in sympathetic nerve activity, which may account for initial increases in vascular resistance. Although both responses subside during long-term treatment, there is no evidence showing a causal relationship between these changes. The long-term hemodynamic adaptation to thiazide treatment may be related to altered cardiovascular reflexes. Changes in sympathetic nerve activity and reduced vascular sensitivity to noradrenaline may contribute to the adaptation. An analysis of the relative importance of these mechanisms requires further studies comparing the time courses for various effects in responders and non-responders to the treatment.
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Davis SN, Mann S, Briscoe VJ, Ertl AC, Tate DB. Effects of intensive therapy and antecedent hypoglycemia on counterregulatory responses to hypoglycemia in type 2 diabetes. Diabetes 2009; 58:701-9. [PMID: 19073776 PMCID: PMC2646069 DOI: 10.2337/db08-1230] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE The physiology of counterregulatory responses during hypoglycemia in intensively treated type 2 diabetic subjects is largely unknown. Therefore, the specific aims of the study tested the hypothesis that 1) 6 months of intensive therapy to lower A1C <7.0% would blunt autonomic nervous system (ANS) responses to hypoglycemia, and 2) antecedent hypoglycemia will result in counterregulatory failure during subsequent hypoglycemia in patients with suboptimal and good glycemic control. RESEARCH DESIGN AND METHODS Fifteen type 2 diabetic patients (8 men/7 women) underwent 6-month combination therapy of metformin, glipizide XL, and acarbose to lower A1C to 6.7% and 2-day repeated hypoglycemic clamp studies before and after intensive therapy. A control group of eight nondiabetic subjects participated in a single 2-day repeated hypoglycemic clamp study. RESULTS Six-month therapy reduced A1C from 10.2 +/- 0.5 to 6.7 +/- 0.3%. Rates of hypoglycemia increased to 3.2 episodes per patient/month by study end. Hypoglycemia (3.3 +/- 0.1 mmol/l) and insulinemia (1,722 +/- 198 pmol/l) were similar during all clamp studies. Intensive therapy reduced (P < 0.05) ANS and metabolic counterregulatory responses during hypoglycemia. Antecedent hypoglycemia produced widespread blunting (P < 0.05) of neuroendocrine, ANS, and metabolic counterregulatory responses during subsequent hypoglycemia before and after intensive therapy in type 2 diabetic patients and in nondiabetic control subjects. CONCLUSIONS Intensive oral combination therapy and antecedent hypoglycemia both blunt physiological defenses against subsequent hypoglycemia in type 2 diabetes. Prior hypoglycemia of only 3.3 +/- 0.1 mmol/l can result in counterregulatory failure in type 2 diabetic patients with suboptimal control and can further impair physiological defenses against hypoglycemia in intensively treated type 2 diabetes.
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Affiliation(s)
- Stephen N Davis
- Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA.
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Briscoe VJ, Ertl AC, Tate DB, Davis SN. Effects of the selective serotonin reuptake inhibitor fluoxetine on counterregulatory responses to hypoglycemia in individuals with type 1 diabetes. Diabetes 2008; 57:3315-22. [PMID: 18835927 PMCID: PMC2584138 DOI: 10.2337/db08-1000] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Accepted: 09/18/2008] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Previous work has demonstrated that chronic administration of the serotonin reuptake inhibitor (SSRI) fluoxetine augments counterregulatory responses to hypoglycemia in healthy humans. However, virtually no information exists regarding the effects of fluoxetine on integrated physiological counterregulatory responses during hypoglycemia in type 1 diabetes. Therefore, the specific aim of this study was to test the hypothesis that 6-week use of the SSRI fluoxetine would amplify autonomic nervous system (ANS) counterregulatory responses to hypoglycemia in individuals with type 1 diabetes. RESEARCH DESIGN AND METHODS Eighteen type 1 diabetic patients (14 men/4 women aged 19-48 years with BMI 25 +/- 3 kg/m(2) and A1C 7.0 +/- 0.4%) participated in randomized, double-blind 2-h hyperinsulinemic (9 pmol . kg(-1) . min(-1))-hypoglycemic clamp studies before and after 6 weeks of fluoxetine administration (n = 8) or identical placebo (n = 10). Glucose kinetics was determined by 3-tritiated glucose. Muscle sympathetic nerve activity (MSNA) was determined by microneurography. RESULTS Hypoglycemia (2.8 +/- 0.1 mmol/l) and insulinemia (646 +/- 52 pmol/l) were similar during all clamp studies. ANS, neuroendocrine, and metabolic counterregulatory responses remained unchanged in the placebo group. However, fluoxetine administration significantly (P < 0.05) increased key ANS (epinephrine, norepinephrine, and MSNA), metabolic (endogenous glucose production and lipolysis), and cardiovascular (systolic blood pressure) counterregulatory responses during hypoglycemia. CONCLUSIONS This study has demonstrated that 6-week administration of the SSRI fluoxetine can amplify ANS and metabolic counterregulatory mechanisms during moderate hypoglycemia in patients with type 1 diabetes. These data also suggest that the use of fluoxetine may be useful in increasing epinephrine responses during hypoglycemia in clinical practice.
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Affiliation(s)
| | - Andrew C. Ertl
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Donna B. Tate
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Stephen N. Davis
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
- Department of Medicine, Veterans Affairs, Nashville, Tennessee
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Briscoe VJ, Ertl AC, Tate DB, Dawling S, Davis SN. Effects of a selective serotonin reuptake inhibitor, fluoxetine, on counterregulatory responses to hypoglycemia in healthy individuals. Diabetes 2008; 57:2453-60. [PMID: 18567822 PMCID: PMC2518497 DOI: 10.2337/db08-0236] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Accepted: 06/17/2008] [Indexed: 12/01/2022]
Abstract
OBJECTIVE Hypoglycemia commonly occurs in intensively-treated diabetic patients. Repeated hypoglycemia blunts counterregulatory responses, thereby increasing the risk for further hypoglycemic events. Currently, physiologic approaches to augment counterregulatory responses to hypoglycemia have not been established. Therefore, the specific aim of this study was to test the hypothesis that 6 weeks' administration of the selective serotonin reuptake inhibitor (SSRI) fluoxetine would amplify autonomic nervous system (ANS) and neuroendocrine counterregulatory mechanisms during hypoglycemia. RESEARCH DESIGN AND METHODS A total of 20 healthy (10 male and 10 female) subjects participated in an initial single-step hyperinsulinemic (9 pmol . kg(-1) . min(-1))-hypoglycemic (means +/- SE 2.9 +/- 0.1 mmol/l) clamp study and were then randomized to receive 6 weeks' administration of fluoxetine (n = 14) or identical placebo (n = 6) in a double-blind fashion. After 6 weeks, subjects returned for a second hypoglycemic clamp. Glucose kinetics were determined by three-tritiated glucose, and muscle sympathetic nerve activity (MSNA) was measured by microneurography. RESULTS Despite identical hypoglycemia (2.9 +/- 0.1 mmol/l) and insulinemia during all clamp studies, key ANS (epinephrine, norepinephrine, and MSNA but not symptoms), neuroendocrine (cortisol), and metabolic (endogenous glucose production, glycogenolysis, and lipolysis) responses were increased (P < 0.01) following fluoxetine. CONCLUSIONS This study demonstrated that 6 weeks' administration of the SSRI fluoxetine can amplify a wide spectrum of ANS and metabolic counterregulatory responses during hypoglycemia in healthy individuals. These data further suggest that serotonergic transmission may be an important mechanism in modulating sympathetic nervous system drive during hypoglycemia in healthy individuals.
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Affiliation(s)
| | - Andrew C. Ertl
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Donna B. Tate
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Sheila Dawling
- Department of Pathology, Vanderbilt University, Nashville, Tennessee
| | - Stephen N. Davis
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
- Veterans Affairs Medical Center, Nashville, Tennessee
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Doi H, Niimi Y, Hasegawa Y, Miwa S, Yamana T, Takagi S, Takahashi A, Sobue G. [Relationship between cardiac 123I-metaiodobenzylguanidine scintigraphy and cardiovascular autonomic function test (standing test) in Parkinson's disease]. Rinsho Shinkeigaku 2008; 48:56-9. [PMID: 18386634 DOI: 10.5692/clinicalneurol.48.56] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We investigated the correlation between results of 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy and those of cardiovascular autonomic function tests in patients with Parkinson's disease (PD). 123I-MIBG myocardial scintigraphy and a 5-minute standing test were performed in 50 patients with PD and in 19 control subjects. The value of the basal plasma noradrenaline (NA) level was used as an index of basal sympathetic nerve activity, and %NA was used to assess the response of sympathetic nerve activity. In addition, the parameters of DeltaBP and DeltaHR were evaluated to assess the autonomic response of the cardiovascular system. A mild, but significant correlation was observed between the myocardium to mediastinum (H/M) ratio and the values of the plasma NA baseline (r = 0.35, p < 0.05 in early image, r = 0.29, p < 0.05 in delay image). No significant correlation was observed between the H/M ratio and the other parameters (%NA, DeltaBP, DeltaHR). These results suggest that 123I-MIBG myocardial scintigraphy may be associated with the basal sympathetic nerve activity, but not with autonomic nervous response of the cardiovascular system in patients with PD.
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Affiliation(s)
- Hideki Doi
- Department of Neurology, Higashi General Hospital of Nagoya
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Sverrisdóttir YB, Mogren T, Kataoka J, Janson PO, Stener-Victorin E. Is polycystic ovary syndrome associated with high sympathetic nerve activity and size at birth? Am J Physiol Endocrinol Metab 2008; 294:E576-81. [PMID: 18198350 DOI: 10.1152/ajpendo.00725.2007] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disturbance among women of reproductive age and is proposed to be linked with size at birth and increased prevalence of cardiovascular disease. A disturbance in the sympathetic nervous system may contribute to the etiology of PCOS. This study evaluates sympathetic outflow in PCOS and its relation to size at birth. Directly recorded sympathetic nerve activity to the muscle vascular bed (MSNA) was obtained in 20 women with PCOS and in 18 matched controls. Ovarian ultrasonographic evaluation, biometric, hormonal, and biochemical parameters were measured, and birth data were collected. Women with PCOS had increased MSNA (30 +/- 8 vs. 20 +/- 7 burst frequency, P < 0.0005) compared with controls. MSNA was positively related to testosterone (r = 0.63, P < 0.005) and cholesterol (r = 0.55, P = 0.01) levels in PCOS, which, in turn, were not related to each other. Testosterone level was a stronger predictor of MSNA than cholesterol. Birth size did not differ between the study groups. This is the first study to directly address sympathetic nerve activity in women with PCOS and shows that PCOS is associated with high MSNA. Testosterone and cholesterol levels are identified as independent predictors of MSNA in PCOS, although testosterone has a stronger impact. The increased MSNA in PCOS may contribute to the increased cardiovascular risk and etiology of the condition. In this study, PCOS was not related to size at birth.
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Affiliation(s)
- Yrsa Bergmann Sverrisdóttir
- Institute of Neuroscience and Physiology, Dept. of Physiology, Sahlgrenska Academy, Göteborg Univ., Box 432, SE-405 30 Göteborg, Sweden.
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Plasma catecholamine and nephrine responses to brief intermittent maximal intensity exercise. Amino Acids 2008; 36:209-17. [PMID: 18297236 DOI: 10.1007/s00726-008-0049-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Accepted: 02/12/2008] [Indexed: 10/22/2022]
Abstract
Catecholamines (noradrenaline, NA; adrenaline, AD; dopamine, DA) influence the metabolic and cardiovascular responses to exercise. However, changes in catecholamine metabolism during exercise are unclear. Plasma normetanephrine (NMET), metanephrine (MET) and catecholamine responses to a laboratory-based model of games-type exercise were examined. Twelve healthy men completed a resting control trial and a trial consisting of ten 6 s cycle ergometer sprints interspersed with 30 s recovery, in randomised order. Resting and post-sprint venous blood samples were taken. Plasma NA and AD increased after each sprint but DA was unaltered. Plasma nephrines increased significantly from sprint 4 onwards with peak NMET increasing 60% to 0.76 +/- 0.19 nmol l(-1) and MET 230% to 0.37 +/- 0.16 nmol l(-1) from resting values (P < 0.05). The results demonstrate increased catecholamine metabolism via elevated catechol-O-methyl transferase activity during intermittent sprinting. The results may aid regulation of the metabolic and cardiovascular responses to exercise by maintaining tissue adrenoceptor sensitivity to circulating catecholamines.
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Abstract
Biomarkers are increasingly employed in empirical studies of human populations to understand physiological processes that change with age, diseases whose onset appears linked to age, and the aging process itself. In this chapter, we describe some of the most commonly used biomarkers in population aging research, including their collection, associations with other markers, and relationships to health outcomes. We discuss biomarkers of the cardiovascular system, metabolic processes, inflammation, activity in the hypothalamic-pituitary axis (HPA) and sympathetic nervous system (SNS), and organ functioning (including kidney, lung, and heart). In addition, we note that markers of functioning of the central nervous system and genetic markers are now becoming part of population measurement. Where possible, we detail interrelationships between these markers by providing correlations between high risk levels of each marker from three population-based surveys: the National Health and Nutrition Examination Survey (NHANES) III, NHANES 1999-2002, and the MacArthur Study of Successful Aging. NHANES III is used instead of NHANES 1999-2002 when specific markers of interest are available only in NHANES III and when we examine the relationship of biomarkers to mortality which is only known for NHANES III. We also describe summary measures combining biomarkers across systems. Finally, we examine associations between individual markers and mortality and provide information about biomarkers of growing interest for future research in population aging and health.
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Affiliation(s)
- Eileen Crimmins
- Andrus Gerontology Center, Davis School of Gerontology, University of Southern California, Los Angeles, California 90089, USA
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Agostini D, Manrique A, Hugentobler A, Sabatier R, Belin A, Costo S, Grollier G, Bouvard G. Scintigraphie cardiaque à la 123I-métaiodobenzylguanidine et cardiomyopathies : « le retour ». MEDECINE NUCLEAIRE-IMAGERIE FONCTIONNELLE ET METABOLIQUE 2007. [DOI: 10.1016/j.mednuc.2007.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Wallin BG. Interindividual differences in muscle sympathetic nerve activity: a key to new insight into cardiovascular regulation? Acta Physiol (Oxf) 2007; 190:265-75. [PMID: 17635347 DOI: 10.1111/j.1748-1716.2007.01730.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The paper reviews findings in humans regarding interindividual differences in sympathetic nerve activity. Data come predominantly from microneurographic multi- or single fibre recordings of sympathetic nerve activity in healthy subjects. Findings relate to interindividual differences in muscle sympathetic nerve activity (MSNA) during resting conditions and in response to surprising sensory stimuli. At rest there are marked interindividual differences in the number of multiunit MSNA bursts. At the single fibre level the differences are because of more vasoconstrictor fibres being active in subjects with high than in subjects with low number of bursts. There are inverse relationships between (i) sympathetic burst incidence and cardiac output (CO) and (ii) between sympathetic burst incidence and vascular responsiveness to noradrenaline. Both findings contribute to explaining the absence of correlation between resting levels of MSNA and blood pressure. Surprising visual, somatosensory or auditory stimuli of sufficient strength cause a short lasting inhibition of MSNA in approx. 50-60% of healthy subjects. In subjects who display significant inhibition, the stimulus-induced blood pressure increase is smaller than in subjects without inhibition. The underlying mechanism may be related to fear of blood/injury. It is concluded that analysis of interindividual differences in sympathetic activity improves the understanding of central nervous control of the circulation.
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Affiliation(s)
- B Gunnar Wallin
- Institute of Neuroscience and Physiology, The Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
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Leistad RB, Stovner LJ, White LR, Nilsen KB, Westgaard RH, Sand T. Noradrenaline and cortisol changes in response to low-grade cognitive stress differ in migraine and tension-type headache. J Headache Pain 2007; 8:157-66. [PMID: 17568991 PMCID: PMC3476146 DOI: 10.1007/s10194-007-0384-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Accepted: 04/23/2007] [Indexed: 12/02/2022] Open
Abstract
The goal of this study was to explore the relationship between indicators of sympathoneural, sympathomedullar and hypothalamic-pituitary-adrenocortical (HPA) activity and stress-induced head and shoulder-neck pain in patients with migraine or tension-type headache (TTH). We measured noradrenaline, adrenaline and cortisol levels before and after low-grade cognitive stress in 21 migraineurs, 16 TTH patients and 34 controls. The stressor lasted for 60 min and was followed by 30 min of relaxation. Migraine patients had lower noradrenaline levels in blood platelets compared to controls. Pain responses correlated negatively with noradrenaline levels, and pain recovery correlated negatively with the cortisol change in migraineurs. TTH patients maintained cortisol secretion during the cognitive stress as opposed to the normal circadian decrease seen in controls and migraineurs. There may therefore be abnormal activation of the HPA axis in patients with TTH when coping with mental stress, but no association was found between pain and cortisol. A relationship between HPA activity and stress in TTH patients has to our knowledge not been reported before. In migraine, on the other hand, both sympathoneural activation and HPA activation seem to be linked to stress-induced muscle pain and recovery from pain respectively. The present study suggests that migraineurs and TTH patients cope differently with low-grade cognitive stress.
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Affiliation(s)
- Rune Bang Leistad
- Department of Neuroscience, Norwegian University of Science and Technology, N-7489 Trondheim, Norway.
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Shepherd JT, Mancia G. Reflex control of the human cardiovascular system. Rev Physiol Biochem Pharmacol 2006; 105:1-99. [PMID: 3541137 DOI: 10.1007/bfb0034497] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Murai H, Takata S, Maruyama M, Nakano M, Kobayashi D, Otowa KI, Takamura M, Yuasa T, Sakagami S, Kaneko S. The activity of a single muscle sympathetic vasoconstrictor nerve unit is affected by physiological stress in humans. Am J Physiol Heart Circ Physiol 2005; 290:H853-60. [PMID: 16126820 DOI: 10.1152/ajpheart.00184.2005] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recording of neural firing from single-unit muscle sympathetic nerve activity (MSNA) is a new strategy offering information about the frequency of pure sympathetic firing. However, it is uncertain whether and when single-unit MSNA would be more useful than multiunit MSNA for analysis of various physiological stresses in humans. In 15 healthy subjects, we measured single-unit and multiunit MSNA before and during handgrip exercise at 30% of maximum voluntary contraction for 3 min and during the Valsalva maneuver at 40 mmHg expiratory pressure for 15 s. Shapes of individual single-unit MSNA were proved to be consistent and suitable for further evaluation. Single-unit and multiunit MSNA exhibited similar responses during handgrip exercise. However, acceleration of neural firing determined from single-unit MSNA became steeper than multiunit MSNA during the Valsalva maneuver. During the Valsalva maneuver, unlike handgrip exercise, the distribution of multiunit burst between 0, 1, 2, 3, and 4 spikes was significantly shifted toward multiple spikes within a given burst (P < 0.05). These results indicated that evaluation of single-unit MSNA could provide more detailed and accurate information concerning the role and responses of neuronal discharges induced by various physiological stresses in humans, especially amid intense sympathetic activity.
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Affiliation(s)
- Hisayoshi Murai
- Dept. of Internal Medicine, Graduate School of Medical Science, Kanazawa Univ., 13-1 Takara-machi, Kanazawa 920-8641, Japan.
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Karpe F, Fielding BA, Coppack SW, Lawrence VJ, Macdonald IA, Frayn KN. Oscillations of fatty acid and glycerol release from human subcutaneous adipose tissue in vivo. Diabetes 2005; 54:1297-303. [PMID: 15855313 DOI: 10.2337/diabetes.54.5.1297] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We sought evidence for pulsatility of lipolysis in human subcutaneous adipose tissue in vivo. Arterialized and adipose tissue venous blood samples were drawn at 2-min intervals from nine healthy subjects. This procedure was repeated during hyperinsulinemic-euglycemic clamp to remove insulin pulsatility. We found evidence for pulsatile release of both nonesterified fatty acids (NEFAs) (seven of nine subjects) and glycerol (five of six subjects) with a period of approximately 12-14 min. This pulsatility was maintained even during the hyperinsulinemic clamp. Checks were made for spurious pulse detection, including the creation of "mock" venoarterialized differences by subtracting one subject's arterialized concentrations from another's venous; the peaks detected were less consistent in character than with real data (peak width, P = 0.006; peak interval, P < 0.004). Significant cross-correlations between NEFA and glycerol release also provided evidence of a real effect. Arterialized norepinephrine concentrations were also pulsatile, but the period did not match that of NEFA and glycerol release. Insulin concentrations were pulsatile with a typical period of 12 min, but this was not significantly cross-correlated with lipolysis. We conclude that release from adipose tissue of the products of lipolysis is pulsatile in humans.
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Affiliation(s)
- Fredrik Karpe
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford OX3 7LJ, UK
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Shindo K, Shimokawa C, Watanabe H, Iida H, Ohashi K, Nitta K, Nagasaka T, Tsunoda SI, Shiozawa Z. Chronological changes of sympathetic outflow to muscles in amyotrophic lateral sclerosis. J Neurol Sci 2005; 227:79-84. [PMID: 15546595 DOI: 10.1016/j.jns.2004.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Revised: 07/20/2004] [Accepted: 08/19/2004] [Indexed: 11/16/2022]
Abstract
To confirm correlations between muscle sympathetic nerve activity (MSNA) and patients' chronological data, we selected 40 consecutive patients with sporadic amyotrophic lateral sclerosis (ALS) recorded by similar methods. MSNA at rest was quantified as the number of sympathetic bursts per 100 heartbeats and as the value expressed as a percentage of the predicted value based on control data. Twelve patients who underwent recordings of MSNA twice at intervals of 6 months or more showed marked decreases in MSNA amplitudes and frequencies between examinations. There was a slightly positive correlation between the frequency of MSNA and age, though younger patients exhibited higher values of MSNA than older patients. The standardized value of MSNA correlated negatively with disease duration and disability levels (p<0.01, 0.05, respectively), but several patients with duration shorter than 12 months showed low values of MSNA. Twelve patients who underwent repeated recordings of MSNA showed a significant decrease in the mean standardized value of MSNA (102.6+/-24.9%) at the second examination, compared to the value (114.3+/-18.9%) at the first one. In ALS, sympathetic outflow to muscles tends to increase initially and then decrease with increasing age and duration. This pattern may be similar to chronological changes at motor neurons.
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Affiliation(s)
- Kazumasa Shindo
- Department of Neurology, University of Yamanashi Hospital, 1110 Tamaho, Yamanashi 409-3898, Japan.
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