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Devin B Phillips, Craig D Steinback, Sophie É Collins, Desi P Fuhr, Tracey L Bryan, Eric Y L Wong, Vincent Tedjasaputra, Mohit Bhutani, Michael K Stickland
COPD patients have increased central arterial stiffness and muscle sympathetic nervous activity (MSNA), both of which contribute to cardiovascular (CV) dysfunction and increased CV risk. Previous work suggests that COPD patients have elevated carotid chemoreceptor (CC) activity/sensitivity, which may contribute to the elevated MSNA and arterial stiffness. Accordingly, the effect of CC inhibition on central arterial stiffness, MSNA and CV function at rest in COPD patients was examined in a randomized placebo-controlled study...
March 12, 2018: Journal of Physiology
Jacqueline K Limberg, Elizabeth P Ott, Walter W Holbein, Sarah Elizabeth Baker, Timothy B Curry, Wayne T Nicholson, Michael J Joyner, J Kevin Shoemaker
To study how changes in baroreceptor afferent activity affect patterns of sympathetic neural activation, we manipulated arterial blood pressure using intravenous nitroprusside (NTP) and phenylephrine (PE) and measured action potential (AP) patterns with wavelet-based methodology. We hypothesized: 1) Baroreflex unloading (NTP) would increase firing of low-threshold axons and recruitment of latent axons, and 2) Baroreflex loading (PE) would decrease firing of low-threshold axons. Heart rate (HR, ECG), arterial blood pressure (BP, brachial catheter), and muscle sympathetic nerve activity (MSNA, microneurography of the peroneal nerve) were measured at baseline and during steady-state systemic, intravenous NTP (0...
February 28, 2018: Journal of Neurophysiology
Eric A Schmidt, Fabien Despas, Anne Pavy-Le Traon, Zofia Czosnyka, John D Pickard, Kamal Rahmouni, Atul Pathak, Jean M Senard
Intracranial pressure (ICP) is the pressure within the cranium . ICP rise compresses brain vessels and reduces cerebral blood delivery. Massive ICP rise leads to cerebral ischemia, but it is also known to produce hypertension, bradycardia and respiratory irregularities due to a sympatho-adrenal mechanism termed Cushing response. One still unresolved question is whether the Cushing response is a non-synaptic acute brainstem ischemic mechanism or part of a larger physiological reflex for arterial blood pressure control and homeostasis regulation...
2018: Frontiers in Physiology
J Kevin Shoemaker, Mark B Badrov, Stephen A Klassen, Paul J Fadel
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 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...
February 7, 2018: Journal of Neurophysiology
Massimo Nardone, Anthony V Incognito, Philip J Millar
BACKGROUND: Whether the sympathetic nervous system can directly alter central aortic stiffness remains controversial, mainly because of the difficulty in experimentally augmenting peripheral vasoconstrictor activity without changing blood pressure. METHODS AND RESULTS: To address this limitation, we utilized low-level cardiopulmonary baroreflex loading and unloading shown previously to alter sympathetic outflow without evoking parallel hemodynamic modulation. Blood pressure and carotid-femoral aortic pulse wave velocity (cf-PWV) were measured in 32 healthy participants (24±2 years; women: n=15) before and during 12-minute applications of low-level lower body negative pressure; -7 mm Hg) and lower body positive pressure; +7 mm Hg), applied in a random order...
January 29, 2018: Journal of the American Heart Association
Laura M Reyes, Charlotte W Usselman, Rachel J Skow, Nisha Charkoudian, Jeffery S Staab, Margie H Davenport, Craig D Steinback
The adaptations of sympathetic nerve activity (SNA) during pregnancy remain poorly understood. An increase in blood volume, cardiac output (Q) and SNA with a concomitant drop in total peripheral resistance (TPR), suggest that during pregnancy there is a reduced transduction of SNA into TPR. Most of these findings have originated from cross-sectional studies, thus, we conducted a longitudinal assessment of SNA and TPR in two participants. Measures were made pre-pregnancy (early follicular phase), four occasions during pregnancy, and at two-months postpartum...
January 16, 2018: Experimental Physiology
Keisho Katayama, Joshua R Smith, Kanako Goto, Kaori Shimizu, Mitsuru Saito, Koji Ishida, Teruhiko Koike, Satoshi Iwase, Craig A Harms
We compared changes in muscle sympathetic nerve activity (MSNA) and cardiovascular variables during leg cycle exercise with increased inspiratory muscle resistance in men and women. We hypothesized that sympathetic vasomotor outflow during exercise with increased inspiratory resistance would be attenuated in young women compared with age-matched men. Eight women and seven men completed the study. The subjects performed two 10-min exercise bouts at 40% peak oxygen uptake using a cycle ergometer in a semirecumbent position [spontaneous breathing for 5 min and voluntary hyperventilation with or without inspiratory resistive breathing for 5 min (breathing frequency: 50 breaths min-1 with a 50% duty cycle, inspiratory resistance: 30% of maximal inspiratory pressure)]...
January 15, 2018: Experimental Physiology
Raffaella Dell'Oro, Fosca Quarti Trevano, Pierluigi Gamba, Claudia Ciuffarella, Gino Seravalle, Giuseppe Mancia, Guido Grassi
BACKGROUND: Neurogenic abnormalities characterize overt diabetic state. However, how early is their appearance in the clinical course of the disease is unclear. METHODS: In 26 normotensive and normoweight prediabetic patients, aged 45.2 ± 3.2 years (mean ± SEM), we assessed efferent postganglionic muscle sympathetic nerve traffic (MSNA, microneurography), spontaneous baroreflex sensitivity, and a number of hemodynamic and metabolic variables, including homeostatic model assessment (HOMA) index...
January 2, 2018: Journal of Hypertension
Stephen A Klassen, Steven De Abreu, Danielle K Greaves, Derek S Kimmerly, Philippe Arbeille, Pierre Denise, Richard L Hughson, Hervé Normand, J Kevin Shoemaker
To understand the impact of physical deconditioning with head-down tilt bed rest (HDBR) on the malleability of sympathetic discharge patterns, we studied a) baseline integrated muscle sympathetic nerve activity (MSNA; microneurography) from 13 females participating in the WISE-2005 60-day HDBR study (Female, retrospective analysis), b) integrated MSNA and multi-unit action potential (AP) analysis in 13 males (Male) performed on data collected at baseline and during physiological stress imposed by end-inspiratory apnea, in a new 60-day HDBR study, and c) a repeatability study (Control, n = 6, retrospective analysis, 4 weeks between tests)...
December 6, 2017: Journal of Applied Physiology
Alexandra M Coates, Anthony V Incognito, Jeremy D Seed, Connor J Doherty, Philip J Millar, Jamie F Burr
PURPOSE: Overload training is hypothesized to alter autonomic regulation, though interpretations using indirect measures of heart rate variability are conflicting. The aim of the present study was to examine the effects of overload training on muscle sympathetic nerve activity (MSNA), a direct measure of central sympathetic outflow, in recreational endurance athletes. METHODS: Measurements of heart rate variability, cardiac baroreflex sensitivity (BRS), MSNA (microneurography), and sympathetic BRS were obtained in seventeen healthy triathletes and cyclists after 1-week of reduced training (baseline) and following 3-weeks of either regular (CON, n=7) or overload (OL, n=10) training...
December 2, 2017: Medicine and Science in Sports and Exercise
Anthony V Incognito, Connor J Doherty, Jordan B Lee, Matthew J Burns, Philip J Millar
Negative and positive muscle sympathetic nerve activity (MSNA) responders have been observed during mental stress. We hypothesized that similar MSNA response patterns could be identified during the first minute of static handgrip and contribute to the inter-individual variability throughout exercise. Supine measurements of multi-unit MSNA (microneurography) and continuous blood pressure (Finometer) were recorded in 29 young healthy men during the first (HG1) and second (HG2) minute of static handgrip (30% maximal voluntary contraction) and subsequent post-exercise circulatory occlusion (PECO)...
October 25, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Alan R Needle, Jochen Baumeister, William B Farquhar, Jody L Greaney, Jill S Higginson, Thomas W Kaminski, C Buz Swanik
PURPOSE: Maintaining joint stability is dependent on the ability of the nervous system to prepare for, sense, and react to potentially injuries loads. In attempts to understand the neurophysiologic mechanisms underlying joint stability, this afferent and efferent activity has been quantified separately at the cortical, segmental, and peripheral levels using various electrophysiologic techniques in vivo. However, no studies have attempted to quantify sensory and motor activation at multiple levels of the nervous system in a single subset, in order to understand potential adaptations for optimizing joint stability...
October 23, 2017: International Journal of Neuroscience
Rafael Armani Porello, Marcelo Rodrigues Dos Santos, Francis Ribeiro de Souza, Guilherme Wesley Peixoto da Fonseca, Ana Luiza Carrari Sayegh, Tiago Franco de Oliveira, César Abreu Akiho, Maurício Yonamine, Rosa Maria Rodrigues Pereira, Carlos Eduardo Negrão, Maria-Janieire de Nazaré Nunes Alves
PURPOSE: Increased resting muscle sympathetic nerve activity (MSNA) and lower forearm blood flow (FBF) were observed in young men who use anabolic androgenic steroids (AAS). However, the response of MSNA and FBF in AAS users triggered by muscle mechanoreflex and central command has never been tested. Additionally, we evaluated the blood pressure (BP) and heart rate (HR) responses during these maneuvers. METHODS: Nineteen AAS users (AASU) aged 31±6 yr and 18 AAS nonusers (AASNU) aged 29±4 yr were recruited...
October 16, 2017: Medicine and Science in Sports and Exercise
Connor J Doherty, Anthony V Incognito, Karambir Notay, Matthew J Burns, Joshua T Slysz, Jeremy D Seed, Massimo Nardone, Jamie F Burr, Philip J Millar
The contribution of central command to the peripheral vasoconstrictor response during exercise has been investigated using primarily handgrip exercise. The purpose of the present study was to compare muscle sympathetic nerve activity (MSNA) responses during passive (involuntary) and active (voluntary) zeroload cycling to gain insight into the effects of central command on sympathetic outflow during dynamic exercise. Hemodynamic measurements and contralateral leg MSNA (microneurography) were collected in eighteen young healthy participants at rest and during 2 minutes of passive and active zeroload one-legged cycling...
September 22, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Jody L Greaney, W Larry Kenney, Lacy M Alexander
During moderate cold exposure, cardiovascular-related morbidity and mortality increase disproportionately in hypertensive adults (HTN); however, the mechanisms underlying this association are not well defined. We hypothesized that whole-body cold stress would evoke exaggerated increases in blood pressure (BP) and muscle sympathetic nerve activity (MSNA) in HTN compared to normotensive adults (NTN) and that sympathetic baroreflex function would be altered during cooling in HTN. MSNA (peroneal microneurography) and beat-to-beat BP (Finometer) were measured continuously in 10 NTN (6M/4W; age 53±3 yrs; resting BP 125±3/79±1 mmHg) and 13 HTN (7M/6W; age 58±2 yrs; resting BP 146±5/88±2 mmHg) during whole-body cooling-induced reductions in mean skin temperature (Tsk; water-perfused suit) from 34...
September 14, 2017: Journal of Applied Physiology
Kenichi Kimura, Kazuya Ishida, Noriyo Takahashi, Yasushi Toge, Fumihiro Tajima
The aim of the present study was to determine the effects of acupuncture on post-ganglionic muscle sympathetic nerve activity (MSNA) in humans. MSNA was measured in 8 healthy adult males by microneurography evaluation of the left peroneal nerve. Blood pressure (BP) and heart rate (HR) were simultaneously recorded. MSNA was evaluated as the burst rate, with total MSNA, BP and HR normalized to their respective baseline values. After 10min of rest in the supine position, acupuncture was applied to the right ST-36 point in the tibialis anterior muscle for 15min, with recovery then monitored over a 20-min period...
September 1, 2017: Autonomic Neuroscience: Basic & Clinical
Michael M Tymko, Joshua C Tremblay, Craig D Steinback, Jonathan P Moore, Alex B Hansen, Alexander Patrician, Connor A Howe, Ryan L Hoiland, Daniel J Green, Philip N Ainslie
Evidence indicates that increases in sympathetic nervous activity (SNA), and acclimatization to high-altitude (HA), may reduce endothelial function as assessed by brachial artery flow-mediated dilatation (FMD); however, it is unclear whether such changes in FMD are due to direct vascular constraint, or consequential altered hemodynamics (e.g. shear stress) associated with increased SNA as a consequence of exposure to HA. We hypothesized that: 1) at rest, SNA would be elevated and FMD would be reduced at HA compared to sea-level (SL); and 2) at SL and HA, FMD would be reduced when SNA was acutely increased, and elevated when SNA was acutely decreased...
August 31, 2017: Journal of Applied Physiology
Raffaella Dell'Oro, Edoardo Gronda, Gino Seravalle, Giuseppe Costantino, Luca Alberti, Barbara Baronio, Tiziana Staine, Emilio Vanoli, Giuseppe Mancia, Guido Grassi
BACKGROUND: Baroreflex activation therapy (BAT) exerts in severe heart failure sympathoinhibitory effects, improving clinical variables and reducing hospitalization rate. The current follow-up study was aimed at determining the long-term effects of BAT, assessing whether BAT in heart failure allows to restore physiological levels of sympathetic function. METHODS: Seven patients out of the 11 heart failure patients aged 66.5 ± 3 years (mean ± SEM) in New York Heart Association Class III with left ventricular ejection fraction 40% or less and impaired functional capacity recruited in the study survived at the final follow-up (43...
December 2017: Journal of Hypertension
Rochelle Ackerley, Jean-Marc Aimonetti, Edith Ribot-Ciscar
Emotions can evoke strong reactions that have profound influences, from gross changes in our internal environment to small fluctuations in facial muscles, and reveal our feelings overtly. Muscles contain proprioceptive afferents, informing us about our movements and regulating motor activities. Their firing reflects changes in muscle length, yet their sensitivity can be modified by the fusimotor system, as found in animals. In humans, the sensitivity of muscle afferents is modulated by cognitive processes, such as attention; however, it is unknown if emotional processes can modulate muscle feedback...
August 16, 2017: Scientific Reports
Gino Seravalle, Graziella D'Arrigo, Giovanni Tripepi, Francesca Mallamaci, Gianmaria Brambilla, Giuseppe Mancia, Guido Grassi, Carmine Zoccali
Background: Renal denervation reduces blood pressure (BP) and sympathetic drive in experimental animal models, but the effect of this intervention on sympathetic activity in patients with treatment-resistant hypertension is still unclear. Methods: In an incident series of 29 patients with treatment-resistant hypertension, we performed serial measurements (n = 123) of muscle sympathetic nerve activity (MSNA, microneurography) and standardized BP measurements. Data were analysed by mixed linear modelling (MLM) and by regression analysis of time-integrated changes of both MSNA and synchronous, standardized (in-lab) BP measurements...
August 1, 2017: Nephrology, Dialysis, Transplantation
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