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Jody L Greaney, W Larry Kenney, Lacy M Alexander
Despite ample evidence of dysregulated sympathetic control of the peripheral vasculature in hypertension, no studies have examined integrated neurovascular function during cold stress in hypertensive adults (HTN). We hypothesized that (1) whole-body cooling would elicit greater cutaneous vasoconstriction and greater increases in skin sympathetic nervous system activity (SSNA) in HTN (n = 14; 56 ± 2 yrs) compared to age-matched normotensive adults (NTN; n = 14; 55 ± 2 yrs) and (2) augmented reflex vasoconstriction in HTN would be mediated by an increase in cutaneous vascular adrenergic sensitivity and a greater contribution of non-adrenergic sympathetic co-transmitters...
November 28, 2016: Journal of Physiology
Yu Ogawa, Yoshi-Ichiro Kamijo, Shigeki Ikegawa, Shizue Masuki, Hiroshi Nose
In humans, the cutaneous vasodilatation response to hyperthermia has been suggested to be suppressed by baroreflexes to maintain arterial pressure when the posture was changed from supine to upright, and if the reflexes do not function sufficiently, it can cause heat syncope. However, the efferent signals of the reflexes have not been identified. To identify the signals, we continuously measured skin sympathetic nerve activity (SSNA; microneurography), right atrial volume (RAV; echocardiography, the baroreceptors for the reflexes are reportedly located), cutaneous vascular conductance on the chest (CVCchest ; laser Doppler flowmetry), and oesophageal temperature (Toes ; thermocouple) in young men before and after passive warming with a perfusion suit, during which periods the posture was changed from supine to 30° head-up tilt positions...
November 8, 2016: Journal of Physiology
Nora E Straznicky, Mariee T Grima, Carolina I Sari, Elisabeth A Lambert, Sarah E Phillips, Nina Eikelis, Justin A Mariani, Daisuke Kobayashi, Dagmara Hering, John B Dixon, Gavin W Lambert
Background and Purpose: Elevated sympathetic nervous system (SNS) activity is a characteristic of obesity and type 2 diabetes (T2D) that contributes to target organ damage and cardiovascular risk. In this study we examined whether baseline metabolic status influences the degree of sympathoinhibition attained following equivalent dietary weight loss. Methods: Un-medicated obese individuals categorized as normal glucose tolerant (NGT, n = 15), impaired glucose tolerant (IGT, n = 24), and newly-diagnosed T2D (n = 15) consumed a hypocaloric diet (29% fat, 23% protein, 45% carbohydrate) for 4-months...
2016: Frontiers in Physiology
Anna E Stanhewicz, Jody L Greaney, Lacy M Alexander, W Larry Kenney
Reflex cutaneous vasodilation in response to passive heating is attenuated in human aging. This diminished response is mediated, in part, by age-associated reductions in endothelial function; however, the contribution of altered skin sympathetic nervous system activity (SSNA) is unknown. We hypothesized that 1) healthy older adults would demonstrate blunted SSNA responses to increased core temperature compared to young adults, and 2) the decreased SSNA response would be associated with attenuated cutaneous vasodilation...
October 27, 2016: Journal of Applied Physiology
Mark B Badrov, T Dylan Olver, J Kevin Shoemaker
Sympathetic outflow is modified during acute homeostatic stress through increased firing of low-threshold axons, recruitment of latent axons, and synaptic delay modifications. However, the role of central mechanisms versus peripheral reflex control over sympathetic recruitment remains unknown. Here, we examined sympathetic discharge patterns during fatiguing static handgrip (SHG) exercise and postexercise circulatory occlusion (PECO) to study the central vs. peripheral reflex elements of sympathetic neural coding...
December 1, 2016: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Inge P Kleggetveit, Roland Schmidt, Barbara Namer, Hugh Salter, Tormod Helås, Martin Schmelz, Ellen Jørum
INTRODUCTION: The sodium channel Nav 1.9 is expressed in peripheral nociceptors and has recently been linked to human pain conditions, but the exact role of Nav 1.9 for human nociceptor excitability is still unclear. METHODS: C-nociceptors from two patients with late onset of erythromelalgia-like pain, signs of small fiber neuropathy, and rare genetic variants of Nav 1.9 (N1169S, I1293V) were assessed by microneurography. RESULTS: Compared with patients with comparable pain phenotypes (erythromelalgia-like pain without Nav-mutations and painful polyneuropathy), there was a tendency toward more activity-dependent slowing of conduction velocity in mechanoinsensitive C-nociceptors...
October 2016: Brain and Behavior
T S Nobre, R V Groehs, L F Azevedo, L M Antunes-Correa, D G Martinez, M J N N Alves, C E Negrao
It remains unknown whether or not a reduction in muscle sympathetic nerve activity in heart failure patients is associated over time with the effects of long- or short-term repeated exercise. 10 chronic heart failure patients, age 49±3 years old, functional class I-III NYHA, ejection fraction <40% were randomly submitted to either an acute bout of moderate continuous exercise OR high-intensity interval exercise. Muscle sympathetic nerve activity (microneurography) and forearm blood flow (venous occlusion plethysmography) were evaluated pre- and post-exercise sessions...
December 2016: International Journal of Sports Medicine
Can Öztürk, Robert Schueler, Marcel Weber, Armin Welz, Nikos Werner, Georg Nickenig, Christoph Hammerstingl
OBJECTIVES: This study shows the impact of secondary mitral regurgitation (sMR) and transcatheter mitral valve repair (TMVR) with the MitraClip system on sympathetic nerve activity (SNA). BACKGROUND: An increase in SNA is associated with worse outcomes and limited survival in patients with chronic heart failure (CHF). METHODS: Twenty CHF-patients without relevant sMR and 30 CHF patients with symptomatic sMR were enrolled prospectively. All patients underwent standardized laboratory testing and microneurography...
October 10, 2016: JACC. Cardiovascular Interventions
Andreas M Kist, Dagrun Sagafos, Anthony M Rush, Cristian Neacsu, Esther Eberhardt, Roland Schmidt, Lars Kristian Lunden, Kristin Ørstavik, Luisa Kaluza, Jannis Meents, Zhiping Zhang, Thomas Hedley Carr, Hugh Salter, David Malinowsky, Patrik Wollberg, Johannes Krupp, Inge Petter Kleggetveit, Martin Schmelz, Ellen Jørum, Angelika Lampert, Barbara Namer
Gain-of-function mutations in the tetrodotoxin (TTX) sensitive voltage-gated sodium channel (Nav) Nav1.7 have been identified as a key mechanism underlying chronic pain in inherited erythromelalgia. Mutations in TTX resistant channels, such as Nav1.8 or Nav1.9, were recently connected with inherited chronic pain syndromes. Here, we investigated the effects of the p.M650K mutation in Nav1.8 in a 53 year old patient with erythromelalgia by microneurography and patch-clamp techniques. Recordings of the patient's peripheral nerve fibers showed increased activity dependent slowing (ADS) in CMi and less spontaneous firing compared to a control group of erythromelalgia patients without Nav mutations...
2016: PloS One
Thais S Nobre, Ligia M Antunes-Correa, Raphaela V Groehs, Maria-Janieire N N Alves, Adriana O Sarmento, Aline Villa Nova Bacurau, Ursula Urias, Guilherme Barreto Alves, Maria Urbana P B Rondon, Patricia C Brum, Martino Martinelli, Holly R Middlekauff, Carlos E Negrao
Heart failure(HF) is characterized by decreased exercise capacity, attributable to neurocirculatory and skeletal muscle factors. Cardiac resynchronization therapy(CRT) and exercise training have each been shown to decrease muscle sympathetic nerve activity(MSNA) and increase exercise capacity in patients with HF. We hypothesized that exercise training in the setting of CRT would further reduce MSNA and vasoconstriction and would increase Ca(2+) handling gene expression in skeletal muscle in chronic systolic HF patients...
September 2, 2016: American Journal of Physiology. Heart and Circulatory Physiology
Mark B Badrov, Sophie Lalande, T Dylan Olver, Neville Suskin, J Kevin Shoemaker
In response to acute physiological stress, the sympathetic nervous system modifies neural outflow through increased firing frequency of lower-threshold axons, recruitment of latent subpopulations of higher-threshold axons, and/or acute modifications of synaptic delays. Aging and coronary artery disease (CAD) often modify efferent muscle sympathetic nerve activity (MSNA). Therefore, we investigated whether CAD (n = 14; 61 ± 10 yr) and/or healthy aging without CAD (OH; n = 14; 59 ± 9 yr) modified these recruitment strategies that normally are observed in young healthy (YH; n = 14; 25 ± 3 yr) individuals...
October 1, 2016: American Journal of Physiology. Heart and Circulatory Physiology
Florent Besnier, Marc Labrunée, Atul Pathak, Anne Pavy-Le Traon, Céline Galès, Jean-Michel Sénard, Thibaut Guiraud
Patients with cardiovascular disease show autonomic dysfunction, including sympathetic activation and vagal withdrawal, which leads to fatal events. This review aims to place sympathovagal balance as an essential element to be considered in management for cardiovascular disease patients who benefit from a cardiac rehabilitation program. Many studies showed that exercise training, as non-pharmacologic treatment, plays an important role in enhancing sympathovagal balance and could normalize levels of markers of sympathetic flow measured by microneurography, heart rate variability or plasma catecholamine levels...
August 16, 2016: Annals of Physical and Rehabilitation Medicine
K Dimitriadis, C Tsioufis, E Andrikou, A Kasiakogias, K Kyriazopoulos, A Frantzeskakis, T Kalos, I Liatakis, E Koutra, D Tousoulis
OBJECTIVE: Resistant hypertension is related to sympathetic overdrive and arterial stiffening, while there are scarce data whether metabolic syndrome further potentiates sympathetic activity and vascular abnormalities in this setting. The aim of this study was to assess the effect of the metabolic syndrome on muscle sympathetic nerve activity (MSNA) and arterial stiffness in resistant hypertensive patients. DESIGN AND METHOD: We studied 36 patients with resistant hypertension [age: 59 ± 10 years, 24 males, office blood pressure (BP): 178/93 ± 14/11 mmHg, 24-hour BP: 146/84 ± 13/11 mmHg, under 4...
September 2016: Journal of Hypertension
Luke A Henderson, Vaughan G Macefield
PURPOSE OF REVIEW: Obstructive sleep apnoea (OSA) is associated with both nocturnal and daytime hypertensions which increase cardiovascular morbidity and mortality. It is thought that the repeated episodes of hypoxia and hypercapnia during nocturnal airway obstructions that characterise OSA result in increased sympathetic drive that persists during wakefulness. Although the underlying mechanisms responsible for this hypertension remain to be elucidated, several neural and humoral mechanisms have been proposed and recent evidence suggesting changes in the central nervous system may play a significant role...
July 2016: Current Hypertension Reports
Raphaela V Groehs, Ligia M Antunes-Correa, Thais S Nobre, Maria-Janieire Nn Alves, Maria Urbana Pb Rondon, Antônio Carlos Pereira Barreto, Carlos E Negrão
BACKGROUND: We investigated the effects of muscle functional electrical stimulation on muscle sympathetic nerve activity and muscle blood flow, and, in addition, exercise tolerance in hospitalised patients for stabilisation of heart failure. METHODS: Thirty patients hospitalised for treatment of decompensated heart failure, class IV New York Heart Association and ejection fraction ≤ 30% were consecutively randomly assigned into two groups: functional electrical stimulation (n = 15; 54 ± 2 years) and control (n = 15; 49 ± 2 years)...
October 2016: European Journal of Preventive Cardiology
Dagrun Sagafos, Inge P Kleggetveit, Tormod Helås, Roland Schmidt, Jan Minde, Barbara Namer, Martin Schmelz, Ellen Jørum
OBJECTIVES: Nerve growth factor (NGF) is a protein important for growth and survival, but also for modulation of sensitivity of nociceptors and sympathetic neurons. The purpose of the present study was to investigate the effects of reduced NGF signaling in patients with hereditary sensory and autonomic neuropathies type V, congenital insensitivity to pain, caused by a mutation of the NGFβ gene, including a characterization of single nociceptive fibers using microneurography (MNG). MATERIALS AND METHODS: One homozygote and 2 heterozygote patients with this mutation were examined with electromyography/neurography, thermal testing, quantitative sudomotor axon reflex test, and electrically induced axon reflex erythema in addition to MNG...
July 2016: Clinical Journal of Pain
Daniel Boulton, Chloe E Taylor, Vaughan G Macefield, Simon Green
During voluntary contractions, muscle sympathetic nerve activity (MSNA) to contracting muscles increases in proportion to force but the underlying mechanisms are not clear. To shed light on these mechanisms, particularly the influences of central command and muscle afferent feedback, the present study tested the hypothesis that MSNA is greater during voluntary compared with electrically-evoked contractions. Seven male subjects performed a series of 1-min isometric dorsiflexion contractions (left leg) separated by 2-min rest periods, alternating between voluntary and electrically-evoked contractions at similar forces (5-10% of maximum)...
2016: Frontiers in Physiology
V Donadio, R Liguori, A Incensi, G Chiaro, A Bartoletti-Stella, S Capellari, P Cortelli
Skin biopsy and microneurography are autonomic tests directly evaluating adrenergic and cholinergic sympathetic fibers to identify selective deficiency of a specific peripheral sympathetic subdivision. We describe a patient with tomacular neuropathy due to a deletion of the PMP22 gene who complained of chronic orthostatic hypotension due to a dopamine-β-hydroxylase deficiency confirmed by genetic analysis demonstrating two novel mutations in the DβH gene. To further characterize autonomic dysfunctions the proband underwent skin biopsy and microneurography...
May 2016: Autonomic Neuroscience: Basic & Clinical
Paolo Florent Felisaz, Francesco Balducci, Salvatore Gitto, Irene Carne, Stefano Montagna, Roberto De Icco, Anna Pichiecchio, Maurizia Baldi, Fabrizio Calliada, Stefano Bastianello
RATIONALE AND OBJECTIVES: The aims of this study were to propose a semiautomated technique to segment and measure the volume of different nerve components of the tibial nerve, such as the nerve fascicles and the epineurium, based on magnetic resonance microneurography and a segmentation tool derived from brain imaging; and to assess the reliability of this method by measuring interobserver and intraobserver agreement. MATERIALS AND METHODS: The tibial nerve of 20 healthy volunteers (age range = 23-69; mean = 47; standard deviation = 15) was investigated at the ankle level...
August 2016: Academic Radiology
Daniele C B Aprile, Bruna Oneda, Josiane L Gusmão, Luiz A R Costa, Claudia L M Forjaz, Decio Mion, Tais Tinucci
BACKGROUND: This study aimed at evaluating the after effects of a single bout of aerobic exercise on muscle sympathetic nerve activity (MSNA), peripheral vascular resistance and blood pressure (BP) in stages 2-3 chronic kidney disease (CKD) patients. We hypothesized that CKD patients present a greater decline in these variables after the exercise than healthy individuals. METHODS: Nine patients with stages 2-3 CKD (50 ± 8 years) and 12 healthy volunteers (50 ± 5 years) underwent 2 sessions, conducted in a random order: exercise (45 min, cycle ergometer, 50% of peak oxygen uptake) and rest (seated, 45 min)...
2016: American Journal of Nephrology
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