Sex differences in hemodynamic and sympathetic neural firing patterns during orthostatic challenge in humans

2012 ◽  
Vol 112 (10) ◽  
pp. 1744-1751 ◽  
Author(s):  
Huan Yang ◽  
William H. Cooke ◽  
Kristen S. Reed ◽  
Jason R. Carter
Keyword(s):  
Sex Differences ◽  
Arterial Pressure ◽  
Orthostatic Intolerance ◽  
Muscle Sympathetic Nerve Activity ◽  
Young Men ◽  
Orthostatic Stress ◽  
Neural Firing ◽  
Men And Women ◽  
Firing Patterns ◽  
Arterial Blood

Recent evidence suggests that young men and women may have different strategies for regulating arterial blood pressure, and the purpose of the present study was to determine if sex differences exist in diastolic arterial pressure (DAP) and muscle sympathetic nerve activity (MSNA) relations during simulated orthostatic stress. We hypothesized that young men would demonstrate stronger DAP-MSNA coherence and a greater percentage of “consecutive integrated bursts” during orthostatic stress. Fourteen men and 14 women (age 23 ± 1 yr) were examined at rest and during progressive lower body negative pressure (LBNP; −5 to −40 mmHg). Progressive LBNP did not alter mean arterial pressure (MAP) in either sex. Heart rate increased and stroke volume decreased to a greater extent during LBNP in women (interactions, P < 0.05). DAP-MSNA coherence was strong (i.e., r ≥ 0.5) at rest and increased throughout all LBNP stages in men. In contrast, DAP-MSNA coherence was lower in women, and responses to progressive LBNP were attenuated compared with men (time × sex, P = 0.029). Men demonstrated a higher percentage of consecutive bursts during all stages of LBNP (sex, P < 0.05), although the percentage of consecutive bursts increased similarly during progressive LBNP between sexes. In conclusion, men and women demonstrate different firing patterns of integrated MSNA during LBNP that appear to be related to differences in DAP oscillatory patterns. Men tend to have more consecutive bursts, which likely contribute to a stronger DAP-MSNA coherence. These findings may help explain why young women are more prone to orthostatic intolerance.

Arterial pressure and muscle sympathetic nerve activity are increased after two hours of sustained but not cyclic hypoxia in healthy humans

2005 ◽  
Vol 98 (1) ◽  
pp. 343-349 ◽  
Author(s):  
Renaud Tamisier ◽  
Amit Anand ◽  
Luz M. Nieto ◽  
David Cunnington ◽  
J. Woodrow Weiss
Keyword(s):  
Blood Pressure ◽  
Arterial Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Activity ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Arterial Oxygen ◽  
Nerve Activity ◽  
Arterial Blood ◽  
Sustained Hypoxia

Sustained and episodic hypoxic exposures lead, by two different mechanisms, to an increase in ventilation after the exposure is terminated. Our aim was to investigate whether the pattern of hypoxia, cyclic or sustained, influences sympathetic activity and hemodynamics in the postexposure period. We measured sympathetic activity (peroneal microneurography), hemodynamics [plethysmographic forearm blood flow (FBF), arterial pressure, heart rate], and peripheral chemosensitivity in normal volunteers on two occasions during and after 2 h of either exposure. By design, mean arterial oxygen saturation was lower during sustained relative to cyclic hypoxia. Baseline to recovery muscle sympathetic nerve activity and blood pressure went from 15.7 ± 1.2 to 22.6 ± 1.9 bursts/min ( P < 0.01) and from 85.6 ± 3.2 to 96.1 ± 3.3 mmHg ( P < 0.05) after sustained hypoxia, respectively, but did not exhibit significant change from 13.6 ± 1.5 to 17.3 ± 2.5 bursts/min and 84.9 ± 2.8 to 89.8 ± 2.5 mmHg after cyclic hypoxia. A significant increase in FBF occurred after sustained, but not cyclic, hypoxia, from 2.3 ± 0.2 to 3.29 ± 0.4 and from 2.2 ± 0.1 to 3.1 ± 0.5 ml·min−1·100 g of tissue−1, respectively. Neither exposure altered the ventilatory response to progressive isocapnic hypoxia. Two hours of sustained hypoxia increased not only muscle sympathetic nerve activity but also arterial blood pressure. In contrast, cyclic hypoxia produced slight but not significant changes in hemodynamics and sympathetic activity. These findings suggest the cardiovascular response to acute hypoxia may depend on the intensity, rather than the pattern, of the hypoxic exposure.

scholarly journals Sympathetic baroreflex gain in normotensive pregnant women

2015 ◽  
Vol 119 (5) ◽  
pp. 468-474 ◽  
Author(s):  
Charlotte W. Usselman ◽  
Rachel J. Skow ◽  
Brittany A. Matenchuk ◽  
Radha S. Chari ◽  
Colleen G. Julian ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Arterial Pressure ◽  
Pregnant Women ◽  
Sympathetic Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Arterial Blood ◽  
Sequence Method ◽  
Normotensive Pregnancy ◽  
Dependent Mechanism

Muscle sympathetic nerve activity is increased during normotensive pregnancy while mean arterial pressure is maintained or reduced, suggesting baroreflex resetting. We hypothesized spontaneous sympathetic baroreflex gain would be reduced in normotensive pregnant women relative to nonpregnant matched controls. Integrated muscle sympathetic burst incidence and total sympathetic activity (microneurography), blood pressure (Finometer), and R-R interval (ECG) were assessed at rest in 11 pregnant women (33 ± 1 wk gestation, 31 ± 1 yr, prepregnancy BMI: 23.5 ± 0.9 kg/m2) and 11 nonpregnant controls (29 ± 1 yr; BMI: 25.2 ± 1.7 kg/m2). Pregnant women had elevated baseline sympathetic burst incidence (43 ± 2 vs. 33 ± 2 bursts/100 heart beats, P = 0.01) and total sympathetic activity (1,811 ± 148 vs. 1,140 ± 55 au, P < 0.01) relative to controls. Both mean (88 ± 3 vs. 91 ± 2 mmHg, P = 0.4) and diastolic (DBP) (72 ± 3 vs. 73 ± 2 mmHg, P = 0.7) pressures were similar between pregnant and nonpregnant women, respectively, indicating an upward resetting of the baroreflex set point with pregnancy. Baroreflex gain, calculated as the linear relationship between sympathetic burst incidence and DBP, was reduced in pregnant women relative to controls (−3.7 ± 0.5 vs. −5.4 ± 0.5 bursts·100 heart beats−1·mmHg−1, P = 0.03), as was baroreflex gain calculated with total sympathetic activity (−294 ± 24 vs. −210 ± 24 au·100 heart beats−1·mmHg−1; P = 0.03). Cardiovagal baroreflex gain (sequence method) was not different between nonpregnant controls and pregnant women (49 ± 8 vs. 36 ± 8 ms/mmHg; P = 0.2). However, sympathetic (burst incidence) and cardiovagal gains were negatively correlated in pregnant women ( R = −0.7; P = 0.02). Together, these data indicate that the influence of the sympathetic nervous system over arterial blood pressure is reduced in normotensive pregnancy, in terms of both long-term and beat-to-beat regulation of arterial pressure, likely through a baroreceptor-dependent mechanism.

Effect of gender on vestibular sympathoexcitation

2000 ◽  
Vol 279 (4) ◽  
pp. R1330-R1333 ◽  
Author(s):  
Chester A. Ray
Keyword(s):  
Sympathetic Nerve Activity ◽  
Orthostatic Intolerance ◽  
Muscle Sympathetic Nerve Activity ◽  
Premenopausal Women ◽  
Cardiovascular Responses ◽  
Otolith Organs ◽  
Men And Women ◽  
Vestibulosympathetic Reflex ◽  
Prone Posture ◽  
Stimulation Of

Studies have suggested that premenopausal women are more prone to orthostatic intolerance than men. Additionally, it has been postulated that the vestibulosympathetic reflex is important in regulating postural-related changes in sympathetic activity. The purpose of the present study was to determine whether men and women differ in their sympathetic and cardiovascular responses to stimulation of the otolith organs elicited by head-down rotation (HDR). Heart rate (HR), arterial pressure, calf blood flow (CBF), and leg muscle sympathetic nerve activity (MSNA) were measured during 3 min of HDR in the prone posture in 33 women and 30 men. With the exception of HR (71 ± 2 and 63 ± 1 beats/min for women and men, respectively; P < 0.01), all baseline variables were not different between genders. There were no gender differences in responses to HDR. MSNA increased 72 ± 33 units (43%) in the men and 88 ± 15 units (59%) in the women during HDR ( P < 0.01). CBF decreased [−0.6 ± 0.1 (15%) and −0.5 ± 0.1 (19%) ml · min−1 · 100 ml−1] and calf vascular resistance increased [8 ± 2 (21%) and 11 ± 3 (25%) units during HDR for men and women, respectively ( P < 0.01)]. Both in the men and women, HR increased 2 ± 1 beats/min ( P < 0.01). These results demonstrate that sympathetic activation during HDR in the prone posture is similar in men and women. Therefore, these findings suggest that the vestibulosympathetic reflex is not different between healthy men and women.

Cardiovascular regulation: associations between exercise and head-up tilt

2019 ◽  
Vol 97 (8) ◽  
pp. 738-745
Author(s):  
J. Koschate ◽  
U. Drescher ◽  
A. Werner ◽  
L. Thieschäfer ◽  
U. Hoffmann
Keyword(s):  
Oxygen Uptake ◽  
Orthostatic Intolerance ◽  
Peripheral Resistance ◽  
Cycle Ergometer ◽  
Orthostatic Stress ◽  
Differential Analysis ◽  
Arterial Blood ◽  
Head Up Tilt ◽  
Underlying Mechanisms ◽  
Response To Exercise

It was hypothesized that faster cardiorespiratory kinetics during exercise are associated with higher orthostatic tolerance. Cardiorespiratory kinetics of 14 healthy male subjects (30 ± 4 years, 179 ± 8 cm, 79 ± 8 kg) were tested on a cycle ergometer during exercise with changing work rates of 30 and 80 W. Pulmonary oxygen uptake ([Formula: see text]) was measured breath-by-breath and heart rate (HR), mean arterial blood pressure (MAP), and total peripheral resistance (TPR) were measured beat-to-beat. Muscular oxygen uptake ([Formula: see text]) was estimated from HR and [Formula: see text]. Kinetic parameters were determined by time-series analysis, using cross-correlation functions (CCFmax(x)) between the parameter and the work rate. Cardiovascular regulations of MAP, HR, and TPR during orthostatic stress were measured beat-to-beat on a tilt seat. Changes between the minima and maxima during the 6° head-down tilt and the 90° head-up tilt positions were calculated for each parameter (Δtilt-up). [Formula: see text] correlated significantly with ΔTPRtilt-up (r = 0.790, p ≤ 0.001). CCFmax(HR) was significantly correlated with ΔHRtilt-up (r = –0.705, p = 0.002) and the amplitude in HR from 30 to 80 W (rSP = –0.574, p = 0.016). The observed correlations between cardiorespiratory regulation in response to exercise and orthostatic stress during rest might allow for a more differential analysis of the underlying mechanisms of orthostatic intolerance in, for example, patient groups.

Effects of gender and hypovolemia on sympathetic neural responses to orthostatic stress

2005 ◽  
Vol 289 (1) ◽  
pp. R109-R116 ◽  
Author(s):  
Qi Fu ◽  
Sarah Witkowski ◽  
Kazunobu Okazaki ◽  
Benjamin D. Levine
Keyword(s):  
Blood Pressure ◽  
Stroke Volume ◽  
Lower Body Negative Pressure ◽  
Muscle Sympathetic Nerve Activity ◽  
Peripheral Resistance ◽  
Orthostatic Stress ◽  
Stroke Index ◽  
Orthostatic Tolerance ◽  
Neural Responses ◽  
Men And Women

We tested the hypothesis that women have blunted sympathetic neural responses to orthostatic stress compared with men, which may be elicited under hypovolemic conditions. Muscle sympathetic nerve activity (MSNA) and hemodynamics were measured in eight healthy young women and seven men in supine position and during 6 min of 60° head-up tilt (HUT) under normovolemic and hypovolemic conditions (randomly), with ∼4-wk interval. Acute hypovolemia was produced by diuretic (furosemide) administration ∼2 h before testing. Orthostatic tolerance was determined by progressive lower body negative pressure to presyncope. We found that furosemide produced an ∼13% reduction in plasma volume, causing a similar increase in supine MSNA in men and women (mean ± SD of 5 ± 7 vs. 6 ± 5 bursts/min; P = 0.895). MSNA increased during HUT and was greater in the hypovolemic than in the normovolemic condition (32 ± 6 bursts/min in normovolemia vs. 44 ± 15 bursts/min in hypovolemia in men, P = 0.055; 35 ± 9 vs. 45 ± 8 bursts/min in women, P < 0.001); these responses were not different between the genders (gender effect: P = 0.832 and 0.814 in normovolemia and hypovolemia, respectively). Total peripheral resistance increased proportionately with increases in MSNA during HUT; these responses were similar between the genders. However, systolic blood pressure was lower, whereas diastolic blood pressure was similar in women compared with men during HUT, which was associated with a smaller stroke volume or stroke index. Orthostatic tolerance was lower in women, especially under hypovolemic conditions. These results indicate that men and women have comparable sympathetic neural responses during orthostatic stress under normovolemic and hypovolemic conditions. The lower orthostatic tolerance in women is predominantly because of a smaller stroke volume, presumably due to less cardiac filling during orthostasis, especially under hypovolemic conditions, which may overwhelm the vasomotor reserve available for vasoconstriction or precipitate neurally mediated sympathetic withdrawal and syncope.

Race and Sex Differences in Quits by Young Workers

ILR Review ◽  
1981 ◽  
Vol 34 (4) ◽  
pp. 563-577 ◽  
Author(s):  
Francine D. Blau ◽  
Lawrence M. Kahn
Keyword(s):  
Sex Differences ◽  
Young Men ◽  
Longitudinal Surveys ◽  
Men And Women ◽  
Variable Approach ◽  
Blacks And Whites ◽  
Training Opportunities ◽  
Sample Heterogeneity ◽  
Instrumental Variable Approach

This study uses data from the National Longitudinal Surveys of young men and women to analyze race and sex differences in the probability and consequences of quitting. The authors find that overall quit rates in this group are higher for women than for men and about the same for blacks and whites. When several personal and job characteristics are held constant, however, the quit rates of young men and women are about the same and young blacks actually quit less frequently than young whites. When an instrumental variable approach is used to account for sample heterogeneity, it is found that, for all race and sex groups, quitting improved both current wages and long-term earnings prospects. Further, the improvement in long-term earnings prospects is found to be greater than the gain in current earnings, suggesting that training opportunities are an important consideration in the job shifts of all young people.

scholarly journals SEX DIFFERENCES OF FATIGUE IN YOUNG MEN AND WOMEN

1998 ◽  
Vol 47 (5) ◽  
pp. 581-591 ◽  
Author(s):  
HIDETSUGU KOBAYASHI ◽  
SHIN-ICHI DEMURA ◽  
FUMIO GOSHI ◽  
SUSUMU SATO ◽  
JINZABURO MATSUZAWA
Keyword(s):  
Sex Differences ◽  
Young Men ◽  
Men And Women

scholarly journals Sex differences in forearm vasoconstrictor response to voluntary apnea

2014 ◽  
Vol 306 (3) ◽  
pp. H309-H316 ◽  
Author(s):  
Hardikkumar M. Patel ◽  
Matthew J. Heffernan ◽  
Amanda J. Ross ◽  
Matthew D. Muller
Keyword(s):  
Sex Differences ◽  
Postmenopausal Women ◽  
Young Women ◽  
Young Men ◽  
Breath Hold ◽  
Doppler Flowmetry ◽  
Men And Women ◽  
Female Sex Hormones ◽  
Vasoconstrictor Response ◽  
Obstructive Sleep

Clinical evidence indicates that obstructive sleep apnea is more common and more severe in men compared with women. Sex differences in the vasoconstrictor response to hypoxemia-induced sympathetic activation might contribute to this clinical observation. In the current laboratory study, we determined sex differences in the acute physiological responses to maximal voluntary end-expiratory apnea (MVEEA) during wakefulness in healthy young men and women (26 ± 1 yr) as well as healthy older men and women (64 ± 2 yr). Mean arterial pressure (MAP), heart rate (HR), brachial artery blood flow velocity (BBFV, Doppler ultrasound), and cutaneous vascular conductance (CVC, laser Doppler flowmetry) were measured, and changes in physiological parameters from baseline were compared between groups. The breath-hold duration and oxygen-saturation nadir were similar between groups. In response to MVEEA, young women had significantly less forearm vasoconstriction compared with young men (ΔBBFV: 2 ± 7 vs. −25 ± 6% and ΔCVC: −5 ± 4 vs. −31 ± 4%), whereas ΔMAP (12 ± 2 vs. 16 ± 3 mmHg) and ΔHR (4 ± 2 vs. 6 ± 3 bpm) were comparable between groups. The attenuated forearm vasoconstriction in young women was not observed in postmenopausal women (ΔBBFV −21 ± 5%). We concluded that young women have blunted forearm vasoconstriction in response to MVEEA compared with young men, and this effect is not evident in older postmenopausal women. These data suggest that female sex hormones dampen neurogenic vasoconstriction in response to apnea-induced hypoxemia.

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