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- Barnes, J. N., et al.
(författare)
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Aging enhances autonomic support of blood pressure in women
- 2014
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Ingår i: Hypertension. - 0194-911X .- 1524-4563. ; 63:2, s. 303-308
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Tidskriftsartikel (refereegranskat)abstract
- The autonomic nervous system plays a central role in both acute and chronic blood pressure regulation in humans. The activity of the sympathetic branch of the autonomic nervous system is positively associated with peripheral resistance, an important determinant of mean arterial pressure in men. In contrast, there is no association between sympathetic nerve activity and peripheral resistance in women before menopause, yet a positive association after menopause. We hypothesized that autonomic support of blood pressure is higher after menopause in women. We examined the effect of ganglionic blockade on arterial blood pressure and how this relates to baseline muscle sympathetic nerve activity in 12 young (25±1 years) and 12 older postmenopausal (61±2 years) women. The women were studied before and during autonomic blockade using trimethaphan camsylate. At baseline, muscle sympathetic nerve activity burst frequency and burst incidence were higher in the older women (33±3 versus 15±1 bursts/min; 57±5 versus 25±2 bursts/100 heartbeats, respectively; P<0.05). Muscle sympathetic nerve activity bursts were abolished by trimethaphan within minutes. Older women had a greater decrease in mean arterial pressure (-29±2 versus-9±2 mm Hg; P<0.01) and total peripheral resistance (-10±1 versus-5±1 mm Hg/L per minute; P<0.01) during trimethaphan. Baseline muscle sympathetic nerve activity was associated with the decrease in mean arterial pressure during trimethaphan (r=-0.74; P<0.05). In summary, our results suggest that autonomic support of blood pressure is greater in older women compared with young women and that elevated sympathetic nerve activity in older women contributes importantly to the increased incidence of hypertension after menopause. © 2013 American Heart Association, Inc.
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| 2. |
- Charkoudian, N, et al.
(författare)
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Integrative mechanisms of blood pressure regulation in humans and rats: cross-species similarities.
- 2010
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Ingår i: American journal of physiology. Regulatory, integrative and comparative physiology. - : American Physiological Society. - 1522-1490 .- 0363-6119. ; 298:3
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Tidskriftsartikel (refereegranskat)abstract
- As our understanding of the importance of individualized medicine continues to grow, the clinical relevance of interindividual variability in hemodynamic variables is receiving increasing attention. However, it is not known whether the rat, which is often used for studies of cardiovascular regulation, exhibits similar interindividual variability. In the present study, we evaluated whether the magnitude of interindividual variability in cardiac output (CO) and total peripheral resistance (TPR) was similar in humans and in rats. We assessed interindividual variability of mean arterial pressure (MAP), CO, and TPR during control conditions in normotensive humans (n = 40) and during normotension and deoxycorticosterone acetate-salt hypertension in Sprague-Dawley rats (n = 16). Humans and rats showed marked interindividual variability in CO and TPR but low variability in MAP. During deoxycorticosterone acetate-salt hypertension, CO was maintained, but TPR was elevated compared with the baseline period. We conclude that the magnitudes of interindividual variability of MAP, CO, and TPR are quantitatively similar in humans and rats, providing support for the relevance of this variability in both species and suggesting that studies in rats could be designed to address questions specific to individualized medicine in hypertension.
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| 3. |
- Hart, E. C., et al.
(författare)
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Sympathetic nerve activity and peripheral vasodilator capacity in young and older men
- 2014
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Ingår i: American Journal of Physiology-Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 306:6
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Tidskriftsartikel (refereegranskat)abstract
- Interindividual variability in sympathetic nerve activity (SNA) has provided insight into integrative mechanisms contributing to blood pressure (BP) regulation in humans. In young people, the influence of high SNA on BP is balanced by lower cardiac output and less adrenergic vasoconstrictor responsiveness. Older people have higher SNA and higher BP. We hypothesized that SNA has a restraining effect on peripheral vasodilator responsiveness in young and older men, such that individuals with higher tonic SNA would show less forearm vasodilatation to exogenous vasodilators. We measured muscle SNA (MSNA; microneurography) and forearm vasodilator responses to intra-arterial infusions of acetylcholine (ACh; endothelium dependent) and sodium nitroprusside (SNP; endothelium independent) in 13 young (age; 27 +/- 1 yr) and 16 older (61 +/- 2 yr) men. Forearm vascular conductance (FVC) responses to ACh were lower in the older men at the two highest doses (2 and 4 mu g.100 ml(-1).min(-1); Delta 395 +/- 81 vs. 592 +/- 87% and 412 +/- 87 vs. 616 +/- 132%, P < 0.05), and MSNA was higher (64 +/- 4 vs. 41 +/- 2 bursts/100 hb; P < 0.05). There was no difference in the FVC response to SNP between young and older men (P > 0.05). In young men, there was an inverse relationship between resting MSNA and FVC responses (%change) to both ACh and SNP (r = -0.83 and r = -0.83, respectively; P < 0.05). In older men, however, this relationship was not observed. Tonic SNA may act to restrain vasodilator responses in young men, whereas in older men a lack of such restraint may be protective against the pressor effects of higher SNA.
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| 6. |
- Wallin, Gunnar B, 1936, et al.
(författare)
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Relationship between breathing and cardiovascular function at rest: sex-related differences.
- 2010
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Ingår i: Acta physiologica. - : Wiley. - 1748-1716 .- 1748-1708. ; 200:2, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- AIM: to compare relationships at rest between breathing rate, levels of muscle sympathetic nerve activity, total peripheral resistance and cardiac output among young men and women. METHODS: recordings were made of respiratory movements, sympathetic nerve activity (peroneal microneurography), intra-arterial blood pressure, electrocardiogram, cardiac output (open-circuit acetylene uptake technique) in 19 healthy men (age 27 (+/-) 2years, mean (+/-) SEM) and 17 healthy women (age 25 (+/-) 1years). Total peripheral resistance and stroke volume were calculated. Four minutes epochs of data were analysed. RESULTS: breathing rates and sympathetic activity were similar in men and women but compared to men, women had significantly lower blood pressures, cardiac output and stroke volume. In men breathing rate correlated positively with sympathetic activity (r = 0.58, P < 0.05) but not in women (r = 0.12, P > 0.05). Furthermore, in men, respiratory rate correlated positively with total peripheral resistance (r = 0.65, P < 0.05) and inversely with cardiac output (r =-0.84, P < 0.05) and heart rate (r = -0.60, P < 0.05) but there were no such relationships in women (P > 0.05 for all). CONCLUSIONS: the positive relationship between breathing and sympathetic activity in men, and the inverse coupling of breathing to cardiac output and heart rate suggest that influences of respiration may be important not only for dynamic but also for 'tonic' cardiovascular function. The lack of relationships among these variables in women shows that there are fundamental differences in basic blood pressure regulation between the sexes.
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