Vasomotor sympathetic neural control is maintained during sustained upright posture in humans
Open accessAbstract
Vasomotor sympathetic activity plays an important role in arterial pressure maintenance via the baroreflex during acute orthostasis in humans. If orthostasis is prolonged, blood pressure may be supported additionally by humoral factors with a possible reduction in sympathetic baroreflex sensitivity. We tested the hypothesis that baroreflex control of muscle sympathetic nerve activity (MSNA) decreases during prolonged upright posture. MSNA and haemodynamics were measured supine and during 45 min 60 deg upright tilt in 13 healthy individuals. Sympathetic baroreflex sensitivity was quantified using the slope of the linear correlation between MSNA and diastolic pressure during spontaneous breathing. It was further assessed as the relationship between MSNA and stroke volume, with stroke volume derived from cardiac output (C 2 H 2 rebreathing) and heart rate. Total peripheral resistance was calculated from mean arterial pressure and cardiac output. We found that MSNA increased from supine to upright (17 ± 8 (s.d.) versus 38 ± 12 bursts min−1; P < 0.01), and continued to increase to a smaller degree during sustained tilt (39 ± 11, 41 ± 12, 43 ± 13 and 46 ± 15 bursts min−1 after 10, 20, 30 and 45 min of tilt; between treatments P < 0.01). Sympathetic baroreflex sensitivity increased from supine to upright (−292 ± 180 versus−718 ± 362 units beat−1 mmHg−1; P < 0.01), but remained unchanged as tilting continued (−611 ± 342 and −521 ± 221 units beat−1 mmHg−1 after 20 and 45 min of tilt; P= 0.49). For each subject, changes in MSNA were associated with changes in stroke volume (r= 0.88 ± 0.13, P < 0.05), while total peripheral resistance was related to MSNA during 45 min upright tilt (r= 0.82 ± 0.15, P < 0.05). These results suggest that the vasoconstriction initiated by sympathetic adrenergic nerves is maintained by ongoing sympathetic activation during sustained (i.e. 45 min) orthostasis without obvious changes in vasomotor sympathetic neural control.
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These findings suggest that the orthostatic tachycardia in POTS is a physiological compensatory response to the smaller stroke volume in the setting of cardiac atrophy and reduced blood volume.
“These findings suggest that the orthostatic tachycardia in POTS is a physiological compensatory response to the smaller stroke volume (61,62) in the setting of cardiac atrophy and reduced blood volume (Figure 2B).”
From Postural Orthostatic Tachycardia Syndrome (2019) · cites this paper as [61]
The Results report that heart rate rose while stroke volume fell during upright tilt, and the Discussion links falling stroke volume to sympathetic activation. However, the study involved healthy individuals; it does not establish that tachycardia in POTS compensates for smaller stroke volume. The citation is attached to the smaller-stroke-volume explanation, not specifically to the cardiac-atrophy and reduced-blood-volume phrase. (LLM, conf=0.85)
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References 41 · Cited by 80
Research works printed but not linked: 2
- Rowell LB. Human Cardiovascular Control. New York, Oxford: Oxford University Press; 1993. [Google Scholar]
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- Authors
- Fu, Q., Shook, R. P., Okazaki, K., Hastings, J. L., Shibata, S., Conner, C. L., Palmer, M. D., & Levine, B. D.
- Affiliations
- Texas Health Dallas (US)
- The University of Texas Southwestern Medical Center (US)
- Corresponding author
- Levine, Benjamin D.
- Venue
- The Journal of Physiology
- Publisher
- Wiley
- Published
- 2006-11-24
- Volume
- 577
- Issue
- 2
- Pages
- 679-687
- ISSN
- 0022-3751 (ISSN-L)
- 1469-7793
- PMC
- PMC1890429
- OpenAlex
- W2140374409
- Cited by
- 80
- References
- 41
- Citations by year
- 2026: 4 · 2025: 3 · 2024: 2 · 2023: 4 · 2022: 4 · 2021: 2 · 2020: 5 · 2019: 5 · 2018: 5 · 2017: 5 · 2016: 2 · 2015: 5 · 2014: 1 · 2013: 1 · 2012: 8
- FWCI
- 6.12
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Locations
- The Journal of Physiology (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Funders
- American Heart Association
- National Institutes of Health
- National Heart, Lung, and Blood Institute (K23HL075283)
- National Center for Research Resources (RR 00633, M01RR000633)
- NIH Clinical Center
- Topics
- Health Sciences › Medicine › Surgery › Cardiovascular Syncope and Autonomic Disorders
- Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Heart Rate Variability and Autonomic Control
- Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
- Keywords
- muscle sympathetic nerve activity, orthostatic tolerance, tilt table, systemic vascular resistance, stroke volume, hemodynamics, blood pressure regulation, sympathetic vasoconstriction
- MeSH terms
- Adult, Blood Pressure, Cardiac Output, Cardiovascular Physiological Phenomena, Dizziness, Female, Heart Rate, Humans, Male, Middle Aged, Muscle, Smooth, Vascular, Peroneal Nerve, Posture, Sympathetic Nervous System, Time Factors, Vascular Resistance, Vasomotor System, Supine Position, Baroreflex, Muscle, Skeletal, Tilt-Table Test
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