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Interaction of the vestibular system and baroreflexes on sympathetic nerve activity in humansMuscle sympathetic nerve activity (MSNA) is altered by vestibular otolith stimulation. This study examined interactive effects of the vestibular system and baroreflexes on MSNA in humans. In study 1, MSNA was measured during 4 min of lower body negative pressure (LBNP) at either -10 or -30 mmHg with subjects in prone posture. During the 3rd min of LBNP, subjects lowered their head over the end of a table (head-down rotation, HDR) to engage the otolith organs. The head was returned to baseline upright position during the 4th min. LBNP increased MSNA above baseline during both trials with greater increases during the -30-mmHg trial. HDR increased MSNA further during the 3rd min of LBNP at -10 and -30 mmHg (Delta32% and Delta34%, respectively; P < 0.01). MSNA returned to pre-HDR levels during the 4th min of LBNP when the head was returned upright. In study 2, MSNA was measured during HDR, LBNP, and simultaneously performed HDR and LBNP. The sum of MSNA responses during individual HDR and LBNP trials was not significantly different from that observed during HDR and LBNP performed together (Delta131 +/- 28 vs. Delta118 +/- 47 units and Delta340 +/- 77 vs. Delta380 +/- 90 units for the -10 and -30 trials, respectively). These results demonstrate that vestibular otolith stimulation can increase MSNA during unloading of the cardiopulmonary and arterial baroreflexes. Also, the interaction between the vestibulosympathetic reflex and baroreflexes is additive in humans. These studies indicate that the vestibulosympathetic reflex may help defend against orthostatic challenges in humans by increasing sympathetic outflow.
Document ID
20040112705
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Ray, C. A.
(General Clinic Research Center, Pennsylvania State University College of Medicine Hershey, Pennsylvania 17033, United States)
Date Acquired
August 21, 2013
Publication Date
November 1, 2000
Publication Information
Publication: American journal of physiology. Heart and circulatory physiology
Volume: 279
Issue: 5
ISSN: 0363-6135
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: HL-58503
CONTRACT_GRANT: M01 RR-10732
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Neuroscience
Non-NASA Center
Clinical Trial

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