Interaction between vestibulosympathetic and skeletal muscle reflexes on sympathetic activity in humans

• Published in: Journal of applied physiology (1985) Vol. 90; no. 1; pp. 242 - 247
• Main Author: Ray, Chester A
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Am Physiological Soc 01-01-2001; American Physiological Society
• Subjects: Adult; Biological and medical sciences; Blood Pressure; Exercise; Female; Fundamental and applied biological sciences. Psychology; Hand Strength - physiology; Head - physiology; Heart Rate; Humans; Isometric Contraction - physiology; Life Sciences (General); Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Muscle, Skeletal - innervation; Muscular system; Nervous system; Posture - physiology; Reference Values; Reflex - physiology; Reflexes; Rotation; Space life sciences; Sympathetic Nervous System - physiology; Vertebrates: nervous system and sense organs; Vestibular Nuclei - physiology; Non-Nasa Center; Nasa Discipline Neuroscience; Human; Sympathetic nerve; Reflex; Nervous control; Interaction; Central nervous system; Activation; Striated muscle; Sympathetic nervous system; Inner ear; Autonomic nervous system; Vestibular nucleus; Otolith; Afferent projection; Arterial pressure; Medulla oblongata; Hemodynamics; Vestibular system; NASA Discipline Neuroscience; Non-NASA Center
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2001.90.1.242

Division of Cardiology, Departments of Medicine and of Cellular
and Molecular Physiology, General Clinic Research Center,
Pennsylvania State University College of Medicine, Hershey,
Pennsylvania 17033
Evidence from animals
indicates that skeletal muscle afferents activate the vestibular nuclei
and that both vestibular and skeletal muscle afferents have inputs to
the ventrolateral medulla. The purpose of the present study was to
investigate the interaction between the vestibulosympathetic and
skeletal muscle reflexes on muscle sympathetic nerve activity (MSNA)
and arterial pressure in humans. MSNA, arterial pressure, and heart
rate were measured in 17 healthy subjects in the prone position during
three experimental trials. The three trials were 2 min of 1 )
head-down rotation (HDR) to engage the vestibulosympathetic reflex,
2 ) isometric handgrip (IHG) at 30% maximal voluntary
contraction to activate skeletal muscle afferents, and 3 )
HDR and IHG performed simultaneously. The order of the three trials was
randomized. HDR and IHG performed alone increased total MSNA by 46 ± 16 and 77 ± 24 units, respectively ( P  < 0.01). During the HDR plus IHG trial, MSNA increased 142   ± 38 units ( P  < 0.01). This increase was not significantly
different from the sum of the individual trials (130 ± 41 units).
This finding was also observed with mean arterial pressure (sum = 21 ± 2 mmHg and HDR + IHG = 22 ± 2 mmHg). These
findings suggest that there is an additive interaction for MSNA and
arterial pressure when the vestibulosympathetic and skeletal muscle
reflexes are engaged simultaneously in humans. Therefore, no central
modulation exists between these two reflexes with regard to MSNA output
in humans.
autonomic nervous system; exercise; muscle sympathetic nerve
activity; muscle afferents; neural control; otolith organs