We have shown previously that head-down neck flexion (HDNF) in @entity1 elicits increases in muscle sympathetic nerve activity (MSNA). The purpose of this study was to determine the effect of neck muscle afferents on MSNA. We studied this question by measuring MSNA before and after @entity717 that would activate neck muscle afferents but not the vestibular system (i.e., no stimulation of the otolith organs or semicircular canals). After a 3-min baseline period with the head in the normal erect position, subjects rotated their head to the side (approximately 90%) and maintained this position for 3 min. @entity717 was performed by the subjects in both the prone (n = 5) and sitting (n = 6) positions. @entity717 did not elicit changes in MSNA. Average MSNA, expressed as burst frequency and total activity, was 13 +/- 1 and 13 +/- 1 bursts/min and 146 +/-34 and 132 +/- 27 units/min during baseline and @entity717 , respectively. There were no significant changes in @entity291 blood flow (2.6 +/- 0.3 to 2.5 +/- 0.3 ml.100 ml-1.min-1, n = 8) and @entity291 vascular resistance (39 +/- 4 to 41 +/- 4 units; n = 8). Heart rate (64 +/- 3 to 66 +/- 3 beats/min; P = 0.058) and mean arterial pressure (90 +/- 3 to 93 +/- 3; P < 0.05) increased slightly during @entity717 . Additional neck flexion studies were performed with subjects lying on their side (n = 5), MSNA, heart rate, and mean arterial pressure were unchanged during this maneuver, which also does not engage the vestibular system. HDNF was tested in 9 of the 13 subjects. MSNA was significantly increased by 79 +/- 12% (P < 0.001) during HDNF. These findings indicate that neck afferents activated by horizontal neck rotation or flexion in the absence of significant force development do not elicit changes in MSNA. These findings support the concept that HDNF increases MSNA by the activation of the vestibular system.

Neck afferents and muscle sympathetic activity in XXXX : implications for the vestibulosympathetic reflex.

@entity1 :: ('9606', 'Species') :: ['humans'] @entity717 :: ('MESH:D009069', 'Disease') :: ['Head rotation', 'head rotation'] @entity291 :: ('9913', 'Species') :: ['calf']
@entity1 :: (9606,Species) :: ['humans']
