Effects of short-term and prolonged bed rest on the vestibulosympathetic reflex.

The mechanism(s) for post-bed rest (BR) orthostatic intolerance is equivocal. The vestibulosympathetic reflex contributes to postural blood pressure regulation. It was hypothesized that muscle sympathetic nerve responses to otolith stimulation would be attenuated by prolonged head-down BR.

Glycerol-induced fluid shifts attenuate the vestibulosympathetic reflex in humans.

The glycerol dehydration test (GDT) has been used to test for the presence of Ménière's disease and elicits acute alterations in vestibular reflexes in both normal and pathological states. Activation of the vestibulosympathetic reflex (VSR) increases muscle sympathetic nerve activity (MSNA) and peripheral vascular resistance. We hypothesized that the GDT would attenuate the VSR through fluid shifts of the inner ear.

Effect of baroreflex loading on the responsiveness of the vestibulosympathetic reflex in humans.

Activation of the vestibular otolith organs with head-down rotation (HDR) increases muscle sympathetic nerve activity (MSNA) in humans. Previously, we demonstrated this vestibulosympathetic reflex (VSR) elicits increases in MSNA during baroreflex unloading (i.e.

Effect of acute hyperlipidemia on autonomic and cardiovascular control in humans.

Blood lipids may detrimentally affect autonomic and circulatory control. We tested the hypotheses that acute elevations in free fatty acids and triglycerides (acute hyperlipidemia) impair baroreflex control of cardiac period [cardiovagal baroreflex sensitivity (BRS)] and muscle sympathetic nerve activity (MSNA: sympathetic BRS), increase MSNA at rest, and augment physiological responses to exercise. Eighteen young adults were examined in this randomized, double-blinded, and placebo-controlled study.

Determinants of skin sympathetic nerve responses to isometric exercise.

Exercise-induced increases in skin sympathetic nerve activity (SSNA) are similar between isometric handgrip (IHG) and leg extension (IKE) performed at 30% of maximal voluntary contraction (MVC). However, the precise effect of exercise intensity and level of fatigue on this relationship is unclear. This study tested the following hypotheses: 1) exercise intensity and fatigue level would not affect the magnitude of exercise-induced increase in SSNA between IHG and IKE, and 2) altering IHG muscle mass would also not affect the magnitude of exercise-induced increase in SSNA.