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Keywords:

  • orthostatic intolerance;
  • sympathetic nervous system;
  • vestibulosympathetic reflex

Abstract

Aim: The vestibulosympathetic reflex refers to sympathetic nerve activation by the vestibular system. Animal studies indicate that the vestibular system assists in blood pressure regulation during orthostasis. Although human studies clearly demonstrate activation of muscle sympathetic nerve activity (MSNA) during engagement of the otolith organs, the role of the vestibulosympathetic reflex in maintaining blood pressure during orthostasis is not well-established. Examination of the vestibulosympathetic reflex with other cardiovascular reflexes indicates that it is a powerful and independent reflex. Ageing, which is associated with an increased risk for orthostatic hypotension, attenuates the vestibulosympathetic reflex. The attenuated reflex is associated with a reduction in arterial pressure.

Conclusion: These findings suggest that the vestibulosympathetic reflex assists in blood pressure regulation in humans, but future studies examining this reflex in other orthostatically intolerant populations are necessary to address this hypothesis.