Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 288, Issue 2, Pages H904-H907Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00569.2004
Keywords
otolith stimulation; vestibulosympathetic reflex; arterial pressure control; mental arithmetic
Funding
- NCI NIH HHS [CA-00207] Funding Source: Medline
- NHLBI NIH HHS [HL-58503] Funding Source: Medline
- NIDCD NIH HHS [DC-006459] Funding Source: Medline
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Autonomic responses may underlie associations among anxiety, vestibular dysfunction, and unexplained syncope. Mental stress (MS), an anxiety-inducing stimulus, causes forearm vasodilation, whereas the vestibulosympathetic reflex (VSR) causes forearm vasoconstriction. The purpose of this study was to examine the combined effects of mental and vestibular stimulation on neurovascular control in the forearm. Heart rate, arterial pressure (Finapres), and forearm blood flow (Doppler) were measured in 10 healthy volunteers in the prone position during 1) head-down rotation (HDR), 2) MS ( mental arithmetic), and 3) HDR + MS. Forearm vascular resistance (FVR) increased during HDR ( from 232 +/- 40 to 319 +/- 53 units) and decreased during MS ( from 260 +/- 57 to 154 +/- 22 units). During HDR + MS, FVR did not change [ change (Delta) = - 31 +/- 50 units] and was not significantly different from the algebraic sum of each trial performed alone (Delta = - 20 +/- 42 units). Arm muscle sympathetic nerve activity (MSNA; microneurography) was measured in seven additional subjects. MSNA increased during HDR ( from 13 +/- 2 to 17 +/- 2 bursts/min) and HDR + MS ( from 11 +/- 2 to 16 +/- 2 bursts/min). Increases in MSNA during HDR + MS ( Delta = 5 +/- 2 bursts/min) were not different from the algebraic sum of each trial performed alone ( Delta = 6 +/- 2 bursts/min). We conclude that an additive neurovascular interaction exists between MS and the VSR in the forearm. Activation of the VSR prevented forearm vasodilation during MS, suggesting that activation of the VSR may help protect against stress-induced syncope.
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