Feed-forward changes in carotid blood flow velocity during active standing.
Orthostatic changes induce temporary loss of circulatory regulation. Feedback systems react to cardiovascular alterations to compensate for the instability. To clarify the existence of anticipatory cardiovascular regulation during active standing, we continuously recorded blood flow velocity (BFV) in the common carotid artery and cerebral blood volume (CBV) in healthy men. The maximum BFV value decreased significantly before standing in the reaction-time condition. The decrease significantly correlated with the change in systolic blood pressure that accompanies upright standing from a supine position. The anticipatory BFV decrease disappeared during self-paced standing, and all BFV parameters significantly declined after the self-paced standing. The CBV recording showed a significant increase in oxyhemoglobin levels before standing in the reaction-time condition. Our study suggests that some feed-forward cardiovascular regulation triggered by central command could be activated before standing, and it may play a functional role in the maintenance of cerebral perfusion during standing.
Kitaoka
Kazuyoshi
K
Department of Physiology, The University of Tokushima Graduate School, Tokushima 770-8503, Japan. kitaoka@basic.med.tokushima-u.ac.jp
Miura
Hajime
H
Kitamura
Mitsuo
M
Akutagawa
Masatake
M
Kinouchi
Yohsuke
Y
Yoshizaki
Kazuo
K
D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D017536:Carotid Artery, Common / Q000502:physiology*; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D055815:Young Adult