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Murine orthostatic response during prolonged vertical studies: Effect on cerebral blood flow measured by arterial spin‐labeled MRI
Author(s) -
Foley Lesley M.,
Hitchens T. Kevin,
Kochanek Patrick M.,
Melick John A.,
Jackson Edwin K.,
Ho Chien
Publication year - 2005
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.20621
Subject(s) - cerebral blood flow , orthostatic vital signs , blood flow , autoregulation , blood pressure , hemodynamics , phenylephrine , medicine , magnetic resonance imaging , arterial spin labeling , blood volume , saline , nuclear magnetic resonance , anesthesia , cardiology , chemistry , nuclear medicine , physics , radiology
High‐field MRI scanners are, in principle, well suited for mouse studies; however, many high‐field magnets employ a vertical design that may influence the physiological state of the rodent. The purpose of this study was to investigate the orthostatic response of cerebral blood flow (CBF) in mice during a prolonged MR experiment in the vertical position. Arterial spin‐labeled (ASL) MRI was performed at 4.7‐Tesla with a 15‐cm gradient insert that allowed horizontal and vertical CBF measurements to be obtained with the same scanner. For mice in the head‐up (HU) vertical position, CBF decreased by approximately 40% compared to the horizontal position, although blood pressure did not differ. Furthermore, CBF values for vertically positioned mice treated with phenylephrine remained constant while blood pressure increased. These results support the conclusion that cerebral autoregulation was intact, albeit at a lower level. Since CBF recovers to near horizontal values by volume loading with saline, it appears that a decrease in central venous pressure (CVP) leading to an increase in sympathetic tone may be a contributing mechanism for lowered CBF. This suggests that using an HU vertical position for MRI in mice may have broader implications, especially for studies that rely on CBF (such as BOLD and fMRI). Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.