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Department of Exercise Science, The University of Iowa, Iowa City, Iowa 52242
Brief exposure to
Gz ("push") reduces eye-level blood pressure
(ELBP) during subsequent exposure to +Gz
("pull"). This is called the "push-pull effect." To evaluate
the influence of gender and the axis of rotation (pitch vs. roll) on
the push-pull effect, 10 isoflurane-anesthetized male and 10 female
Sprague-Dawley rats were restrained supine on a heated tilt board. Rats
were subjected to two G profiles: a control profile consisting of
rotation from 0 Gz to 90° head-up tilt (+1
Gz) for 10 s and a push-pull profile consisting of
rotation from 0 Gz to 90° head-down tilt (
1
Gz) for 2 s immediately preceding 10 s of +1
Gz stress. A total of 16 tilts consisting of equal numbers
of control and push-pull trials and equal numbers of pitch and roll
rotations were imposed by using a counterbalanced design. Gender
exerted a significant effect on baseline (0 Gz) ELBP
(pressure was ~4 mmHg higher in females). In males and
females, ELBP rose to a similar extent (~8 mmHg) during push, fell to
a similar extent (~18 mmHg) during control +Gz stress,
and fell to a similar extent (~22 mmHg) during push-pull
+Gz stress. Altering the axis of rotation between the x-axis (roll) and the y-axis (pitch) did not
influence the results. Thus males and females exhibit a push-pull
effect; however, gender and axis of rotation do not appear to influence
the push-pull effect in anesthetized rats subjected to tilting.
hypogravity; hypergravity; gravity tolerance; cerebral perfusion; orthostatic tolerance
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