Male and female rats express similar blood pressure responses to “push-pull” gravitational stress
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.