Gender affects sympathetic and hemodynamic response to postural stress

Abstract

We tested the hypothesis that differences in sympathetic reflex responses to head-up tilt (HUT) between males (n = 9) and females (n = 8) were associated with decrements in postural vasomotor responses in women. Muscle sympathetic nerve activity (MSNA; microneurography), heart rate, stroke volume (SV; Doppler), and blood pressure (Finapres) were measured during a progressive HUT protocol (5 min at each of supine, 20 degrees, 40 degrees, and 60 degrees ). MSNA and hemodynamic responses were also measured during the cold pressor test (CPT) to examine nonbaroreflex neurovascular control. SV was normalized to body surface area (SV(i)) to calculate the index of cardiac output (Q(i)), and total peripheral resistance (TPR). During HUT, heart rate increased more in females versus males (P < 0.001) and SV(i) and Q(i) decreased similarly in both groups. Mean arterial pressure (MAP) increased to a lesser extent in females versus males in the HUT (P < 0.01) but increases in TPR during HUT were similar. MSNA burst frequency was lower in females versus males in supine (P < 0.03) but increased similarly during HUT. Average amplitude/burst increased in 60 degrees HUT for males but not females. Both males and females demonstrated an increase in MAP as well as MSNA burst frequency, mean burst amplitude, and total MSNA during the CPT. However, compared with females, males demonstrated a greater neural response (DeltaTotal MSNA) due to a larger increase in mean burst amplitude (P < 0.05). Therefore, these data point to gender-specific autonomic responses to cardiovascular stress. The different MSNA response to postural stress between genders may contribute importantly to decrements in blood pressure control during HUT in females.

Discordant Orthostatic Reflex Renin–Angiotensin and Sympathoneural Responses in Premenopausal Exercising-Hypoestrogenic Women

“…By contrast, information concerning the effects of endogenous and exogenous estrogen on reflex MSNA responses to orthostatic stress is both limited and inconsistent. For example, head-up tilt has been reported to elicit both lower 21 and similar 22 MSNA responses in young women compared with men. Simulated orthostatic stress augments MSNA more during the mid-luteal phase (high estrogen and progesterone) than in the early follicular phase (low estrogen and progesterone) of the menstrual cycle.…”

Cold pressor test in tetraplegia and paraplegia suggests an independent role of the thoracic spinal cord in the hemodynamic responses to cold

“…The hemodynamic CPT effect is maximal about 60 s after limb immersion, and most people find it remarkably painful to hold their hand in freezing water for more than 120 s. 1 HR and BP changes following CPT stimulation were not affected by either age or gender. 2 Cerebral blood flow velocity (CBFV) showed variable response to CPT. Some studies found bilateral or unilateral (in the brain hemisphere that is contralateral (Co) to the cold applied hand) CBFV increase during CPT.…”

The effect of gender on the sympathetic nerve hyperactivity of essential hypertension

“…4,14 On the other hand, previously reported findings in normotensive populations have not been consistent as to whether MSNA levels are different between men and women. Young women may have a lower [15][16][17][18][19] or similar 20,21 level of resting MSNA relative to young men. Also, older women may have a lower 15 or similar 17,19 level of resting MSNA relative to older men.…”