Key result
Sympathetic activation via cold pressor test restrained the peak and average forearm vascular conductance increments after circulatory reperfusion to a similar degree in both young men and women (p < 0.003).
Why the study?
It was unknown whether the interaction between sympathetic vasoconstriction and endothelial vasodilation leads to different regulation of vascular conductance between sexes.
Does cold pressor test-induced sympathetic activation differentially blunt forearm vasodilation in young healthy men compared to women?
Observational (n=25)
No
Does cold pressor test-induced sympathetic activation differentially blunt forearm vasodilation in young healthy men compared to women?
p-value: p=< 0.003
Sympathetic-mediated restriction of normal forearm vasodilation is similar between young men and women, suggesting similar dynamic regulation of vascular conductance despite differences in isolated sympathetic vasoconstriction.
Similar sympathetic restraint of post-reperfusion vasodilation occurs in young men and women; leaves open differential effects in aging or disease.
BACKGROUND: The in-vivo regulation of vascular conductance (VC) is a continuous balance between endothelial vasodilation and sympathetic vasoconstriction. Although women may report blunted sympathetic vasoconstriction along with higher endothelial vasodilation than men, it is currently unknown whether the interaction between vasoconstriction and vasodilation leads to different regulation of VC between sexes. This study assessed sex differences in sympathetic-mediated blunting of endothelial vasodilation after a brief period of ischemia and whether any restriction of vasodilation blunts tissue blood flow (BF) and re-oxygenation. METHODS: 13 young women and 12 young men underwent two 5-min forearm circulatory occlusions followed by reperfusion, one in basal conditions and the other during cold pressor test-induced sympathetic activation (SYMP). Brachial artery diameter and BF, mean arterial pressure, total peripheral resistance (TPR), and thenar eminence oxygenation were collected. Percent changes normalized to baseline values of forearm VC, brachial artery BF and flow-mediated dilation (FMD), TPR, and hand oxygenation after circulatory reperfusion were calculated. RESULTS: TPR increased during SYMP in men (p = 0.019) but not in women (p = 0.967). Women showed a greater brachial artery FMD than men (p = 0.004) at rest, but sex differences disappeared after normalization to shear rate and baseline diameter (p > 0.11). The percent increases from baseline of peak and average forearm VC after circulatory reperfusion did not differ between sexes in basal conditions (p > 0.98) or during SYMP (p > 0.97), and were restrained by SYMP similarly in both sexes (p < 0.003) without impairing the hand re-oxygenation (p > 0.08) or average hyperemic response (p > 0.09). CONCLUSIONS: Although women may report blunted sympathetic vasoconstriction than men when assessed separately, the similar sympathetic-mediated restriction of vasodilation suggests a similar dynamic regulation of VC between sexes. SYMP-mediated restrictions of the normal forearm vasodilation do not impair the average hyperemic response and hand re-oxygenation in both sexes.
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Gentilin et al. (2022) conducted an observational in Healthy (n=25). Cold pressor test-induced sympathetic activation (SYMP) vs. Basal conditions (rest) was evaluated on Percent increase from preceding baseline values of forearm vascular conductance (VC) upon cuff release (p=< 0.003). Sympathetic activation via cold pressor test restrained the peak and average forearm vascular conductance increments after circulatory reperfusion to a similar degree in both young men and women (p < 0.003).
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