Sympathetic nerve hyperactivity and its effect in postmenopausal women

Abstract

Objectives: Hypertension and its subsequent cardiovascular complications have been associated with sympathetic neural activation, and their prevalence in women increases after the menopause. However, there have been no data on the level of sympathetic activation and its relationship to vascular blood flow following the menopause. Therefore, we planned to find out whether the behavior of muscle sympathetic nerve activity (MSNA) and calf blood flow (CBF) in women with and without essential hypertension (EHT) is changed following the menopause.

Methods: Peroneal nerve activity was measured as mean frequency of single units and of multiunit bursts with simultaneously measured CBF in two matched groups of postmenopausal women with and without EHT in comparison with two matched groups of premenopausal women with and without EHT.

Results: As expected, nerve activity was greater in the hypertensive than in normotensive groups and in postmenopausal than in premenopausal normotensive groups. We found that single unit frequency in postmenopausal hypertensives (65 ± 3.9 impulses/100 cardiac beats) was not significantly different from that in postmenopausal normotensives (54 ± 2.2 impulses/100 cardiac beats) or in premenopausal hypertensives (57 ± 2.8 impulses/100 cardiac beats). Similar results were obtained for burst frequency. In addition, a statistically significant negative correlation between the frequency of nerve activity and CBF was found only in postmenopausal normotensive (at least r = -0.42, P < 0.04) and hypertensive women (at least r = -0.45, P < 0.03).

Conclusion: These findings suggest that sympathetic nerve hyperactivity in postmenopausal women may have greater vascular effects than in premenopausal women, and could have implications in the management of EHT in postmenopausal women.