School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom.
Translational Health Sciences, University of Bristol, Bristol, United Kingdom.
Am J Physiol Heart Circ Physiol. 2023 Nov 1;325(5):H1108-H1117. doi: 10.1152/ajpheart.00226.2023. Epub 2023 Sep 1.
Sympathetic nerve activity (SNA) is tightly coupled with the respiratory cycle. In healthy human males, respiratory modulation of SNA does not change with age. However, it is unclear how this modulation is affected by age in females. We investigated whether respiratory sympathetic modulation is altered in healthy postmenopausal (PMF) versus premenopausal female (YF), and younger male (YM) adults, and determined its relationship to resting blood pressure. Muscle SNA (MSNA; microneurography), respiration (transducer belt), ECG, and continuous blood pressure were measured in 12 YF, 13 PMF, and 12 YM healthy volunteers. Respiratory modulation of MSNA was quantified during two phases of the respiratory cycle: mid-late expiration and inspiration/postinspiration. All groups showed respiratory modulation of MSNA ( < 0.0005). There was an interaction between the respiratory phase and group for MSNA [bursts/100 heartbeats (HB) ( = 0.004) and bursts/min ( = 0.029)], with smaller reductions in MSNA during inspiration observed in PMF versus the other groups. Respiratory modulation of blood pressure was also reduced in PMF versus YF (6 [2] vs. 12 [9] mmHg, = 0.008) and YM (13 [13] mmHg, = 0.001, median [interquartile range]). The magnitude of respiratory sympathetic modulation was related to resting blood pressure in PMF only, such that individuals with less modulation had greater resting blood pressure. The data indicate that aging in postmenopausal females is associated with less inspiratory inhibition of MSNA. This correlated with a higher resting blood pressure in PMF only. Thus, the reduced modulation of MSNA could contribute to the age-related rise in blood pressure that occurs in females. The current study demonstrates that respiratory modulation of sympathetic nerve activity (SNA) is reduced in healthy postmenopausal (PMF) versus premenopausal females (YF). Furthermore, respiratory sympathetic modulation was negatively related to resting blood pressure in postmenopausal females, such that blood pressure was greater in individual with less modulation. Reduced respiratory sympathetic modulation may have implications for the autonomic control of blood pressure in aging postmenopausal females, by contributing to age-related sympathetic activation and reducing acute, respiratory-linked blood pressure variation.
交感神经活动（SNA）与呼吸周期紧密耦合。在健康的男性中，SNA 的呼吸调节不会随年龄而变化。然而，目前尚不清楚这种调节在女性中是如何随年龄而变化的。我们研究了健康绝经后（PMF）和绝经前（YF）女性以及年轻男性（YM）的呼吸交感神经调节是否发生改变，并确定了其与静息血压的关系。在 12 名 YF、13 名 PMF 和 12 名 YM 健康志愿者中，通过微神经记录法测量肌肉 SNA（MSNA）、呼吸（传感器带）、心电图和连续血压。在呼吸周期的两个阶段（中期呼气和吸气/后吸气）量化了 MSNA 的呼吸调节。所有组均显示出 MSNA 的呼吸调节（<0.0005）。MSNA 的呼吸阶段和组之间存在相互作用[爆发/100 次心跳（HB）（=0.004）和爆发/分钟（=0.029）]，与其他组相比，PMF 中观察到的吸气过程中 MSNA 的减少幅度较小。PMF 中血压的呼吸调节也低于 YF（6[2]与 12[9]mmHg，=0.008）和 YM（13[13]mmHg，=0.001，中位数[四分位数范围]）。PMF 中，MSNA 的呼吸交感调节幅度与静息血压相关，即调节幅度较小的个体静息血压较高。数据表明，绝经后女性的衰老与 MSNA 的吸气抑制减少有关。这仅与 PMF 中的更高静息血压相关。因此，MSNA 调节的减少可能导致女性中与年龄相关的血压升高。本研究表明，健康绝经后（PMF）女性的交感神经活动（SNA）呼吸调节降低。此外，PMF 中 SNA 的呼吸交感调节与静息血压呈负相关，即调节幅度较小的个体血压较高。呼吸交感神经调节减少可能会影响绝经后女性的自主血压控制，导致与年龄相关的交感神经激活增加，并减少与呼吸相关的急性血压变化。
