Division of Integrative Physiology, Tottori University Faculty of Medicine, Yonago, Japan.
J Appl Physiol (1985). 2012 Sep 1;113(5):719-26. doi: 10.1152/japplphysiol.00396.2012. Epub 2012 Jun 21.
In women, sympathoexcitation during static handgrip exercise is reduced during the follicular phase of the ovarian cycle compared with the menstrual phase. Previous animal studies have demonstrated that estrogen modulates the exercise pressor reflex, a sympathoexcitatory mechanism originating in contracting skeletal muscle. The present study was conducted in female rats to determine whether skeletal muscle contraction-evoked reflex sympathoexcitation fluctuates with the estrous cycle. The estrous cycle was judged by vaginal smear. Plasma concentrations of estrogen were significantly (P < 0.05) higher in rats during the proestrus phase of the estrus cycle than those during the diestrus phase. In decerebrate rats, either electrically induced 30-s continuous static contraction of the hindlimb muscle or 30-s passive stretch of Achilles tendon (a maneuver that selectively stimulates mechanically sensitive muscle afferents) evoked less renal sympathoexcitatory and pressor responses in the proestrus animals than in the diestrus animals. Renal sympathoexcitatory response to 1-min intermittent (1- to 4-s stimulation to relaxation) bouts of static contraction was also significantly less in the proestrus rats than that in the diestrus rats. In ovariectomized female rats, 17β-estradiol applied into a well covering the dorsal surface of the lumbar spinal cord significantly reduced skeletal muscle contraction-evoked responses. These observations demonstrate that the exercise pressor reflex function and its mechanical component fluctuate with the estrous cycle in rats. Estrogen may cause these fluctuations through its attenuating effects on the spinal component of the reflex arc.
在女性中，与月经周期相比，卵巢周期的卵泡期在进行静态手握运动时交感兴奋会减少。先前的动物研究表明，雌激素调节运动加压反射，这是一种起源于收缩骨骼肌的交感兴奋机制。本研究在雌性大鼠中进行，以确定骨骼肌收缩引起的反射交感兴奋是否随发情周期而波动。通过阴道涂片判断发情周期。发情周期中发情前期大鼠的雌激素血浆浓度明显（P < 0.05）高于发情后期大鼠。在去大脑大鼠中，无论是通过电刺激后肢肌肉连续 30 秒的静态收缩，还是通过被动拉伸跟腱（一种选择性刺激机械敏感肌肉传入纤维的操作），发情前期动物的肾脏交感兴奋和升压反应均低于发情后期动物。与发情后期大鼠相比，发情前期大鼠 1 分钟间歇性（1-4 秒刺激-松弛）的静态收缩引起的肾脏交感兴奋反应也明显减少。在卵巢切除的雌性大鼠中，17β-雌二醇应用于覆盖腰椎脊髓背表面的小室内，显著降低了骨骼肌收缩引起的反应。这些观察结果表明，运动加压反射功能及其机械成分在大鼠中随发情周期而波动。雌激素可能通过其对反射弧脊髓成分的抑制作用引起这些波动。
