Schmitt Petra M, Kaufman M P
TB-172, Univ. of California, Davis, CA 95616, USA.
J Appl Physiol (1985). 2003 Oct;95(4):1418-24. doi: 10.1152/japplphysiol.00368.2003. Epub 2003 Jun 20.
In humans, the pressor and muscle sympathetic nerve responses to static exercise are less in women than in men. The difference has been attributed to the effect of estrogen on the exercise pressor reflex. Estrogen receptors are abundant in areas of the dorsal horn receiving input from group III and IV muscle afferents, which comprise the sensory limb of the exercise pressor reflex arc. These findings prompted us to investigate the effect of estrogen on the spinal pathway of the exercise pressor reflex arc. Previously, we found that the threshold concentration of 17beta-estradiol needed to attenuate the exercise pressor reflex in male decerebrate cats was 10 microg/ml (Schmitt PM and Kaufman MP. J Appl Physiol 94: 1431-1436, 2003). The threshold concentration for female cats, however, is not known. Consequently, we applied 17beta-estradiol to a well covering the L6-S1 spinal cord in decerebrate female cats. The exercise pressor reflex was evoked by electrical stimulation of the L7 or S1 ventral root, a maneuver that caused the hindlimb muscles to contract statically. We found that the pressor response to contraction averaged 38 +/- 7 mmHg before the application of 17beta-estradiol (0.01 microg/ml) to the spinal cord, whereas it averaged only 23 +/- 4 mmHg 30 min after application (P < 0.05). Recovery of the pressor response to contraction was not obtained for 2 h after application of 17beta-estradiol. Application of 17beta-estradiol in a dose of 0.001 microg/ml had no effect on the exercise pressor reflex (n = 5). We conclude that the concentration of 17beta-estradiol required to attenuate the exercise pressor reflex is 1,000 times more dilute in female cats than that needed to attenuate this reflex in male cats.
在人类中，女性对静态运动的升压和肌肉交感神经反应比男性小。这种差异归因于雌激素对运动升压反射的影响。雌激素受体在背角接受Ⅲ类和Ⅳ类肌肉传入神经输入的区域丰富，而这些传入神经构成了运动升压反射弧的感觉支。这些发现促使我们研究雌激素对运动升压反射弧脊髓通路的影响。此前，我们发现，在雄性去大脑猫中，减弱运动升压反射所需的17β-雌二醇阈值浓度为10微克/毫升（施密特PM和考夫曼MP。《应用生理学杂志》94：1431 - 1436，2003）。然而，雌性猫的阈值浓度尚不清楚。因此，我们将17β-雌二醇应用于去大脑雌性猫覆盖L6 - S1脊髓的区域。通过电刺激L7或S1腹根诱发运动升压反射，该操作可使后肢肌肉静态收缩。我们发现，在向脊髓应用17β-雌二醇（0.01微克/毫升）之前，对收缩的升压反应平均为38±7毫米汞柱，而应用后30分钟平均仅为23±4毫米汞柱（P < 0.05）。应用17β-雌二醇后2小时内，对收缩的升压反应未恢复。应用剂量为0.001微克/毫升的17β-雌二醇对运动升压反射无影响（n = 5）。我们得出结论，减弱雌性猫运动升压反射所需的17β-雌二醇浓度比减弱雄性猫该反射所需的浓度稀释1000倍。
