Hucklebridge F, Mellins J, Evans P, Clow A
Psychophysiology and Stress Research Group, Department of Biomedical Sciences, University of Westminster, 115, New Cavendish Street, W1M 8JS, London, UK.
Life Sci. 2002 Jun 28;71(6):639-46. doi: 10.1016/s0024-3205(02)01726-5.
It has recently been reported that the orthostatic challenge associated with postural change from sitting to an upright position is stimulatory to the hypothalamic-pituitary-adrenal axis as evidenced by increased salivary free cortisol. This stimulatory influence is potentially a confound for the many psychoneuroendocrine studies for which salivary free cortisol is the main dependent variable. This particularly relates to laboratory psychosocial stress procedures in which subjects are invited to stand in order to deliver public speech and the studies which have explored the cortisol response to awakening in which postural shift has not been controlled for. We therefore examined, in a balanced cross over design whether the awakening cortisol response was influenced by standing, shortly after awakening or remaining supine during the response study period. In addition and in the same subjects we measured the cardiovascular response and saliva cortisol response to the orthostatic challenge of shifting from a supine to a standing position later in the diurnal cortisol cycle. The expected cortisol response to awakening was demonstrated but there was no evidence that the postural shift, supine to standing, confounded the response. This same postural shift later in the day induced the expected increase in heart rate but cortisol simply followed the circadian decline. Under the conditions of the present study we found no evidence that the postural shift supine to standing could induce a cortisol secretory episode such as to contribute towards the awakening response.
最近有报道称，从坐姿变为直立姿势所伴随的直立位应激对下丘脑 - 垂体 - 肾上腺轴具有刺激作用，唾液游离皮质醇增加即为证据。这种刺激作用可能会干扰许多以唾液游离皮质醇作为主要因变量的心理神经内分泌研究。这尤其涉及实验室心理社会应激程序，即让受试者站立以进行公开演讲的研究，以及那些探索皮质醇对觉醒反应但未控制体位变化的研究。因此，我们采用平衡交叉设计，研究在反应研究期间，觉醒后不久站立或保持仰卧位是否会影响觉醒时的皮质醇反应。此外，在同一批受试者中，我们还测量了在昼夜皮质醇周期后期从仰卧位转变为站立位的直立位应激时的心血管反应和唾液皮质醇反应。结果显示出了预期的觉醒时皮质醇反应，但没有证据表明从仰卧位到站立位的体位变化会干扰该反应。当天晚些时候同样的体位变化导致心率出现预期的增加，但皮质醇只是随昼夜节律下降。在本研究条件下，我们没有发现证据表明从仰卧位到站立位的体位变化会引发一次皮质醇分泌事件，从而对觉醒反应产生影响。
