Abstract
BackgroundCortisol is an essential hormone in the regulation of the stress response along the HPA axis, and salivary cortisol has been used as a measure of free circulating cortisol levels. Recently, salivary alpha-amylase (sAA) has also emerged as a novel biomarker for psychosocial stress responsiveness within the sympathetic adrenomedullary (SAM) system.Principal FindingsWe measured sAA and salivary cortisol in healthy volunteers after exposure to the Trier Social Stress Test (TSST) and electric stimulation stress. One hundred forty-nine healthy volunteers participated in this study. All subjects were exposed to both the TSST and electric stimulation stress on separate days. We measured sAA and salivary cortisol levels three times immediately before, immediately after, and 20 min after the stress challenge. The State (STAI-S) and Trait (STAI-T) versions of the Spielberger Anxiety Inventory test and the Profile of Mood State (POMS) tests were administered to participants before the electrical stimulation and TSST protocols. We also measured HF, LF and LF/HF Heart Rate Variability ratio immediately after electrical stimulation and TSST exposure. Following TSST exposure or electrical stimulation, sAA levels displayed a rapid increase and recovery, returning to baseline levels 20 min after the stress challenge. Salivary cortisol responses showed a delayed increase, which remained significantly elevated from baseline levels 20 min after the stress challenge. Analyses revealed no differences between men and women with regard to their sAA response to the challenges (TSST or electric stimulations), while we found significantly higher salivary cortisol responses to the TSST in females. We also found that younger subjects tended to display higher sAA activity. Salivary cortisol levels were significantly correlated with the strength of the applied electrical stimulation.ConclusionsThese preliminary results suggest that the HPA axis (but not the SAM system) may show differential response patterns to distinct kinds of stressors.
Highlights
Over half a century ago, Selye and McKeown [1] defined ‘‘stress’’ as the body’s response when a human being is subjected to an outside stimulus
These preliminary results suggest that the HPA axis may show differential response patterns to distinct kinds of stressors
Three participants did not answer the questionnaires (2 men, 1 women), one participant did not meet the inclusion criteria (1 woman; SAD), twenty participants dropped out during the procedure, one participant had an inappropriate stressor during the resting period, and eleven subjects were excluded for other technical errors
Summary
Over half a century ago, Selye and McKeown [1] defined ‘‘stress’’ as the body’s response when a human being is subjected to an outside stimulus. Stress responsiveness is primarily regulated by two neuroendocrine axes: the hypothalamic-pituitary-adrenocortical (HPA) and sympathetic adrenomedullary (SAM) systems [2,3,4]. A role for HPA axis activity in mediating stress responses has been intensively investigated for decades. Cortisol is an essential hormone in the regulation of stress responsiveness. It exists in both free (active) and protein-bound (inactive) forms in serum but only in a free form in saliva. Cortisol is an essential hormone in the regulation of the stress response along the HPA axis, and salivary cortisol has been used as a measure of free circulating cortisol levels. Salivary alpha-amylase (sAA) has emerged as a novel biomarker for psychosocial stress responsiveness within the sympathetic adrenomedullary (SAM) system
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