Salivary alpha-amylase and noradrenaline responses to corticotropin-releasing hormone administration in humans

- Sympathetic activation induced by peripheral administration of corticotropin-releasing hormone increased NA and sAA activity levels.
- Correlation analysis revealed no associations between NA and sAA at any measured time point.
- However, total increase of NA production (area under the curve with respect to increase) significantly correlated with sAA activity.

Salivary alpha-amylase (sAA) is a digestive enzyme mainly responsible for the hydrolysis of starch and glycogen in the oral cavity. Since the secretion of sAA is largely under the control of the sympathetic nervous system, sAA activity is also considered to be a non-invasive marker of sympathetic activation. However, the direct association between sAA activity and other sympathetic parameters remains questionable. Therefore, we employed the corticotropin-releasing hormone (CRH) stimulation test to pharmacologically activate the sympathetic nervous system and to analyze plasma noradrenaline response together with sAA activity. Thirty-one healthy male volunteers (mean age of 25.2 ± 3.1 years) were randomized into two groups and received injections with either CRH (100 μg, N = 17) or placebo (0.9% NaCl, N = 14). Blood samples were taken at baseline and 15, 30, 60, 120 min after injection. Results showed that CRH administration increased plasma noradrenaline and cortisol concentrations, sAA activity, heart rate, as well as self-reported side effects (i.e. flushing in the facial area, heart rate changes, giddiness, malaise and restlessness) and stress perception, while plasma adrenaline levels remained unaffected. In the CRH group, the total increase of sAA activity significantly correlated with noradrenaline release, indicating that sAA activity reflects pharmacologically induced sympathetic activation.