Free salivary cortisol is an established non-invasive marker of hypothalamus pituitary adrenal (HPA) axis activity. In contrast, such a well-characterized salivary marker for activity of the sympatho-adrenal medullar (SAM) system is still missing. As one potential candidate salivary alpha amylase (sAA) has been suggested. In humans increases in sAA levels have been observed in response to physiological and psychological stress. The present study aimed at exploring the effects of a pharmacological manipulation (betablockade) on sAA in the context of a stressful fMRI experiment on emotional information processing. Thirty young healthy subjects participated in a double blind group comparison study and received 80 mg of the betablocker (BB) propranolol or a placebo (PL). Salivary samples were obtained before and 90 min (pre-scan) and 135 min (post-scan) after drug application. In addition heart rate and blood pressure were assessed. During rest a significant drug by time interaction was observed, lowering sAA levels as well as heart rate and systolic blood pressure in the betablocker treatment group. During the scanning procedure, in which participants were confronted with highly negative emotional pictures, the significant increase in sAA levels in the PL group compared to the BB group persisted. No additional change was noticed in heart rate or blood pressure during scanning in the PL or BB group. The current pharmacological study in the human provides direct evidence for the sensitivity of sAA to changes in adrenergic activation, specifically in reaction to psychological stress.