Salivary VIP concentrations are elevated in humans after acute stress

The purpose of this research was to evaluate two salivary neuropeptides in the context of the stress response. The research was focused first and foremost on evaluating the usefulness of salivary Neuropeptide Y (NPY) and salivary vasoactive intestinal peptide (VIP) as stress indicators. Secondly, we questioned whether these markers help us in distinguishing between physical and psychological stress. Psychological stress can be experienced in a situation such as that in anticipation of an important exam or mental task. Physical stress can be experienced usually by strenuous exercise. Salivary NPY and salivary VIP are two neuropeptides that are released as a result of sympathetic and parasympathetic activity respectively. These two biomarkers are measured extensively in the blood or plasma but they are not routinely measured in saliva (Morgan et al., 2000). These neuropeptides will be evaluated in conjunction with the following salivary indicators cortisol, dehydroepiandrosterone (DHEA) (Morgan et al., 2004) and amylase (Nater et al., 2006) of the stress response. Depending on the stressful situation or stress paradigm, we used an indicator or biomarker profile in conjunction with the use of psychological assessments in order to measure the intensity of the stress response. In other situations, the biomarker profile with the aid of psychological and physical assessment tools helped us differentiate between psychological stress and physical stress. In essence, we used a matrix approach using a combination of physiological and psychological measures to develop a stress profile that could be used to determine both the degree and the nature of the stress response experienced by subjects. In this study we evaluated NPY and VIP as salivary biomarkers using different stress paradigms. We also studied the effects of the following possible confounders on the stress response: circadian variation, water, and coffee intake. Therefore, to accomplish this salivary samples were taken and s-cortisol, s- DHEA, s-amylase, s-NPY and s-VIP were measured. Assessments (Thayer Activation-Deactivation Checklist, State-Trait Anxiety Inventory, and Borg Rating of Perceived Exertion Scale) were also administered in order to evaluate the psychological state of the subjects with respect to anxiety and their perception of physical exertion. The main findings of the study indicate that a brief intense exercise lasting minutes elicited a stress response with significant increases in s-cortisol, s-DHEA, s-amylase and s-VIP. A less rigorous exercise did not elicit a stress response with no significant increases in s-cortisol, s-DHEA ,s-amylase and s-VIP. A longer intense exercise lasting hours elicited a stress response with significant increases only in s-cortisol. In addition, s-VIP displays a circadian variation which peaks with cortisol at 0800h