Stress Responsivity of Endocannabinoids and Related Biomolecules in Plasma and Saliva

Introduction: The endocannabinoid system regulates numerous physiological functions, including the stress response, and is frequently implicated in stress-related disorders. Understanding how this system is altered during stress is therefore critical for both diagnostic and therapeutic applications. The primary ligands of the endocannabinoid system, N-arachidonoylethanolamine (AEA) and 2-arachidonoyl glycerol (2-AG), are measurable in circulation and are commonly used to assess endocannabinoid function under various conditions in humans. More recently, endocannabinoids have also been detected in saliva; however, the physiological relevance of their salivary responses remains poorly understood. The present study, therefore, aims to compare stress-induced changes in endocannabinoid and related molecule levels in saliva and plasma, with the goal of advancing understanding of stress-related alterations in salivary endocannabinoids. Methods: The Maastricht Acute Stress Test was used to induce acute stress in 59 participants, with plasma and saliva samples collected at baseline, immediately after stress, and 25-min post-stress. Stress-induced changes in AEA, 2-AG, N-palmitoylethanolamine, N-oleoylethanolamine, arachidonic acid, cortisol, cortisone, and dehydroepiandrosterone sulfate (DHEA-S) were measured using liquid chromatography-tandem mass spectrometry. Norepinephrine was also analyzed in plasma using an enzyme-linked immunosorbent assay. Changes over time and associations among these analytes in response to stress were then examined. Results: Salivary endocannabinoid concentrations were independently stress-responsive of those in plasma, suggesting they reflect distinct physiological functions. Although changes in salivary endocannabinoid concentrations were not associated with changes in plasma norepinephrine, post-stress changes in salivary 2-AG correlated with changes in DHEA-S and subjective stress ratings. Conclusions: The findings from this study provide new evidence that salivary endocannabinoids offer a novel approach to examining the endocannabinoid system during the stress response and may reflect its crosstalk with other physiological systems.