Stress Responsivity of Endocannabinoids and Related Biomolecules in Plasma and Saliva

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.

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.

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.

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.