Cannabinoids & Stress: The Impact of Endogenous and Exogenous Cannabinoids on Anxiety Behaviors In an Acute Stress Model

Abstract

Although the impact of cannabinoids (CBs) on anxiety has been thoroughly studied, current research paradigms fail to incorporate acute stressors. The present study investigated the synthetic CB HU-210’s anxiolytic potential in an acute stress CD1 male mouse model, where the animals were subject to a 10-minute Forced Swimming (FS) test between treatment and behavioral tests. Surprisingly, HU-210 did not show anxiolytic action in the Open Field (OFT) and Elevated-Plus Maze (EPM) stressed mice as previously reported in the naïve model literature. The combination of acute stress and high HU-210 doses produced severe locomotor impairments in ambulatory movement that were not previously observed in unstressed mice. It is hypothesized that this anxiogenic phenotype results from the summation of exogenous CB treatment and stress-induced endocannabinoid (eCB) release. Subsequently, the impact of the eCB signaling on anxiety behaviors was examined. Systemic administration of KML29, the selective inhibitor of 2-AG degradative enzyme, returned stress-induced anxiety-like behaviors to baseline levels, without significantly affecting locomotion. KML29’s anxiolyticism was abolished when combined with the cannabinoid receptor antagonist AM281, implying this is a CB receptor-mediated process. A GABAA receptor agonist muscimol was co-administered with KML29 in order to pharmacologically investigate the role of GABAergic neurotransmission in this anxiolytic phenomenon, but it did not alter KML29’s effects. Collectively, these findings suggest that exogenous CBs and acute stress act synergistically in an anxiogenic manner, but that enhanced 2-AG signaling in response to stress demonstrates anxiolytic potential.