Endocannabinoid system activation participates in the regulation of the acute stress response

SURKIN, PABLO NICOLÁS; FERNÁNDEZ-SOLARI, JAVIER; GALLINO, SOFÍA; RETTORI, VALERIA; CORREA, FERNANDO; DE LAURENTIIS, ANDREA

Bethesda

Simposio; Marijuana and Cannabinoids: A Neuroscience Research Summit; 2016

National Institutes of Health

Activation of the hypothalamic-pituitary-adrenal (HPA) axis is critical for the survival upon exposure to stressful stimuli. A growing body of work indicates that the endocannabinoid system (ECS) is an integral regulator of the stress response. Pharmacologically, the endocannabinoid system can be modulated by either antagonists or agonists of cannabinoid receptors or inhibition of metabolic degradation of endogenous cannabinoids with consequent increases in brain and peripheral levels. The present study focuses on ECS regulation of the hypothalamic-pituitary-adrenal (HPA) axis response to acute stress in rats.As a model of acute stress, Sprague-Dawley male adult rats were immobilizated during 30 min. Each group received intracerebroventricular (icv) injection of: anandamide (AEA, 50ng/5ul), or the inhibitor of FAAH (URB597, 50ugr/5ul), or antagonists for CB1 receptor (AM251, 500ng/5ul) or CB2 receptor (AM630, 500ng/5ul) or vehicle 15 min before the application of stress.In another set of experiments the animals received intraperitoneal (ip) injection of Methanandamide (MetAEA, 2.5mg/kg), AM251 (2mg/kg), URB597 (0.3mg/kg) or vehicule 15 min before stress. These rats were sacrificed immediately; troncal blood collected for the measurement of corticosterone by RIA and the hypothalami excised for nitric oxide synthase (NOS) activity determination. Another group of control and stressed animals were sacrificed 4 hs after stress, blood collected for corticosterone and hypothalami and adrenal glands excised for PCR determination of CB1, CB2 and TRPV1 receptors mRNAs.Finally, we performed in vitro experiments with adrenal glands from control rats incubated in Krebs Ringer buffer in a Dubnoff shaker at 37ºC for 60 min in the presence of ACTH (10-9M) with AEA (10-9M) or URB597 (3uM) or AM251 (10-5M) or vehicle. At the end of the incubation period corticosterone in media and NOS activity in the tissue were determined.Our results show that the eCB anadamide blocks the increase of corticosterone levels during acute stress at both, central and peripheral levels. At hypothalamic level both subtypes of cannabinoid receptors (CB1 and CB2) are involved while in adrenal gland anandamide inhibits corticosterone release through CB1 and vanilliod TRPV1 receptors, being necessary the action of both. Finally, nitric oxide participates as a mediator of anandamide action at hypothalamic and adrenal levels.These data indicate that an eCB tone provides a steady-state inhibition of HPA axis activity, which, when disrupted, results in activation of the HPA axis and then the eCB act to end the stress response allowing homeostasis.Therefore we conclude that eCB signaling is an important regulatory system in the brain and periphery that largely functions to buffer against many of the effects of stress. These findings also suggest that pharmacological augmentation of eCB signaling could serve as an approach to the treatment of anxiety-related disorders.