Fear extinction, the learned inhibition of a fear response, is readily quantifiable in laboratory rodents and provides an important behavioral assay for translational studies of anxiety disorders, which often entail impaired extinction.1,2 Implicating the endocannabinoid system in fear extinction, brain-wide deletion of the endocannabinoid CB1 receptor (CB1R) in mice results in profoundly impaired extinction and adaptation.3,4 However, because CB1Rs are ubiquitously expressed in the brain5 and mediate manifold functions in the brain and periphery, global activation of CB1R would produce widespread effects,6,7 some clinically undesirable.
