The CB1 receptor is a membrane associated G-protein coupled receptor that is expressed widely, but not exclusively, within the central nervous system. The CB1 receptor is activated by the principle psychoactive constituent of Cannabis sativa, Δ9-tetrahydrocannabinol (THC), as well as synthetic and endogenous ligands (Pertwee, 2005). In situ hybridization (ISH) studies in developing and adult rodents and humans have repeatedly classified CB1-expressing neurons into two groups: low-expressing and high-expressing. High CB1-expressing cells are sparsely distributed within the BLA and other cortical structures, whereas low CB1-expressing cells are more evenly distributed and found within both the BLA and centromedial nuclei (Mailleux and Vanderhaeghen, 1992; Matsuda et al., 1993; Marsicano and Lutz, 1999; Chhatwal et al., 2005; Hermann and Lutz, 2005; Yoshida et al., 2011).
