Marsicano and Lutz provided the first detailed description of CB1 receptor mRNA expression within the mouse amygdala (Marsicano and Lutz, 1999). These authors reported the presence of both high CB1− and low CB1-expressing cells within the BLA and low levels of CB1 mRNA in the central amygdala. These authors showed that ~95% of high CB1-expressing cells co-expressed the GABAergic marker glutamic acid decarboxylase 65 (GAD65). Furthermore, almost all high CB1-expressing cells, and 90% of low CB1-expressing cells, co-express the peptide cholecystokinin (CCK). Subsequent work by this group demonstrated that 38% of CB1-expressing neurons within the BLA co-expresses corticotrophin releasing hormone receptor type-1 (CRHR1) mRNA, and all CRHR1-expressing neurons within the BLA co-express CB1 mRNA (Hermann and Lutz, 2005).
