Journal of Psychopharmacology 26(1) 3 –6 © The Author(s) 2012 Reprints and permission:

jop.sagepub.com Although the pharmacological and medicinal properties of the plant Cannabis sativa have long been known and appreciated, the discovery of the endocannabinoid system began with the isolation of Δ9-tetrahydrocannabinol (THC), the major psychoactive com-ponent of the plant, in the mid-1960s (Gaoni and Mechoulam, 1964). Extensive pharmacological studies followed, and, by the end of the last century, the endogenous cannabinoid (endocan-nabinoid) system was known to comprise at least two metabo-tropic receptors, cannabinoid receptor types 1 and 2 (CB1 and CB2); two endogenous ligands, the ethanolamine of arachidonic acid, also known as anandamide (AEA), and 2-arachidonoyl-glyc-erol (2-AG); and the enzymes responsible for their synthesis and catabolism. However, in the last decade (2000–2010), our under-standing of the endocannabinoid system has experienced a tru