The primary eCBs are anandamide (AEA) and 2-arachidonoylglycerol (2-AG) (reviewed in [5]). Anandamide (N-arachidonoylethanolamine) was the first endogenous cannabinoid-like substance to be identified [33], which was then followed by 2-AG [34,35]. Both AEA and 2-AG were characterized as endogenous ligands by their capacity to bind and modulate CB1R and CB2R. Other endogenous molecules capable of modulating CB1/CB2 receptors have also been identified [36] and these include 2-AG ether [37], N-arachidonoyl-dopamine [38], O-arachidonoyl ethanolamine, [39], and oleamide [40]. However, the physiological roles of these latter substances have not been completely established yet [5].
