MG(0:0/20:4(5Z,8Z,11Z,14Z)/0:0), also known as 2-arachidonoylglycerol (2-AG), is a unique molecular species of monoacylglycerol isolated in 1995 from rat brain and canine gut as an endogenous ligand for the cannabinoid receptors. 2-AG is rapidly formed from arachidonic acid-containing phospholipids through increased phospholipid metabolism, such as enhanced inositol phospholipid turnover, in various tissues and cells upon stimulation. 2-AG binds to the cannabinoid receptors CB1 and CB2 and exhibits a variety of cannabimimetic activities in vitro and in vivo. 2-AG is an endogenous cannabinoid (endocannabinoid). Endocannabinoids are a class of fatty acid derivatives defined by their ability to interact with the specific cannabinoid receptors that were originally identified as the targets of delta9-tetrahydocannabinol (delta9-THC), the psychoactive component of cannabis. Endocannabinoids have been implicated in a growing number of important physiological and behavioral events. Endocannabinoids are amides, esters, and ethers of long-chain polyunsaturated fatty acids, which act as new lipidic mediators. 2-AG is one of the main endogenous agonists of cannabinoid receptors, able to mimic several pharmacological effects of delta9-THC, the active principle of Cannabis sativa preparations like hashish and marijuana. The activity of AEA and 2-AG at their receptors is limited by cellular uptake through an anandamide membrane transporter (AMT), followed by intracellular degradation. A fatty acid amide hydrolase (FAAH) is the main AEA hydrolase, whereas a monoacylglycerol lipase (MAGL) is critical in degrading 2-AG.