Endocannabinoids are amphiphilic molecules which are synthesized from phospholipids in the nervous system. Together with their G-protein coupled receptors they form the endocannabinoid system. The best studied endocannabinoids are the N-arachidonylethanolamide (anandamide) and the 2-arachidonoylglycerol (2-AG). They consist of an amide or an ester head, and linked with an arachidonyl chain.