Endogenous cannabinoid ligand that acts as a potent agonist at GPR55 (EC50 values are 3, 519 and 618 nM at GPR55, CB1 and CB2 respectively; Ki values are 472 and 1400 nM at CB1 and CB2 respectively). Found in the brain at concentrations 1000-fold higher than that of anandamide. Effects are enhanced by combined administration with 2-palmitoylglycerol (Cat. No. 2206) in vivo.