The emerging role of the endocannabinoid system in the sleep-wake cycle modulation.

The endocannabinoid system comprises amides, esters and ethers of long chain polyunsaturated fatty acids. Narachidonoylethanolamide (anandamide; ANA) and 2-arachidonoylglycerol (2-AG) are endogenous cannabinoids (endocannabinoids) ligands for the cannabinoid family of G-protein-coupled receptors named CB1 and CB2. Endocannabinoids are released upon demand from lipid precursors in a receptor-dependent manner and behave as retrograde signaling messengers, as well as modulators of postsynaptic transmission, interacting with other neurotransmitters systems. The two principal enzymes that are responsible for the metabolism of ANA and 2-AG are fatty acid amide hydrolase and monoacylglycerol lipase, respectively. Pharmacological experiments have shown that the administration of endocannabinoids induce cannabimimetic effects, including sleep promotion. This review will focus on some of the current evidence of the pharmacological potential of the endocannabinoid system on sleep modulation.