The modulatory role of endocannabinoids in sleep

Introduction. The endogenous cannabinoid, or endocannabinoid, system is present in the central nervous system (CNS) of rodents and humans. This system includes receptors, endogenous ligands and enzymes. The presence of cannabinoid receptors, called CB₁, in the CNS has been reported in the cerebral cortex, the hippocampus, the cerebellum and the brain stem. This neuroanatomical location suggests that this receptor could modify several physiological functions, such as the consolidation of memory, motor control and the generation of sleep. Development. Recent reports have described the presence of lipids in the CNS that bind to the CB₁ receptor. Administration of said molecules induces cannabimimetic effects, and hence it has been suggested that these lipids are endogenous cannabinoids or endocannabinoids. Anandamide, 2-arachidonylglycerol, virodhamine, noladin ether and N-arachidonyldopamine are molecules that belong to the endocannabinoid family. Anandamide has received more attention from researchers because it was the first endocannabinoid to be reported. Pharmacological experiments have shown that this endocannabinoid induces several different intracellular and behavioural changes. Conclusions. In this study, we review the most important pharmacological aspects of exogenous cannabinoids and the neurobiological role played by the endocannabinoid system, including endogenous and exogenous ligands and receptors. We also examine their pharmacological effects on different behaviours, with particular attention given to the modulation of sleep.