N-arachidonyl glycine receptor also known as G-protein coupled receptor 18 (GPR18) is a protein that in humans is encoded by the GPR18 gene. Along with the other previously "orphan" receptors GPR55 and GPR119, GPR18 has been found to be a receptor for endogenous lipid neurotransmitters, several of which also bind to cannabinoid receptors.
Research supports the hypothesis that GPR18 is the abnormal cannabidiol receptor and N-arachidonoyl glycine, the endogenous lipid metabolite of anandamide, initiates directed microglial migration in the CNS through activation of GPR18, though recent evidence demonstrates that NAGly was not shown to be a GPR18 agonist in rat sympathetic neurons.