N-arachidonyl glycine receptor also known as G-protein coupled receptor 18 (GPR18) is a protein that in humans is encoded by the GPR18gene. 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.
Resolvin D2 (RvD2), a member of the specialized proresolving mediators (SPM) class of polyunsaturated fatty acid metabolites, is an activating ligand for GPR18; RvD2 and its activation of GPR18 contribute to the resolution of inflammatory responses as well as inflammation-based and other diseases in animal models and are proposed to do so in humans. Furthermore, RvD2 is a metabolite of the omega-3 fatty acid, docosahexaenoic acid (DHA); the metabolism of DHA to RvD2 and RvD2's activation of GPR18 is proposed to one among many other mechanisms for the anti-inflammatory and other beneficial effects attributed to omega-3 fatty acid-rich diets
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