GPR55 in the CNS

The identification of GPR55 as a possible cannabinoid receptor generated a flurry of interest as based on the hope that this receptor might explain some of the non-CB1/CB2/TRPV1 effects of cannabinoid compounds. However, it rapidly became clear that the pharmacology and signaling of GPR55 were quite complicated. Work over the last few years has found that lysophosphatidyl inositol is a major endogenous ligand for GPR55, with phytocannabinoids and endocannabinoids having a lesser role. This review briefly summarizes our current understanding of GPR55 signaling and its role in the central nervous system.