GPR55 Receptor Antagonists: ProductsMembers of the G protein-coupled receptor (GPCR) family, such as GPR55, play important roles in signal transduction from the external environment to the inside of the cell. GPR55 is a receptor for L-alpha-lysophosphatidylinositol (LPI). LPI induces Ca2+ release from intracellular stores via the heterotrimeric G protein GNA13 and RHOA. GPR55 is expressed in the caudate nucleus and putamen, but not detected in the hippocampus, thalamus, pons cerebellum, frontal cortex of the brain or in the liver. It is expressed in osteoclasts and osteoblasts. GPR55 may play a role in bone physiology by regulating osteoclast number and function. GPR55 may also be involved in hyperalgesia associated with inflammatory and neuropathic pain.