Cannabinoid compounds include exogenous drugs such as delta9-THC, the main psychoactive component of the plant Cannabis sativa, and endogenous mediators, such as anandamide, that belong to eicosanoid family.The biological effects of cannabinoids are mediated by a family of two Gi -coupled 7-transmembrane receptors, CB1 and CB2. The CB1 receptor is found primarily in brain and mediates the psychoactive effects of cannabinoid ligands. The CB2 receptor is expressed mainly in immune cells, including mast cells and CD40-activated B cells, where it mediates proliferation and inhibition of migration. Activation of CB2 inhibits the development of liver fibrosis. In bone, CB2 is expressed in both osteoblasts and osteoclasts, and functions to prevent bone loss. In addition, activation of CB2 has an antinociceptive effect in animal models of neuropathic, inflammatory, and acute pain; this effect is mediated by release of endogenous opioids in the periphery.