CB1 is a GPCR that is expressed primarily in brain and nervous tissue, and mediates numerous CNS responses such as analgesia, appetite, cognition, memory and locomotor activity. A number of cannabinoid ligands bind to CB1 and activate Gi/o-mediated downstream responses, including inhibition of cAMP production and activation of ion channels and MAP kinases. Such ligands include exogenous agonists such as Delta9-THC, the main psychoactive component of the plant Cannabis sativa, and endogenous agonists such as anandamide that belong to eicosanoid family. A number of synthetic agonists such as CP55940 and R-(+)-WIN55212, and antagonists, such as SR141716A, for CB1 have been developed. CB1 agonists have clinical utility in analgesia and antiemetic properties, whereas CB1 antagonists show promise for treatment of appetite in obesity disorders.