Anandamide (N-arachidonoylethanolamide), an arachidonic acid derivative, is an endogenous ligand for cannabinoid receptors, which are members of the G protein (Gi)-coupled receptors family. Ananamide is mainly found in central nervous system, immune system and uterus etc and mimics most of the effects of (－)Δ⁹-tetrahydrocannabinoid ［(－)Δ⁹-THC］, a psycoactive derivative of marijuana. Fatty-acid amide hydrolase (FAAH), which is involved in hydrolyzing anandamide to arachidonic acid and ethanolamide, may quickly regulate level of anandamide in vivo.