Prostaglandin D2 ethanolamide (PGD2-EA) is a bioactive lipid produced by the sequential metabolism of anandamide (arachidonoyl ethanolamide) by cyclooxygenase (COX) enzymes, in particular by COX-2, and PGD synthase. The biosynthesis of PGD2-EA from anandamide can also be increased when anandamide metabolism is diminished by deletion of fatty acid amide hydrolase. PGD2-EA is inactive against recombinant prostanoid receptors, including the D prostanoid receptor. It increases the frequency of miniature inhibitory postsynaptic currents in primary cultured hippocampal neurons, an effect which is the opposite of that induced by anandamide.. PGD2-EA also induces apoptosis in colorectal carcinoma cell lines.