Cyclooxygenase (COX), also known as prostaglandin G/H synthase, is a membrane bound enzyme partly responsible for the catalysis of prostanoid synthesis. COX is expressed as at least three different isoforms. COX-1 is constitutively expressed and thought to regulate a number of 'housekeeping' functions such as vascular hemostasis, renal blood flow, and glomerular function. COX-2 expression is tightly regulated and induced by inflammatory mediators such as growth factors, cytokines, and endotoxin. COX-3 appears to be much more strictly regulated spatially and is observed in greatest abundance in cerebral cortex.