NMDA And Its Receptor Mediated Up-regulation Of COX-2 Expression In The Spinal Dorsal Horn During Nociceptive Inputs In Rats

Objective: Prostaglandins (PGs) play an important role in the nociceptive transmission at the spinal cord. Cyclooxygenases (COXs) are the key enzymes catalyzing the synthesis of PGs. Three isozymes of COX have been identified. COX-1 is thought to be a constitutive or supported enzyme, and expresses universally in various cells of normal organism. It catalyzes the production of PGs to preserve the integrity of the gastric mucosa, renal function, endotheliocyte of blood vessel and function of thrombocyte. COX-2 is a form highly inducible in response to various nociceptive stimuli. PGs catalyzed by COX-2 induce the delivery of inflammatory mediators, which induce pain, inflammation, and the activation of immune cells. COX-3 was cloned by Chandrasekhavan in 2002. Little is known about the function of COX-3.In the pain and hyperalgesia induced by neciceptive stimulation, COX-2 and PGs play an important role. Oral administration or intrathecal injection of nonselective COX inhibitors or selective COX-2 inhibitors produced equally antinociceptive effect and the selective COX-2 inhibitors reduced hyperalgesia in a dose-dependent manner. Electro-...