The enzyme Cox-2 (cyclooxygenase-2), released at sites of inflammation, stimulates the production of prostaglandin E₂, which promotes a region of localized hypersensitivity surrounding the injury. Non-steroidal anti-inflammatory drugs (NSAIDs) are thought to give pain relief by targeting Cox-2 at sites of inflammation. But two studies published in 22 March Nature show that local inflammation can also cause pain in nearby non-inflamed areas through mediators, such as the pro-inflammatory cytokine interleukin-1β, that upregulate the production of Cox-2 in the central nervous system (CNS).

Tarek Samad, of the Massachusetts General Hospital, and co-workers observed that local inflammation in the rat paw led to a generalized increase in Cox-2 mRNA expression in spinal cord neurons and in other areas of the CNS (Nature 2001, 410:471-475). Cox-2 induction was associated with elevated levels of interleukin-1β and prostaglandin E₂ in the cerebrospinal fluid. When interleukin-converting enzyme or a Cox-2...