NO pain: potential roles of nitric oxide in neuropathic pain.

The disabling human syndrome of "neuropathic pain" is an intractable complication of peripheral nerve injury or degeneration. A complex interaction between injured peripheral axons, sensory neurons and central nervous system signaling is thought to account for it. In this brief review, we present evidence that the free radical signaling molecule, nitric oxide (NO) may act at several levels of the nervous system during the development of experimental neuropathic pain. For example, NO may directly influence injured axons in the periphery, may indirectly influence pain by its role in the process of Wallerian degeneration, and may signal in the dorsal horn of the spinal cord. While it is premature to argue for therapeutic approaches that alter NO actions, it may be an important player in the cascade of events that generate neuropathic pain.