The role of nitric oxide in nociception.

Pharmacologic, electrophysiologic, and immunohistochemical studies have suggested a role of nitric oxide (NO) in nociception processing. Recent studies have indicated that NO may modulate spinal and sensory neuron excitability through multiple mechanisms that may underlie its distinctive roles in different pain states. Differential regulation of a family of NO-producing enzymes, NO synthases, contributes mainly to the complexity underlying the role of NO in nociception. This review summarizes the latest advances in our understanding of the contribution of NO to pain transduction. Possible cellular mechanisms regarding the connection between NO production and the abnormal sensation derived from different stimuli and pathologic conditions are discussed.