Sensory neuron-specific actions of capsaicin: mechanisms and applications.

Capsaicin acts specifically on a subset of primary afferent sensory neurons to open cation-selective ion channels, probably by interacting directly with a membrane receptor-ion channel complex. Another plant product--resiniferatoxin--has structural similarities to capsaicin and opens the same channels, but is up to 10,000 times as potent. Capsaicin-sensitive neurons are involved in nociception, are responsible for the neurogenic component of the inflammatory response and may also have efferent actions in the peripheral target tissues. In addition to its excitatory actions, capsaicin can have subsequent antinociceptive and anti-inflammatory effects. For these reasons Stuart Bevan and János Szolcsányi argue that drugs based on capsaicin and resiniferatoxin may have important clinical uses.