A new pharyngitis model using capsaicin in rats.

1. Application of capsaicin solution onto the rat pharyngeal mucosa caused a well-reproducible increase in vascular permeability in the pharynx. 2. Capsaicin-induced pharyngeal inflammation was unaffected by a histamine H1 blocker and non-steroidal anti-inflammatory agents, whereas dexamethasone was effective in its inhibition. 3. FK224, a dual antagonist of tachykinin NK1 and NK2 receptors, and FK888, a selective antagonist of NK1 receptor, significantly inhibited capsaicin-induced plasma exudation in the pharynx. 4. In capsaicinized animals, the application of capsaicin solution in the pharyngeal mucosa did not induce pharyngitis. 5. These results suggest that the mechanism of the capsaicin-induced pharyngitis primarily involves tachykinins.