Vanilloid receptor antagonist capsazepine

Known antagonists of vanilloid receptors include capsazepine, which acts competitively but with low potency at the capsaicin binding sites (Bevan et al., 1992), iodo-RTX, which binds with high affinity (Wahl et al., 2001), the unselective antagonist ruthenium red (Amann and Maggi, 1991) and synthetic arginine-rich hexapeptides (Planells-Cases et al., 2000), which are putative channel blockers. 

Scheme 5 Chemical structures of known vanilloid receptor antagonists a, capsazepine, a weak but competitive synthetic compound from Novartis, b, iodo-resiniferatoxin, a potent and competitive synthetic compound from Novo Nordisk, c, ruthenium red, a weak, non-competitive and non-selective antagonists.

VANILLOID RECEPTOR ANTAGONISTS act at sites activated by sensory irritants, e.g. capsaicin see VANILLOID receptor agonists. Capsazepine, a synthetic compound developed out of vallinoids such as capsaicin, is a high-afflnity competitive vanilloid receptors antagonist. It is used as a pharmacological tool. There is some variation in affinity between different sites and species, suggesting receptor subtypes and species variants. Ruthenium Red also acts as an inhibitor at these sites in a non-competitive manner. 

---