ABSTRACT
Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide)(Fig. 1) is a naturally occurring lipophile alkaloid derived from plants of the nightshade family and is the major pungent of hot chili peppers (1). Capsaicin is an exogenous, but not an endogenous expressed, ligand at a capsaicin-specific receptor, i.e.,
Figure 1 Structural formula of capsaicin. (From Ref. 1.)
the vanilloid receptor I (VR1) (2,3). Vanilloid receptor 1 is also activated by the endogenous cannabinoid anandamide (4-6), increase in temperature (above 42°C), and protons (pH below 5.9) (2-8). Recently, other members of the vanilloid receptor family were identified (9-14). These include vanilloid receptor-like protein I (VRL-1), vanilloid receptor-like protein 2 (VRL-2), vanilloid receptor 5' splice variant (VR.5'sv), and a mechanosensitive stretchinhibitable cation channel (SIC) with different distributions in the tissues together with corresponding ligands and biological functions. However, capsaicin has been, up to now, known only to exert its functions via the VRI.
