ABSTRACT
Evodiamine, a quinozole alkaloid constituent of Evodia rutaecarpa, has been reported previously to induce several responses comparable to capsaicin in animal systems. Here, we characterize evodiamine as an agonist for rat TRPV1 expressed heterologously in CHO cells. Evodiamine bound to rat TRPV1 with a Ki of 5.95 +/- 0.87 microM, as measured by inhibition of [3H] RTX binding (capsaicin, Ki = 1.8 +/- 0.3 microM). Evodiamine was a full agonist for induction of 45Ca2+ uptake, with an EC50 of 856 +/- 43 nM (capsaicin, EC50 = 45 +/- 4 nM) and was competitively antagonized by capsazepine, as revealed by a Schild plot. The pattern of cellular response, as determined by calcium imaging, was similar to that with capsaicin and yielded an EC(50) of 1.03 +/- 0.21 [micro sign]M. Molecular modeling suggested a consistent pattern of overlap between evodiamine and TRPV1 agonists. We conclude that evodiamine represents a novel class of agonists for rat TRPV1, albeit 3-19-fold less potent than capsaicin, and thus represents a new potential class of lead molecules for drug development.