Olopatadine attenuates the enhancement of capsaicin-evoked substance P release by bradykinin from cultured dorsal root ganglion neurons.

Olopatadine, a second-generation antihistamine, has recently been suggested to have an inhibitory effect on the tachykinin release from guinea-pig tracheobronchial smooth muscle preparation. In the present study, using a highly sensitive radioimmunoassay for substance P, we observed that olopatadine attenuated the enhancement of capsaicin-induced substance P release by bradykinin with an IC(50) value of 12.5 microM, without any inhibitory effect on the substance P release induced by capsaicin, potassium or bradykinin from cultured dorsal root ganglion neurons. These data suggest that olopatadine may therefore be involved in the bradykinin-induced sensitization of the transient receptor potential vanilloid 1 in cultured dorsal root ganglion neurons.