Ruthenium red selectively prevents capsaicin-induced nociceptor stimulation

The effect of Ruthenium Red on capsaicin-induced stimulation of polymodal nociceptors was investigated in the isolated perfused rabbit ear with an intact neuronal connection. Ruthenium Red, 20 microM, completely prevented the response to capsaicin but not that to acetylcholine or bradykinin. It is therefore suggested that capsaicin activates sensory nerve terminals by a mechanism which is different from that for bradykinin or acetylcholine, and which can be blocked selectively by Ruthenium Red.