Involvement Of Transient Receptor Potential Vanilloid-1 Clacium Current Inhibition By Capsaicin

Capsaicin has been used as a topical analgesic to treat diverse pain conditions. We investigated the molecular mechanisms that mediate the inhibition of high-voltage-activated calcium channel currents I-Ca) using trigeminal ganglion neurons and a heterologous expression system. Capsaicin inhibited I-Ca in capsaicin-sensitive trigeminal ganglion neurons, but not in capsaicin-insensitive neurons. Single-cell reverse-transcription polymerase chain reaction revealed the expression of TRPVI only in capsaicin-sensitive neurons. Capsaicin inhibited I-Ca, in transient receptor potential vanilloid-1-expressing C2D7 cells stably expressing human N-type calcium channels, whereas capsaicin failed to inhibit I-Ca in na:ive C2D7 cells with no endogenous transient receptor potential vanilloid-1 expression. Calcium influx via transient receptor potential vanilloid-1 is not likely to play a critical role in capsaicininduced I-Ca inhibition in trigerninal ganglion neurons. I-Ca inhibition might be one of the mechanisms for the analgesic effect of capsaicin.