OBJECTIVE  To clarify the mechanism of per-acupoint penetration of Sanfu patch, study the effects of the active ingredients of Sanfu patch including sinapine thiocyanate (SPT) and tetrahydropalmatine (THP) on TRP channels, and further evaluate the influence of activating TRP channels on the transdermal behavior of Sanfu patch.

  METHODS  The activation of TRP channels in dorsal root neurons (DRG) by the active ingredients of Sanfu patch was investigated by calcium-imaging experiments. The expressions of TRPV1 and TRPA1 in the skin of Feishu (FS) acupoints and non-Feishu (NFS) acupoints were detected by Western blot and immunofluorescence, and the changes of TRPA1 expression after administration with Sanfu patch were also measured by immunofluorescence. The effect of activating TRP channels by Sanfu patch on acupoint transdermal behavior was studied using in vivo transdermal and confocal laser 3D scanning.

  RESULTS  The active ingredient SPT in Sanfu patch could promote the influx of Ca²⁺ mediated by TRP channels. The expression levels of TRPV1 and TRPA1 channels in the skin of FS acupoints were significantly higher than those of NFS acupoints skin (P < 0.05), and TRPA1 channels decreased after sustained treatment with Sanfu patch. After the activation of TRPV1 and TRPA1 channels in the skin, the retention of SPT and THP in the skin of FS acupoints significantly increased (P < 0.05), but there was no significant effect on NFS acupoints skin.

  CONCLUSION  The active ingredient SPT in Sanfu patch has an agonistic effect on TRP channels, and the expression of TRPV1 and TRPA1 channels in FS acupoint skin is higher than those in NFS acupoint. The higher expressions of TRPV1 and TRPA1 channels and their activation by Sanfu patch are one of the mechanisms of its penetration-promoting through acupoint administration.