The Effects of Capsaicin Cream on Prostaglandin-Induced Allodynia

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Abstract
Although intradermal injection of capsaicin produces acute pain and secondary hyperalgesia, long-term topical application of capsaicin cream has been used as a medication for pain relief in various pain conditions. We previously reported that intrathecal administration of prostaglandin (PG) E2 and PGF2α into mice induced touch-evoked pain (allodynia) through capsaicin-sensitive and capsaicin-insensitive afferent fibers, respectively. To clarify the mechanism of an analgesic effect by capsaicin cream, here we applied it to the tail and hind paws of mice and investigated its effects on PGE2- and PGF2α-induced allodynia. Twenty-four-hour pretreatment of mice with 0.025% or 0.05% capsaicin cream markedly alleviated allodynia induced by PGE2, but not by PGF2α. These results suggest that the topical application of capsaicin cream modulates capsaicin-sensitive afferents and ameliorates allodynia evoked by PGE2 at the spinal level.