The effects of capsaicin cream on prostaglandin-induced allodynia

Although intradermal injection of capsaicin produces acute pain and seconda ry hyperalgesia, long-term topical application of capsaicin cream has been used as a medication for pain relief in various pain conditions. We previou sly reported that intrathecal administration of prostaglandin (PG) E-2 and PGF(2 alpha) into mice induced touch-evoked pain (allodynia) through capsai cin-sensitive and capsaicin-insensitive afferent fibers, respectively. To c larify the mechanism of an analgesic effect by capsaicin cream, here we app lied it to the tail and hind paws of mice and investigated its effects on P GE(2)- and PGF(2 alpha)-induced allodynia. Twenty-four-hour pretreatment of mice with 0.025% or 0.05% capsaicin cream markedly alleviated allodynia in duced by PGE(2), but not by PGF(2 alpha). These results suggest that the to pical application of capsaicin cream modulates capsaicin-sensitive afferent s and ameliorates allodynia evoked by PGE(2) at the spinal level.