Intrathecal spermine and spermidine at high-doses induce antinociceptive effects in the mouse capsaicin test

The antinociceptive effects of intrathecally (i.t.) administered high doses of spermine and spermidine, endogenous polyamines, were examined in the mouse capsaicin test. Spermine (2.5-10 nmol) and spermidine (10 and 15 nmol), when administered i.t. 5 min before the injection of capsaicin solution (1600 ng) into the plantar surface of a hindpaw, produced a significant reduction of the nociceptive behavioral response. Ifenprodil (2 and 4 nmol), an antagonist of the polyamine recognition site on N-methyl-D-aspartate (NMDA) receptor ion-channel complex, co-administered with spermine or spermidine significantly inhibited antinociception induced by both polyamines. These results indicate that spermine- and spermidine-induced antinociception may be mediated via the polyamine recognition site on NMDA receptor ion-channel complex in the mouse spinal cord.