Hyperalgesic effect of intrathecally administered interleukin-1 in rats.

The present study demonstrates that intrathecal injection of interleukin-1 (IL-1) in rats at a dose of 50 pg or 500 pg induced a significant hyperalgesic effect in the hot-plate test. The hyperalgesia or the altered nociceptive responses were not considered to be the result of sensitization to the hot plate, since the nociceptive alteration caused by intrathecal administration of IL-1 stopped after 20 min. The results suggest that IL-1 can affect pain responsiveness in a dose-dependent manner and that it is able to modulate neuronal functions. Taken together, our findings and the data from the literature suggest that IL-1-induced hyperalgesia is related not only to the route of administration but also to the algesia testing method used.