Expression of IL-2 receptor in dorsal root ganglion neurons and peripheral antinociception.

Interleukin-2 (IL-2), a T-cell growth factor, could exert an antinociceptive effect. Intraplantar injection of human recombinant IL-2 (rIL-2) at a dose of 10000/20 microl significantly enhanced pain threshold as measured by paw withdrawal latency (PWL) to noxious radiant heat in the rat. Reverse transcription modification of polymerase chain reaction (RT-PCR) analysis showed that IL-2R alpha and beta chains were constitutively expressed in rat dorsal root ganglion (DRG) neurons. Immunohistochemistry further demonstrated that IL-2R was mainly localized to small and medium-sized neurons, which are predominantly responsible for nociceptive transmission. These observations suggest that IL-2/IL-2R system may affect neural activities including nociceptive processing in DRG.