Interleukin-2-induced antinociception in morphine-insensitive rats.
AIM
To investigate interleukin-2-induced antinociception in morphine-insensitive rats.


METHODS
Paw withdrawal latencies (PWL) to noxious radiant heat were taken as the measurement of pain threshold.


RESULTS
Intraplantar injection of human recombinant interleukin-2 (1.5 x10(4) U) significantly increased PWL in normal rats. PWL was also markedly increased by IL-2 in 45-d-post-complete Freund's adjuvant (CFA)-treated rats, which have been proven morphine-insensitive. IL-2-induced antinociception in CFA-treated rats were significantly lower than that in normal rats. IL-2-induced antinociception was partially blocked by naloxone (1 mg/kg, ip) in normal rats but remained unchanged in CFA group.


CONCLUSION
IL-2-induced antinociception is partially mediated by mu-opioid receptors. Therapeutic applications of IL-2 may also be expanded to relieve morphine-insensitive pain.