Interleukin 2-induced antinociception partially coupled with mu receptor

The present study was designed to investigate the involvement of CI recepto r in interleukin 2-induced antinociception. Intraplantar injection of human recombinant interleukin 2 (rIL-2) (1.5 x 10(4) U) significantly enhanced p ain threshold as measured by paw withdrawal latencies (PWLs) to noxious rad iant heat in normal rats. After administration of rIL-2, PWLs were also mar kedly increased in morphine-tolerant and chronic constriction injury (CCI)- operated rats, which have been proven morphine-insensitive. rIL-2-induced a ntinociception in both morphine-tolerant and CCI-operated rats was signific antly lower than that in normal rats. rIL-2 antinociception was partially b locked by naloxone(1 mg/kg i.p.) in normal rats but remained unchanged in t he CCI group. Our results suggest that the use of rIL-2 in human medical pr actice may be extended for its effectiveness in relief of neuropathic pain induced by CCI. Here we infer that mu receptor plays an critical role in IL -2-induced antinociception and that there are also some other receptors inv olved in this process. (C) 2000 Academic Press.