Additive anti-hyperalgesia of electroacupuncture and intrathecal antisense oligodeoxynucleotide to interleukin-1 receptor type I on carrageenan-induced inflammatory pain in rats

Accumulating evidence shows that spinal interleukin-1β (IL-1β) plays a critical role in inflammatory pain. Electroacupuncture (EA) can effectively attenuate inflammatory hyperalgesia both in clinical practices and experimental studies. However, little is known about the relationship between spinal IL-1β and EA analgesia. The present study was designed to evaluate the effects of EA and antisense oligodeoxynucleotide (ODN) to IL-1 receptor type I (IL-1RI) on carrageenan-induced thermal hyperalgesia and the expression of IL-1β as well as IL-1RI. It was demonstrated that carrageenan induced marked thermal hyperalgesia in the injected paw, hence making paw withdrawal latency (PWL) decrease to 3.47 ± 0.31 s at 180 min post-injection. Nevertheless, when EA was administered for 30 min at 180 min post-carrageenan injection, the PWLs were significantly increased between 10 and 90 min following the beginning of EA treatment and peaked at 30 min to 5.91 ± 0.61 s. And also EA partly reversed the elevation of IL-1β and IL-1RI expression induced by carrageenan. Down-regulation of IL-1RI expression by repeated intrathecal antisense ODN (50 μg/10 μl) significantly increased the mean PWL up to 5.75 ± 0.15 s in 180–300 min post-carrageenan injection. Additionally, when the combination of EA with antisense ODN was used, thermal hyperalgesia was further alleviated than EA or antisense ODN alone, with a maximum PWL of 7.66 ± 0.50 s at 30 min post the beginning of EA treatment. The results suggested an involvement of the spinal IL-1β/IL-1RI system in EA-induced anti-hyperalgesia in inflammatory pain.