Involvement of spinal neurotrophin-3 in electroacupuncture analgesia and inhibition of spinal glial activation in rat model of monoarthritis.

UNLABELLED: Although electroacupuncture (EA) has been proven to effectively relieve pain associated with arthritis, the underlying mechanism of EA analgesia requires further investigation. Here, the involvement of spinal neurotrophin-3 (NT-3) in EA's analgesic effects on complete Freund's adjuvant (CFA)-induced inflammatory pain was examined. The present study demonstrated that: 1) repeated EA stimulation of ipsilateral GB30 and GB34 acupoints remarkably suppressed CFA-induced hyperalgesia; 2) EA treatment markedly enhanced the upregulation of spinal NT-3 mRNA and protein levels following CFA injection; 3) antisense oligodeoxynucleotides (ODN) specifically against NT-3 intrathecally administered during EA treatment for 7 days significantly attenuated the EA analgesia; and 4) the suppressed expression of spinal GFAP (astrocytic marker), OX-42 (microglial marker) as well as proinflammatory cytokines, interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α by EA treatment was significantly attenuated following NT-3 antisense ODN delivery. These results suggested that endogenous NT-3 may be involved in the analgesic effect of EA on inflammatory pain in rats, mediated through the inhibition of spinal glial activity as well as proinflammatory cytokine production. PERSPECTIVE: The present study may initiate a discussion on the possible roles of NT-3/glia/cytokines in the therapeutic effects of acupuncture and provide insight on the mechanism underlie the analgesic effects of acupuncture on pain associated with arthritis.