Objective: To observe the effect of electroacupuncture (EA) on incisional pain and expression of tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10) and interleukin-4 (IL-4) of cervical dorsal part of spinal cord in rats with incisional neck pain, so as to explore its analgesic mechanisms.
Methods: Eighty-four male SD rats were randomly divided into normal control, model, EA-Futu(LI18) and EA-Zusanli(ST36)-Yanglingquan(GB34, EA-ST36-GB34) groups (n=21 in each group). The incisional neck pain model was established by making a longitudinal incision along the bilateral cervical thyroid regions and repeated mechanical separation stimulation. For rats of the EA groups, EA (2 Hz/100 Hz, 1 mA) was applied to bilateral LI18 or ST36-GB34 for 30 min/ time during the surgery, and 20 and 44 h after surgery, respectively. The thermal pain threshold (TPT) of the incisional region was detected. The immunoactivity of TNF-α and IL-10 of the dorsal portion of the cervical spinal cord (C2-C5) was detected by immunofluorescence, and the expression of TNF-α, IL-10, IL-4 and IL-4 receptor (IL-4R) mRNAs was determined by quantitative real-time PCR.
Results: Compared with the normal group, the TPT of the incisional area was significantly decreased at 4, 24 and 48 h after neck-incision (P<0.05), the levels of TNF-α mRNA, IL-10 mRNA and TNF-α IL-10 immunoactivity at 24 h were remarkably increased (P<0.05), and the expression of IL-4R mRNA was considerably decreased at 24 h in the model group (P<0.05). Following EA intervention, the TPT, and expression levels of IL-4 mRNA and IL-4R mRNA were significantly increased at 24 h after surgery in the EA-LI18 group relevant to the model group (P<0.05), while the expression level of TNF-α(coexpressed with microgliacytes) in the EA-LI18 group, and TNF-α mRNA expression at 24 h in both EA-LI18 and EA-ST36-GB34 groups, as well as the expression of IL-10 and IL-10 mRNA at 24 h in both EA-LI18 and EA-ST36-GB34 groups were significantly decreased (P<0.05). The effect of EA LI18 was significantly superior to that of EA ST36-GB34 in up-regulating TPT and expression of IL-4 mRNA and IL-4R mRNA at 24 h (P<0.05).
Conclusion: EA of LI18 has an analgesic effect in incisional neck pain rats, which may be related to its effect in down-regulating the expression of TNF-α, IL-10 and promoting IL-4 /IL-4R signaling in dorsal portions of the cervical spinal cord. The analgesic effect of EA LI18 is better than that of EA ST36-GB34.
Keywords: Dorsal horns of cervical spinal cord; Electroacupuncture; Incisional neck pain; Inflammatory cytokines.