[Lower frequency electroacupuncture is better in promoting recovery of limb locomotion in rats with sciatic nerve injury by reducing local inflammatory reaction].

Objective: To observe the effect of different frequencies (2 Hz, 100 Hz) of electroacupuncture (EA) on limb locomotion and the expression of inflammatory factors IL-1β, IL-6, TNF-α in sciatic nerve, and nuclear factor kappa B (NF-κB) in lumber(L)4-L5of spinal cord in rats with sciatic nerve injury (SNI), so as to reveal its mechanisms underlying improvement of SNI.
Methods: A total of 48 SD rats (half male and half female) were equally divided into blank control, model, low frequency (2 Hz) EA and high frequency (100 Hz) EA groups. The SNI model was established by clamping the spinal nerve. EA intervention (2 Hz, 100 Hz, 1 mA), starting on the 8 ^th day after modeling, was applied to "Huantiao" (GB30) on the injured side for 15 min, once daily for 14 consecutive days. The sciatic function index (SFI) was calculated to assess the injured hindlimb recovery with reference to BAIN's and colleagues' methods. Histopathological changes of the sciatic nerve were displayed by H.E. staining. The expressions of IL-1β, IL-6 and TNF-α in the sciatic nerve tissue were detected by immunohistochemistry, and the expression of NF-κB in the spinal cord was detected by using Western blot.
Results: After modeling, the SFI level on day 8 was significantly decreased in the model group ( P <0.01), and no significant differences were found among the model, low frequency EA and high frequency EA groups before the EA intervention ( P >0.05). Following the treatment (at the 22 ^nd day), the SFI values of both low frequency EA and high frequency EA groups were significantly increased ( P <0.01), suggesting an improvement of the limb motor function, and the SFI of the low frequency EA group was notably higher than that of the high frequency EA group ( P <0.01). In comparison with the blank control group, the expression levels of IL-1β, IL-6, TNF-α in the sciatic nerve and NF-κB protein in the spinal cord were significantly up-regulated ( P <0.05). Following EA intervention, the increased expression levels of IL-1β, IL-6, TNF-α and NF-κB proteins were significantly down-regulated in both low frequency EA and high frequency EA groups ( P <0.05), and the therapeutic effect of low frequency EA was markedly superior to that of high frequency EA in down-regulating the expression levels of IL-1β, IL-6, TNF-α and NF-κB protein ( P <0.05). H.E. staining showed increase of Schwann cells in number, cellular swelling, and disintegration of the axons and myelin sheath, and appearance of vacuolar degeneration in the model group, which was relatively milder in both low frequency EA and high frequency EA groups, particularly in the low frequency EA group.
Conclusion: EA of GB30 at 2 Hz and 100 Hz can promote the recovery of hindlimb motor function in SNI rats, which is probably related to its function in inhibiting the inflammatory response, and facilitating the repair of the damaged sciatic nerve. 2 Hz EA is better than 100 Hz EA in the therapeutic effect.