Objective To investigate the effect of electroacupuncture stimulation at "Zusanli"(ST36) and "Kunlun"(BL60) on the morphological changes of the spinal dorsal horn and the expression of p38 mitogen-activated protein kinase(p38 MAPK) in the injured spinal cord of rats with neuropathic pain. Methods Male Sprague-Dawley rats were randomly divided into sham model group

model group

electroacupuncture group

and medication group

with 10 rats in each group. Spinal nerve ligation of the L5 lumbar vertebra was performed to establish a rat model of neuropathic pain. The rats in the electroacupuncture group were given electroacupuncture at ST36 and BL60 of the operation side with dilatational wave at a frequency of 2 Hz/100 Hz and an intensity of 1.5 mA once a day

30 minutes each time

and those in the medication group were given intraperitoneal injection of 100 mg/mL Gabapentin solution(100 mg/kg) once a day; the one-week intervention was started at one week after surgery. Mechanical withdraw threshold(MWT) and thermal withdrawal latency(TWL) were observed and recorded before modeling and on days 1

3

5

7

10

12 and 14 after modeling

and the motor function of the affected hindlimb was scored. Methenamine silver stain was used to observe the morphological changes of the spinal dorsal horn

and Western blot was used to measure the relative protein expression of p38 MAPK and phospho-p38 MAPK(p-p38 MAPK) in L4—L6 spinal segments. Results Compared with the sham model group

the model group had significant reductions in MWT and TWL at each time point(P<0.001) and a significant increase in motor function score(P<0.001); compared with the model group

the electroacupuncture group and the medication group had significant increases in MWT and TWL and a significant reduction in motor function score after treatment(P<0.05). The model group had obvious neuronal fibrillary tangles

particle vacuolar degeneration

and vacuoles containing argyrophilic grains in the cytoplasm of neural cells under a light microscope

while there were fewer neuronal fibrillary tangles in the electroacupuncture group and reduced vacuolar degeneration in the medication group. Compared with the sham model group

the model group had significant increases in the protein expression of p-p38 MAPK in the spinal dorsal horn(P<0.001)

and compared with the model group

the electroacupuncture group and the medication group had significant reductions in the protein expression of p-p38 MAPK in the spinal dorsal horn(P<0.05). Conclusion Electroacupuncture stimulation at ST36 and BL60 can increase pain threshold

improve the motor function of the affected hindlimb

and improve the necrosis of neurofibrils in the spinal dorsal horn in rats with neuropathic pain

possibly by regulating the expression of p-p38 MAPK in the spinal dorsal horn.