Abstract: Objective To investigate the phased expression of gene and protein of NogoA and its receptor (NgR) that affects axon growth of spinal cord injury (SCI), and to explore the time window effect of electroacupuncture on SCI rats. Methods A total of 144 female Sprague-Dawley rats were randomly assigned to sham operation group (group A, n=48) and model group (n=96). In the model group, Allen's method was used to establish SCI rats model, and they were further subdivided into model control group (group B, n=48) and electroacupuncture group (group C, n=48). Group C received electroacupuncture on Dazhui (GV14), Yaoyangguan (GV3), bilateral Ciliao (BL32) and Zusanli (ST36) with loose-tight wave, for 20 minutes every day, one day, seven days and 14 days after modeling. The rats at every interventional therapy time were randomly subdivided into two subgroups, which accepted seven or 14 days of treatment. Groups A and B were killed and the injured spinal cord tissue was extracted one day, three days, seven days, 14 days and 28 days after modeling, group C at the corresponding time. The hind limb motor function was assessed with BBB score before all of rats were killed. Four samples at every time in each group were randomly selected to detect the expression of mRNA and protein of NogoA and NgR at different stage of SCI using reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) and Western blotting.Results The BBB score began to increase 14 days after modeling, and significantly increased until 28 days after modeling (P<0.05), compared with one day, three days and seven days after modeling in group B. The BBB score increased in group C than in group B at all the time points (P<0.05), except 14 days after electroacupuncture one day after modeling. The BBB score was higher as electroacupuncture intervening seven days and 14 days after modeling than that at one day after modeling in group C, and no significant difference was found between seven days and 14 days of treatment at either electroacupuncture time point (P>0.05). The expression of gene and protein of NogoA and NgR in group B was in the increasing tendency after SCI, and was at the peak until 21 days after modeling, and was higher in group B than in group A at each time point (P<0.01). The expression of gene and protein of NogoA decreased at all the time points in group C than in group B (P<0.05), except seven days of electroacupuncture intervening one day after modeling in the expression of NogoA mRNA (P>0.05). The expression of gene and protein of NogoA and NgR was lower as electroacupuncture intervening 14 days after modeling than one day after modeling in group C (P<0.05). There was no significant difference in the expression of gene and protein of NogoA and NgR between electroacupuncture intervening 14 days and seven days after modeling, and seven days and one day after modeling (P>0.05); as well as between seven days and 14 days of treatment at each time point (P>0.05).Conclusion Elerctroacupuncture could improve the hind limb motor function, which may associate with the inhibition of the expression of gene and protein of NogoA and NgR in injured spinal cord of rats after SCI. Elerctroacupuncture is effective in the treatment of SCI at the early time, however, it is much better in the recovery stage.

Key words: spinal cord injury, electroacupuncture, time window effect, NogoA, NgR, rats