ABSTRACT
Objective:To investigate the effect of treadmill training on spasticity and the expression of potassium chloride co-transporter 2 (KCC2) after blocking BDNF-TrkB signaling pathway in rats with incomplete spinal cord injury (SCI).Methods:Forty female Sprague-Dawley rats were randomly divided into a sham-operation group (Sham group), an SCI+ phosphate-buffered saline group (SCI/PBS group), an SCI-treadmill training+ PBS group (SCI-TT/PBS group), an SCI/TrkB-IgG group and an SCI-TT/TrkB-IgG group. All of the rats underwent 1 week of intrathecal catheterization, and then T 10 incomplete SCI was induced. In the Sham group the spinal cord was only exposed. Seven days later, BDNF-TrkB signaling was blocked in the SCI/TrkB-IgG and SCI-TT/TrkB-IgG groups using the TrkB-IgG. The remaining three groups were controls treated with PBS. The SCI-TT/PBS and SCI-TT/TrkB-IgG groups began exercising 7 days after the SCI and continued for 4 weeks. The spasticity in their hind limbs was assessed using the Asworth assessment and H reflex (H-max/M-max ratio). The expression of KCC2 in the distal spinal cord was detected using western blotting and immunohistochemistry. Results:After the SCI the average Ashworth spasticity grades of the four SCI groups increased significantly compared with the Sham group. The average Ashworth spasticity grade of the SCI-TT/PBS group was significantly lower than those of the SCI/PBS and SCI/TrkB-IgG groups in the 3rd through the 5th week, and the SCI-TT/PBS group′s average grade was significantly less than that of the SCI-TT/TrkB-IgG group after 4 weeks. Within 5 weeks the average H-max/M-max ratio of the Sham group remained unchanged, significantly lower than the other 4 groups′ averages. There was no significant difference in the H-max/M-max ratio among the 4 groups of injured rats within 2 weeks after the SCI, but after 3-5 weeks the average H-max/M-max ratio of the SCI-TT/PBS group was significantly lower than those of the SCI/PBS, SCI/TrkB-IgG and SCI-TT/TrkB-IgG groups. At the 4th and 5th week the average H-max/M-max ratio in the SCI-TT/TrkB-IgG group was significantly lower than that in the SCITrkB-IgG group. And after 5 weeks the average expression of KCC2 in the anterior horn of the injured spinal cord was significantly lower in the 4 SCI groups than in the Sham group. Exercise significantly increased the expression of KCC2 in the SCI-TT/PBS group, and its immune intensity and relative optical density were significantly higher than those in the SCI/PBS, SCI/TrkB-IgG and SCI-TT/TrkB-IgG groups. However, there was no significant difference between the SCI/TrkB-IgG group and the SCI-TT/TrkB-IgG group.Conclusions:Treadmill training can improve spasticity after incomplete SCI and the expression of KCC2 in the distal spinal cord, at least in rats.