| [Objective]: In the present study, we investigated the changes in the expression of BDNF in the spinal cord and its precentral gyrus and gastrocnemius by western blot following spinal cord transection, aiming to explore the role of endogenous BDNF in repairing the injured spinal cord and the relationship between BDNF and neuroplasticity.[Materials and Methods]: A total of 30 adult SD rats were used in this study, and they were divided into 5 groups randomly: sham-operated control group, 3d, 7d, 14d and 21d groups, among which 1 was used for immunohistochemistry and the left 5 rats were used for western blot. Rats in the control group were opened the vertebral canal only, left the spinal cord untouched, while rats in the experimental groups were performed spinal cord transected between T10-T11 vertebral levels. Locomotor functions of hindlimbs were assessed by BBB rating scale. For immunohistochemistry, animals were perfused through intracardiac administration of isotonic saline and 4% paraformaldehyde. After perfusion, the precental gyrus, spinal cord and gastrocnemius were obtained, which were then cut at 20μm thickness. ABC method was used to detect the BDNF positive profiles. For Western blot, about 1cm rostral and caudal segments of the spinal cord, precentral gyrus, and gastrocnemius were obtained after anesthesia and homogenized on ice. Samples were electrophoresed and transferred to nitrocellulose membranes. The membrane were incubated with primary antisera (BDNF 1:200) at 4°C and rinsed in TBST before final incubation in the peroxidase conjugated goat anti-rabbit IgG. It was then developed in ECL kit and exposed against X-ray film in a dark room. The One-way AVOVA were adopted in this study.[Results]: 1. BDNF positive profiles were observed in the precentral gyrus, spinal cord and gastrocnemius both of the control and leisioned rats; 2. After spinal cord transection, the expression of BDNF in the precentral gyrus were increased significantly from 3d and maintained till 21d (P＜0.05); in the rostral spinal segment of transection, it decreased at 3d, but then increased and peaked at 21d; in the caudal spinal segment of lesion, it increased since 3d and peaked between 7d and 14d, however, decreased to the control level at 21d; in the gastrocnemius, the expression of BDNF decreased gradually from 3d to 14d, and then recovered somewhat at 21d; 3. The BBB scales of the sham-operated and normal rats were 21, after spinal cord transection, the rats showed complete paralysis (0), however, spontaneous functional recovery of the rats' hindlimbs occurred during the time-course, and peaked at 21d (2.5).[Conclusion]: 1. BDNF positive profiles were observed in the precentral gyrus, spinal cord and gastrocnemius both of control and experimental groups, suggesting BDNF played essential roles in the phiological function both of the normal and injured neurons; 2. The changing tendencies of the expression of BDNF differed with each other in different tissues at different time points; 3. Spontaneous functional recovery of the hindlimbs of the cord transected rats occurred with the time-course, which suggesting endogenous mechanism involved in the repair of injured spinal cord; Since the changing tendency of the caudal cord segment was similar to that of functional recovery of hindlimbs, and the caudal part of the spinal cord was related closely with the locomotor function, we proposed that BDNF might participate the neuroplasticity of the injured neurons and contribute to the locomotor functional recovery.
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