Changes Of GAP-43 Expression In The Spinal Cord And Its Associated Precentral Gyrus And Skeletal Muscles In Adult Rats Subjected To Spinal Cord Contusion

[Objective]: To investigate the changes in the expression of GAP-43 in the spinal cord and its associated precentral gyrus as well as gastrocnemius using immunohistochemistry and western blot technique following spinal cord contusion, and further explore the role of endogenous GAP-43 in repairing the injured spinal cord and the relationship between GAP-43 expression and spinal cord plasticity.[Materials and Methods]: 30 adult SD rats were used in this study, and they were divided into 5 groups randomly (n=6): normal group, 3 days post operation (dpo), 7dpo,14dpo and 21 dpo, and in each group two and four cats were used for immunohistochemistry and western blot respectively. Rats in the experimental groups were performed spinal cord contusion between T8 to T10 vertebral levels. Locomotor functions of hindlimbs were assessed by BBB rating scale in each group. For immunohistochemistry, rats were perfused with 4% paraformaldehyde solution under anesthetized. After perfusion, the precentral gyrus, T8 to T10spinal cords and gastrocnemius were obtained, which were then cut at 5μm thickness. Sections were randomly harvested for immunohistochemistry and ABC method was used to detect the GAP-43 positive profiles. The positive cells were observed and photographed, and then counted using manufactured square grids. For western blot, T8 to T10 spinal cords, precentral gyrus, and gastrocnemius were obtained after anesthesia and homogenized on ice. The supernatant was collected and stored at -80℃. The samples were followed by immunoblotting detection. The area and densities of protein bands were quantified using VersaDoc imaging system and the One-way AVOVA were adopted in this study. [Results]: 1, GAP-43 immunoreactivities were observed in the precentral gyrus, spinal cord and gastrocnemius. The positive products were seen only in cytoplasm. 2, Following spinal cord contusion, the expression of GAP-43 was significantly increased form 3 to 21 dpo in precentral gyrus compared with that of in normal group.3, In the spinal cord, GAP-43 expression was increased after spinal cord contusion. The increase of GAP-43 expression was occurred at 3dpo, and the expression up to the peak at 14dpo.4, In the gastrocnemius, the expression of GAP-43 was increased obviously compared with that of normal group at 3 dpo, and showed a sustaining heighten expression following spinal cord contusion. The peak was detected at 21 dpo; 4, The BBB scales of the normal rats were 21, following spinal cord contusion, the rats was partially paralysis (3), but the BBB score was increased gradually at 7 to 21 dpo and peaked at 21 dpo (19).[Conclusion]: 1, GAP-43 immunoreactivities were observed in both of the normal and experiment precentral gyrus, spinal cord and gastrocnemius, suggesting that GAP-43 played a crucial role of physiological functions in the normal and injured neurons.2, Following spinal cord contusion, GAP-43 expression was gradually increased before 14 dpo and peaked at 14 dpo in precentral gyrus and spinal cord, while GAP-43 expretion was observed to sasfain increase to 21 dpo in gastrocnemius, suggesting that there was only a similar change tendency for the GAP-43 expression in different position.3, The tendency of the motor function restoration was matched with the GAP-43 expression in cerebral spinal cord andskeletal museed, indicating that GAP-43 might play a crucial role in promoting spinal cord recovery and the changes of GAP-43 expression was involved in the mechanism of spinal cord plasticity following spinal cord contusion.