Objective: To investigate the spatiotemporal change rule of NGF, BDNF, NT-3 and their mRNA expression in spinal cord of cats after partial dorsal rhizotomy.
Methods: Rhizotomy of unilateral L1-L5, L7-S2 dorsal roots of cats was performed, leaving L6 as a spared dorsal root. By using ABC immunohistochemistry and in situ hybridization techniques, the dynamic changes of the above three factors and their mRNA in spinal lamina II of different segments were analysed.
Results: 1. In normal cat, NGF and it's mRNA were detected in part of neurons; BDNF, in nerve fiber terminals, varicosities and neurons; NT-3, in part of neurons, neuroglias and few nerve fiber terminals and varicosities. The mRNAs of the later two were negative. 2. The population of NGF and NGGmRNA positive neurons, NT-3 positive neurons and neuroglias increased significantly 3d-5d after rhizotomy. However, the quantity and density of positive varicosity of BDNF decreased. At 10-11d, the population of NGF and NGF mRNA positive neurons was still on the high level as that at 3-5d, and that of NT-3 began to decrease; the quantity of BDNF recovered to normal except for L, segment, but the density of positive varicosity of BDNF did not yet. The mRNAs of BDNF and NT-3 were still negative. 3. The change of each factor varied with the segments. The highest level time of NGF was earlier in L5, L6 than in L3; the recovery of the quantity of BDNF was the latest in L7; the change of NT-3 positive neuroglia was the same at each segment, but the number of NT-3 positive neuron in L5, L7 returned to normal at 10-11d, and that of L3 did not.
Conclusion: The three factors all play roles in spinal plasticity after partial rhizotomy, but they function at different time phase and last different time length.