[Effect of partial dorsal root rhizotomy on expression of GDNF and FGF-2 in spared dorsal root ganglia].

OBJECTIVE:To explore the temporal change on the expression of GDNF and FGF-2 in spared dorsal root ganglia after partial dorsal root rhizotomy. METHODS:Fifteen cats were divided into the normal group, and the partial dorsal root rhizotomy groups. The partial dorsal root rhizotomy groups were sacrificed on day 7 or 14 and the L6 dorsal root ganglia were taken out from each animal and were made into frozen sections 20 microm in thickness respectively. The sections were stained under the same condition using specific GDNF (1 : 500) and FGF-2 (1 : 500) antibody by ABC method. The GDNF and FGF-2 positive large-sized, and medium-small-sized neurons in DRG were counted in each group. All data were analyzed by q test. RESULTS:GDNF immunoreactivity was observed in both large-sized and medium-small-sized DRG neurons. The number of total positive neurons decreased 7 days after partial dorsal root rhizotomy, and was still small after 14 days. Interestingly, the tendency in the number of positive medium-small-sized DRG neurons was just the same as that of total positive neurons while the positive large sized neurons displayed no difference between the 7th day group and the 14th day group, though the number also decreased after operation. FGF-2 immunoreactivity was noted in both large sized and medium-small-sized DRG neurons. After partial dorsal root rhizotomy, the number of total positive neurons decreased on the 7th day and came back to normal level on the 14th day. The number of positive medium-small sized neurons also showed declination followed by escalation, just the same as that of total positive neurons while the number of positive large-sized neurons exhibited no difference between the normal group and the rhizotomy groups. CONCLUSION:Partial dorsal root rhizotomy can lead to continuously declination of total GDNF immunoreactive neurons in spared ganglia, till the 14th day. FGF-2 expression showed declination on the 7th day, but returned to normal level on the 14th day after partial dorsal root rhizotomy. These findings indicate that the expression change of GDNF and FGF-2 after partial dorsal root rhizotomy correlates with the plasticity of spinal cord.