Objective: To investigate the expression of semaphorin 3A (Sema3A) and neuropilin 1 (NP-1) in spinal cord and dorsal root ganglion after partial dorsal root rhizotomy.
Methods: 15 adult cats were used for this study and divided into 3 groups: normal control group, 7 d and 14 d postoperative groups (7Th day and 14th day groups) undergoing unilateral partial dorsal root rhizotomy. The L3, L5 and L6 segments of spinal cord and L6 dorsal root ganglia (DRG) in operated side were made into frozen sections. By immunohistochemistry ABC method, the sections of spinal cord were stained with specific Sema3A antibody, and L6 DRG were stained with NP-1 antibody. The mean optical density (OD) of Sema3A immunoreactivity in dorsal horn was measured and the number of NP-1 positive medium-small sized neurons in spared DRG was counted.
Results: After partial dorsal root rhizotomy, in L3 segment the expression of Sema3A decreased in 7th day group (0.25 +/- 0. 14) compared with that in normal group(0. 37 +/- 0.87) (P < 0.05), but kept the level along to 14th day group (0.27 +/- 0.09); in L5 segment, the expression of Sema3A decrea sed in 7th day group (0.26 +/- 0.11) (P < 0.05), and then recovered to normal level in 14th day group (0.33 +/- 0.09); in L6 segment, OD values in dorsal horn had no changes to all groups. The number of NP-1 positive medium-small sized neurons in spared DRG (30.85 +/- 10.26) was decreased in 7th day group (P < 0.05), compared with that in normal group (45.06 +/- 12.47), while increased in 14th day group (P < 0.05).
Conclusion: Changes in the expression of Sema3A in spinal cord and the expression of NP-1 in L6 DRG after partial root rhizotomy may be involved in collateral sprouting of spared root in superficial lamina.