Experimental study on GDNF expression of dorsal root ganglion in the conditioning lesions of sciatic nerve in rats

Objective To investigate the effect of sciatic nerve injury on the expression of GDNF of dorsal root ganglion(DRG)and sciatic nerve in rats.?Methods Forty five adult female Wistar rats were divided into three groups randomly: group A(n=5) served as control group, B(n=20)were subjected to sciatic nerve crush and group C(n=20) were subjected to sciatic nerve transection/ligtion. The latter two groups were further divided into four subgroups according to different survival periods (3 day, 2 week, 1 month and 2 month), respectively. The rats were sacrificed on above time points respectively. Ipsilateral L5 DRG or proximal and distal segment of injuried sciatic nerve were removed, Immunohistochemical technique was used for detection of the expression of GDNF.?Results (1)?The positive GDNF immunoreactivity was found predominantly in the small neurons of normal DRG;only a few of the large neurons also expressed GDNF weakly.(2)?Sciatic nerve injury induced significantly the expression of GDNF of primary sensory neurons in DRG which reached its peak at 2 weeks postlesion. The expression of GDNF of DRG in group B was reduced slightly at 1 month and reached control level at 2 month postlesion, however,in group C, the expression of GDNF kept at higher level at 2 month observed.(3)? GDNF of Schwann cells was upregulated in the injuried sciatic nerve distally and proximally,but this increase was more modest proximally;?the satellites in DRG was also upregulated GDNF remarkedly.Expression of GDNF in these cells continued 2 weeks in group B and 1 month in group C postlesion respectively.?Conclusion These findings suggest that GDNF is an important factor in the event following adult primary sensory neurons injury and may be involved in the trophic support to these cells.