Abstract: 【Abstract】Objective: To observe the effects of different radioactivity of 125I seeds on the histomorphology of dorsal root ganglion and tissues around by implanting radioactive seeds 125I around dorsal root ganglion.Methods: The experiment were carried out using twenty four adult male Sprague-Dawley rats (220-250g), randomly assigned to four groups. the different radioactivity 125I seeds were implanted around dorsal root ganglion ,respectively named 0mCi group (n=6), 0.4mCi group(n=6), 0.6 mCi group(n=6), 0.8 mCi group(n=6). CT scan were used to check the seeds whether locating in 1cm range around dorsal root ganglion.if not in the range ,the rat must be rejected. the two rats were killed at 60 days randomly to observe the histomorphology of L5 dorsal root ganglion and the surrounding tissues. Results: the implantion of 125I seeds was successful around L5 DRG in 24 rats.(2 rats were rejected, then supplement in time), CT scan ensure exact position. The cellular swelling of the 0mCi group was moderate The cell edema was more severe , the nucleus was not in center and Karyopyknosis、fragmentation in the 0.4 mCi group. In the 0.6 mCi group, a large of DRG cell became karyolysis and nuclear condensation. Mass DRG cell revealed karyolysis、nuclear condensation and degeneration. The ratio of positive cells（the nucleus was not in center or Cytoplasmic were 73.80±2.38% in 0.8 mCi group . Conclusion 1.DRG can be injured after implanting radioactive 125I around DRG, mainly characterized by necrosis, the intensity of which were increased as radiological dose increased.

Key words: 125I seeds, dosal root ganglion, neuropathic pain, injury