Study on the rat＇s dorsal root ganglion after ^125I brachytherapy

Objective To observe the changes of the ultrastructure of dorsal root ganglion （DRG） and the behaviors of hind limb after implantation of radioactive 125I seeds around the DRG in rats. Methods 36 adult male Sprague-Dawley rats were randomly divided into three groups with different radioactivity 125I seeds implanted around DRG, named control group （no irradiation, n=12）, low radioactivity group （14.8 MBq, n=12） and high radioactivity group （29.6 MBq, n=12）. The paw withdrawal threshold and combined behavior score were observed 24 h prior to seed implantation and at 48, 168, 336, 720 and 1440 h after the treatment. Two rats were killed at 336 h and 1440 h to observe the ultrastructure of L5 DRG. Results Compared to the control without operation, PWT of the high radioactivity group were significantly higher than that of other groups （t=2.972,P〈0.05）. The in most of DRG low radioactivity group at 336 h were normal with a few abnormal cells. The DRG at 1440 h in low radioactivity group and in at 336 h high radioactivity group showed nuclear membrane buckling, nucleolus-set, mitochondrial swelling, lysosome increase, endoplasmic reticulum dilation and vacuolization. At 1440 h in the high radioactivity group, most of nuclear membrane invaginated, part of nuclear membrane obscured and mitochondrial swelled, but nuclear pyknosis and apoptotic body were not observed. Conclusions DRG can be injured after implantation of radioactive 125I around DRG, and the threshold of mechanical pain would be elevated after implanting radioactive 125I seeds. Key words: ^125I seeds Brachytherapy Dosal root ganglion Injury