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Previous studies have showed that the degeneration and death of retinal ganglion cells in glaucoma were accompanied with the activation of glial cells, glutamate metabolic disturbance and the release of cytokines.Here,we investigate the role of Müller cells in retinal injuries of rats after optic nerve transection.Adult Sprague-Dawley rats (200-250 g weight) were randomly divided into normal control and optic nerve transection (ONT)-injured groups, and then were assigned as 1, 3, 7, 14 and 28 d post-lesion.Double-labeling immunofluorescence staining was used to detect the expression of glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), excitatory amino acid transporters (EAAT1/GLAST), tumor necrosis factor alpha (TNF-α).Nuclei were visualized by using 4,6-diamidino-2 phenylindole (DAPI) staining.The protein expression levels of GS, GLAST and TNF-α in rat retina were determined by using Western blot analysis.We found that strong GFAP (astrocyte-specific marker)immunofluorescence signals could be observed in retina at 7-28 d post ONT when compared with that of normal control group.This enhanced GFAP expression was co-localized with GS positive cells (Müller cell-specific marker) under the view of confocal microscope.In addition, the increased expressions of GLAST were only observed in GS positive Müiler cells at 7-28 d post ONT groups by using double-labeled immunofluorescence.The results of Western blot analysis showed that GLAST protein expression levels increased significantly (P<0.05, n=4per group) in retina at 1-7 d post ONT compared with that of normal control group (n=4).Similarly, the increased protein expressions of TNF-α could be observed in glial cells at 1-28 d post ONT by using immunofluorescence staining and Western blot analysis.The further quantitative analysis results demonstrated significant increase of TNF-α protein expressions (P<0.05, n=4 per group) in retina at 3-28 d post ONT when we compared with that of nommal control group (n=4).The results suggest that the activation of Müller cells may play an important role in retinal injuries of rats after ONT by affecting the glutamate metabolism and TNF-α protein expression.The specific effects of GLAST and TNF-α on retinal ganglion cells of ONT rats need to be determined in the following experiments.