Objective To observe the expression of Toll-like receptor 4 (TLR4) and inflammatory cytokines,leucocytic density and permeability in retina of diabetic rat.Methods A total of 106 Brown Norway rats were randomly divided into experimental group and control group with 53 rats in each group.Diabetic model was established in experimental group by intraperitoneal injection of streptozotocin,and control rats received intraperitoneal injection of an equal volume of citric acid-sodium citrate buffer.Four weeks later,the retinas were collected for further analysis.TLR4 RNA and protein expression were measured by quantitative polymerase chain reaction and Western blot.Inflammatory cytokines,including tumor necrosis factor-α (TNF-α),interleukin-1β (IL-1β),monocyte chemo-attractant protein-1 (MCP-1),were measured by enzyme-linked immunosorbent assay in rat retina homogenate.Leukocyte density in the retina was measured by acridine orange fundus angiography.The retinal permeability was evaluated by Evans blue (EB) staining.Results TLR4 expression was significantly increased in diabetic rats of experimental group compared with non-diabetic rats of control group (F =1.606,0.789; P ＜ 0.05).Inflammatory cytokines (TNF-α,IL-1β and MCP-1) were significantly increased in retina of diabetic rats of experimental group versus non-diabetic rat of control group (F=24.622,5.758,4.829; P＜0.05).The retinal leukocyte density was (6.2±0.5) × 10-5,(2.2±0.3) × 10-5 cells / pixel2 in experimental and control group respectively,the difference was statistically significant (F=2.025,P＜0.05).The amount of retinal EB leakage was (23.41 ± 4.47),(13.22 ± 3.59) ng/mg in experimental and control group respectively,the difference was statistically significant (F=21.08,P＜0.05).Conclusion TLR4 and inflammatory cytokines expression,leucocytic density and permeability increased significantly in retina of diabetic rat.