Abstract:  Objective To observe the expression and significance of phosphorylated tau protein in the optic nerve of nomal and chronic ocular hypertension rats model. Design Experimental study. Participants 43 Sprague-Dawley（SD） rats. Methods Three rats whose average intraocular pressure (IOP) was above or below the normal range were excluded after adaptive domestication and successive measurement for 3 days. Chronic ocular hypertension model was established by ligating four episcleral veins in 40 rats. 14 rats died during the experiment, the IOP of 5 rats did not elevated. The remaining 21 rats whose IOP was increased were randomly divided into two groups: one group enucleated at 7 days after IOP elevating(10 rats), and another group enucleated at 14 days after IOP elevating (11rats). Tono-pen XL tonometer was used to measure IOP at the time before and right now after operation, and also 3 days, 7 days, 14 days after the operation. The optic nerve samples were harvested for observing the expression of Tau［pS396］ in the normal and model eyes by immunohistochemistry at 7 days or 14 days respectively. The immunohistochemistry image was acquired with laser scanning confocal microscopy, then analyzed with Image pro plus 6.0. Main Outcome Measures IOP, the expression of Tau［pS396］(integrated optical density). Results The IOP of experimental eyes instantly reached a peak after operation and significantly higher than that of the control group（P<0.01）, and then gradually decreased after 7 days. The positive expression of Tau［pS396］ was detected in all the normal and model eyes. Compared with control eyes, the expression of Tau［pS396］ was increased at 7 days, and decreased at 14 days （P<0.05）. Conclusions Abnormal hyperphosphorylation of tau protein may play a role in the axon damage of retinal ganglion cells during the exposure of chronic ocular hypertension, and glaucoma may share a common mechanism with the damage of neuronal cells in neurodegenerative diseases.

Key words: glaucoma, animal model, chronic ocular hypertension, phosphorylated tau protein, optic nerve