Research on flash visual evoked potential and dynamic changes of Tau and its phosphorylation in rat model of traumatic optic neuropathy

Abstract

AIM: To detect the visual dysfunction, and investigate the changes of Tau and its phosphorylated Ser396/Ser404 forms in retinas and optic nerves in traumatic optic neuropathy(TON)model rats by using FVEP technique.METHODS: Totally 30 SD rats were conducted FVEP electrode implantation. One week later, all rates were implemented TON operation with the optic nerve of left eye crushed and the optic nerve of right eye exposed(sham-operated). FVEP detections were performed respectively in these TON model rats at 1, 3, 7, 14, and 28d post crush, with 5 rats tested at each time point. After FVEP tests were taken, rats were sacrificed and then retinas and optic nerves of left eyes were separated for detecting the expression levels of Tau and pTau-Ser396/404 by Western Blot.RESULTS: Typical FVEP waves were observed in the sham-operated eyes. Compared to the sham group, the N2 waves were significantly delayed and the amplitude of N2-P2 were greatly reduced at each time point in the operation eyes. However, the differences of N2 wave and the amplitude reduction of N2-P2 were not significant at each time point after crush. The contents of total Tau protein in retinas of TON rats sharply decreased at 1d post crush, briefly recovered at 7d post crush, and remained a slightly lower level than normal condition till 28d. The changes of pTau-Ser396/404 were consistent with the changes of total Tau in retains and the Ser396 was the main phosphorylation site. However, the total Tau contents in optic nerves of TON rats increased gradually, and peaked at the 14d post crush and remained till 28d. The changes of pTau-Ser396/404 were similar to the changes of total Tau in optic nerves, which peaked at 7d post crush. However, Ser404 was the main phosphorylation site of Tau in optic nerves.CONCLUSION: The related indexes of N2 and P2 waves in FVEP can be used to detect the visual dysfunction in TON rats. After TON, the content changes of total Tau in retinas and optic nerves were much different while the changes of pTau-Ser396/404 followed the alterations of total Tau in the two locations. However, the main phosphorylation site of Tau was differnet according to the locations.

Keywords

• traumatic optic neuropathy
• flash visual evoked potential
• optic nerve
• retina
• tau proteins
• tau phosphorylation