Creation of standard animal model of optic nerve injury in rats

Objective To create a standard animal model of optic nerve injury in rats.Method The right and left optic nerves of Wister rats were beaten with the pressure of 6.9±0.6atm and 2.4±0.2atm respectively using fluid percussion brain injury device(FPI).Flash-visual evoked potential(F-VEP),orbital magnetic resonance imaging(MRI),histopathological examines of retinae and optic nerves were taken before and 1,3days,1,2,4,6,8 weeks after injury for evaluation.Results(1) F-VEP showed the latency prolonged and the amplitude decreased after injury compared to the values before injury,the changes were significant(P0.05).The changes were more significant in severe injury eyes than that in mild injury eyes(P0.05).(2) Orbital MRI showed that abnormal high signal could be seen on optic nerve after injury,8 weeks after injury the injured segment of optic nerve still showed high signal and the signal of optic nerve on the globe side of the injury part was uneven.The difference between severe and mild injury groups was not obvious.(3) 1 day after injury ruptured capillary could be seen in ganglion cell layer(GCL),4 weeks after injury cells in each layer arranged sparsely and disorderedly,in some RGCs chromatin became dense,8 weeks after injury the cells in each layer became fewer and large amount of RGCs without nucleus could be seen.(4) 4 weeks after injury the axons of the optic nerve atrophied and degenerated,and the myelin sheath swelled;8 weeks after injury,new axons which displayed in clusters and well-developed could be seen adjacent to the protuberances of astrocyte and the vessels.The new axons could be easily seen in mild injury group. Conclusions A standard animal model of optic nerve injury in rats can be successfully created using FPI.