[A model of calibrated optic nerve crush injury in rats]

To establish a calibrated optic nerve crush injury model in rats.

Twenty-eight healthy Sprague-Dawley (SD) rats were randomly divided into two groups. Seven rats were in normal control group, i.e. group A. In group B, model of partial optic nerve crush injury group, partial optic nerve crush injury model was induced in the right eyes of another 21 rats by a special designed optic nerve clip with 40-gram holding force at optic nerve 2 mm behind the eyeball clipped for four seconds to partially block the optic nerve axoplasmic transport. The left eyes served as a control. According to the sacrificing date of the rats, three subgroups in group B were further divided. Therefore, seven rats were in each subgroup. One, eleven and eighteen days later, 3% fast blue was injected into both superior colliculi to each subgroup and group A. The eyes were enucleated another three days later, flat mounts of the retinal from both eyes were prepared on a slide and observed under a fluorescence microscope. Four photos with 400 x magnification were taken from quadrants of the retina 1 mm away from the optic disc. The labeled retinal ganglion cells (RGCs) photos were counted by a computerized image analyzer. The labeled RGCs rate, a comparison of the labeled RGCs from both eyes in a rat were used for statistical analyzing. (The labeled RGCs rate = RGCs from injured right eye/RGCs from uninjured left eye x 100%).

In group A, the group of normal control group, the labeling rate from the ratio of RGCs counting of right eye to left eye was 99.79% +/- 13.05% and from the ratio of the RGCs of left eye to right eye was 101.86% +/- 13.91%. In group B, model of partial optic nerve crush injury group, the labeled RGCs rate were 77.79% +/- 7.11%, 63.76% +/- 3.79% and 54.66% +/- 4.75% in day 4, day 14 and 21 respectively.

Using a special designed clip with 40-gram holding force constantly pressed for four seconds to create an optic nerve crush injury model in rats. As time past along, it is revealed that the labeled RGCs rate gradually reduced.