Abstract: Objective To observe the morphological changes of retina and the alteration of Bcl-2 and Bax expression in rat retina at various intervals after optic nerve transection, and to explore the pathogensis of optic nerve injury and their usefulness in estimation of the post-injury interval. Methods Animal model of posterior intraorbital optic nerve transected rats was used. Retinal samples were collected from these rats killed at various post-injury intervals. Changes of retinal ganglion cells (RGCs) were observed by microscopic examination of the hemtoxylin and eosin (H&E) stained slides. Bcl-2 and Bax expressions in the retina were studied by immunohistochemistry and imaging analysis technique. Results The numbers of RGCs decreased significantly after optic nerve transection(ONT) with an accelerated reduction during the first 2 week after ONT and a slower reduction thereafter. Both Bcl-2 and Bax proteins showed a linear increase in their expressions levels after ONT, with Bcl-2 expression earlier than Bax expression. The levels of both Bcl-2 and Bax expressions maintained for quite a long period of time, and then started to decline. The ratio of Bcl-2/Bax expressions appeared to be related to the numbers of residual RGCs. Conclusion The expressions of both Bcl-2 and Bax proteins in the rat retina alters during various post optic nerve injury intervals, and these changes in Bcl-2 and Bax expressions may be useful in estimation of optic nerve injury interval.

Key words: optic nerve transection, retinal ganglion cells, Bcl-2/Bax, apoptosis, injury interval