Research Of Mechanism On Brimonidine Treating The Rat Optic Nerve Crush Injury

Objective: Traumatic optic neuropathy (TON) is an common ophthalmopathy that can leading to blind which can be indirectly caused by the extra-power passing from bone or eye ball. This kind of injury occupies 0.5%～5% in the closed brain trauma[1,2]. Degrees of the visual acuity damage indirectly caused by the TON differ from each other, however, about 50% of them are"light perception"or"non-light perception". There is still no surely useful treatment plan for treating this kind of disease at present. With the development of the research on cell apoptosis and the optic nerve trauma and renovation, the view that nerve can not regeneration evoks more and more doubts in medical field. The continuing of research on the nerve regenation may initiates another breakthrough in medical domain.Many researches in our nation and overseas indicate that lots of new treatment methods show invariably effection in promoting the regeneration of the RGCs, such as medicine therapy, operation therapy and gene therapy.Author refers to lots of authority documents in domestic or overseas, and understands that the regeneration of the axonal after the optic nerve trauma is an complicated process including multiple factors and elements, andα2-selective adrenergic agonists (α2-SAs) has been proved to have evident effection in animal experiment, but its concrete mechanism of action is still unknown. This topic aims to research the concrete mechanism of action of the 0.2%brimonidine tartrate in therapying the optic nerve crush injury rat from immunohistochemistry of the Bcl-2, Bax, bFGF and the transmission electron microscope (TEM). We expect that this research may provide us some new strategies for treating optic nerve trauma and expand our recognition on nerve regeneration.Methods1 90 female adult Sprague-Dawley rats were randomly divided into normal group, untreated group and treated group. The untreated and treated groups received an optic nerve crush injury by reverse pliers; Then the treated group was gieven drops of 0.2%brimonidine tartrate topically before and after the crush injury;The untreated and normal groups received none intervention.2 All three groups were anesthetized with ketamine by 1, 3, 5, 7, 14, 21d after the optic nerve crush injury,and all the eye balls were enucleate and fixed into 4% paraformaldehyde for 72 hours,then the eye balls were sheared along the ambitus ,eye protomerite and eye content were removed.The part of temple upper quadrant rat retina which leave optic papillary within 2mm was selected to cutting sheet and HE dyeing,then RGCs number were counted out under the light microscope.3 Rats for immunohistochemistry were anesthetized with the same method , and all the eye balls were enucleate and fixed into 4% paraformaldehyde ,then the part of temple upper quadrant rat retina that leave the optic papillary within 2mm was selected for Bcl-2,Bax,bFGF immunohistochemistry staining.4 Rats from three groups for TEM were anesthetized by 3,7,21d,and eye balls were enucleate quickly and fixed into 2.5% glutaraldehyde. Retina tissue around the optic papillary was selected for TEM in order to observe the microcosmic morphologic change among three groups.Results1 Bax expression was observed in normal group rats retina and its potitive staining mainly located at ganglion cell layer, inner plexiform layer,inner nuclear layer.The expression of Bax was gradually strengthened by 3, 5, 7d in untreated group.The expression of Bax in untreated group is higher than that in treated group,and the statistics difference is significant (p<0.05) .2 The positive expression of Bcl-2 in normal group rat retina was mainly located at ganglion cell layer, The expression of Bcl-2 was gradually strengthened in untreated group and showed strong positive action by 7, 14, 21d. The expression of Bcl-2 in treated group is higher than that in untreated group,and the statistics difference is significant (p<0.01) . 3 The positive expression of bFGF in normal group rat retina was mainly located at ganglion cell layer and inner nuclear layer.The staining in ganglion cell layer and inner nuclear layer were increased in untreated group ,and positive cells were observed in outer nuclear layer. The expression of bFGF in treated group is higher than that in untreated group,and the statistics difference is significant (p<0.01) .4 Every sheet of cells in normal group rats retina lined up in order under the light microscope and TEM;Cells in untreated group lined up irregularly,the whole thickness thinningzed,and manifest apoptosis morphologic change was observed.Mohphologic change in treated group was lessened obviously.Conclusions1 0.2%brimonidine tartrate relieves the apoptosis morphologic change and elevate survival rate of RGCs, showing obvious effect in threapying rat optic nerve crush injury.2 0.2% brimonidine tartrate elevates the expression of bFGF,Bcl-2 ,cuts down the expression of the Bax in optic nerve crush injury rat retina,this hints that the therapeutic mechanism of 0.2% brimonidine tartrate may relevants with its effects of promoting the expression of bFGF and inhibiting apoptosis.