Abstract
Purpose: :
To examine the effect of intravitreal BDNF on rabbit retinal ganglion cell survival following optic nerve transection
Methods: :
Dutch Belted rabbits of either sex were anesthetized with ketamine/xylazine and each mounted on rabbit stereotaxic instrument. Using predetermined stereotaxic coordinates of P10, H5 and L3, retinal ganglion cells (RGC) were labeled retrogradely with fluorogold injection, 2.5 ul into the superior colliculus. Optic nerve transection was performed 7 days after fluorogold injection and 10ul of BDNF (1ug/ul) was injected intravitreally about 10 minutes post surgery. Contralateral eyes received equivalent volume of vehicle. All animals were sacrificed 10 or 14 days after optic nerve transection. In one study, retina from rabbit's eyes were flat mounted and imaged under fluorescence microscope. RGCs were quantified using MetaMorph software. In other studies, eyes from vehicle control and drug treated animals were enucleated and fixed for retinal histology.
Results: :
In the visual streak, ganglion cell density was 1352±45.94 cells/mm2 (n=10) in normal eyes and in eyes contralateral to transection. However, RGC density 10 and 14 days after optic nerve transection in the same retinal eccentricity was significantly reduced to 44% and 6.3% of control values, respectively. Treatment with a single application of BDNF (1ug/ul) significantly increased ganglion cell density to 95% after optic nerve transection. Histological data showed significantly reduced ganglion cell layer in transected retina compared to normal.
Conclusions: :
This is the first study to demonstrate flurogold retrograde labeling of rabbit RGC from the superior colliculus. In addition, BDNF-induced RGC survival validates this model of optic nerve transection as potential substitute in studies requiring large eyes for ocular drug delivery device.
Keywords: optic nerve • ganglion cells • microscopy: light/fluorescence/immunohistochemistry