NERVE GROWTH-FACTOR PROMOTES FUNCTIONAL RECOVERY OF RETINAL GANGLION-CELLS AFTER ISCHEMIA

Purpose. To investigate the effect of a transient complete ischemia on the function of cat retina and to determine whether nerve growth fact or (NGF), which was previously shown to enhance retinal ganglion cell (RGC) survival after optic nerve section in the adult rat, can promote recovery of retinal neurons after the ischemic insult. Methods. Funct ion of distal and proximal retina was assessed by recording the electr oretinogram in response to both homogenous flickering light (FERG) and contrast reversing gratings (PERG), respectively, 30 days after the i nduction of a 60-minute episode of ischemia. Visual evoked potentials in response to contrast reversing gratings were also recorded to evalu ate visual acuity and contrast thresholds. Cell survival after ischemi a was assessed in retinal whole-mounts stained with cresyl violet. Cat s were intraocularly treated with NGF every other day, 3 times a week, for 30 days. Controls were treated with either phosphate buffered sal ine or cytochrome c. Results. After ischemia, the FERG was not signifi cantly affected. On the contrary, the PERG, visual acuity, and contras t thresholds were severely impaired. After NGF treatment, PERG respons e amplitudes were much less reduced compared to controls, and visual a cuity and contrast thresholds were virtually normal. In addition, a la rger number of presumed RGCs was present in the NGF-treated retinas co mpared to the cyt c-treated ones. Conclusions. The more proximally loc ated retinal neurons, in particular RGCs, are highly vulnerable to isc hemia. Intraocular NGF treatment was effective in enhancing the surviv al and functional recovery of these neurons. This suggests that NGF ma y represent a novel therapeutic agent for the treatment of ischemic oc ular pathologies.