Facilitatory and neurotoxic effects of intravitreal ornithine on the electroretinographic responses of albino rats

The effect of an intravitreal injection of ornithine on the retina of rats was studied electroretinographically. Rats were injected intravitreally wit h 5 mul of 0.02, 0.25 and 0.5 Mornithine. Electroretinograms (ERGs) were re corded before, and 1, 3 and 9 days after the injection. High doses of ornit hine (0.5 M) reduced while low doses (0.02 M) enhanced the ERG amplitudes. The implicit time of the a-wave was delayed at all concentrations after orn ithine injection, which suggests that implicit times may be a more sensitiv e parameter of the ornithine effect. There were significant changes in the stimulus intensity necessary to obtain the one half of the maximum amplitud e of the b-wave that may have been caused by damage of the photoreceptors a nd retinal pigment epithelium cells by ornithine. We conclude that the effe ct of ornithine on retinal function is dose dependent and can either enhanc e or depress the ERG amplitudes. Copyright (C) 2001 S. Karger AG, Basel.