Effects of ornithine on the electroretinogram in cat retina.

PURPOSE To study the acute effects of L-ornithine hydrochloride on the function of cat retina in vivo. METHODS A small amount of ornithine was administered intravitreously or intravenously. Changes in retinal function were monitored by vitreal electroretinogram (ERG) and intraretinal ERG with K(+)-selective microelectrodes. RESULTS Intravitreal injections (0.2 to 0.5 M; 15 microliters) of ornithine caused a decrease in the standing potential and the vitreal ERG c-wave amplitude. The ERG c-wave decreased continuously during a 5-hour period. Intravenous injection (0.2 M; 10 ml) of ornithine also diminished the c-wave. Intraretinal recording showed that the amplitudes of the retinal pigment epithelium (RPE) component and the Müller cell component of the ERG c-wave were reduced after intravitreal injection. The light-evoked [K+]o decrease in the subretinal space did not change. The change in transepithelial resistance contributed little to the decrease in the c-wave. CONCLUSION These results demonstrated that ornithine selectively affects the c-wave and suggested that it affects RPE and Müller cells directly without affecting photoreceptors.