Alterations of the electroretinogram by intravitreal kainic acid in the rat.

PURPOSE To relate the electrophysiological changes in the retina induced by the excitatory neurotoxin, kainic acid (KA), to its receptor sites in the rat. METHODS Fifty-five Wistar rats were injected intravitreally with 100, 50, 25, 12.5, 6.25, 3.12, or 1.56 nmol of KA. The electroretinograms (ERGs) including oscillatory potentials (OPs) elicited by a series of increasing intensities were recorded before, and 6 hours, 1 day, 1 week, and 1 month after the injection of KA. RESULTS After KA injection, the a-waves showed no significant change at all intensity levels (P > .05), but the amplitudes and implicit times of the b-wave were significantly altered. The abolition of the b-wave by KA resulted in a negative response, which decreased progressively with time. The implicit times of the b-wave showed a marked prolongation after injection of 100 nmol of KA (P < .01). The OPs disappeared at the KA dose of 6.25 nmol and higher; doses of 1.56 to 3.12 nmol of KA depressed the Ops. CONCLUSIONS We conclude that KA altered the above-mentioned ERG components in a dose-dependent manner. These alterations of the ERG can be explained by alterations of neurons in the inner retinal layers.