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Alterations of the electroretinogram by intravitreal kainic acid in the rat
S Li1, A Mizota, E Adachi-Usami
1Department of Ophthalmology, Chiba University School of Medicine, Japan.
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.