Rod and cone signaling transmission in the retina of zebrafish: An ERG study

It has been suggested that in lower vertebrates, visual signals are propagated in the retina using mixed bipolar cell pathways. In this article, we examined rod and cone signaling transmission in the retina of teleost zebrafish. Full-field electroretinograms (ERGs) were recorded from the cornea of control or 2-amino-4-phosphonobutyric acid (APB)-treated zebrafish. During dark adaptation following bright light adaptation, the intensity-response (V-log I) curve for both the ERG b- and d-waves shifted. In control animals, the b-wave response displayed a typical visual Purkinje shift and became more sensitive. By contrast, the d-wave became less sensitive. In the early dark adaptation, cone-dominant signals were readily recorded in both b- and d-waves. In the late dark adaptation, rod signals became dominant. However, no obvious d-wave was recorded. Intraocular injections of APB selectively blocked the b-wave, but revealed the d-wave in both early and late dark adaptation.