Effects of ethanol on photoreceptors and visual function in developing zebrafish

Area of Science:

• Developmental biology
• Neuroscience
• Toxicology

Background:

• Maternal alcohol consumption during pregnancy can lead to fetal alcohol spectrum disorders, including visual impairments.
• Rodent models have limitations for studying early embryonic development due to in utero gestation.
• Zebrafish offer a valuable ex utero model for investigating embryonic development and teratogenic effects.

Purpose of the Study:

• To characterize the effects of ethanol on visual system development and function in zebrafish embryos.
• To determine the specific developmental windows and concentrations of ethanol that cause visual defects.
• To utilize the zebrafish model for understanding ethanol's teratogenic impact on the visual system.

Main Methods:

• Zebrafish embryos were exposed to varying ethanol concentrations from 2 to 5 days post-fertilization.
• Retinal morphology was assessed using histological and immunohistochemical techniques.
• Retinal function was evaluated via optokinetic response (OKR) and electroretinography (ERG).

Main Results:

• Moderate to high ethanol levels caused optic nerve hypoplasia and inhibited photoreceptor outer segment growth.
• Ethanol exposure increased visual threshold (OKR) and reduced ERG a- and b-waves, indicating photoreceptor dysfunction.
• Low ethanol concentrations, without apparent morphological changes, still impaired visual function.

Conclusions:

• Ethanol impacts photoreceptor function at low concentrations that do not alter retinal morphology.
• Higher ethanol concentrations inhibit photoreceptor development and cause optic nerve hypoplasia.
• The zebrafish ex utero model effectively demonstrates ethanol's teratogenic effects on the developing visual system.