Effects of abnormal light-rearing conditions on retinal physiology in larvae zebrafish

PURPOSE. Anatomic studies have found that zebrafish retinal neurons develop in a sequential fashion. In addition, exposure to abnormal light-rearing c onditions produces deficits in visual behavior of larvae zebrafish, even th ough there appears to be little effect of the light-rearing conditions on t he gross morphology of the retina. The purpose of this study was to assess the effects of abnormal light-rearing conditions on larvae zebrafish retina l physiology. METHODS. Larvae zebrafish (Danio rerio) were exposed to constant light (LL) , constant dark (DD), or normal cyclic light (LD) from fertilization to 6 d ays postfertilization (dpf). After 6 days, the animals were placed into nor mal cyclic light and rested at 6 to 8, 13 to 15, and 21 to 24 dpf. Electror etinogram (ERG) responses to visual stimuli, consisting of various waveleng ths and irradiances, were recorded. Comparisons were made across the three age groups and the three light-rearing conditions. RESULTS. Deficits from the light-rearing conditions were seen immediately a fter exposure (6-8 dpf). The LL-condition subjects showed the greatest defi cit in the UV and short-wavelength areas and the DD-condition subjects show ed a slight deficit across the entire spectrum. At 13 to 15 dpf, the LL and DD groups showed an increase in sensitivity and by 21 to 24 dpf, the group s no longer differed from controls. CONCLUSIONS. Abnormal lighting environments can adversely influence the phy siological development of the larvae zebrafish retina. The pattern of damag e that was seen in zebrafish is similar to that found in other vertebrates, including higher vertebrates. However, unlike higher vertebrates, the zebr afish appears to be capable of regeneration. This suggests that the zebrafi sh would be a viable model for light environment effects and neural regener ation.