Age-dependent effects of embryonic ethanol exposure on anxiety-like behaviours in young zebrafish: A genotype comparison study.

Fetal Alcohol Spectrum Disorder (FASD) is characterized by a variety of morphological, behavioural and cognitive deficits, ranging from mild to severe. Numerous animal models, including the zebrafish, have been employed to better understand the onset, expression and progression of this disorder. Embryonic ethanol-induced deficits in learning and memory, anxiety, social responses and elevated alcohol self-administration have been successfully demonstrated in zebrafish. Studies in zebrafish have also shown the expression of these behavioural deficits depends upon the developmental stage of ethanol exposure, the age of observation, as well as the genotype (strain or population origin) of the tested zebrafish. Here, we investigate how the genotype and age of observation may influence embryonic ethanol-induced alterations in anxiety-like responses in zebrafish. Zebrafish embryos exposed to either 0% or 1% (vol/vol) ethanol at 24hpf were tested in an open tank at one of three stages: larval (6-8 days post fertilization (dpf)), mid-larval (16-18dpf), or juvenile (26-28dpf). Two genotypes were tested in this manner, ABNS (a quasi-inbred strain) and ABSK (a mix of AB, TU and TL strains). We found embryonic ethanol induced behavioural changes to significantly differ depending on the genotype and age of observation. For example, significant differences between control and ethanol exposed zebrafish in both genotypes were observed in juvenile zebrafish, but few significant treatment effects were observed in larval zebrafish. Additionally, ethanol appeared to alter anxiety-like behaviours in the ABNS genotype but did not have as robust of an effect on the ABSK genotype. Lastly, there were significant behavioural differences between unexposed (control) zebrafish of the two genotypes, suggesting baseline behavioural differences despite a common AB genetic origin.