title: Embryonic alcohol exposure impairs associative learning performance in adult zebrafish.
abstract: The zebrafish has been proposed for modeling fetal alcohol spectrum disorders (FASD). Previous FASD research with zebrafish employed high concentrations of alcohol and/or long exposure periods. Here, we exposed zebrafish eggs to low doses of alcohol (0, 0.25, 0.50, 0.75 and 1.0% (vol/vol); external bath application of which 1/20th may reach the inside of the egg) at 16-h post-fertilization (hpf) and only for a short duration (2h) in the hope to avoid gross morphological aberrations and to mimic the more frequent FASD exposure levels. Upon reaching adulthood the exposed and control zebrafish were tested for their associative learning performance in a plus-maze. Embryonic alcohol exposure led to no gross anatomical abnormalities and did not increase mortality. Unexposed (control) zebrafish showed excellent acquisition of association between a conditioned visual stimulus (CS) and food reward, demonstrated by their preference for the target zone of the maze that contained the CS during a probe trial in the absence of reward. However, alcohol-exposed fish showed no such preference and performed indistinguishable from random chance. Locomotor activity during training and the probe trial or the amount of food consumed during training did not differ between the embryonic alcohol exposed and unexposed (control) fish, suggesting that the impaired learning performance found was unlikely to be caused by altered motivation or motor function. Our results suggest that even very small amounts of alcohol reaching the embryo for only a short duration of time may have long lasting deleterious effects on cognitive function in vertebrates.
authors.affiliation: Department of Cell and System Biology, University of Toronto, Canada.
authors.forename: Yohaan
authors.initials: Y
authors.lastname: Fernandes
authors.affiliation: Department of Cell and System Biology, University of Toronto, Canada.
authors.forename: Steven
authors.initials: S
authors.lastname: Tran
authors.affiliation: Department of Psychology, University of Toronto, Canada.
authors.forename: Emil
authors.initials: E
authors.lastname: Abraham
authors.affiliation: Department of Cell and System Biology, University of Toronto, Canada; Department of Psychology, University of Toronto, Canada. Electronic address: robert_gerlai@yahoo.com.
authors.forename: Robert
authors.initials: R
authors.lastname: Gerlai
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000187:drug effects*; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004625:Embryo, Nonmammalian / Q000187:drug effects*; D000431:Ethanol / Q000494:pharmacology*; D007859:Learning Disabilities / Q000139:chemically induced*; D018782:Maze Learning / Q000187:drug effects; D015027:Zebrafish / Q000196:embryology
chemical_list: D002492:Central Nervous System Depressants; D000431:Ethanol
keywords: Embryonic alcohol exposure; Fetal alcohol spectrum disorders; Learning impairment; Zebrafish