Background Individuals with fetal alcohol spectrum disorders (FASD) often show processing deficits in all sensory modalities. Using an operant light reinforcement model, we tested whether prenatal ethanol exposure (PE) alters operant responding to elicit a contingent sensory stimulus—light onset (turning on the light) and habituation to this behavior in rats. We also explored whether postnatal environmental enrichment could ameliorate PE‐induced deficits. Methods Pregnant Sprague Dawley rats were gavaged twice/day with 0 or 3 g/kg/treatment ethanol (15% w/v) during gestational days 8–20, mimicking second‐trimester heavy PE in humans. The offspring were reared in a standard housing condition or an enriched condition. Adult male and female offspring underwent an operant light reinforcement experiment with either a short‐access or a long‐access procedure. A dishabituation test was also conducted to characterize the habituation process. Results In the short‐access procedure, PE led to increased operant responding to the contingent light onset in both sexes reared in the standard housing condition. Such an effect was not observed in rats reared in enriched conditions due to an overall decrease in responding. Moreover, rats reared in enriched conditions showed greater short‐term habituation. In the long access procedure, PE rats showed increased responding and impaired long‐term habituation. The long‐access procedure facilitated both short‐term and long‐term habituation in control and PE rats. Conclusion Prenatal ethanol exposure increases responding to contingent light onset and impairs the long‐term habituation process. The PE‐induced deficits were ameliorated by rearing in the enriched environment and increasing the duration and frequency of exposure to light onset. The PE‐induced effects are like increased sensation‐seeking, a subtype of sensory‐processing deficit that is often observed in individuals with FASD. Our findings could inform a suitable animal model for investigating the underlying mechanisms and possible intervention strategies for sensory deficits in FASD.
BackgroundFetal alcohol spectrum disorders (FASD) caused by prenatal ethanol exposure (PE) consist of many cognitive/behavioral deficits. Studies have reported that PE leads to impairments of learning and memory, attention, executive function, and anxiety. Open field (OF) is a common behavioral model which offers comprehensive ethological information. Here, we analyzed multiple parameters of OF to examine anxiety behavior and habituation after PE.Material and MethodsPregnant Sprague Dawley rats were gavaged twice/day with 0 or 3 g/kg/treatment ethanol (15% w/v) during gestational day (GD) 8–20, mimicking second-trimester heavy PE in humans. The control and PE adult offspring were subjected to OF task in different ambient light levels with or without acute stress.ResultsPrenatal ethanol exposure did not influence the overall locomotor activities or habituation in the OF. In lower ambient light, no PE effects could be detected. In higher ambient light, female PE rats showed less activities in the center zone, indicative of increased anxiety. Males show lower activities in the center zone only after acute stress. Rats spent <2% of the time in the center zone compared to >75% of the time in the corner zone where they engaged in frequent rearing activities (vertical exploration; exploratory rearing). Prenatal ethanol exposure led to lower rearing activities in the corner in both males and females. Acute stress masks the PE effects in males but not in females.DiscussionThe results support that heavy PE leads to persistent anxiety-like behavior during adulthood in both sexes. This conclusion is supported by using multiple parameters of exploratory behavior in the OF, including the rearing activities in the corner to reach reliable quantification of anxiety-like behavior.
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