Postnatal stress of early weaning exacerbates behavioral outcome in prenatal alcohol-exposed juvenile rats

Abstract

Some of the behavioral deficits caused by prenatal or postnatal alcohol exposure have been demonstrated to be ameliorated by environmental manipulations such as handling or environmental enrichment. This experiment, in contrast, investigated whether behavioral deficits due to prenatal alcohol exposure could be exacerbated by a stressful experience, early weaning. Pregnant dams were given either a liquid diet with 35% of the calories derived from alcohol, a liquid diet without alcohol to control for any effects of the liquid diet administration, or ad libitum food and water. Half of each litter were weaned at 15 days of age (early weaning) and half were weaned at 21 days of age (normally weaned). Offspring were weighed, tested for activity in an open field at 18 days of age, and trained to find a hidden platform in the Morris water maze at 22–24 days of age. Alcohol-exposed subjects who were weaned early were more impaired in spatial navigation ability than any other group. Similarly, the combination of early weaning and prenatal alcohol exposure caused the slowest growth. All subjects exposed to alcohol, regardless of weaning condition, had greater latencies to find the platform than those from the two control groups. There was no synergistic effect of alcohol and stress on activity levels, but all early-weaned females were more active than normally weaned females; males did not show this effect. Thus, environmental stressors such as early weaning can compound detrimental symptoms of prenatal alcohol exposure. These results have implications for the understanding of the effects of the environment on neuronal plasticity.