Maternal age as a factor in determining the reproductive and behavioral outcome of rats prenatally exposed to ethanol

Abstract

Nulliparous Long-Evans rats were bred at one of four different ages and assigned to one of three treatment groups within each age condition. Maternal ages were 9, 18, 32, and 36 weeks. Treatment groups were ethanol (E), administered by gavage as 8 g/kg in two divided doses on days 10–14 of gestation, pair-fed (PF) controls, administered as an isocaloric sucrose solution by gavage on days 10–14 of gestation, and ad lib fed controls (C). All offspring were surrogate fostered shortly after delivery to untreated recently parturient dams. Litter sizes were standardized to 8 on the day of birth. Offspring were assessed longitudinally for growth, mortality, and behavior (olfaction, locomotor activity, maze learning, avoidance acquisition and startle). Approximately 85% of the 36 week old dams did not produce viable litters. In the remaining maternal age conditions, ethanol delayed offspring olfactory orientation and increased locomotor activity, the latter dissipating after 50–60 days of age. These ethanol-related effects occurred independent of maternal age condition. Maternal age, independent of ethanol, was a factor which reduced litter size and offspring weight up to 50 days, but produced few effects on behavior. The combination of maternal age and prenatal ethanol interacted to increase pregnancy loss (oldest maternal age), reduce offspring weight up to day 99 (oldest and middle maternal age), alter olfactory orientation performance (oldest and middle maternal age), reverse the typical ethanol-induced increase in activity for males in the figure-8 test (oldest maternal age group), shift the pattern of open-field activity, and change errors in a complex water maze. Not all of these interactions turned out to be specific to the ethanol × old maternal age condition. Several of the interactions occurred in both the old and middle maternal age conditions. The only effect of old maternal age that interacted strongly with ethanol was in their combined effects on reproduction. Here the combination of the two factors increased maternal mortality, the number of early pregnancy losses, and the number of litters where all members were dead or resorbed. It was concluded that short-term prenatal ethanol combined with advanced maternal age produces additive interactions on pregnancy success without affecting longer-term outcomes, while young maternal age showed no clear detrimental effects compared to the middle maternal age reference group.