Impact of combined prenatal ethanol and prenatal stress exposure on anxiety and hippocampal-sensitive learning in adult offspring.

BACKGROUND: Prenatal ethanol (EtOH) and prenatal stress have both been independently shown to induce learning deficits and anxiety behavior in adult offspring. However, the interactive effects of these 2 developmental teratogens on behavioral outcomes have not been systematically evaluated.
METHODS: We combined an established moderate prenatal EtOH consumption paradigm where Long-Evans rat dams voluntarily consume either a 0 or 5% EtOH solution in 0.066% saccharin water (resulting in a mean peak maternal serum EtOH concentration of 84 mg/dl) with a novel prenatal stress paradigm. Pregnant rats were exposed to 3% 2,3,5-trimethyl-3-thiazoline (TMT) for 20 minutes a day on gestational days 13, 15, 17, and 19. Adult female offspring were evaluated for anxiety-like behavior using an elevated plus-maze and hippocampal-sensitive learning using a 2-trial trace conditioning (TTTC) task.
RESULTS: TMT exposure produced a threefold increase in maternal serum corticosterone compared to nonexposed, unhandled controls. Neither prenatal exposure paradigm, either alone or in combination, altered maternal weight gain, EtOH consumption, maternal care of litters, litter size, pup birth weight, or pup weight gain up to weaning. Offspring exposed to prenatal stress displayed significant increases in anxiety-like behavior in the elevated plus maze in terms of open arm entries and time spent on the open arms, with no significant effect of prenatal EtOH exposure and no interaction of the 2 prenatal exposures. Performance in a TTTC task revealed a significant effect of prenatal EtOH exposure on freezing behavior on the testing day, with no significant effect of prenatal stress exposure and no interaction of the 2 prenatal exposures.
CONCLUSIONS: While each prenatal exposure independently produced different behavioral outcomes, the results indicate that there is no significant interaction of prenatal EtOH and prenatal stress exposures on learning or anxiety at the exposure levels employed in this dual exposure paradigm. Subsequent studies will examine whether similar outcomes occur in male offspring and whether other measures of anxiety or learning are differentially impacted by these prenatal exposure paradigms.