Impact of Combined Prenatal Ethanol and Prenatal Stress Exposure on Anxiety and Hippocampal-Sensitive Learning in Adult Offspring

Abstract

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 two 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 two-trial trace conditioning task. Results TMT exposure produced a three-fold increase in maternal serum corticosterone compared to non-exposed, unhandled controls. Neither prenatal exposure paradigm, either alone or in combination, altered maternal weight gain, ethanol 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 two prenatal exposures. Performance in a two-trial trace conditioning task revealed a significant effect of prenatal ethanol exposure on freezing behavior on the testing day, with no significant effect of prenatal stress exposure and no interaction of the two prenatal exposures. Conclusions While each prenatal exposure independently produced different behavioral outcomes, the results indicate that there is no significant interaction of prenatal ethanol 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.

Impact of combined prenatal ethanol and prenatal stress exposures on markers of activity-dependent synaptic plasticity in rat dentate gyrus

“…Prenatal ethanol-exposed and prenatal stress-exposed rat offspring were generated as previously described by Staples et al (2013). Briefly, Long-Evans females and breeder males (Harlan Industries, Indianapolis, IN) were single-housed and maintained on a reverse light/dark cycle.…”

“…1), because evidence has demonstrated that developing rodent fetuses are only susceptible to stress during the third week of gestation (Diaz, Brown, & Seckl, 1998). This paradigm has been shown to elevate maternal serum corticosterone levels 3-fold over non-stressed controls, and the rat dams do not acclimate to this stressor with repeated TMT exposure episodes (Staples et al, 2013). Additionally, this prenatal stress paradigm does not elicit significant growth deficits in the offspring, as noted in Staples et al (2013), thereby reducing the number of potential confounding factors.…”

“…This paradigm has been shown to elevate maternal serum corticosterone levels 3-fold over non-stressed controls, and the rat dams do not acclimate to this stressor with repeated TMT exposure episodes (Staples et al, 2013). Additionally, this prenatal stress paradigm does not elicit significant growth deficits in the offspring, as noted in Staples et al (2013), thereby reducing the number of potential confounding factors. Following delivery, dams and litters were left undisturbed until weaning on postnatal day 25 when the offspring were moved into sex-matched group housing with littermates.…”

“…These models allow for precise experimental control, as well as providing for potential cellular and molecular analysis of animals demonstrating behavioral deficits, which parallel those observed in humans. Studies of adult animals exposed to moderate amounts of ethanol during gestation have reported reductions in hippocampus-sensitive learning and memory tasks (Berman & Hannigan, 2000; Brady, Allan, & Caldwell, 2012; Savage, Becher, de la Torre, & Sutherland, 2002; Savage et al, 2010; Staples, Rosenberg, Allen, Porch, & Savage, 2013; Sutherland, McDonald, & Savage, 2000; Weeber, Savage, Sutherland, & Caldwell, 2001), as well as deficits in measures of hippocampal synaptic plasticity, an important process associated with learning (Brady et al, 2013; Savage et al, 2002; Sutherland, McDonald, & Savage, 1997; Titterness & Christie, 2012; Varaschin, Akers, Rosenberg, Hamilton, & Savage, 2010). …”

“…Using a novel model of combined prenatal ethanol and prenatal stress exposure, we recently reported that moderate prenatal ethanol exposure decreased learning of a behaviorally challenging TTTC paradigm (Staples et al, 2013). Employing the training portion of TTTC as a behavioral activation paradigm, we tested the hypothesis that prenatal ethanol exposure and/or prenatal stress exposure would diminish TTTC-induced elevations in ARC- and AMPA-receptor subunit expression.…”