Prenatal binge ethanol exposure on gestation days 19-20, but not on days 17-18, increases postnatal ethanol acceptance in rats.

Previous research shows that prenatal binge ethanol exposure during gestation days (GD) 17 to 20 of the rat, increases postnatal ethanol intake and enhances ethanol's palatability, both effects being mediated by the opioid system. The amniotic fluid of the last period of gestation (GD 20) of the rat has been found to activate the opioid system and to induce conditioned preference in fetal and neonatal rats. We aimed to investigate whether enhanced acceptance for ethanol is observed when rat fetuses are exposed to it either on GD 17-18 or on GD 19-20. The results show that 14-day old pups whose mothers received ethanol on GD 19-20 consumed more ethanol and found ethanol more palatable when compared to pups exposed to ethanol on GD 17-18, or to pups experiencing ethanol and naloxone on GD 19-20. The augmented ethanol intake was observed as well after weaning (PD 26-27). These data indicate that exposure to ethanol on GD 19-20, but not before, triggers appetitive learning related to ethanol's flavor. This prenatally acquired memory is retained for at least 4 weeks and can be detected postnatally as enhanced palatability of ethanol's flavor as well as increased intake of ethanol. This increased liking of ethanol is mediated by the opioid system, although it cannot be clearly determined whether the prenatal activation of the opioid system is induced by the action of ethanol or by the activity of amniotic fluid components at that gestational age.