Prenatal ethanol exposure increases ethanol reinforcement in neonatal rats

Interactions between prenatal ethanol exposure and postnatal learning about ethanol in rat pups

Exposure to ethanol during the last days of gestation (1 or 2/kg) has been shown to induce greater ethanol intake as well as enhanced ethanol palatability in infant rats compared to pups without previous experience with the drug. This higher acceptance of ethanol seems to result from the prenatal association between the chemosensory aspects of ethanol and its reinforcing properties; the latter mediated at least in part by the opioid system. A series of experiments analyzed how this prenatal experience with ethanol affected postnatal conditioning of the flavor of ethanol. In the first experiment, pups exposed prenatally to ethanol (2g/kg during gestational days 17-20) were tested for acquisition and extinction of a conditioned aversion to the taste of ethanol (conditioned stimulus), employing lithium chloride as the aversive unconditioned stimulus. In the next two experiments, pups with the same prenatal exposure to ethanol were tested for the extinction of an aversion, employing three (Experiment 2) or one (Experiment 3) conditioning trials, using a high dose of ethanol (3g/kg) as the aversive agent. The first experiment showed that prenatal ethanol exposure delayed the postnatal acquisition of a conditioned aversion to the taste of ethanol. In the next two experiments, the same effect was observed during the extinction trials. These results provide additional support to the hypothesis of an appetitive associative memory established prenatally as a consequence of fetal ethanol exposure.