Heightened ethanol intake in infant and adolescent rats after nursing experiences with an ethanol-intoxicated dam

Preweanling rats detect ethanol (175 mg/100 ml) in maternal milk when the dam is moderately intoxicated. Repeated experiences with the intoxicated dam facilitate subsequent recognition of ethanol's chemosensory attributes and promote ethanol-related memories with a negative hedonic content. This memory has been attributed to the infant's acquired association between ethanol's chemosensory attributes and its disruptive effects on maternal care. In this study, infant and adolescent ethanol intake patterns were analyzed as a function of prior interactions, during early infancy, with their intoxicated dams.

During postpartum days 3, 5, 7, 9, 11, and 13, breast-feeding dams received an intragastric administration of either 2.5 g/kg of ethanol or water. Pups whose dams had been given one of these two maternal treatments were tested on postnatal day 15 for ingestion of 0% (water), 2.5, 5.0, or 10% v/v ethanol solution. During adolescence, remaining animals from these litters were first adapted to ingest water from drinking tubes and then were given simultaneous access to tap water and a given ethanol solution. The first day, a 3% v/v ethanol solution was used. This solution was increased by 1% ethanol each following day until the solution was 6% v/v ethanol.

Maternal drug treatment did not affect the body weights of dams, infants, or adolescents. Water intake during infancy and adolescence also was unaffected by prior maternal treatment. However, infants that had previously interacted with ethanol-intoxicated dams exhibited heightened ethanol intake scores (grams per kilogram and percentage body weight gains), especially when tested with 5 or 10% v/v ethanol solutions. Similarly, adolescent males (but not females) that had interacted with an intoxicated dam during infancy also had higher ethanol consumption levels than those that had interacted with a nonintoxicated dam.

Contrary to what might be expected in animals that acquire an aversive memory for ethanol's chemosensory cues as a function of prior interactions with an intoxicated mother, these results indicate that such interactions promote a long-lasting increase in ethanol intake. These results suggest that rats reared by intoxicated dams become sensitive to the negative reinforcing properties of ethanol.