Differential deficits in regional brain growth induced by postnatal alcohol.

Neonatal rats were exposed to alcohol during a period of brain development equivalent to part of the human third trimester. Rat pups were fed a milk formula containing either alcohol (9.8 g/kg/day) or isocaloric maltose/dextrin using artificial rearing techniques from postnatal days 4-10. Blood alcohol concentrations reached 345.8 +/- 15.6 mg/dl on postnatal day 6. All animals, including a group of normally reared suckle controls, were sacrificed on postnatal day 10, and the brains were perfused and processed for the Timm histochemical technique. Significant microencephaly (30% reduction in brain growth) was found in the alcohol-exposed animals. Growth deficits also were found in specific brain regions of the alcohol-exposed rats. The overall area of the hippocampus proper at a midtemporal level was reduced by 26.1% compared to controls. Sublaminae within the hippocampus were stunted as much as 40.5%. An overall reduction of 14.5% was found in the midsagittal (vermal) cerebellum. In contrast, growth of the dentate gyrus appeared much less affected (6.8% deficit) by the alcohol exposure. These data indicate that not all regions of the brain are affected equally by alcohol exposure during the third trimester equivalent.