FOREBRAIN HYPOPLASIA FOLLOWING ACUTE PRENATAL ETHANOL EXPOSURE - QUANTITATIVE-ANALYSIS OF EFFECTS ON SPECIFIC FOREBRAIN NUCLEI

The effects of acute prenatal exposure to ethanol on the volumes and n euronal populations of selected forebrain nuclei of postnatal animals have been examined in a mouse model, Pregnant mice were exposed to eth anol (25% ethanol, either two doses at 0.015 ml/g separated by 4 hrs, or a single dose at 0.03 ml/g) on the 8th gestational day and the cyto architecture of the basal forebrain, paleo- and neocortex examined qua ntitatively at P15, Significant reductions in the volume and total num ber of neurons of ventromedial and central forebrain structures, such as the olfactory bulb, septal nuclei, diagonal band nuclei and caudato putamen, were observed in mice exposed to the divided ethanol dose, bu t not following the single dose. The neocortex and primary olfactory c ortex were also reduced in volume in offspring exposed to the divided ethanol dose, However increased neuronal density in some neocortical r egions of ethanol-exposed offspring suggests that the total number of neocortical neurons is not significantly affected by acute ethanol exp osure. The findings indicate that pulse exposure to ethanol on a singl e day of early development causes deficits in neuronal populations of the ventromedial forebrain and caudatoputamen even in offspring withou t other major malformations. The results also indicate that caution sh ould be exercised in interpreting the significance of nuclear volume r eduction in human infants with fetal alcohol syndrome (FAS) in the abs ence of neuronal density estimates.