Morphological alterations in the medial preoptic area after prenatal administration of phenobarbital

Pregnant Sabra mice received 3 g phenobarbital per kilogram milled food from gestational days (GD) 9 to 18 as their only food source; control females received milled food. All the females were divided into three groups and injected intraperitoneally with a single dose of 3H-thymidine on GD 13, 15 or 17. At 50 days of age of the offspring were perfused with 10% neutral formalin and their brains removed and prepared for autoradiography. Matching sagittal sections of the offspring were selected for the study of the medial preoptic area (MPOA) of the hypothalamus. The total number of cells per section was not significantly different between males and females, however, there was a greater cellular packing density (cell/mm2) in females (p less than 0.05). This sex difference disappeared in treated offspring, possibly due to a 76% decrease on GD 13 in the rate of cell proliferation in females (number of labeled cells but not in males (p less than 0.001); the greatest decrease in the number of labeled cells occurred in the sexually dimorphic areas of the MPOA (p less than 0.001). The area of the sagittal section of the MPOA did not differ significantly between sexes or treatments.