Stereologic study of Purkinje cells in mice after early exposure to phenobarbital

The present investigation was designed to study the dendritic tree of the Purkinje cells surviving after prenatal (Pre B) or neonatal (Neo B) exposure to phenobarbital (PhB). Prenatal exposure in mice was accomplished transplacentally by feeding the pregnant mother 3 g PhB/kg milled food on getation days 9 to 18. Neonatal exposure was conducted directly by injecting the neonates daily (50 mg PhB/kg) on postnatal days 2 to 21. Brains were removed at 14, 21, and 50 days of age. They were cut in the sagittal plane and prepared according to the Golgi method for analysis of the Purkinje cells dendrites. A few brains of 50-day-old Neo B and controls were cut and stained with hemotoxylin and eosin for the assessment of number of Purkinje cells. Neonatal PhB exposure caused 9% reduction in the number of dendritic spines per millimeter at age 14 and 21 days. This deficit was only transient as it disappeared by day 50. However, when the injection dose was reduced to 40 mg PhB/kg the deficits persisted to day 50. Possibly, selection against the most affected individuals accounted for the lesser effect of the higher dose. Prenatal PhB exposure had no long-lasting effect on the dendritic spines. No deficit in the area of the dendritic tree or the number of branches of all orders could be detected in any of the PhB-treated groups studied. Early PhB administration which had severe effects on the neuronal number, had a relatively small effect on the dendrites of the surviving Purkinje cells. Unlike some milder insults, it did not decrease the ratio of granule cells: Purkinje cells, and it is possible that the dendritic effects were dependent on changes in this ratio.