Granule cell genesis in the hippocampus of rats treated neonatally with hydrocortisone

Rats were injected with hydrocortisone acetate on postnatal days 1–4 and the genesis of granule cells in the dentate gyrus was followed by autoradiographic techniques using tritiated thymidine. In short-survival autoradiographic experiments, the number of cells labeled by [³H] thymidine throughout the dentate hilus and stratum granulosum was decreased during and immediately after hydrocortisone treatment, but recovered to control values during the second week. Growth of this region was retarded as indicated by a 20% reduction in volume of the stratum granulosum at 7 days and 14% deficit in de-oxyribonucleic acid content in the whole hippocampus on days 4–6. At 60 days, however, the volume of the stratum granulosum in treated rats was not significantly different from that of controls. Granule cell ‘birthdays’ at dorsal and ventral levels of the hippocampus were investigated by longsurvival autoradiography in treated and control groups. Dorsally, the pattern of granule cell birthdays over the first 3 postnatal weeks was not significantly affected. Ventrally, granule cell genesis in treated rats was significantly depressed on day 5 when that in controls was maximal. This delayed the peak of granule cell birthdays at this level by several days. These experiments demonstrate that the rate and pattern of postnatal granule cell genesis in the rat hippocampus are altered by neonatal glucocorticoid treatment. Specific effects are compared to those previously reported for cerebellar neurogenesis in the glucocorticoid-treated rat.