Neuronal Change in the Dentate and Hippocampus of Adrenalectomized and Adrenal Corticosteroid Injected Neonatal Rats

The influences of adrenal corticosteroid on the development and regression of neurons of dentate and hippocampus were studied by adrenalectomy and steroid overload in neonatal rats. The results obtained were as follows. 1. The cell death occurred naturally in numerous dentate granule cells and hippocampal pyramidal cells. 2. The number of dentate granule cells undergoing cell death decreased by injection of adrenal corticosteroid, but increased in adrenalectomized rat brains. The changes occurred prominently at postnatal day 6. 3. The number of hippocampal pyramidal cells undergoing cell death decreased in CA3 region by injection of adrenal corticosteroid, but was not changed in adrenalectomized rat brains. However, other regions exhibited no change by adrenal corticosteroid and adrenalectomy. 4. The cell death of pyramidal cells of CA3 region occurred in close relationship with the cell death of dentate granule cells, which was different from other CA regions. In summary, the cell death of dentate and hippocampal neurons occurred naturally but seemed to be influenced by other factors as well as adrenal corticosteroid.