Impairments to the Establishment of the Various Hippocampal Fields in Rats as a Long-Term Consequence of Acute Perinatal Hypoxia

The aim of the present work was to study the long-term consequences of acute normobaric hypoxia during the perinatal period on the establishment of the hippocampal formation in rats. The experiments showed that hypoxia on day 2 of postnatal development led to significant damage to the structure of the hippocampal field, which showed different levels of sensitivity to the harmful factor. On day 20, all fields showed cell death and depletion of the pyramidal cell layers. The most marked neuron death occurred in fields CA4 and CA3. On day 30, a significant level of neuron death persisted in field CA4, though it decreased in field CA3 and was not seen in field CA1; neuron death in the granule layer of the dentate fascia increased. In addition, there were decreases in the sizes of pyramidal neuron bodies in all hippocampal fields. All hippocampal fields also showed activation of astrocyte reactions, which was more marked in field CA4, where gliosis persisted to prepubertal age (30 days).