Prenatal hypoxia impairs brain formation, leading to the development of cognitive deficit in the postnatal period. The probable causes of this deficit may be linked with derangement of the functioning of the dorsal hippocampus and areas of the neocortex involved in its afferentation, particularly the entorhinal cortex, whose projection neurons innervate field CA1. The aim of the present work was to assess the effects of prenatal hypoxia on formation of nervous tissues in the entorhinal cortex during early ontogeny in rats subjected to prenatal hypoxia on days 14 or 18 of embryogenesis. In vivo labeling of neuroblasts formed in embryos at the moment of exposure to hypoxia with 3’-ethinyl-5-deoxyuridine showed that depending on the time of exposure, hypoxia impaired the formation and migration of neuroblasts to the lower (hypoxia on day 14 of pregnancy) or upper (hypoxia on day 18) layers of the entorhinal cortex. Hypoxia on E14 but not E18 led to a reduction in the number of neurons in the entorhinal cortex in rat pups in the first month of postnatal ontogeny. This reduction is evidence of neuron death. Impairment to the process of neurogenesis affected the formation of projection pyramidal neurons but had no effect on the population of inhibitory interneurons. Electron microscopy revealed pathological changes to neurons in the entorhinal cortex of rat pups on postnatal day 20 (cytoplasmic organelle lysis or hyperchromatosis). Hypoxia on day 18 of pregnancy produced no changes in cell composition or pyramidal neuron death in the postnatal period in the offspring. Prenatal hypoxia on day E14 evidently leads to impairment to the radial migration of neuroblasts in the entorhinal cortex and increases elimination of projection neurons in early postnatal ontogeny. Projection neuron death in the entorhinal cortex can lead to impairment to afferentation of hippocampal neurons. The selective action of prenatal hypoxia on the excitatory neuron population of the entorhinal cortex of the rat cerebral cortex may lead to disturbance of the balance between excitatory and inhibitory processes during subsequent development.
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Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 106, No. 10, pp. 1278–1288, October, 2020.
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Vasilev, D.S., Tumanova, N.L. & Kalinina, D.S. Prenatal Hypoxia Leads to Impaired Formation of Nervous Tissue in the Entorhinal Area of the Cerebral Cortex in Rats. Neurosci Behav Physi 51, 681–686 (2021). https://doi.org/10.1007/s11055-021-01121-2
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DOI: https://doi.org/10.1007/s11055-021-01121-2