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Characteristics of Serotoninergic Neurons of the Nucleus Raphe Obscurus in Normal Conditions and in Deficiency of the Serotoninergic System in Rats during the Prenatal Period of Development

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Morphological studies were performed on the serotoninergic neurons forming the nucleus raphe obscurus (NRO) of the medulla oblongata in rats at the early periods (5, 10, 12, and 14 days) of the postnatal period in normal animals and in animals undergoing prenatal development with serotonin deficiency. The NRO was found to contain three subpopulations of serotonin-synthesizing neurons (large, medium, and small) with different sensitivities to serotonin levels during the developmental period. The results showed that serotoninergic system deficiency during the prenatal period leads to changes in the structural organization of the NRO, with slowing of the rate of formation of the nucleus and differentiation of serotonin-synthesizing neurons, along with a 1.6-fold reduction in the total number of these cells. The sizes of all types of serotoninergic neurons underwent significant changes. In control animals, large neurons were 1.8 times larger than those in experimental animals, while intermediate cells were 1.4 times larger and small cells were 1.5 times larger. Decreases in neuron size were combined with changes in the nucleus:cytoplasm ratio. Cytoplasm volume decreased significantly, as did detectable chromatophilic material. Clear astrocyte reactions, which could subsequently lead to gliosis, developed synchronously with these changes.

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Authors and Affiliations

  1. Nervous System Ontogeny Laboratory, Pavlov Institute of Physiology, Russian Academy of Sciences, 6 Makarov Bank, 19903, St. Petersburg, Russia

    L. I. Khozhai

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  1. L. I. Khozhai
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Correspondence to L. I. Khozhai.

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Translated from Morfologiya, Vol. 144, No. 4, pp. 19–24, July–August, 2013.

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Khozhai, L.I. Characteristics of Serotoninergic Neurons of the Nucleus Raphe Obscurus in Normal Conditions and in Deficiency of the Serotoninergic System in Rats during the Prenatal Period of Development. Neurosci Behav Physi 44, 779–783 (2014). https://doi.org/10.1007/s11055-014-9983-5

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