CHARACTERISTIC OF SEROTONINERGIC NEURONS OF MEDULLARY NUCLEUS RAPHE OBSCURUS IN NORM AND IN SEROTONINERGIC SYSTEM DEFICIENCY DURING THE PRENATAL PERIOD OF DEVELOPMENT IN RATS

Abstract

Morphological characteristics of the serotoninergic neurons forming nucleus raphe obscurus (NRO), were studied in rats at the early stages (days 5, 10, 12 and 14) of the postnatal period in normal rats and in animals whose prenatal development took place under the conditions of serotonin deficiency. NRO was found to contain three subpopulations serotonin-producing neurons (large, medium and small), which had different sensitivity to serotonin level during development. The results have shown that serotoninergic system deficiency during the prenatal period resulted in the changes of NRO structural organization and in the decrease of the rate of this nucleus formation, serotonin-producing neurons differentiation and the reduction of their total number by approximately a factor of 1.6. At the same time, the significant changes of the dimensions of serotoninergic neurons of all types took place. In control animals, the size of large, medium and small neurons was 1.8, 1.4 and 1.5 times greater than that in experimental animals, respectively. Reduction of the neuron dimensions was associated with the changes of a nucleo-cytoplasmic ratio. The volume of the cytoplasm and of Nissl bodies was significantly decreased. Along with it, the cell destruction was noted that increased with age. Synchronously with it, the marked astrocytic reaction developed, which could further lead to gliosis.

Keywords

medulla / nucleus raphe obscurus / neurons / postnatal development / serotonin

References

[1] Отеллин В. А., Хожай Л. И. и Ордян Н. Э. Пренатальные стрессорные воздействия и развивающийся головной мозг. СПб., Десятка, 2007.

[2] Broadbelt K. G., Paterson D. S., Rivera K. D. et al. Neuroanatomic relationships between the GABAergic and serotonergic systems in the developing human medulla. Auton. Neurosci., 2010, v. 154, № 1–2, p. 30–41.

[3] Cao Y., Matsuyama K., Fujito Y. and Aoki M. Involvement of medullary GABAergic and serotonergic raphe neurons in respiratory control: electrophysiological and immunohistochemical studies in rats. Neurosci. Res., 2006, v. 56, № 3, p. 322–331.

[4] Keller H. H. Depletion of cerebral monoamines by p-chlorophenylalanine in the cat. Experientia, 1972, v. 28, № 2, p. 177–178.

[5] Kovacs G. G., Klöppel S., Fischer I. et al. Nucleus-specific alteration of raphe neurons in human neurodegenerative disorders. Neuroreport, 2003, v. 14, № 1, p. 73–76.

[6] Lauder J. M., Towle A. C. and Patrick K. Decreased serotonin content of embryonic raphe neurons following maternal administration of p-chlorophenylalanine: a quantitative imminocytochemical study. Dev. Brain Res., 1985, v. 20, № 1, p. 107–114.

[7] Levitt P. and Moore R. Y. Origin and organization of brainstem catecholamine innervation in the rat. J. Comp. Neurol., 1979, v. 186, p. 505–528.

[8] Paterson D. S. and Darnall R. 5-HT2A receptors are concentrated in regions of the human infant medulla involved in respiratory and autonomic control. Auton Neurosci., 2009, v. 147, № 1–2, p. 48–55.

[9] Petko M. and Stunya E. Ontogenesis of serotoninergic nuclei in the rat stem. Folia Histochem. Cytobiol., 1987, v. 25, № 2, p.143–148.

[10] Schwarzacher S. W., Pestean A., Gunter S. and Ballanyi K. Sero to ninergic modulation of respiratory motoneurons and interneurons in brainstem slices of perinatal rats. Neuroscience, 2002, v. 115, № 4, p. 1247–1259.

[11] Weissheimer K. V. and Machado B. H. Inhibitory modulation of chemoreflex bradycardia by stimulation of the nucleus raphe obscurus is mediated by 5-HT3 receptors in the VTS of awake rats. Auton. Neurosci., 2009, v. 132, № 1–2, p. 27–38.

RIGHTS & PERMISSIONS

Eco-Vector