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Neural Plasticity
Volume 8, Issue 4, Pages 271-284
http://dx.doi.org/10.1155/NP.2001.271

Tyrosine Hydroxylase Expression in Differentiating Neurons of the Rat Arcuate Nucleus: Stimulatory Influence of Serotonin Afferents

1Laboratory of Hormonal Regulations, Institute of Developmental Biology, Russian Academy of Medical Sciences, Moscow, Russia
2Laboratory of Neurohistology, Institute of Normal Physiology, Russian Academy of Medical Sciences, Moscow, Russia
3Département des Signaux Intercellulaires, Institut des Neurosciences, Université P. et M. Curie, paris, France
4Laboratoire de Neurobiologie Moléculaire, Université Paris, Créteil, France

Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The influence of serotonin afferents on tyrosine hydroxylase expression in differentiating neurons of the rat arcuate nucleus was studied in vivo and in vitro. In the in vivo study, pchlorophenylalanine inhibited serotonin synthesis in fetal brain from the 11th to the 20th embryonic day. We then used semiquantitative immunocytochemistry to evaluate tyrosine hydroxylase levels in neurons of the arcuate nucleus in fetuses at the 21st embryonic day or in offspring at the 35th postnatal day. Serotonin depltion significantly decreased the tyrosine hydroxylase content in neurons of males and females at the 21st embryonic day and in males at the 35th postnatal day. For the in vitro study, embryonic neurons of the arcuate nucleus were cocultured with embryonic neurons of the raphe nucleus, the main source of serotonin innervation of the brain, including the arcuate nucleus. Co-culture of the neurons resulted in a genderspecific increase of the tyrosine hydroxylase level in the neurons of the arcuate nucleus. In turn, the neurons of the raphe nucleus showed increased levels .of serotonin in both males and females, with no sexual dimorphism. Thus, our results suggest a stimulatory, long-lasting effect of serotonin afferents on tyrosine hydroxylase expression in the differentiating neurons of the rat arcuate nucleus during prenatal ontogenesis.