[Tyrosine hydroxylase expression in differentiating neurons of the rat arcuate nucleus: inhibitory effect of serotoninergic afferents].

In vivo studies, serotonine synthesis in the rat fetal brain was inhibited by p-chlorphenylalanine from the 11th to the 20th embryonic day. Serotonine depletion significantly decreased thyrosine hydroxylase content in the neurones of males and females on the 21st embryonic day and in males--on the 35th postnatal day. In vitro, a co-culture of arquate nucleus' and raphe nucleus' embryonic neurones resulted in a sex-specific increase of the thyrosine hydroxylase level in the former neurones. The raphe nucleus' neurones manifested an increased level of serotonine. The findings suggest an activating long-lasting effect of serotonine afferents on the thyrosine hydroxylase expression in differentiating neurones of the arquate nucleus in rats during prenatal ontogenesis.