The effects of serotonin on the differentiation of neurons producing vasoactive intestinal polypeptide in the suprachiasmatic nucleus of the rat.

The morphogenetic influences of serotonin on the differentiation of neurons synthesizing vasoactive intestinal polypeptide (VIP) in the suprachiasmatic nucleus were studied in rats. This was addressed by comparative morphofunctional analysis of VIP neurons in adult rats whose brains developed prenatally in conditions of normal and deficient serotonin metabolism. Serotonin deficiency was created in fetuses by treatment of their mothers with p-chlorophenylalanine (PCPA). Pregnant females in controls were treated with 0.9% NaCl. VIP neurons in experimental and control animals were found to show no differences in VIP mRNA concentrations and, probably, in the level of VIP synthesis. However, inhibition of serotonin synthesis led to an increase in the number of VIP-immunoreactive neurons and an increase in the VIP concentration within these cells. This was not associated with any change in neuron size, which was an indicator of the absence of functional hypertrophy accompanying activation of specific synthesis. Comparison of the data obtained here showed that during prenatal ontogenesis, serotonin has an imprinting influence on the differentiation of VIP neurons and is probably involved in the formation of the mechanism of VIP secretion.

[Effect of serotonin on differentiation of neurons producing vasoactive intestinal polypeptide in the rat suprachiasmatic nucleus]. / Vliianie serotonina na differentsirovku neironov, produtsiruiushchikh vazoaktivnyi intestinal'nyi polipeptid, v suprakhiazmaticheskom iadre u krys.

This study was aimed to evaluate the morphogenetic influence of serotonin on the differentiating vasoactive intestinal polypeptide (VIP) neurons of the suprachiasmatic nucleus (SCN) in rats. The comparative morpho-functional analysis of VIP neurons was made in adult rats which developed under normal metabolism of serotonin or in its deficiency. The serotonin deficiency was induced in foetuses by injections of p-chlorophenilalanine to pregnant mothers. Control rats received the saline. According to our data, there was no difference in the VIP mRNA concentration and most probably in VIP synthesis in the SCN in adult rats following prenatal serotonin depletion compared to the control. However, the serotonin deficiency resulted in increase of the VIP concentration in cell bodies and of the VIP neurones number. The size of the VIP-neurones did not change in pharmacologically treated rats compared to the controls showing no functional hypertrophy of the neurones as a result of the activation of specific syntheses. From the above data, it follows that serotonin provides an imprinting influence differentiating the VIP neurones, contributing most probably to development of the VIP release mechanism.

[The source of transitory innervation of suprachiasmatic nucleus by tyrosine hydroxylase-immunoreactive fibers during the postnatal period in rats]. / Istochnik tranzitornoi innervatsii suprakhiazmaticheskogo iadra tirozingidroksilaza-immunoreaktivnymi voloknami v postnatal'nom periode u krys.

Suprachiasmatic nucleus in the rats during early postnatal development is transitorily innervated by tyrosine hydroxylase-immunoreactive fibers that are neither catecholamine- nor serotoninergic. The goal of this immunocytochemical investigation was to find out if tyrosine hydroxylase-immunoreactive neurons of anterior hypothalamus could be the source of this innervation. According to the obtained immunocytochemical data, multiple multipolar tyrosine hydroxylase-immunoreactive neurons are localized around the suprachiasmatic nucleus in the rats at days 2 and 10 of postnatal development. Most of them were observed ventrally and laterally to the nucleus. The axons of the neurons are oriented towards the suprachiasmatic nucleus. Further investigation demonstrated considerably decreased number of tyrosine hydroxylase-immunoreactive neurons surrounding the suprachiasmatic nucleus in the adult animals as compared to early postnatal period, which correlates to the number of tyrosine hydroxylase-immunoreactive fibers in this nucleus. Hence, tyrosine hydroxylase-immunoreactive neurons in the ventral region of anterior hypothalamus can be considered as a potential source of transitory innervation of suprachiasmatic nucleus by tyrosine hydroxylase-immunoreactive fibers during early postnatal development.

[Epidemiology of viral hepatitis in the Estonian SSR]. / Voprosy épidemiologii virusnogo gepatita v Estonskoi SSR.

The epidemiological peculiarities of viral hepatitis in the Estonial SSR as a whole, as well as in Tallinn and in the surrounding Harju region were studied. The study revealed that during the last 10 years the total decrease of morbidity in viral hepatitis was observed due to a decrease in infectious hepatitis, pronounced periodic and seasonal morbidity fluctuations being absent. A sharp decrease in infectious hepatitis morbidity had been achieved by carrying out planned gamma globulin prophylaxis among children. Viral hepatitis morbidity in the republic was determined by the adult population and manifested as sporadic cases of infectious and serum hepatitis. Infectious hepatitis was transmitted mainly through every day contacts, while the leading factor in the transmission of serum hepatitis consisted in various injections. The relatively high morbidity level of serum hepatitis was mainly determined by morbidity in large cities.