Effects of male sex hormones on specific uptake and release of 3H-serotonin in the rat hypothalamus in vitro]

With the use of "isotopic method" a study was made of the main parameters of functional activity of serotoninergic elements of hypothalamus--the specific uptake and release of 5-OT. The animals used were sexually mature rats castrated on the first postnatal day. In sexually mature intact males the specific uptake of 3H-5-OT by serotoninergic structures of the anterior hypothalamus was significantly lower than in females. Castration of animals on the first day of life resulted in the increase of specific 5-OT uptake in sexually mature males up to that observed in females. There were no differences between the sexes in the rate of spontaneous release of 5-OT. However, response to K(+)-depolarization in the anterior hypothalamus of intact males was significantly lower than that in females. In the hypothalamus of males castrated neonatally the amplitude of the response to the effect of the depolarizing agent was increase up to the level observed in females. By the results obtained it is indicated that elimination of the effect of male hormones on the first postnatal day results in the increase of 5-OT uptake and release in the hypothalamus of sexually mature rat males.     

mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species

Reconstructions of the human-African great ape phylogeny by using mitochondrial DNA (mtDNA) have been subject to considerable debate. One confounding factor may be the lack of data on intraspecific variation. To test this hypothesis, we examined the effect of intraspecific mtDNA diversity on the phylogenetic reconstruction of another Plio- Pleistocene radiation of higher primates, the fascicularis group of macaque (Macaca) monkey species. Fifteen endonucleases were used to identify 10 haplotypes of 40-47 restriction sites in M. mulatta, which were compared with similar data for the other members of this species group. Interpopulational, intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of divergence time and branching order incorporating this variation were substantially different from those based on single representatives of each species. We conclude that intraspecific mtDNA diversity is substantial in at least some primate species. Consequently, without prior information on the extent of genetic diversity within a particular species, intraspecific variation must be assessed and accounted for when reconstructing primate phylogenies. Further, we question the reliability of hominoid mtDNA phylogenies, based as they are on one or a few representatives of each species, in an already depauperate superfamily of primates.      

The brain as an endocrine gland in adult and in developing ofranism

It is suggested that the abult mammals' brain is, on the one hand, a conglomerate of neuronal assemblies within which information is being transmitted with the aid of chemical signals, and on the other hand, a considerable part of the neurons are secreting cells and their accumulations by their functional characteristics are identical to endocrine glands. Proceeding from the brain dualism, a question arises: which of the two functions is the pimary one? It seems that, prior to forming specific interneuronal links and blood-brain barrier, the neurons function as secreting cells and the brain--as an endocrine gland. The physiologically active substances (FASs) entering the general circulation system from the brain seem to take part in regulation of development of the visceral target organs and the brain itself. Forming of the interneuronal links and blood-brain barrier leads to a qualitative jump in the brain development followed by a considerable limitation of its endocrine functions. According to this concept, the brain, prior to the moment of forming of the interneuronal links and blood-brain barrier, does not influence the development of the whole organism whereas development of the brain itself is regulated by the hormones of the foetus and placenta's endocrine glands.     

The source of transitory innervation of suprachiasmatic nucleus by tyrosine hydroxylase-immunoreactive fibers during the postnatal period in rats

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.     

Compensatory reaction during degeneration of arcuate nucleus dopaminergic neurons in rats

The study has been carried out to verify the authors' hypothesis that degeneration of dopaminergic (DA-ergic) neurons of the hypothalamic tuberoinfundibular system and concomitant development of hyperprolactinemia are accompanied by involvement of compensatory synthesis of dopamine (DA) by non-dopaminergic neurons expressing single complementary enzymes of synthesis of this neurotransmitter. Degeneration of DA-ergic neurons was produced by a stereotaxic injection into the brain lateral ventricles of 6-hydroxydopamine (6-OHDA) - a specific neurotoxin of DA-ergic neurons. 14 and 45 days after the toxin administration there were determined concentration of prolactine in peripheral blood by methods of immunoenzyme and radioimmunological analyses as well as the DA amount in the arcuate nucleus by the method of highly efficient liquid chromatography with electrochemical detection. In a part of the animals, slices were prepared from the mediobasal hypothalamus (arcuate nucleus and medial eminence) and perfused with Krebs-Ringer medium; then the DA concentration was determined in the slices and in the incubation medium. 14 days after the neurotoxin administration there were revealed an increase of blood prolactine concentration and a decrease of DA concentration in the arcuate nucleus in vivo as well a decrease of the total DA amount in the slices and incubation medium in experiments in vitro. 45 days after the neurotoxin administration, all the above parameters returned to the normal level. This, the obtained data indicate that the hyperlactinemia and DA deficit appearing during degeneration of the arcuate nucleus DA-ergic neurons seem to be compensated due to an enhancement of DA synthesis by non-dopaminergic monoenzyme neurons of arctuate nucleus.     

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.