[Development of serotonergic neurons of dorsal raphe nuclei in mice with knockout of monoamine oxidase A and 5-HT1A and 5-HT1B autoreceptor].

The morphological changes in the development of serotonergic neurons of the dorsal raphe nuclei in the medulla oblongata was studied by immunocytochemistry in mice with knockout of 1A and 1B serotonin autoreceptors as well as monoamine oxidase A. Serotonin autoreceptors regulate electric activity of serotonergic neurons as well as the synthesis and release of the neurotransmitter, while monoamine oxidase A catalyzes its degradation. These genetic modifications proved to have no effect on the number of serotonergic neurons in the medulla oblongata but induced morphofunctional changes. Decreased cell size and increased intracellular serotonin level were observed in the case of monoamine oxidase A deficiency, while excessive cell size and decreased intracellular serotonin level were observed in the case of autoreceptor deficiency. The data obtained confirm the hypothesis of autoregulation of serotonergic neurons in development.

[Development of central and peripheral serotonin-producing systems in rats in ontogenesis].

The work deals with study of development of central and peripheral serotonin-producing systems in rat ontogenesis before and after formation of the blood-brain barrier. By the method of highly efficient liquid chromatography it has been shown that the serotonin level in peripheral blood before formation of the blood-brain barrier (in fetuses and neonatal rats) is sufficiently high for realization of physiological effect on target cells and organs. At the period of formation of the blood-brain barrier the serotonin level in brain sharply rises, whereas the serotonin concentration and amount in plasma and duodenum increase insignificantly. Completion of formation of the blood-brain barrier is accompanied by a significant increase of the serotonin content in duodenum, probably for maintenance of the high serotonin level in blood. To evaluate secretory activity, the mean rate of daily increment of the serotonin in the studied tissues was calculated. In brain, this parameter was maximal at the period of formation of the blood-brain barrier and then sharply fell, whereas in duodenum it rose markedly after completion of the barrier formation. In plasma this parameter decreased statistically significantly at the period of formation of the blood-brain barrier - from the 4th to the 16th postnatal days. This allows thinking that brain before formation of the blood-brain barrier is a most important source of serotonin in peripheral blood.

[Brain is a source of blood serotonin in rats during perinatal development].

The aim of this study was to test our hypothesis that the brain functions as an endocrine organ before the blood-brain barrier is formed. A model of drug-inhibited serotonin synthesis in the brain using a single stereotactic administration of p-chlorophenylalanine, an inhibitor of serotonin synthesis, was developed. The inhibitor dose inducing the maximum effect in the brain and no effect on serotonin synthesis in the periphery was experimentally selected. The concentration of serotonin and its metabolites (5-hydroxytryptophan and 5-hydroxy-indoleacetic acid) was studied by high performance liquid chromatography in the brain, duodenum, and blood (separately in plasma and platelets). The optimal p-chlorophenylalanine dose (200 mg/kg) was shown to induce a sharp decrease in the brain level of serotonin (70%), a moderate decrease in plasma (16%) and platelets (26%), and an insignificant decrease in the duodenum (12%). At the same time, this dose did not decrease the 5-hydroxytryptophan level in the intestine. This suggests that the decrease in the blood level of serotonin was due to the inhibition of its synthesis in the brain, whereas the decrease in the duodenum level of serotonin was due to the compensatory release to blood while its synthetic rate remained unaltered. Thus, the developing brain before the blood-brain barrier formation was shown to secrete serotonin into blood.

[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.

[Changes in blood plasma volume in rats during ontogenesis].

The dynamics of blood plasma volume were studied for the first time in rats during ontogenesis. The significance of blood plasma volume is estimated in the transport of physiologically active substances to cells and target organs during development. The blood plasma volume was measured in male and female rats during embryogenesis on day 18 (E18), perinatal development on E21 and day of postnatal development (P3), and postnatal development on P15 and P30. Body mass was determined in the same animals and correlation was estimated between the blood plasma volume and body mass. The plasma volume increased 1.9-fold from E18 to E21, 1.4-fold from E21 to P3, 2.1-fold from P3 to P15, and 3.4-fold from P15 to P30. The body mass increased 5-fold from E18 to E21, 2-fold from E21 to P3, 2.3-fold from P3 to P15, and 3.2-fold from P15 to P30. The ratio of blood plasma to body mass was the highest on E18 (19%) and decreased twice by E21. This index varied from 5.4 to 4.8% during postnatal development. No sex-related differences in these indices were found in rats. The results obtained make it possible to determine the total content of physiologically active substances on the basis of their plasma concentration and, thereby, estimate the efficiency of secretory organs.

[The brain is one of the most important sources of dopamine in general circulation during perinatal ontogenesis in rats].

This study was aimed to test our hypothesis that dopamine synthesized in the neurons of the brain is delivered to the general circulation in rats during prenatal and early postnatal periods, i.e. before the establishment of the blood-brain barrier. Using the high performance liquid chromatography, it was demonstrated that the dopamine concentration and content in the peripheral blood in fetuses and neonatal rats (i.e. before the establishment of the blood-brain barrier) greatly exceeded those in adult rats. Moreover, the establishment of the blood-brain barrier was accompanied by the significant increase of the dopamine concentration in the brain. A drop of the dopamine concentration in fetal plasma after the microsurgical lesion of the forebrain and mesencephalon (encephalectomy) are considered as direct evidence in favour of our hypothesis.

[The formation and regulation of the lactotrophic function of the hypophysis in the prenatal period of rat development. I. Prolactin secretion by the hypophysis and the role of dopamine in this process]. / Stanovlenie i reguliatsiia laktotrofnoi funktsii gipofiza v prenatal'nom periode razvitiia krys. I. Sekretsiia prolaktina gipofizom i rol' dofamina v étom protsesse.

Using radioimmunologic assay, we have studied the content of prolactin in the pituitary and its release into general circulation in 18-, 20-, and 22-day-old rat fetuses under normal conditions and after pharmacological block of dopamine receptors. Prolactin was found in the pituitaries of the fetuses from day 5 and in blood serum, from day 18; its levels were progressively increasing up to the end of prenatal development. Administration of haloperidol, an inhibitor of dopamine D2 receptors, to pregnant female increased the level of prolactin in fetus plasma from day 20 and diminished its content in the pituitary gland from day 22. These data provide evidence for secretion of prolactin by the pituitary and sensitivity of lactotrophs to dopamine during prenatal development.

[The formation and regulation of the lactotrophic function of the hypophysis in the prenatal period of rat development. II. Dopamine inhibitory control of prolactin secretion]. / Stanovlenie i reguliatsiia laktotrofnoi funktsii gipofiza v prenatal'nom periode razvitiia krys. II. Dofaminovyi ingibitornyi kontrol' sekretsii prolaktina.

Using the technique of radioimmunoassay, we studied the secretion of prolactin and its control by dopaminergic system in 22-day-old rat fetuses under normal conditions and after pharmacological inhibition of dopamine receptors. In order to elucidate the origin of prolactin and dopamine participating in this process, we used decapitation and encephalectomy of fetuses in utero. Decapitation of fetuses did not result in any changes of baseline prolactin secretion into blood in males and insignificantly decreased it in females as compared with nonoperated controls. We conclude that prolactin detected in blood plasma of nonoperated fetuses does not originate in the pituitary, and any prolactin synthesized in the pituitary is not secreted into blood. Inhibition of dopamine receptors in decapitated fetuses did not result in any changes of prolactin level in blood. This provided evidence that in nonoperated fetuses, it is pituitary prolactin which is secreted in response to haloperidol, while the secretion of nonpituitary prolactin is not controlled by dopamine. Encephalectomy increased prolactin level in plasma and resulted in a drastic decrease of its level in the pituitary. The block of dopamine receptors did not affect the level of prolactin in blood plasma or pituitary of encephalectomized fetuses. We conclude that the inhibitory dopaminergic control of prolactin secretion by the pituitary during the prenatal period is accomplished just as in adult animals by dopaminergic neurons of hypothalamus.

[Effects of male sex hormones on specific uptake and release of 3H-serotonin in the rat hypothalamus in vitro]. / Vliianie muzhskikh polovykh gormonov na spetsificheskii zakhvat i vydelenie 3H-serotonina gipotalamusom krysy 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.

[The formation of the catecholaminergic system of the hypothalamus in rats. Dopamine uptake and release]. / Formirovanie katekholaminergicheskoi sistemy gipotalamusa u krys. Zakhvat i vydelenie dofamina.

The development of the hypothalamic catecholaminergic (CA) system during ontogenesis in rats has been studied with the isotopic biochemical technique in vitro. It has been demonstrated, that at the 15th fetal day, the CA system was functionally inactive at least in its ability for the uptake and K(+)-stimulated release of catecholamines. Since the 16th fetal day, hypothalamic neuronal elements gained an ability for specific uptake and K(+)-stimulated release of the exogenous radioactively labeled dopamine increased significantly. The specific uptake doubled from the 20th fetal till the 9th postnatal day, whereas K(+)-stimulated release doubled between the 9th 45th postnatal days.

[Ca2+-dependent secretion of serotonin by the rat hypothalamus during ontogenesis]. / Ca2+-zavisimaia sekretsiia serotonina iz gipotalamusa krys v ontogeneze.

A study was made of functional maturity of the terminal part of serotoninergic system of rat hypothalamus in perinatal period: the maturity was estimated by the ability to release serotonin. The release of specifically taken up serotonin (3H-5-OT) by the tissue of hypothalamus of 16-20-day-old rat fetuses, 8-9-day males and adult males was studied in the perfusion system. Spontaneous release of the labelled amine was recorded in the earliest studied period--on the 16th day of the prenatal period, but the response to K+ depolarization was absent at this time. For the first time the increase of the rate of 3H-5-OT release in response to depolarization was noted on the 17th day of development. In the absence of Ca2+ depolarizing stimulus produced no increase in the release of the labelled product. Similar results were obtained with perfusion of fetal hypothalamus on the 18t hand 20th days of development. In neonatal animals the release of 5-OT in response to depolarization was equal to that in adults. The data obtained point to a possible functioning of serotoninergic elements of hypothalamus in the perinatal period in rats.

[Participation of intestinal hormones in the development of the pancreatic B-cell reactivity of rat fetuses to the action of glucose]. / Uchastie kishechnykh gormonov v razvitii reaktivnosti B-kletok podzheludochnoi zhelezy plodov krys k deistviiu gliukozy.

The involvement of intestinal hormones in the development of insulin release from rat fetal pancreas was investigated. B-cell responses were determined by changes in the concentration of immunoreactive insulin after glucose addition to the incubation medium. Coincubation of fragments of fetal pancreas and duodenum from adult and newborn rats and from 21.5-day-old fetus has shown that intestinal factors can recover the response of pancreas to glucose in fetuses with experimentally removed hypothalamus and hypophysis. Besides, the intestinal factors in the fetus were found to potentiate the effect of high glucose concentrations on B cells, but had no insulinotropic effect at physiological glucose concentration in the medium. The data obtained suggest that even in the antenatal period the intestinal, along with cephalic factors, can serve as modulators of glucose action on islet B cells.

[Possible direct action of hypothalamic factors on the development of pancreatic hormonal activity]. / Vozmozhnosti priamogo deistviia gipotalamicheskikh faktorov na razvitie gormonal'noi aktivnosti podzheludochnoi zhelezi.

Possible mechanisms of hypothalamic control of the pancreas endocrine function in prenatal ontogenesis were investigated. For this purpose reactivity of pancreatic B-cells to glucose was studied in vitro and in vivo on rat fetuses. Incubation of pancreas fragments of encephalectomized fetuses in the medium containing preincubated hypothalamus fragments of adult rats, newborn rats or 21.5-day old fetuses did not compensate the operation effects. The glands remained refractory to glucose. Similar results were obtained with the introduction of hypothalamus homogenate to decapitated fetuses. Hypothalamus homogenate did not reduce the response to glucose in the absence of hypophysis. The data obtained indicate that hypothalamic insulinotropic factors have no direct action on the insular tissue of the fetus, the effect being hypophysis-mediated.