[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.

[Hypothalamo-pituitary system controls the development of humoral immune response during prenatal ontogenesis in rats]. / Gipotalamo-gipofizarnaia sistema kontroliruet razvitie gumoral'nogo immunnogo otveta u krys v prenatal'nom ontogeneze.

We studied the influence of the neuroendocrine system on the development of humoral immune response to sheep erythrocytes in rat fetuses. The removal of brain in utero by decapitation of 18-day fetuses induced a fourfold increase in the number of antibody-forming cells in the liver, as compared to the unoperated fetuses. After the removal of the forebrain, including hypothalamus (encephalectomy), the number of antibody-forming cells was comparable to that in unoperated fetuses. The observed increase in the number of antibody-forming cells in the liver was not due to a disturbed migration of precursors of B-lymphocytes in the spleen, since their content in the spleen was also four times that in the encephalectomized and unoperated fetuses. The increased number of antibody-forming cells in decapitated fetuses could be due to an enhanced proliferative activity of the lymphocytes in the liver of these fetuses. It has been proposed that humoral immunity is controlled by the hypothalamo-pituitary-adrenal system already during prenatal development; the adrenocorticotropic hormone and glucocorticoids appear to be involved in this regulation.

[Tyrosine hydroxylase expression in differentiating neurons of the rat arcuate nucleus: inhibitory effect of serotoninergic afferents]. / Ekspressiia tirozingidroksilazy v differentsiruiushchikhsia neironakh arkuatnogo iadra krys: ingibitornoe vliianie serotoninergicheskikh afferentov.

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.

[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.

[The uptake of 3H-serotonin by neural elements of the rat hypothalamus in ontogeny]. / Zakhvat 3H-serotonina nervnymi élementami gipotalamusa krys v ontogeneze.

Development of serotoninergic system of rat hypothalamus has been studied. The level of its maturity was measured by specific absorption of 3H-serotonin by hypothalamus of fetuses (days 16-20 of intra-uterine development), newborn (9 days after birth) and adult rats. Inhibitors of specific serotonin capture by serotoninergic neural elements (cocaine, fluoxetin and cytalopram) were used in control experiments. Specific uptake of 3H-serotonin by hypothalamus was detected on day 16 of intra-uterine development. It increased twice by day 18 and remained unchanged until birth. No statistically significant increase of 3H-serotonin uptake was detected in newborn and adult animals.

[Changes in testosterone levels in rabbit embryo testes after removal of the hypothalamus (encephalectomy)]. / Izmenenie kontsentratsii testosterona v semennikakh plodov krolika posle udaleniia gipotalamusa (éntsefaléktomii).

Brain hypothalamus region was removed by encephalectomy in utero in 21-23-day-old rabbit fetuses to find out when hypothalamic control over testicular androgenous function was set up during rabbit prenatal development. Testosterone concentration in testicular tissue was measured by radioimmunoassay at different terms after the operation. Encephalectomy resulted in a reliable decrease of testosterone concentration in 29- and 25-day-old fetuses, however, no significant changes were observed in 23-day-old fetuses. The greatest reduction in hormone gland concentration was noted in 25-day-old fetuses, encephalectomized on day 23 of their development. Introduction of LH-RH to 25-day-old encephalectomized fetuses 30 min before fixation significantly increased androgen concentration in the gland. The data obtained indicate that hypothalamic control over testicular androgenous function is set up on days 23-25 of prenatal development.

[Changes in testosterone levels in the testes of rat fetus after removal of the hypothalamus]. / Izmenenie kontsentratsii testosterona v semennikakh plodov krys posle udaleniia gipotalamusa.

To specify the time of setting in of the hypothalamic control over testicular androgenous function in the prenatal development of rats, the brain hypothalamic area of 18.5-day-old fetuses was excised by encephalectomy in utero. Three days after the operation, i. e. on day 21.5 of the development, testosterone concentration in the testes was measured by radioimmunoassay. Testosterone concentration in the testes of encephalectomized fetuses was significantly decreased as compared with intact fetuses. Administration of LH-RH into the encephalectomized fetuses 2 hours prior to fixation removed the effect of encephalectomy on testosterone concentration in the testicular tissue. The data evidence the establishment of the hypothalamic control over androgenous function of the testes in rat fetuses at the end of the prenatal development.

[Reaction of rat fetal adrenals to stress exposure under encephalectomy]. / Reaktsiia nadpochehnikov plodov krysy na stressornoe vozdeistvie v usloviiakh éntsefaléktomii.

The concentration of corticosterone in the suprarenals after the stress effect (injection of formol) was studied in 20.5 days old foetuses of the adrenalectomized rats, using the method of competitive binding. The concentration of corticosterone in the suprarenals of normal foetuses increased reliably within 30 min after the injection of formol; this reaction was absent in the encephalectomized foetuses. The results obtained suggest the participation of embryonic hypothalamus in the organization of stress response during prenatal development of rats.

[Changes in the concentration of triiodothyronine and thyroxine in rabbit fetuses following encephalectomy]. / Izmenenie kontsentratsii triiodotironina i tiroksina u plodov krolika posle éntsefaléktomii.

Triiodothyronine (T3) and thyroxin (T4) were detected by radioimmunoassay in the thyroid gland and serum of encephalectomized and intact rabbit fetuses. Encephalectomy performed on the 22-23d day of development did not produce any effect on thyroid hormone concentrations in 29-day-old fetuses. However, on the 30th day the concentrations of T2 and T4 in the thyroid gland were significantly lower in the encephalectomized fetuses than in the intact ones. These findings were consistent with changes in the morphological structure of the thyroid gland. The results obtained indicate that the hypothalamus begins to control thyroid function in the rabbit fetuses apparently from the 30th day of prenatal life.

[Determination of thyroxine and triiodothyronine in the thyroid glands of encephalectomized rat fetuses]. / Opredelenie tiroksina i triiodtironina v schchitovidnoi zheleze éntsefaléktomirovannykh zarodyshei krysy.

Concentration of thyroxin and triiodothyronine in the thyroid gland of encephalectomized and intact fetuses of rats with normal and prolonged gestation period was determined by means of isotope methods. Encephalectomy of 19-day old fetuses did not produce any significant effect on the concentration of thyroid hormones in the gland 2 and 4 days after the operation. The results obtained pointed to the absence of the hypothalamic control over the thyroid function in prenatal development of rats.