The aim of the present work was to study the involvement of the dopaminergic system of the telencephalic and diencephalic areas of the vertebrate brain in the organization of the sleep-waking cycle in cold-blooded and warm-blooded vertebrates. Immunohistochemical studies of tyrosine hydroxylase content, this being the key enzyme in dopamine synthesis, in the striatum, supraoptic and arcuate nuclei, and zona incerta of the hypothalamus of sturgeon and mammals (rats) of three age groups (14 and 30 days and adults), in conditions of tactile and sleep-deprivation stressors. In fish, transient stress was followed by the detection of tyrosine hydroxylase-immunoreactive cells in all parts of the brain. In prolonged stress, tyrosine hydroxylase-immunoreactive cells and fibers were not found in the forebrain, though they were well represented in the hypothalamic nuclei. In 14-day-old rat pups, 2-h sleep deprivation increased the tyrosine hydroxylase content of fibers in the caudate nucleus and cells in the zona incerta of the hypothalamus, while 30-day-old animals subjected to 6-h sleep deprivation showed increases in tyrosine hydroxylaseimmunoreactive material contents in cells in the paraventricular nucleus and decreases in the quantity in fibers. In adult rats, the arcuate nucleus and zona incerta showed decreases in the content of tyrosine hydroxylase-immunoreactive material on the background of sleep deprivation, with increases during postdeprivation sleep. These data are discussed in the light of the phylo- and ontogenetic development of the neurosecretory and neurotransmitter functions of the dopaminergic system in the evolutionarily ancient diencephalic and evolutionarily young telencephalic areas of the vertebrate brain as major systems triggering and maintaining the functional states of the body during the sleep-waking cycle.

We studied the effect of Hypericum extract on activity of the hypothalamic-pituitary-adrenal system in rats. In rats exposed to stress after a 30-day daily oral treatment with Hypericum extract, the weight of the adrenals and ACTH concentration were lower than in controls. Hence, treatment with Hypericum extract improved resistance to stress and prevented exhausting of the hypothalamic-pituitary-adrenal system.

In vivo and in vitro experiments on rats and isolated fragments of the thyroid gland showed 3H-oxytocin incorporation into thyrocytes followed by activation of the synthesis and release of thyroid hormones. Norepinephrine in vivo activates the thyroid gland, but combined action of norepinephrine and oxytocin suppressed in vivo and in vitro thyroid-stimulating effects of oxytocin. Key Words: thyroid gland; oxytocin; epinephrineVarious stress factors increase blood content of some hormones, responsible for the reaction to specific and nonspecific stress components. The increase in blood concentrations of catecholamine neurohormones of the adrenal medulla, epinephrine and norepinephrine (NE), is the major component of the hormonal reaction to stress. Hypothalamic nonapeptide hormones vasopressin and oxytocin (OT) are also released into the blood under the effect of various factors [4][5][6][7]. In light of this, combined effects of various neurohormones on target organs during stress are of considerable interest. In our previous experiments, we studied the reactions of rat thyroid gland (TG) in vivo [1] and thyrocytes in vitro [8] to combined action of vasopressin and epinephrine. However, there are no published data on the effects of combined treatment with OT and NE on mammalian TG. MATERIALS AND METHODSExperiments were performed on adult male Wistar rats weighing 140-160 g.In in vivo experiments, neurohormones and their combination were injected intraperitoneally 30 rain Laboratory of Neuroendocrinology, I. M. Sechenov Institute of Evolutional Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg before decapitation. The animals were divided into 4 groups (n=5) and injected with 1 ml physiological saline (control), 15 ng/100 g body weight OT, 30 ng/ 100 g body weight NE, and OT and NE in the same doses, respectively.After decapitation, TG was refnoved, fixed in Bouin's fluid, and subjected to routine histological treatment. The height of thyrocytes was measured on slices stained with azan by Heidenhain's method (x900).In vitro experiments were performed on 20 rats. Cross-sections (400 /.t) from the central zone of TG lobes were incubated in medium 199M saturated with carbogen (95% 02 and 5% CO2) at 37~ The medium was changed every 30 min. After 90-rain preincubation, the slices were transferred into the medium containing test neurohormones (60 min). We analyzed 5 groups of TG fragments incubated in media containing various neurohormones (100 pg/ml 3H-OT, 100 pg/ ml OT, 10 pM NE hydrotartrate, or both neurohormones in the same concentrations) or without neurohormones (control).All samples (except for those incubated with 3H-OT) were initially incubated in the medium containing 3H-leucine for 30 min. Some slices were then transferred into the medium without 3H-leucine, and others were further incubated with 3H-leucine. This method allows to assess the dynamics of thyroglobulin formation in thyrocytes and to determine the intensity of its transfer into the colloid or release from follicles [3,12,1...

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