Vasopressin and oxytocin in stress.

Though oxytocin and vasopressin are similar in structure and are produced in the same brain regions, they show specific responses under stress conditions. In humans, increases in peripheral blood vasopressin appear to be a consistent finding during many acute stress situations, while in rats, vasopressin secretion is unresponsive to several stimuli known to induce ACTH and catecholamine release. Even decreases in vasopressin levels during stress were described. In accordance with others, we observed enhanced vasopressin release in response to stress stimuli with an osmotic component such as hypertonic saline injection but also during exposure of rats to a warm environment. Immobilization stress which fails to induce vasopressin release was reported to increase hypothalamic vasopressin mRNA and plasma vasopressin levels in chronically adreno-demedullated rats. Unlike vasopressin, oxytocin may be considered a typical stress hormone responding to osmotic as well as other stress stimuli. We found that acute exposure of rats to immobilization stress resulted in an increase in oxytocin mRNA level. In addition, we have shown that magnocellular neurons of the paraventricular nucleus, but not the supraoptic nucleus, are essential for oxytocin release during immobilization stress. The release of posterior pituitary hormones represents an important component of the stress response.

Albumin content in the developing rat brain in relation to the blood-brain barrier.

The problem of functional development of the blood-brain barrier (BBB) has been the subject of intensive discussion for many years. Some morphological data indicate that the cerebral endothelium becomes impermeable to macromolecules already before birth. On the other hand, specific features in transport of macromolecular markers in fetuses and neonates were described supporting the hypothesis of an immature BBB. Part of the confusion seems to result from inadequately designed experiments, concerning frequently the administration of markers. In our study we decided not to use an exogenous marker and to follow up to changes of endogenous albumin content in selected brain regions of rats from the neonatal period to adulthood. Shortly after birth, the concentrations of albumin in all brain regions studied (hypothalamus, hippocampus, cortex, striatum, brainstem, cerebellum) were significantly higher compared to those of adult animals. Moreover, the distribution of albumin within these structures in newborns differed from that in adults. Several factors may contribute to the accumulation of albumin in the developing rat brain, including increased permeability of the BBB.

[The circadian rhythm of the formation of stress stomach ulcers in rats]. / Tsirkadiannyi ritm obrazovaniia stressornykh iazv zheludka u krys.

Areas of stress-induced gastric ulceration vary parallels with changes of corticosterone levels. The ulceration was greater in the morning during low basal corticosterone level than in the evening during high one. Adrenalectomy ceased the circadian basal rhythm of corticosterone and the rhythm of stress-induced ulceration. The decrease of ulceration in the evening seems to indicate an increase of the body adaptability resulting from the circadian corticosterone increase.

[The circadian rhythm of the content of corticosteroids and of pain sensitivity in humans and rats]. / Tsirkadiannyi ritm soderzhaniia kortikosteroidov i bolevoi chuvstvitel'nosti u liudei i krys.

The circadian relationships between blood corticosteroids and latent period of pain reaction to hot stimulation were investigated in man and rats. There were no correlation of blood corticosteroids levels and pain latent period but the latent period increased during those time of day when the corticosteroids levels were higher in total: man--morning and day, rats--evening and night.