[Behavioral effects of oxidative stress].

It is known that oxidative stress is involved in the development of many pathological processes, but at the same time it became clear that it can play a significant role in processes of physiological adaptation. There are suggestions that oxidative stress can make a significant contribution to the disorders of learning and memory processes. This assumption served as a basis of this study, in which we tried to reveal the effects of low and high-level oxidative stress on behavior of rats in a multi-way maze. As an experimental model of oxidative stress, induced by hydrogen peroxide (H2O2) we used oral administration of 0.1 and 0.2% aqueous solution of H2O2. It was found that animals treated with 0.1% hydrogen peroxide, significantly increased their behavioral activity and in the stage of "automatic behavior" they passed all the maze twice as fast as animals from the control group. But in case of 0.2% H2O2 locomotor activity of animals decreased sharply and for maze passing they spent in average 4-fold more time in comparison with the control group. In our opinion, the first dose of stress was within the range of hormetic mechanism's stimulation, but increased dose, led to its inhibition, which is a classic manifestation of hormetic effects of oxidative stress.

[THE ROLE OF NITRIC OXIDE AND BLOOD RHEOLOGICAL PROPERTIES IN THE MAINTENANCE OF A TEMPERATURE HOMEOSTASIS IN THE BRAIN TISSUE].

The problem of temperature regulation in the brain tissue in conditions of whole body hyperthermia was investigated in experiments on white rats. The received results revealed that the brain is provided with a highly efficient system for temperature autoregulation against the changes in environmental temperature. According to our data the upper limit of this autoregulation (for rats, at least) is about the 450C of environmental temperature. The important role in functioning of this autoregulatory system belongs to Nitric Oxide. It is revealed also that the increase in the index of red cells aggregability may significantly hinder (among other things) maintaining of the temperature homeostasis in the brain.

Local blood flow in the dorsal hippocampus and cerebellar cortex in the offspring of iodine-deficient rats.

Experimental studies demonstrated that hypothyroidism can lead to depressive behavior and that thyroid hormones can have antidepressant effects. Postnatal changes in local blood flow in the dorsal hippocampus and cerebellar cortex were studied in the offspring of rats kept in conditions of iodine deficiency at conception and throughout gestation. The data obtained from these studies showed that severe limitation of iodine intake before and during gestation leads to marked deficiency in the blood supply to both of these brain structures, though the decrease in local blood flow in the dorsal hippocampus was more marked. Addition of iodine to the diet of females prevented this deficit of blood flow in both structures.

The effects of fentanyl and morphine on local blood flow and oxygen tension in the frontoparietal cortex and nucleus accumbens of the brain in white rats.

Studies on white rats showed that intraperitoneal administration of small doses of fentanyl (0.005 mg/kg) and morphine (1 mg/kg) decreased local blood flow and increased partial pressure of oxygen (pO2) in the frontoparietal area of the cerebral cortex but had the opposite effects in the nucleus accumbens--where there was a significant increase in local blood flow and just as significant a decrease in pO2. Analysis of the data led to the conclusion that these changes must result from significant changes in functional-metabolic activity in these structures, induced by intraperitoneal administration of fentanyl or morphine.

Behavioral impairments in acute and chronic manganese poisoning in white rats.

Single p.o. doses of manganese chloride (MnCl2 x 4H2O; 50 mg/kg) induced significant and reversible decreases in total activity in white rats, along with worsening of the acquisition of an avoidance reaction in response to unconditioned and conditioned stimuli, increases in the latent period of conditioned reflex activity, and a temporary worsening of the learning process. Chronic manganese poisoning (daily p.o. manganese chloride at 20 or 50 mg/kg for one month) led to significant impairment of learning processes in a multipath maze but had no significant effect on reproduction of previously acquired stereotypical behavior.