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We compared the levels of functional activity of cells in each adrenal zone with blood levels of corticosterone, testosterone, and neuropeptide Y in control and hippocampectomized F1(C57BL/6×DBA/2) mice during modeling of metabolic, motivational, and cognitive tension. The morphofunctional state of the adrenal glands was studied using a new morphometric approach. It was found that hippocampectomy changed the testosterone response to neurobiological stimuli; similar changes were observed in the zona reticularis of the adrenal cortex producing dehydroepiandrosterone that is involved in the regulation of testosterone secretion. At the same time, hippocampectomy enhanced the response of the peptide hormone; the index of functional activity of chromaffin cells producing this hormone also increased. These findings allow us to put forward a hypothesis that the hippocampus is involved in the regulation of mutual influences of the studied hormones and that it modulates the sensitivity of testosterone and NPY to metabolic and cognitive factors.

It was found that male BALB/c and F1(C57BL/6×DBA/2) mice are able to recognize the structure of a complex food-gathering task, when modeling the information loading similar to intellectual work in humans. There were significant differences between linear and hybrid animals in the pattern of learning process formation and prevailing psychoemotional reactions that accompany information load. Factors of information loading (uncertainty of maze environment and solution of the food-gathering task) had a specific influence on the CNS and manifested in individual non-specific features. The presented experimental conditions (changes in the metabolic and functional state) revealed pronounced intergroup differences in the reaction of the functional zones of the adrenal cortex. In hybrid mice, information loading induced a significant decrease in testosterone level and thickness of the zona reticularis producing precursor hormones. This is probably due to disruption of interactions in the adrenal-thyroid system in hybrid mice, whereas in BALB/c mice, these interactions fully protect from suppression of testosterone production, the main anabolic hormone. The individual characteristics of the response to information loading can be formed as a result of unequal involvement of the psychophysiological, psychological, and autonomic systems responsible for adaptation to environmental factors.

The serum hormone concentrations were studied in a group of male F1 (C57BL/6×DBA/2) mice in different states of food activity (satiety, 24-h food deprivation, and cognitive load against the background of food deprivation). The hormonal response depended on food activity: the content of leptin, triiodothyronine, and testosterone decreased in hungry animals, while during cognitive load (learning), we observed a decrease in the concentrations of ghrelin, leptin, thyroxine, and testosterone. The exceptions were neuropeptide Y (its concentration increased in hungry animals) and corticosterone (its level remained unchanged). The use of hierarchical cluster analysis allowed identifying functional organization of the relationships within the hormonal ensemble that underwent plastic changes depending on the state of the organism. It was shown that the hormonal ensemble was system-organized in the form of a "core" that determines stability of the system and the "field", within which functional interactions of the hormones are preserved.

We report here our studies of the relationship between mitogen-activated secretion of cytokines by splenocytes and the nature of behavior in (C57BL/6 × DBA/2)F1 mice in environments with different levels of spatial complexity: simple, in the form of the home cage, an enriched cage, and a maze. Increases in aggressive and neurotic manifestations in social conditions occurring only in the enriched environment were accompanied by suppression of the secretion of interleukins IL-2, IL-4, IL-6, and IL-10 independently of their structural-functional properties. The opposite effect, with significant increases in the production of all the cytokines studied, was seen in the case of stereotypical goal-directed behavior in the maze. It is suggested that the cellular elements of the immune system – splenocytes – are involved in mediating the body’s highly differentiated adaptive response induced by the social and cognition factors, the extent of which was determined by specific physiological-biochemical systems.

We report here studies of the consequences of lesioning of the dorsal hippocampus of DBA/C57 F1 mice during training in a complex multiple-choice maze in conditions of free selection. Hippocampectomized (HPC) mice were found to be able to form a four-component food-procuring skill in cyclic form. The main features were linked with the nature of the execution of exploratory activity, behavioral effectiveness, and the extinction of errors. While in controls each of these processes followed a common exponential law, each component in HPC mice had independent dynamics. The main hippocampectomy-associated effects at the stabilization stage consisted not only of a sharp decrease in the time during which a high level of motivation was maintained, but also of difficulty in transferring from unorganized behavior to organized behavior. It is suggested that the hippocampus operates not so much in learning and memory as in the organization of the operative dominant supporting the stability of attention on execution of an acquired skill

We report here studies of spatial imprinting on the formation of a cyclical food-procuring skill in a multiple-choice maze in adult DBA/2J C57BL/6J F1 mice in conditions of free choice. In contrast to control mice initially trained in conditions of environmental constancy, the experimental group was exposed to changes in the maze space over the 3 min of 1–2 trials. Control mice were able to solve the food-procuring task after nine experiments, while experimental animals remained at the situational behavior stage, which was inappropriate to the task conditions. The inability to organize the skill on the principle of least action provoked a negative psychoemotional state. The study results showed that spatial information obtained during the period of familiarization with the environment was not only fixed and apparent at the stage of organizing the skill, but also had significant influences on the direction and result of the cognitive process.

We studied the effects of food deprivation, spatial complexity of environment, and cognitive strain on blood level of testosterone in male (C57Bl/6×DBA/2)F1 mice. Hormone concentration decreased after exposure to any factor and this decrease depended on combined impact to the factors. Testosterone concentration was most sensitive to cognitive strain against the background of food deprivation. The total response of testosterone under conditions of enriched environment and activation of social interactions in the form of neurotic and aggressive behavior provoked by food deprivation was not equal to the sum of individual effects of these factors. Testosterone response to combined exposure to external and internal factors reflected systemic effect.

Three groups of BALB/c mice were trained to a food-procuring behavior in a multiple-choice maze allowing operative changes to the environmental geometry. Control animals were trained in maze 1 (M1), which has two variants for transfers between its halves. Maze M2 had a single route for this transfer; animals of experimental group 1 for one trial and those of experimental group 2 for two trials were placed in M2, after which they were placed in M1. The study results showed that regardless of the frequency of and interval between repeats of trajectory segments in M2, the information obtained during this short period was persistently used in solving the task in M1. Despite the fact that the imprinted version of passage contradicted the minimum action principle, the experimental animals differed from controls in not being able to eliminate it from the structure of the skill, which hindered optimization of the behavior.

Studies of the effects of 10-min clinical death in mongrel rats, induced by complete circulatory arrest, on the mechanisms of memory, showed that the content of already formed memories (“what to do?”), i.e., the structure of a food-procuring habit, motivational activity, and the level of organization of behavior, was completely retained 12 days after resuscitation regardless of how many traces were formed before the experimental procedure. Transient changes seen after clinical death mainly affected the process of performing the habit (“how to do it?”): there was a decrease in the ability to work, along with degradation of performance parameters such as readiness, mobilization activity, and the stability with which memory traces were performed. The rate of recovery of these aspects depended on the initial level of conditioned reflex activity in the rats: the higher this level, the more rapidly the performance parameters returned to the baseline level. It is suggested that these disturbances in the process of reproduction were non-specific in nature and could be due to the post-operative hyperexcitability of the animals.

The characteristics of protein metabolism associated with cognitive activity were studied in neurons of layers III and IV of the sensorimotor cortex of rats, using two groups of Wistar rats. Regardless of the success of learning, information loading was most clearly reflected in the associative neurons of layer III. In rats with poor learning ability, these neurons showed increases in nuclear and cytoplasmic size, along with increases in protein concentration and content. The clearest changes in efferent neurons (layer V) were increases in the area and protein content, occurring only in the cytoplasm. In rats with good learning outcomes, all cytochemical parameters responded to information loading with decreases in layer III and increases in layer V protein contents and concentrations, affecting both the cytoplasm and nucleus. The question of whether the vector of changes in neuronal protein metabolism in response to information loading can be regarded as a measure of the individual features of higher nervous activity is discussed, as is the question of whether the magnitude of these changes is a measure of the complexity of a cognitive task.

The effects of 5-fold injections of normal saline were studied in Wistar rats in two conditioned reflex situations: defense and alimentary. Intact animals developed conditioned pain avoidance reflex in repeated tail-flick test after 60 presentations over 3 days. Two injections of normal saline were sufficient for the formation of a stable negative stress status in experimental rats, which manifested by a drastic increase in tactile sensitivity persisting for 5 days after discontinuation of injections. Only 15% experimental rats vs. 40% intact animals developed the food-procuring response in a multialternative maze. Presumably, repeated injections of normal saline should be regarded as a potent negative stress factor modulating animals behavior, and these signs should be taken into consideration, when interpreting the effects observed in pharmacological investigations.

Quantitative cytochemical analysis of the activities of glucose-6-phosphate dehydrogenase, aminopeptidase, and glutamate dehydrogenase in the brain of Wistar rats with different learning abilities revealed a difference in the level of hippocampal aminopeptidase activity. Alcohol-nonpreferring rats showed lower activity of glucose-6-phosphate dehydrogenase in the nucleus accumbens compared with intact rats.