The dynamics of measures reflecting the intensity of metabolic processes were studied in rats after i.p. injections of lipopolysaccharide (LPS, 100 μg/kg) at the end of a single long-lasting stress load in a 24-h restraint model. The volumes of oxygen consumed and cardon dioxide exhaled and the level of heat production were measured using a Phenomaster automated modular system (TSE Systems GmbH, Germany) at 3 h, 1 day, and 8 days after exposure. These metabolic parameters were found to increase 1 day after restraint stress in animals given physiological saline. These changes illustrate intensification of metabolic processes in rats at different times after experimental stress. These alterations persisted even into the long-term period after stress exposure and were present on study day 8. Individuals given LPS showed increased oxygen consumption and carbon dioxide production on day 1 of the poststress period, along with an increase in heat exchange. On day 8 after stress with subsequent immune modulation, metabolic parameters in rats decreased such that they were no different from those in intact animals. Thus, antigenic exposure by systemic administration of LPS had no effect on stress-induced activation of metabolic processes at the early stages of the study period but prevented stable increases in the intensity of metabolism in the long-term poststress period. These results, along with previously published data, suggest that the effects of LPS, which has immunoactive properties, are linked with its modulatory action on neuroendocrine mechanisms regulating homeostasis in mammals, particularly on exposure to stress.

Changes in the Shaganin lymphocyte index (ratio of the number of lymphocytes to segmented neutrophils) in the peripheral blood of rats after intraperitoneal administration of LPS (100 μg/kg) at the end of a single stress exposure in a model of 24-h restraint stress were studied. The lymphocyte index was analyzed 3 h later, on the 1st and 8th days after the stress load. Immobilization was accompanied by a decrease in this parameter 3 h after exposure. One day after the stress load, an increase in the lymphocyte index was noted, which remained on the 8th day of observation. LPS injection did not affect the changes in this parameter caused by 24-h immobilization on the 1st and 8th days of the study, but prevented a pronounced increase in the lymphocyte index on the 1st day after the stress load. The data obtained expand the existing scientific understanding of the specificity of the involvement of immunomodulatory substances in the implementation of adaptive-compensatory processes in mammals under conditions of emotional stress.

OBJECTIVE:To study neurological status and structural changes in the tracheal lymphoid tissue in rats with different resistance to emotional stress in experimental hemorrhagic stroke.MATERIAL AND METHODS:Evaluation of neurological deficit on the Menzies scale and a histological study of structural features of tracheal lymphoid tissue were performed on days 1, 3 and 7 of experimental hemorrhagic stroke in 98 Wistar male rats with different resistance to emotional stress. Stroke simulation was preceded by animal testing to determine individual stress resistance.RESULTS AND CONCLUSION:Neurological disorders are more pronounced in non-stress-resistant animals during all periods of observation. Lymphoid nodules of the tracheal wall of rats react with destruction of lymphoid cells and depletion of small lymphocytes observed in stress-resistant rats already on the 1st day of a stroke. On the 3rd day, the neurological deficit and changes in the cellular composition of the lymphoid formations of the trachea are most pronounced in both groups of rats. By the 7th day, a positive trend towards the restoration of the structure of tracheal lymphoid tissue and normal neurological status is detected only in rats resistant to emotional stress.

We studied the effect of LPS on the state of stress-marker organs in rats at various periods after a single exposure to long-term stress on the model of 24-h immobilization. The animals were intraperitoneally injected with LPS in a dose of 100 μg/kg immediately after the negative emotiogenic exposure. Changes in physiological parameters were evaluated 3 h, 1 day, and 8 days after immune stimulation. Acute stress was accompanied by a decrease in the weight of the thymus during all stages of the post-stress period. An increase in the relative weight of theadrenal glands in animals under these conditions was observed only on day 8 after restraint stress. The induction of immune reactions due to systemic treatment with LPS was shown to prevent involution of the spleen in the late stage after a single exposure to long-term stress (day 8). Hypertrophy of the adrenal glands, which serves as one of the typical reactions of mammals to negative emotiogenic factors, was not revealed during the post-stress period after antigenic stimulation. These data hold much promise for the development of new approaches to the use of immunoactive substances to prevent or reduce the severity of physiological changes after emotiogenic loads.

Specific features of neurological deficit and changes in the cellular composition of tracheal lymphoid structures during the immediate stage (day 1) of hemorrhagic stroke were studied in rats with various behavioral parameters. Modeling of hemorrhage in the left caudate nucleus of the brain was followed by the development of motor disturbances in the forelimb use asymmetry test and corner rotation paradigm. These animals preferred to use the left forelimb (ipsilateral to the side of hemorrhage) to lean on the cylinder wall. The frequency of using the right forelimb or both forelimbs was reduced under these conditions. The number of left-sided rotations increased, while the percentage of right-sided rotations decreased. The observed changes were accompanied by immune dysfunction. It was manifested in the depletion of lymphoid aggregates of the tracheal wall in lymphocytes and plasma cells. The severity of abnormal neurological symptoms and disturbances in immune homeostasis during the immediate stage of hemorrhagic stroke was greater in behaviorally passive rats than in active specimens.

In order to study the role of the lateral amygdala in the peptidergic mechanisms of stress resistance in rats, we measured the levels of beta-endorphin and substance P in the blood and hypothalamus of stress-resistant and stress-responding rats during emotional stress under conditions of a functional blockade of the basolateral amygdala by anodic polarization. Emotional stress was created by immobilization of rats within narrow chambers, with additional aperiodic electrocutaneous stimulation. It was found that lateral areas of the amygdala play an important role in the maintenance of stress-resistance mechanisms in rats. Their bilateral blockade decreased the resistance to stress. As well, in our experiment we found reciprocal relationships between blood plasma and hypothalamic levels of peptides (substance P and beta-endorphin) both in stress-resistant and stress-responding rats. Thus, peptidergic mechanisms of stress resistance are associated with functioning of the amygdala.

A quantitative study of lymphoid cells in the B- and T-cell-dependent areas of intestinal lymphoid nodules and mesenteric lymph nodes in behaviorally passive and active rats was performed at various periods after acute stress on the model of 1-h immobilization with simultaneous electrocutaneous stimulation. Stress exposure is accompanied by a decrease in the number of lymphoid cells in immunogenic structures of the gastrointestinal tract. Post-stress changes in the cytoarchitectonics of B- and T-cell-dependent areas in mesenteric lymph nodes of animals are less pronounced than in lymphoid nodules. Quantitative changes in lymphoid cells of B-cell-dependent areas in the small intestine of rats are greater than in T-cell-dependent areas. Changes in the cellular composition of immunogenic structures in the digestive system are most significant at the early stages of the post-stress period (1st week). Passive rats are characterized by significant changes in the cytoarchitectonics of B- and Tcell-dependent areas in the small intestine after extreme exposure, which illustrates functional exhaustion of the lymphoid tissue in stress-predisposed specimens.

Цель данной работы состояла в изучении структурных особенностей молекулы альбумина в крови поведенчески пассивных и активных крыс, прогностически предрасположенных и устойчивых к стрессорным воздействиям, при введении цитокинов и олигопептидов. Методы. Эксперименты проведены на 319 крысах-самцах Вистар с массой тела 220,0 ± 5,2 г. Крыс предварительно тестировали в открытом поле с оценкой поведенческих показателей и делили на пассивных (n = 126) и активных особей (n = 124). Животные с высокой ориентировочно-исследовательской активностью в данном тесте более устойчивы к стрессорным нагрузкам, чем пассивные особи [20, 21]. Структурные особенности молекулы альбумина в крови пассивных и активных крыс изучали до и после введения цитокинов и олигопептидов. Результаты. Установлено, что острая стрессорная нагрузка приводит к изменению свойств альбуминовых центров. Флуоресценция зонда CAPIDAN, как показатель состояния связывающих центров альбумина, в указанных условиях увеличивается у активных особей, но уменьшается у пассивных животных. Предварительное введение Семакса и пептида, вызывающего дельта-сон, модулирующих чувствительность к отрицательным последствиям стресса, оказывает влияние на альбуминовые показатели крови. В частности, Семакс снимает конформационные изменения молекулы сывороточного альбумина у крыс, предрасположенных к постстрессорным изменениям физиологических функций. Выявлено, что провоспалительный цитокин интерлейкин-1b и противовоспалительный цитокин интерлейкин-4 оказывают однонаправленное действие на свойства связывающих центров альбумина крови у особей с разными параметрами поведения. Интерлейкин-1b и интерлейкин-4 предупреждали вызванные отрицательным эмоциогенным воздействием изменения связывающей способности альбумина как у устойчивых, так и у предрасположенных к стрессу животных. Заключение. Более выраженные эффекты цитокинов на альбуминовые показатели крови у активных крыс по сравнению с пассивными особями связаны с различиями общей концентрации альбумина, обнаруженными у них в исходном состоянии. Кроме этого, указанные особенности могут быть обусловлены спецификой метаболических процессов у животных с разными характеристиками поведения. Structural peculiarities of the albumin molecule in blood samples from behaviorally passive and active rats (prognostically predisposed and resistant to stress exposures, respectively) were evaluated after administration of cytokines and oligopeptides. We revealed that acute stress is followed by a change in the properties of albumin sites. Under these conditions fluorescence of the CAPIDAN probe (criterion for the state of albumin binding sites) is elevated in active specimens, but decreases in passive animals. Pretreatment with Semax and delta sleep-inducing peptide, which modulate the sensitivity to negative consequences of stress, was shown to affect albumin parameters in the blood. For example, Semax abolishes a conformational change of the serum albumin molecule in rats predisposed to post-stress abnormalities in physiological functions. Our study showed that a proinflammatory cytokine interleukin-1b and anti-inflammatory cytokine interleukin-4 have a unidirectional effect on the properties of albumin binding sites in specimens with various behavioral characteristics. Interleukin-1b and interleukin-4 prevent a change in the binding capacity of albumin in stress-resistant and stress-predisposed animals after a negative emotiogenic exposure. The influence of cytokines on blood albumin parameters is more pronounced in behaviorally active rats than in passive specimens, which results from differences in the total albumin concentration in these animals under basal conditions. Moreover, these features can be related to the specifics of metabolic processes in animals with various behavioral characteristics.

Changes in peripheral blood cytokine contents in behaviorally passive and active Wistar rats were assessed at different time points after acute stressing using a restraint model during the dark part of the day. In passive animals, decreases in the concentrations of most of the pro- and anti-inflammatory cytokines studied were most marked immediately and particularly three days after stress. Changes in the cytokine profile of the blood following experimental stress were less marked in behaviorally active individuals: significant decreases from normal were seen only for the proinflammatory cytokine IL-1α and the anti-inflammatory cytokines IL-4 and IL-13. In contrast to passive rats, these changes were more marked in active individuals one day after negative emotional loading. These data illustrate the specific features of the involvement of immunoactive substances in the system controlling the physiological functions and forming individual resistance to the negative sequelae of stress.

Differences in the proteomic profiles of the brain amygdala in rats with different prognostic resistance to stress were found on the model of metabolic stress. Differential expression of tropomodulin-2, GTP-binding protein SAR1, peroxiredoxin-2, calcineurin B homologous protein 1, Ras-related protein Rab-14, glutathione S-transferase omega-1, Tcrb protein, and NADH dehydrogenase [ubiquinone] iron-sulfur protein 8 (mitochondrial) was shown to depend on the behavioral pattern of animals and stage of the study. Specific features were observed in the involvement of the amygdala in the stress response of specimens with various behavioral characteristics.

We compared proteome profiles of selected brain areas (cortex, amygdala, hippocampus, and reticular formation) and measured cathepsins B and D activity in liver lysosomal fraction in rats with different behavioral activity under conditions of emotional stress. In passive rats, the expression of some proteins in various brain regions was changed and baseline cathepsin B activity was higher than in active animals. Taken together, the results attest to differences in the adaptive response formation in rats, depending on behavioral features.

The nature of the effects of melatonin on lipid peroxidation, assessed in terms of changes in thiobarbituric acid (TBA)-reactive products, were studied in the peripheral blood in behaviorally passive and active Wistar rats. The acute rat stress model consisted of 1-h restraint with electrocutaneous stimulation. I.p. injection of melatonin (2 mg/kg) produced virtually no change in the intensity of lipid peroxidation in plasma in passive animals but was followed by an increase in active animals. Specific features of free radical processes in the blood were seen after stress: suppression in passive rats and the absence of change in active individuals. Administration of melatonin promoted decreases in the intensity of lipid peroxidation in the blood of stressed rats as compared with control animals given neurohormone. Thus, the nature of the action of melatonin on free radical processes depended on their initial behavioral parameters and physiological status. This illustrates the importance of an individual approach to analysis of the systemic mechanisms organizing physiological functions in mammals.

Changes in the relative weight of stress-marker organs in rats with various behavioral patterns in the open-field test were studied after repeated stress exposures on the model of daily 4-h immobilization over 8 days. Involution of the thymus and spleen in behaviorally passive specimens was found after single stress, as well as under conditions of 3- and 8-fold immobilizations. The weight of these organs in active animals remained practically unchanged after acute stress, but decreased on day 3 and particularly on day 8 of repeated stress exposures. As differentiated from passive rats (open-field test), behaviorally active specimens were characterized by hypertrophy of the adrenal glands after single and 3-fold stress procedures. Our results complement the data on individual features of the peripheral and central mechanisms for the stress response in mammals. These data illustrate the importance of individual approach to studying systemic organization of physiological functions under normal conditions and during negative emotiogenic exposures.

The effects of melatonin (epiphyseal neurohormone) on the serum cytokine profi les of rats with different behavioral characteristics were studied after acute emotional stress. One-hour immobilization of animals with simultaneous electrocutaneous stimulation of subthreshold intensity served as the stress model. Acute stress exposure of animals with active behavior led to reduction of the peripheral blood concentrations of pro-inflammatory (IL-1α, IL-1β, IL-2, IFN-γ, granulomonocytic CSF) and anti-inflammatory (IL-4, IL-10) cytokines. Passive rats exposed to emotional stress developed a pronounced increase of pro-inflammatory IL-1β concentration. Reduction of pro-inflammatory cytokine levels in active rats exposed to stress was less pronounced after intraperitoneal preinjection of melatonin (2 mg/kg). In passive animals, exogenous melatonin inverted the poststress changes in the serum levels of pro-inflammatory IL-2 cytokine and of anti-inflammatory IL-4 and IL-10 cytokines. The modulatory effect of melatonin on the cytokine profiles of rats with different behavioral parameters seemed to contribute to adaptation of animals to emotional stress exposure.

The effect of the epiphyseal hormone melatonin on the activity of antioxidant enzymes, glutathione peroxidase (GPx), glutathione reductase (GR), and Cu/Zn-superoxide dismutase (Cu/Zn-SOD) was studied in peripheral blood erythrocytes of behaviorally passive and active Wistar rats. Acute emotional stress was modeled by immobilization of animals for1 h with simultaneous electrocutaneous stimulation. Basal activity of antioxidant glutathione enzymes in erythrocytes of behaviorally passive rats was higher than that in active animals. Administration of melatonin (2 mg/kg, intraperitoneally) was accompanied by a decrease in the activity of GPx and GR in erythrocytes from non-stressed passive animals. After experimental stress, passive rats demonstrated a significant increase in the activity of Cu/Zn-SOD and GPx in peripheral blood erythrocytes. The absence of stress-induced changes in functional activity of antioxidant defense enzymes in the blood of behaviorally active animals suggests a relatively constant oxidative status of tissues in these animals under stress conditions. Melatonin administration had little effect on stress-induced changes in functional activity of the erythrocyte antioxidant system in passive rats. Active specimens pretreated with melatonin before stress exposure were characterized by activation of study antioxidant enzymes. Quantitative parameters of the erythrocyte antioxidant defense enzymes did not differ in behaviorally active and passive rats subjected to experimental stress after melatonin injection. Thus, exogenous melatonin abolishes differences in the activity of study antioxidant enzymes in erythrocytes of animals with different behavioral parameters under basal conditions and after experimental stress. In passive rats melatonin mainly reduced the initial tension of oxidative processes. By contrast, administration of this hormone to active specimens is followed by an increase in functional activity of the antioxidant enzyme system under conditions of acute stress.