[Neurological status and structural changes in the tracheal lymphoid tissue in rats with different resistance to emotional stress of experimental hemorrhagic stroke]

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 1^st day of a stroke. On the 3^rd 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 7^th 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.

State of Stress-Marker Organs in Rats after a Single Exposure to Long-Term Stress and Treatment with Lipopolysaccharide

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.

Neurological Deficit and Structural Changes in Lymphoid Structures of the Tracheal Wall in the Immediate Stage of Experimental Hemorrhagic Stroke in Rats with Different Behavioral Activity

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.

Cellular Composition of the B- and T-Cell-Dependent Areas in the Small Intestine during the Post-Stress Period (Experimental Study)

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.

Effect of Coenzyme Q10 on Proteomic Profile of Rat Brain Amygdala during Acute Metabolic 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.

Effect of Acute Emotional Stress on Proteomic Profile of Selected Brain Areas and Lysosomal Proteolysis in Rats with Different Behavioral Activity

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.

[Effect of melatonin on antioxidant enzyme activities in blood erythrocytes of rats during acute emotional stress]

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.

[DYNAMICS OF CYTOKINE CONCENTRATION IN THE BLOOD OF RATS WITH VARIOUS BEHAVIORAL CHARACTERISTICS AFTER ACUTE EMOTIONAL STRESS]

This work was designed to study a change in cytokine content in the peripheral blood of behaviorally passive and active Wistar rats at various time intervals after acute stress on the model of night-time immobilization. A decrease in the concentration of most pro- and anti-inflammatory cytokines in passive animals was most pronounced immediately and, particularly, 3 days after stress exposure. Variations in the blood cytokine profile after experimental stress were lower in behaviorally active specimens. A statistically significant decrease was observed only in the amount of a proinflammatory cytokine IL-1α and anti-inflammatory cytokines IL-4 and IL-13. As differentiated from passive rats, these changes in active specimens were most pronounced 1 day after negative emotiogenic exposure. Our results illustrate a specific involvement of immunoactive substances in the systemic regulation of physiological functions and development of individual resistance to the negative consequences of stress.

[Effect of melatonin on lipid peroxidation in the blood of rats with various behavioral characteristics during acute emotional stress]

This work was designed to study the effect of melatonin on lipid peroxidation in the peripheral blood of behaviorally passive and active Wistar rats. Immobilization of rats with simultaneous electrocutaneous stimulation (1 h) served as a model of acute stress. After intraperitoneal injection of melatonin (2 mg/kg) the intensity of lipid peroxidation in the blood plasma remained practically unchanged in passive specimens, but increased in active animals. Stress exposure was followed by specific variations in free radical processes in the blood (passive rats, inhibition; active specimens, no changes). Administration of melatonin contributed to a decrease in the intensity of lipid peroxidation in the blood of stressed rats (as compared to control specimens receiving this neurohormone). Therefore, the effect of melatonin on free radical processes depends on the initial behavioral characteristics and physiological state of animals. These data illustrate the importance of an individual approach to studying the systemic mechanisms for organization of functions in mammals. Key words: melatonin, emotional stress, lipid peroxidation, blood plasma, rats with various behavioral characteristics.

Melatonin effects on serum cytokine profiles of rats with different behavioral parameters in acute emotional stress

The effects of melatonin (epiphyseal neurohormone) on the serum cytokine profiles 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.

Effect of interleukin-1β on peripheral blood leukocytes in rats with various behavioral characteristics during acute stress

We studied the effect of a pro-inflammatory cytokine IL-1β (5 μg/kg intraperitoneally) on blood leukocytes in Wistar rats various behavioral characteristics during acute emotional stress (1-h immobilization with simultaneous delivery of subthreshold electrocutaneous stimulation). Stress exposure was accompanied by a decrease in the total number of peripheral blood leukocytes in rats. Active animals were characterized by the increase in neutrophil count during stress. The number of eosinophils in passive specimens was shown to decrease under these conditions. Emotional stress was followed by a decrease in the lymphocyte index (by Shaganin) of active rats and increase in the leukocyte intoxication index (according to Kalf-Kalif) of passive specimens. Stress-induced changes in leukocytes differed after pretreatment with IL-1β. The number of blood leukocytes increased in animals receiving a cytokine injection before stress exposure. Exogenous IL-1β inverted (in active rats) or prevented (in passive specimens) a change in the percentage of various types of blood leukocytes, which was found after stress exposure. These data contribute to the understanding of peripheral mechanisms for the involvement of immunomodulatory cytokines in the systemic organization of physiological functions in specimens with different prognostic resistance to a similar stress exposure.

Antistress effect of Semax in the course of recovery of spleen lymphoid structures after the stress in rats with different behavioral activity

We studied the effect of antistress peptide Semax, an ACTH4-10 analogue, on the cellular composition of spleen lymphoid structures in Wistar rats with different stress tolerance in the course of post-stress recovery (days 1, 3, 14, and 30). Preliminary administration of Semax alleviates stress-induced proliferation of macrophages and destructive processes in functionally active zones of the rat spleen on days 1, 3, and 14 after the stress exposure, which attests to its capacity to reduce the adverse effects of 1-h stress load on proliferation of macrophages and destructive processes in functionally active zones of this organ.

[Stress effect on the development of hemorrhagic stroke]

The objective of this work was to study how stress, activity in the open field test, and conformational properties of albumin-binding sites are associated with experimental hemorrhagic stroke in rats. The open-field behavioral pattern in rats was characterized by the previously developed by us activity index. In accordance with this activity index, rats were divided into two groups, i.e., active and passive animals. The animals were subjected to experimental hemorrhagic stroke with or without previous emotional stress. It was shown that the previous stress affected the stroke development. Stress loading before experimental stroke changed albumin conformational properties in rats with active and passive behavioral patterns in different ways. It was associated with different ability of the albumin globule to undergo pH-induced transition N-F and in different accessibility of albumin-bound fluorescent probe CAPIDAN to nitrate-induced fluorescence quenching.

Cellular composition of the thymus in Wistar rats in experimental intracerebral hemorrhage

The time course of changes in cellular composition of the thymus after experimental intracerebral hemorrhage was studied in rats with various prognostic resistance to emotional stress. Increased migration of T lymphocyte precursors to the subcapsular zone, activation of T lymphocyte differentiation in the thymus, reduced number of mitotic cells, destruction and intensive migration of thymocytes from the thymus were observed. The severity of changes in cell composition in all layers of the thymus after experimental intracerebral hemorrhage was different in rats resistant and predisposed to emotional stress. Predisposition to emotional stress and stress before surgical modeling of intracerebral hemorrhage affected the severity of changes in the thymus. It is shown that autoimmune and adaptation mechanisms, which are closely interrelated, play an important role in the pathogenesis of the intracerebral hemorrhage.

[Characteristics of serum albumin in patients with intracerebral hemorrhagic stroke]

Authors studied the influence of the psychoemotional stress preceding the stroke on the dynamics of neurological symptoms (Glasgo coma scale, Scandinavian stroke scale and Barthel index) and on the conformational changes of albumin in 59 patients with intracerebral hemorrhage due to arterial hypertension. The psychoemotional stress was associated with less favorable clinical course and outcome of intracerebral hemorrhage. Conformational properties of albumin were changed in all patients with intracerebral hemorrhage compared to controls. Psychoemotional stress preceding stroke aggravated changes in albumin molecule.

Dizocilpine and cycloheximide prevent inhibition of c-Fos gene expression by delta sleep-inducing peptide in the paraventricular nucleus of the hypothalamus in rats with different resistance to emotional stress

The effects of the non-competitive NMDA-receptor blocker MK-801 (dizocilpine) and the protein synthesis inhibitor cycloheximide on the delta sleep-inducing peptide (DSIP) inhibition of c-Fos immediate early gene expression were studied in the parvocellular subdivision of the hypothalamic paraventricular nucleus (pPVN) of male Wistar rats with either high or low resistance to emotional stress, predicted from differences in their open-field behaviour. The experiments show that intraperitoneal (i.p.) DSIP injection (60 nmol/kg) decreased the number of Fos-immunoreactive (Fos-IR) cells in the pPVN, activated by immobilization. The NMDA-receptor antagonist dizocilpine (MK-801) (90 nmol i.c.v.) prevented the inhibition of c-Fos expression by DSIP in the pPVN of rats predisposed to emotional stress. The protein synthesis inhibitor cycloheximide (210 nmol i.c.v.) prevented the inhibition of c-Fos expression by DSIP in the pPVN of rats that were resistant to emotional stress. The experiments indicate that the DSIP effect on c-Fos gene expression might be mediated by NMDA-receptors. DSIP may induce production of some protein transcription factors, transmitting a signal from membrane NMDA-receptors to the nucleus.

[Immune links in the system organization of behaviour]

The work is devoted to the research of immune mechanisms in self-control of various functional systems of homeostatic and behavioral levels. Distinction of immune mechanisms in rats with different prognostic stress-resistance is established. Immunization of rats by conjugates of various neuromediators with bovine serum albumin selectively changes the animals stress-resistance. Participation cytokines in reactions of a brain's separate neurons and their interaction with a leading neuromediator - norepinephrine is established. Individual changes of pro- and anti-inflammatory cytokines in blood serum are shown in rats with different stress-resistance. There are revealed features of morphological distinctions of immunogenic structures small intestine fabrics in animals with various behavioral activity in the "Open field" test.

[Effect of interleukin-1beta and interleukin-4 on serum albumin parameters in rats with various behavioural characteristics]

We studied the effects of pro-inflammatory cytokine interleukin-1beta and antiinflammatory cytokine interleukin-4 on serum albumin parameters in rats with various behavioural characteristics in the open-field test. Under control conditions, the total concentration of serum albumin in active animals was higher than in passive those. However, the ratio of the effective-to-total concentration of albumin (i.e., binding capacity of this protein) was greater in passive rats. Administration of interleukins was accompanied by a decrease in the total content and effective concentration of albumin in passive and, particularly, in active rats. The initial intergroup differences in the ratio of the effective-to-total concentration of albumin were not found after injection of immunomodulating agents. It was mainly related to a more significant increase in this parameter in active animals. An increase in the binding capacity of albumin after cytokine treatment could be associated with conformational changes in the protein molecule. We believe that interleukin-1b and interleukin-4 exert similar effects on the properties of binding sites of serum albumin in rats with various behavioural characteristics.

[Changes in duodenal lymphoid structures in rats with various behavioral activity, caused by delta sleep-inducing peptide and following acute emotional stress]

The effect of delta sleep-inducing peptide (DSIP) on the lymphoid structures of small intestine, was investigated. Studies were conducted on 42 male Wistar rats, which were previously assessed in an "open field" test. According to the results of the test, rats were divided into behaviorally active animals (prognostically resistant to stress) and passive ones (resistant to the effects of stress). As a stress, immobilization of the animals in pens with an electrical stimulation of their back for 1 hour, was used. Intraperitoneal injection of DSIP resulted in a reduction of eosinophil number in rats of all the experimental groups. After DSIP injection to the active rats of the control group, the increase in small and medium lymphocyte numbers was detected that was more expressed than in the passive rats. After an acute exposure of behaviorally active rats to stress, the number of the cells of lymphoid series was increased,mainly due to the increase in small and medium lymphocytes. In the group of passive rats, stress exposure and DSIP injection resulted in the increase of plasma cell number in all the duodenal mucosa structures studied.

[Morphological characteristics of the Wistar rat thymus in experimental intracerebral hemorrhage]

The purpose of the present investigation was to study thymus structure in 108 Wistar rats possessing different prognostic resistance to an emotional stress under the conditions of experimentally modeled intracerebral hemorrhage. It was demonstrated that after the intracerebral hemorrhage, the thymus underwent changes that were associated with both the stereotyped response to stress and the development of an immune response against the damaged brain tissue: relative thymus mass and the cortico-medullary index were shown to decrease, while the volumetric fractions of the capsule and connective tissue septa were increased. The reaction of the vascular bed included stasis, diapedesis and perivascular edema. These changes were more expressed in the rats predisposed to an emotional stress.

Delta sleep-inducing peptide and Deltaran: potential approaches to antistress protection

The aims of the present work were to perform a comparative study of the effects of delta sleep-inducing peptide and Deltaran on neurons in emotiogenic brain structures and to address the question of whether it is possible to prevent or decrease the negative influences of stress loads on the severity of subsequent cerebral ischemia in rats, using glycine with delta sleep-inducing peptide combined in the neuroprotective formulation Deltaran. The results showed that Deltaran and delta sleep-inducing peptide had largely the same actions on the nature of spike activity of neurons in the dorsal hippocampus, paraventricular nucleus of the hypothalamus, and ventral anterior nuclei of the thalamus, evoking activation of some of the neurons in these brain structures. The dorsal hippocampus was dominated by activation of spike activity in response to administration of delta sleep-inducing peptide; Deltaran produced activation mainly in the paraventricular nuclei of the hypothalamus. In all animals given Deltaran, the index of brain blood supply was significantly greater than in animals not given Deltaran. The survival rate of cerebral ischemia was 100% in animals given Deltaran. Death occurred in 38% of animals not given Deltaran.

[Emotional stress in the development of experimental hemorrhagic stroke in rats with different resistance to stress]

Individual behavioral characteristics of rats in the open-field test reflect their resistance to emotional stress and determine the severity of neurological disorders during intracerebral hemorrhage. Stress-resistant rats are characterized by a more rapid restoration of neurological status and disappearance of locomotor and coordination disturbances on day 7 after unilateral hemorrhage stroke in the caudate nucleus as compared to stress-predisposed animals. After hemorrhage stroke in the caudate nucleus, changes in vessels and neurons of the contralateral sensorimotor cortex were more pronounced in stress-predisposed passive rats than in stress-resistant active animals. The newly formed capillaries were not seen in stress-predisposed specimens. To day 7 of post stress hemorrhage stroke in the caudate nucleus, signs of the involvement of compensatory mechanisms in the contralateral sensorimotor cortex appeared in stress-resistant but not in stress-predisposed rats. This finding suggests the possibility of restoration of structure and normal functioning of neurons.

[Immune mechanisms in the development of hemorrhagic stroke]

The role played by immune mechanisms in intracerebral hemorrhage (ICH) was evaluated based on the studies of thymus structure and cell composition in rats showing different degree of tolerance to emotional stress. A new experimental ICH model is proposed. It is concluded that both stereotype and autoimmune mechanisms are involved in the development of ICH.

Deltaran prevents an adverse effect of emotional stress on the course of cerebral ischemia in low-resistant animals

Local cerebral blood flow in the left hemisphere decreased most significantly in low-resistant Wistar rats preexposed to emotional stress. Deltaran selectively increased blood flow in the left hemisphere and improved blood supply to neuronal activity unit of the brain in these animals. This drug prevented progressive decrease in local cerebral blood flow in both hemispheres during the acute stage of ischemia. The effect of Deltaran was related to modulation of collateral blood flow and adequate blood supply to neuronal activity unit in the brain tissue. Deltaran decreased the mortality rate (by 62%) and alleviated the symptoms of cerebral ischemia. The positive effect of Deltaran was more pronounced in the left hemisphere.

[Pathophysiological mechanisms of hemorrhagic stroke and the ways of differential therapy]

The changes developing in the perifocal area of hematoma and perspectives of antioxidant and chelate therapy were studied on the model of experimental hemorrhagic stroke and in clinical conditions. Microcirculatory, ischemic and inflammation disturbances with a certain time sequence were found in the perifocal areas. These changes, along with hypostasis and oxidative stress, form the pathobiochemical cascade of changes in hemorrhagic stroke and are potential therapeutic targets. Administering of an antioxidant and chelate drug histochrome reduces the intensity of changes in the perifocal area in the experimental conditions. In clinical conditions, it accelerates the dynamics of brain and meningeal symptoms regression and improves the blood rheological properties.

[Delta-sleep inducing peptide and the drug deltaran: possible approaches to antistress protection]

An aim of the present study was a comparative investigation of a delta-sleep inducing peptide and the drug deltaran on the neural activity of the brain structures involved in emotional processing. Another goal was to analyze the possibility to prevent negative effects of emotional stress on brain ischemia using, along with deltaran, glycine and a delta-sleep inducing peptide. Deltaran and the delta-sleep inducing peptide exert in general similar effect on the burst activity of neurons in the dorsal hippocampus, hypothalamic paraventricular nucleus and ventral anterior thalamic nucleus, inducing amplification of the majority of recorded units. The activation of neuronal activity was seen mostly after the delta-sleep inducing peptide microiontophoresis in the dorsal hippocampus and after the deltaran application in the hypothalamic paraventricular nuclei. The index characterizing blood supply was significantly higher in all rats receiving deltaran as compared to the controls. Animals receiving deltaran survived experimental brain ischemia in 100% cases versus 38% in those not exposed to this drug.

Correction of cerebral ischemia in low-resistant animals with an antistress drug Deltaran

Deltaran decreased the amplitude of EEG slow waves and restored neuronal reactivity after carotid artery occlusion in Wistar rats sensitive to cerebral ischemia. Deltaran had no effect on local cerebral blood flow. This drug increased blood supply to a unit of neuronal activity in the brain of intact animals during the acute stage of cerebral ischemia, provided 100% survival rate of rats with cerebral ischemia, and prevented the development of neurological symptoms in survivors. Animal experiments proved the possibility of correcting cerebral ischemia with antistress drug Deltaran.

Conformational properties of serum albumin binding sites in rats with different behaviour in the open field test

In this study, the hypothesis was tested that behaviour of rats under the open field test condition and effects of subsequent acute stress relate to conformational properties of the main plasma carrier protein, albumin.To evaluate albumin properties, fluorescence intensity of a molecular probe CAPIDAN (N-carboxyphenylimide of dimethylaminonaphthalic acid) at N (at pH 7.4) and F (at pH 4.2) albumin conformations was measured and the N-F signal ratio was calculated. The data obtained showed that CAPIDAN fluoresces selectively from albumin in rat serum and its fluorescence is sensitive to binding of fatty acids and some other ligands to albumin. Behaviour of 78 Wistar male rats was characterized from the fraction of time taken for exploratory and ambulatory activity during the open field test. In rats not subjected to stress (n = 40), a negative correlation was revealed between open field activity and CAPIDAN N-to-F ratio for albumin (r = - 0.55, p < 0.0005). In the group of rats subjected to acute stress (immobilization plus stochastic electrocutaneous stimulation) the correlation between behavioural activity and the albumin conformational properties was significantly positive (r = 0.59, p < 0.0001): the CAPIDAN albumin fluorescence ratio increased in the highly active rats and decreased in the low-activity rats. The mechanisms of the observed effects may involve differences in nonesterified fatty acid production during stress.

Structural-functional organization of neurons in the cerebral cortex of rats with different levels of resistance to emotional stress in conditions of exposure to delta sleep-inducing peptide

Wistar rats with different levels of resistance to emotional stress (ES) were subjected to stress and brain sections stained with Nissl cresyl violet were used for quantitative analysis of the structural organization of neurons in layer V of the sensorimotor cortex. Some animals received delta sleep-inducing peptide (DSIP) 1 h before stress. Control ES-susceptible rats, as compared with resistant rats, had lower levels of normochromic and moderately hypochromic neurons. Normochromic neurons were not seen after stress. Rats susceptible to ES showed particularly sharp decreases in moderately hypo- and hyperchromic neurons, along with increases in the proportions of extremely hypo- and hyperchromic neurons, ghost cells, and ischemically altered cells. After administration of DSIP before stress, ischemically altered cells were not seen in any group: the level of reduction of extremely hyperchromic neurons was smaller in ES-susceptible rats than in ES-resistant rats. It is suggested that brain hypoxia plays a particular role in disorganizing the cortex in conditions of ES, while DSIP has both antistress and antihypoxic properties.

Individual Resistance to Cerebral Ischemia and Negative Effect of Emotional Stress on the Course of This Disorder

The ratio of low-activity and high-activity rats differed in autumn, winter, and spring litters. Initially more intensive cerebral blood flow in low-active rats and its more pronounced decrease after common carotid artery occlusion determined their higher sensitivity to cerebral ischemia (compared to high-activity animals). After 18-h immobilization stress cerebral blood flow decreased by 10-15%, which abolished the difference in the individual resistance to cerebral ischemia. Independently on emotional resistance, cerebral ischemia was not accompanied by the development of collateral blood flow in the acute period and caused death of 90% rats.

[Disregulation of collateral blood flow and lipid peroxidation abnormalities as a cause of negative influence of emotional stress on the course of cerebral ischemia]

Under normal conditions, local brain blood flow in young rats determined their individual resistance to ischemia and emotional stress. In low-activity rats predisposed to emotional stress, a level of blood flow was significantly (p<0.05) higher, comparing to high-active animals resistant to emotional stress. An exposure of rats to aggressive- and conflict situation for 18 h was followed by pronounced emotional stress accompanied by the reduction of local cerebral blood flow by 10-15% and abolished individual differences in resistance to cerebral ischemia. Collateral blood flow did not develop in pre-stressed rats during the acute period of cerebral ischemia. The mortality rate reached 90% independently of the animal emotional resistance. In ischemia after 2 h exposure to stress, differences were revealed in the intensity of lipid peroxidation in the brain of animals with divergent emotional resistance. Comparing to stress-resistant rats, in stress-predisposed animals, a level of malonic dialdehyde in the amygdale basal nuclei was 2-fold lower. The results suggest the differences in stress response in animals with various resistance to the effect of adverse factors.

Blood albumin in the mechanisms of individual resistance of rats to emotional stress

This report describes studies of the characteristics of serum albumin in rats with different predicted levels of resistance to emotional stress in control conditions and in conditions of experimental emotional stress. The effects of peptides increasing the resistance of animals to emotional stress (delta sleep-inducing peptide and Semax) on serum albumin were analyzed in rats predicted to be resistant and susceptible to emotional stress.

[Structural and functional organization of the cerebral cortex neurons in rats with various resistance to emotional stress following administration of delta-sleep-inducing peptide]

In Wistar rats with different resistance to emotional stress (ES), subjected to stress exposure (SE), the structural organization of neurons in layer V of sensomotor cortex was studied quantitatively in brain sections stained using Nissl's cresyl violet method. One group of animals was injected with delta sleep-inducing peptide (DSIP) 1 hr before SE. In rats of control group predisposed to ES, the amount of normochromatic and moderately hypochromatic neurons was decreased as compared to the rats resistant to ES. After SE, normochromatic neurons were not demonstrated. In rats predisposed to ES, the contents of moderately hypo- and hyperchromatic neurons was found to fall dramatically with a simultaneous increase in the number of extremely hypo- and hyperchromatic neurons, ghost cells and ischemically changed cells. After DSIP infusion before SE, ischemically damaged cells were not found in any group, while the degree of shrinkage of extremely hyperchromatic neurons was lower in rats predisposed to ES as compared to rats resistant to ES. It is suggested that brain hypoxia plays an important role in cortex disorganization during ES, whereas DSIP, possesses both antistress and antihypoxic effects.

[Effect of dipeptide vilon on emotional stress resistance in rats]

Effects of synthetic thymomimetic vilon on open field behaviour, immediate early gene c-Fos expression in paraventricular hypothalamus properties of organs sensitive to emotional stress, and characteristics of albumin in the blood plasma in male Wistar rats, were investigated and are discussed in the article. It is shown that intraperitoneal vilon injection rises the resistance against emotional stress according to prognostic indexes open field behaviour. Vilon administration also inhibits hypertrophy of the adrenals, involution of the thymus, and elevates concentration of albumin in the blood plasma. The number of Fos-immunoreactive neurons in the paraventricular hypothalamus was lower after vilon administration especially in rats resistant against emotional stress.

[Blood albumin in mechanisms of individual resistance of rats to emotional stress]

Serum albumin parametres in the rats with various prognostic resistance against emotional stress in the control and in conditions of experimental emotional stress were investigated. Analysis of action of peptides raising the animals' resistance against emotional stress (DSIP and SEMAX) in rats with different prognostic resistance against emotional stress, on the serum albumin characteristics, was carried out.

Expression of the c-fos gene during emotional stress in rats: the clocking effect of delta sleep-inducing peptide

Emotional stress induced more marked increases in the expression of the c-fos gene in limbo-reticular structures of the brain in rats prognostically predisposed to emotional stress. I.p. doses of delta sleep-inducing peptide (DSIP) (60 nmol/kg) weakened the stress-induced expression of the c-fos gene. This effect was more apparent in animals predisposed to emotional stress, in which preliminary injections decreased stress-induced c-fos expression in the paraventricular hypothalamus and the medial and lateral parts of the septum. The decreased expression of the early gene c-fos in emotional stress after preliminary dosage with DSIP may reflect the leading mechanism of the anti-stress action of this peptide.

[Mesenteric lymph nodes in rats exposed to emotional stress]

Structural and functional peculiarities of mesenteric lymph nodes were studied in 40 stressed August rats using micro anatomical methods. The stress was induced by limitation of any movement for 5 hrs every day. Peculiarities and intensity of modifications demonstrated was dependent on duration of stress actions. Significant decrease of cortical substance area, its lymphoid nodules length and width and germinal centre area, fraction of large, medium and small lymphocytes was observed following 5 hrs of the experiment, which was combined with expansion of the area, occupied by medullar substance. On the 2nd d of 5 hrs experiment cortical substance area was widened (on histological section), the number and sizes of lymphoid nodules grew up and lymphoid nodules appeared in medullar bands. On the 3rd experimental day mesenteric lymph node structure gradually restored. It showed control values on the 6th experimental day.

Structural and functional characteristics of neurons in the sensorimotor cortex of rats with different resistance to emotional stress

Wistar rats behaviorally active in the open field test (resistant to emotional stress) are characterized by polymorphism of neurons in layer V of the sensorimotor cortex and the presence of hyperchromatic cells, which probably determines resistance to emotional stress in these rats. Atrophy of hyperchromatic neurons reflecting transient inhibition of cell activity was noted in Wistar rats subjected to stress. In the sensorimotor cortex of behaviorally passive animals (predisposed to emotional stress) groups of densely packed hyperchromatic cells and pronounced pericellular edema were revealed. In these rats stress caused irreversible changes in cortical neurons and death of some cells. The presence of ischemic cortical neurons in rats subjected to emotional stress suggests that cerebral hypoxia plays a role in structural and functional disorganization of the sensorimotor cortex during emotional stress.

Delta-sleep inducing peptide (DSIP) and ACTH (4-10) analogue influence fos-induction in the limbic structures of the rat brain under emotional stress

The effects of the ACTH (4-10) analogue, ACTH (4-7)-Pro-Gly-Pro, and delta-sleep inducing peptide (DSIP) on the induction of Fos immunoreactivity in the hypothalamic parvocellular paraventricular nucleus (pPVN) and limbic brain regions were studied in Wistar rats with high (resistant) or low (predisposed) resistance to emotional stress, predicted from differences in their open-field behaviour. Fos-immunoreactive (Fos-IR) cells were counted in brain sections automatically with a computer-based image analyser. Under basal conditions, Fos-IR cell numbers were greater in the pPVN in the predisposed rats, but were lower than in the resistant rats in the basolateral amygdala and medial and lateral septum. Intraperitoneal DSIP injection (30 μg/kg) increased basal Fos-IR cell number in the pPVN and lateral septum in resistant rats, with no effects in predisposed rats. ACTH (4-10) analogue (50 μg/kg)increased Fos expression in the pPVN in both resistant and predisposed rats, with essentially no effects in the basolateral amygdala or medial and lateral septum. Emotional stress (60 min restraint and intermittent subcutaneous electrical shocks) increased Fos expression in the pPVN and medial and lateral septum similarly in predisposed and resistant rats, but in the basolateral amygdala in only the predisposed rats. Intraperitoneal DSIP injection reduced the increases in Fos-IR cell number after emotional stress, particularly in predisposed rats. In predisposed rats DSIP decreased the number of Fos-IR cells in the pPVN and the medial and lateral septum, with no change in the basolateral amygdala. In resistant rats, DSIP decreased Fos expression only in the lateral septum. ACTH (4-10) analogue injection inhibited stress-induced Fos expression in the pPVN and the medial septum, but only in predisposed rats. The experiments indicate that DSIP and ACTH (4-10) analogue reduce pPVN and limbic neurone responses to emotional stress in the rats predisposed to emotional stress; the effects on Fos expression may play a role in the biological activities of these peptides.

[Gene c-Fos expression in brain of rats resistant and predisposed to emotional stress after intraperitoneal injection of the ACTH(4-10)analog--semax]

The effect of the ACTH(4-10) analog Semax on immediate early gene c-Fos expression was studied in Wistar rats with high and low resistance to emotional stress under the usual conditions and during psychoemotional loading. Fos-immunoreactive cells in the were counted automatically with the help of a computer. It was shown that under the usual conditions the intraperitoneal Semax injection induced immediate early gene c-Fos expression in the lateral septal region in rats predisposed to emotional stress and in the paraventricular hypothalamus in rats of both groups. Preliminary Semax injection decreased the stress-induced c-Fos expression in the paraventricular hypothalamus and medial septum in rats predisposed to emotional stress and tended to reduce the number of stress-induced c-Fos-immunopositive cells in the lateral septum and basolateral amygdala in both groups of animals. The obtained data suggest that Semax differently affects the immediate early c-Fos gene expression in the brain of rats resistant and predisposed to emotional stress and this effect reflects the antistressor properties of the regulatory peptide.

[c-fos Gene expression during emotional stress in rats: blocking by delta sleep-inducing peptide]

An emotional stress induces an obvious immediate early gene c-fos expression in the brain limbic structures in the rats predisposed to emotional stress. Administration of the delta-sleep-inducing peptide (DSIP) was shown to inhibit the c-fos expression. It led to an obvious inhibition of the c-fos expression in paraventricular nuclei of the hypothalamus, medial and lateral parts of the septum of rats predisposed to emotional stress. This mechanism seems to play an important role in the DSIP anti-stress effects.