Acute Immobilization Stress Research Articles

Effects of DNA Methylation of HPA-Axis Genes of F1 Juvenile Induced by Maternal Density Stress on Behavior and Immune Traits in Root Voles (Microtus oeconomus)-A Field Experiment.

The literature shows that maternal stress can influence behavior and immune function in F1. Yet, most studies on these are from the laboratory, and replicated studies on the mechanisms by which maternal stress drives individual characteristics are still not fully understood in wild animals. We manipulated high- and low-density parental population density using large-scale field enclosures and examined behavior and immune traits. Within the field enclosures, we assessed anti-keyhole limpet hemocyanin immunoglobulin G (anti-KLH IgG) level, phytohemagglutinin (PHA) responses, hematology, cytokines, the depressive and anxiety-like behaviors and prevalence and intensity of coccidial infection. We then collected brain tissue from juvenile voles born at high or low density, quantified mRNA and protein expression of corticotropin-releasing hormone (CRH) and glucocorticoid receptor gene (NR3C1) and measured DNA methylation at CpG sites in a region that was highly conserved with the prairie vole CRH and NR3C1 promoter. At high density, we found that the F1 had a lower DNA methylation level of CRH and a higher DNA methylation level of NR3C1, which resulted in an increase in the expression levels of the CRH mRNA and protein expression and further reduced the expression levels of the NR3C1 mRNA and protein expression, and ultimately led to have delayed responses to acute immobilization stress. Juvenile voles born at high density also reduced anti-KLH IgG levels and PHA responses, increased cytokines, and depressive and anxiety-like behaviors, and the effects further led to higher coccidial infection. From the perspective of population density inducing the changes in behavior and immunity at the brain level, our results showed a physiological epigenetic mechanism for population self-regulation in voles. Our results indicate that altering the prenatal intrinsic stress environment can fundamentally impact behavior and immunity by DNA methylation of HPA-axis genes and can further drive population fluctuations in wild animals.

Study Of The Stress-Protective Effect Of Sodium 2-((4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate

The aim was to study the stress-protective effect of sodium 2-((4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate. The analysis of the effect of the sample on the behavior and psycho-emotional state of animals, physiological parameters, antioxidant-prooxidant system was studied. Studies of stress-protective properties were performed on white outbred rats. As a comparison drug was used a Mebicar (Adaptol®) (reference sample). One hour after the simulation of immobilization 6-hour stress, the animals were subjected to a series of tests: "Open Field", "Light and Dark Chamber", "Morris Water Labyrinth". Behavioral tests were performed according to generally accepted methods in simplified modifications. Serum and liver homogenate were used to determine the content of markers of the antioxidant-prooxidant system: quantitative content of diene conjugates (DC), thiobarbituric acid reactants (TBA reactants), as well as catalase and superoxide dismutase (SOD) activity. Based on complex behavioral tests data, Catalase, TBA reactants, DC, SOD data in the serum and in the liver homogenate it can be concluded the presence of stress-protective properties of sodium 2-((4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate in the model of acute immobilization stress.

Drinking Sulphate Mineral Water Action Mechanisms at Primary Preventive and Therapeutic Application under Experimental Stress: a Comparative Analysis

INTRODUCTION. Earlier in experimental studies, it was established that sulfate mineral drinking water (MB) under stress causes adaptation effects depending on the mode of its use — during primary prevention or treatment. The question of the role of different modes of drinking mineral water application in the formation of adaptation mechanisms remains unclear.
 AIM. To conduct a comparative analysis of the effect of sulfate MW in primary preventive and therapeutic application on the development of adaptive metabolic and ultrastructural reactions in rats in the early post-stress period.
 MATERIALS AND METHODS. The experiments were carried out on 54 white nonlinear male rats. Acute immobilization stress was modeled using the Selye method. All animals were divided into 5 groups: the 1st experimental group — the primary preventive effect of drinking sulfate MV; the 2nd experimental group — the therapeutic effect of drinking sulfate MV; the 3rd and 4th groups — controls; the 5th group — intact animals. Drinking sulfate MW (concentration of sulfate ions 1.93 g/l, mineralization 3.05 g/l) was administered intragastrically by 3 ml, a total of 18 procedures. Objects of research: liver and testes. Research methods: biochemical, light-optical, morphometric, electron microscopic. The statistical significance of the differences was assessed using the Student’s criterion.
 RESULTS AND DISCUSSION. It was found that the most pronounced development of adaptive-protective reactions (increased activity of the antioxidant system, increased protein synthesis, activation of intracellular regeneration processes) was observed with the action of MW in the primary prevention mode. At the same time, there was the formation of more powerful adaptation mechanisms associated with the additional accumulation of structural and metabolic resources that limit the development of maladaptation and pathological processes. With the therapeutic use of MW, due to post-stress disorders of the mechanisms of regulation, the processes of adaptation and compensation were weaker.
 CONCLUSION. The results reveal some features of the mechanism of action of drinking sulfate MW on the development of compensatory and adaptive processes and indicate the need for a differentiated approach in the use of drinking MW to increase their effectiveness in the comprehensive prevention and treatment of the body from the damaging effects of various stress factors.

Morphological changes of the hepatobiliary system and salivary glands under the influence of stress

Stress can impact our bodies at the cellular level, causing changes to various organs and systems. Chronic stress can indirectly affect the hepatobiliary tract. Salivary gland dysfunction can be a manifestation of a large variety of systemic diseases or the consequence of local structural or functional pathologies. Stress can influence the oral microbiome, leading to changes in microbial diversity. Scientists study stress reactions, new resistance methods, and modern approaches to prevent and treat stress. 
 The aim is to examine the morphological aspects and changes of the blood vessels in the liver and salivary glands of white rats in experiment using acute immobilization stress.
 Materials and methods. In total 22 white male rats were studied, divided into two groups. The first was kept as a control, the second was subjected to acute immobilization stress. The rats were immobilized by hanging them by the neck with a clamp for 6 hours. Animals were euthanized with a sodium thiopental solution. Samples of the liver and parotid gland were examined histologically using hematoxylin and eosin stain.
 Results. The livers of rats were studied after acute immobilization stress. Significant changes were observed in the liver blood vessels, including thrombosis and expansion of perisinusoidal spaces. Liver cells also showed changes such as karyopyknosis, colliquation necrosis, and hydropic dystrophy. The parotid salivary gland histologic examination showed swelling in the connective tissue, periductal regions, and perivascular spaces. In the acinar section, basophilia and swelling of serocytes were observed, along with dystrophic processes leading to remodeling of the acini and ducts. The narrowing of arterioles was observed, reflecting tension in the arterial system.
 Conclusions. Exposure to acute stress can cause changes in the liver and biliary tract, increasing the risk of various diseases, including those that affect the oral cavity.

Administration of the glutamate-modulating drug, riluzole, after stress prevents its delayed effects on the amygdala in male rats.

Extracellular glutamate levels are elevated across brain regions immediately after stress. Despite sharing common features in their genesis, the patterns of stress-induced plasticity that eventually take shape are strikingly different between these brain areas. While stress causes structural and functional deficits in the hippocampus, it has the opposite effect on the amygdala. Riluzole, an FDA-approved drug known to modulate glutamate release and facilitate glutamate clearance, prevents stress-induced deficits in the hippocampus. But whether the same drug is also effective in countering the opposite effects of stress in the amygdala remains unexplored. We addressed this question by using a rat model wherein even a single 2-h acute immobilization stress causes a delayed expression of anxiety-like behavior, 10 days later, alongside stronger excitatory synaptic connectivity in the basolateral amygdala (BLA). This temporal profile-several days separating the acute stressor and its delayed impact-allowed us to test if these effects can be prevented by administering riluzole in drinking water after acute stress. Poststress riluzole not only prevented the delayed increase in anxiety-like behavior on the elevated plus maze but also blocked the increase in spine density on BLA neurons 10 days later. Further, stress-induced increase in the frequency of miniature excitatory postsynaptic currents recorded in BLA slices, 10 days later, was also blocked by the same poststress riluzole administration. Together, these findings underscore the importance of therapeutic strategies, aimed at glutamate uptake and modulation, in correcting the delayed behavioral, physiological, and morphological effects of stress on the amygdala.

Забруднювач довкілля бісфенол А порушує програмування статевої поведінки у жіночого потомства щурів

Bisphenol A (BPA) is a common environmental pollutant and, due to its estrogenic properties, can cause disorders of the reproductive and other physiological systems of the body, especially in males. It is known that in male rats it disrupts the sexual differentiation of the brain (SDB) of the fetus in utero. Studies of the effects of perinatal exposure of fetuses and newborn females through the mother’s body under the conditions of long-term administration of BPA during pregnancy and lactation did not reveal significant changes in SDB. Identification of long-term endocrine, neuromorphological, and behavioral consequences of exposure of female rat fetuses to a low dose of BPA administered to mothers during the last week of pregnancy, which corresponds to the temporal period of SDB, was the aim of this study. Rats were orally administered BPA suspended in Dorfman gel at a daily dose of 25 μg/kg b.w., which is 200 times less than the NOAEL (no observed adverse effect level) for rats, via a gavage, or, as a positive control, estradiol diacetate (E2D) subcutaneously at a dose of 10 μg/kg b.w., during 15-21 days of pregnancy. Control animals received gel without BPA. The levels of estradiol, testosterone, and corticosterone in blood plasma, the response of the hypothalamic-pituitary-adrenal (HPA) axis to acute immobilization stress, sexual behavior, and the histological structure and karyometric parameters of neurocytes of the medial-preoptic nuclei (MPN) of the hypothalamus were studied in adult female offspring. Prenatal exposure to BPA or E2D decreased the concentration of estradiol in the blood plasma, while the levels of testosterone and corticosterone remained normal. In the females of the BPA and E2D groups, a masculinization of sexual behavior (mounting to a receptive female, approaching her, etc.) was observed, which, according to the number of lordosis reactions in the presence of a sexually experienced male, not accompanied by her defeminization. Changes in the morphology of the MPN, which belongs to the sex-dimorphic area of the brain, conformed to the masculinization of female sexual behavior due to prenatal exposure to a low dose of BPA. Karyometry of neurocytes of the hypothalamic MPN of rats revealed no difference between the control and the BPA group. The response of the HPA axis to immobilization stress did not change in both experimental groups. It is found for the first time that maternal exposure of in utero female rat fetuses to an ultra-low relative to the NOAEL dose of BPA during the last gestational week, which corresponds to the critical period of SDB impairs programming of sexual behavior in the direction of its masculinization and causes hypoestrogenemia at adulthood. Disorders of sexual behavior conformed to morphological changes of the hypothalamic MPN. The unidirectionality of functional disorders induced by prenatal exposure to BPA and the reference estrogenic drug E2D indicates that they are caused by the estrogenic properties of both substances.

Endocrine and behavioral effects in male rats after birth with their pregnant mother taking ibuprofen

Ibuprofen, a non-selective inhibitor of cyclooxygenase, is one of the most used non-steroidal anti- inflammatory drugs (NSAID) and pain relievers. Its effect on developing fetal neuroendocrine system when taken by a pregnant mother does not well established. The aim of this study was to evaluate the long-term consequences of the administration of ibuprofen to pregnant rats with regard to hormonal profile and sexual differentiation of the brain in male offspring. Pregnant rats were given ibuprofen per os in a dose of 30 mg/kg bw twice a day during days 15-21 of gestation. On the 2 and 10 postnatal days (PND), anogenital distance (AGD) was measured in male pups. In adulthood, sexual behavior, hormone levels, and hypothalamic-pituitary-adrenal axis (HPAA) response to acute immobilization stress were studied. Prenatal ibuprofen increased AGD on PND 2 and caused incomplete masculinization of copulative behavior in adult offspring. Significant increases in the latent periods of the first mount, the first intromission, and a decrease in the number of intromissions were observed. Basal blood plasma levels of testosterone, estradiol, and corticosterone, as well as HPAA response to immobilization stress, did not change. Orchidectomized and primed with estradiol and progesterone males did not exhibit lordosis response to the presence of a sexually experienced male. Conclusion: Administration of ibuprofen to female Wistar rats during the last week of gestation disrupts partially neuroendocrine programming of male-type copulative behavior in male offspring with no changes in female-type sexual behavior and HPAA function. It is hypothesized that incomplete masculinization of the developing fetal brain with ibuprofen is due to two co-operative mechanisms: inhibition of synthesis of testosterone in the fetal gonads and prostaglandin E2 in the preoptic area of the hypothalamus.

Involvement of the opioidergic and nociceptinergic systems in the analgesic effects of novel nociceptin analogues after acute and chronic immobilization stress

Stress is known to exert an influence on neuroendocrine, autonomic, hormonal functioning. Various stress models have been reported to induce analgesia. This is a phenomenon, referred to as stress-induced analgesia (SIA). Nociceptin/Orphanin FQ(N/OFQ) is a heptadecapeptide that has been found to play a direct role on pain perception. This study aimed to investigate the effects of novel nociceptin analogues on nociception after acute and chronic immobilization stress (CIS) and the involvement of the opioid and nociceptinergic systems in analgesic effects. Analgesic effects were examined by paw-pressure (PP) and hot-plate (HP) tests. Our data showed that acute immobilization stress induced hypoalgesia. The analgesic effect was more pronounced in pain caused by a mechanical stimulus than by a thermal one. CIS attenuated the hyperalgesic effect of naloxone and JTC-801 for mechanical and thermal stimulation. The effects of the opioid system are more pronounced in acute immobilization stress, while the nociceptin mechanisms predominate after chronic stress.

Morphological changes of the exocrine part of the pancreas under immobilization stress on the background of hypothyrosis

Annotation. Stress is a condition that causes the body's cells to use large amounts of energy to acclimate to abnormal environmental conditions. Hypothyroidism affects almost all organs and systems of the body, in particular, the pancreas. The goal of our research is to study the effect of chronic immobilization stress against the background of hypothyroidism on the tissue structure of the exocrine part of the pancreas. The experimental rats were divided into three groups: I – intact animals (10), II – animals with immobilization stress (10), III – animals with hypothyroidism and immobilization stress (10). Hypothyroidism was modeled by daily per os injection using a probe of the pharmacopoeial mercazolil thyreostatics at a dose of 25 mg/kg during the 21 day. Acute immobilization stress was modeled by tying experimental rats in a supine position in 4 limbs without restriction of head mobility for 3 hours. Histological studies were carried out according to generally accepted methods. Histological preparations were studied using a SEO SСAN light microscope and photo-documented using a Vision CCD Camera with a system of image output from histological preparations. In the 1st control group, the pancreas had a general structure plan of a parenchyme in organ. In the II group, remodeling of the exocrine part of the pancreas, slight disturbances in the structure of the acini, blood vessels, and moderate edema of the connective tissue were observed, compared to the control group of animals. In the III group, more significant changes of the gland were revealed, compared to the II experimental group, manifested by swelling and growth of connective tissue, changes in the shape of the acini, violation and loss of polarity of exocrinocytes, blood-filling of vessels. Thus, under conditions of simulated chronic stress, slight changes in the parenchyma of the gland were detected, and during chronic immobilization stress against the background of hypothyroidism, alterative changes of the gland were detected, compared to the II experimental group.

Acute immobilization stress evokes sexually dimorphic peripheral and hippocampal neuroimmune responses in adult rats

Stress perception and response vary across sexes and may contribute to the sex differences in susceptibility to psychopathology. Stress also engages the immune system and baseline immune system markers are known to be sexually dimorphic. Here, we investigated if the neuroimmune consequences following a single episode of acute immobilization stress (AIS) are sexually dimorphic in male and female Sprague-Dawley rats. We analyzed immune parameters in the periphery, and markers of neuroinflammation in the hippocampus, a key target of stress effects in the brain. We observed sexual dimorphism in the pattern of regulation of peripheral cytokines following stress, with males showing a significant increase in the levels of specific cytokines compared to females. Hippocampal cytokine and neuroinflammation-associated gene expression level analysis did not reveal any sexually dimorphic effects of AIS. However, we noted lower baseline expression levels for specific cytokines and many of the genes analyzed in the hippocampus of control females compared to control males. Finally, we assessed the levels of components of the NLRP3 inflammasome in the hippocampus and observed increased NLRP3 protein levels at baseline in females. We further noted that while males showed an increase in NLRP3 levels following AIS, females failed to show a similar change. Together, our results highlight a sexual dimorphism in neuroimmune consequences following AIS, both in the periphery and within the hippocampus, with males displaying robust proinflammatory changes and similar changes not observed in females. Our study underlines the importance of investigating the effect of sex on neuroimmune consequences following acute stress.

SUBMICROSCOPIC CHANGES IN HEMOCAPILLARIES OF ADRENAL GLAND AND PANCREATIC ISLETS OF LANGERHANS IN CASES OF IMMOBILIZATION STRESS WITH UNDERLYING HYPOTHYROIDISM

Background. Today, among the increasing number of various diseases, stress is a trigger in the development of diseases and mortality among the population. Objective. To establish submicroscopic changes in the hemocapillaries of the islets of Langerhans of the pancreas and adrenal glands in the presence of immobilization stress with underlying hypothyroidism. Methods. The experiment was carried out on 20 mature white male rats. Hypothyroidism was modeled by daily per os injection with a probe of the pharmacopoeial mercazole thyreostatics at a dose of 25 mg/kg for 21 days. Acute immobilization stress was modeled by tying the experimental rats in a supine position in 4 limbs without restricting head mobility for 3 hours. The study was conducted 2 hours later (anxiety stage) after the end of the stress impact. The material was collected for electron microscopy and tissue processing was performed according to generally accepted methods. Results. Electron microscopic examination of the blood capillaries of the islets of Langerhans in the pancreas and the hemocapillaries of the adrenal cortex after the action of the stress factor in cases of hypothyroidism showed slightly enlarged lumens and moderate perivascular edema. The basement membrane was moderately thickened but clearly contoured. Endotheliocyte nuclei were mostly hypertrophied, euchromatin was uniformly located in the nucleoplasm, and nucleoli were defined. The karyolemma was clearly contoured, the number of nuclear pores was small, and the perinuclear lumen was locally widened. Endoplasmic reticulum with moderately expanded and short tubules, moderately thickened cisterns of the Golgi complex were observed in the cytoplasm of endotheliocytes. There were two types of mitochondria: hypertrophied with an electron-light matrix, single cristae, and with clear visible cristae and a moderately electron-dense matrix. In addition to the capillaries mentioned above, there were also single narrowed microvessels that had perivascular edema and vaguely contoured fenestrae. Conclusions. When modeling a stressor in cases of hypothyroidism, structural changes of all components of the walls of blood capillaries of the pancreas and adrenal glands take place.

Immune System Response after Immobilization Stress in the Background of Ionizing Radiation

We studied the combined effect of gamma radiation (6 Gy, remote period) and immobilization stress on immunological reactivity. Materials and methods. To address this, we carried out experiments on 40 white male Wistar rats weighing 220 ± 20 g, which were divided into 4 groups: Group I - intact animals, group II - animals exposed to gamma radiation (dose of 6 Gy), group III - animals exposed to immobilization stress and group IV - animals exposed to combined exposure to gamma radiation (dose of 6 Gy) and immobilization stress. Animals in groups II and IV were irradiated 90 days before the study on the TERAGAM radiotherapeutic cobalt unit. In groups III and IV, animals were modeled for acute immobilization stress by immobilization for 6 h in bright light. Results. At the early period of immobilization stress, all indicators of the immune system, such as cellular, humoral and nonspecific phagocytic links of immunity were activated, indicating the activation of the general adaptive syndrome of the organism. The suppressive action of gamma radiation on the immune system was preserved in a remote period, with this suppression being revealed not only on the T-cellular link, but also on nonspecific phagocytic links, and the functional metabolic activity of neutrophils. In the remote period after the combined effect of sublethal gamma radiation and immobilization stress in the early stage of the adaptation syndrome, there was a decrease in all cells of the T system of immunity, in the functional ability of leukocytes, and in the mononuclear phagocytic system of the body. The experimental immobilization-radiation pathological process was accompanied by disorders of the functional activity of the essential adaptive systems of the body. Based on our results, we could conclude about the dominant role of ionizing radiation in immunological reactivity.
 HIGHLIGHTS
 
 At an early stage, after exposure to stress, the general adaptation syndrome is activated in the body
 The suppressive effect of gamma radiation on the immune status and phagocytic activity persists in the long term
 The pathological process that occurs under the combined effects of radiation and immobilization stress is accompanied by a violation of the functional activity of the most important adaptive systems of the body
 Under the combined influence of radiation and non-radiation factors, the radiation factor has a predominant influence
 
 GRAPHICAL ABSTRACT

HISTOLOGICAL STUDY OF A CORRECTIVE INFLUENCE OF SODIUM 2-((4-AMINO-5-(THIOPHEN-2-YLMETHYL)-4H-1,2,4-TRIAZOL-3-YL)THIO)ACETATE ON THE STATE OF RATS LIVER UNDER CONDITIONS OF ACUTE IMMOBILIZATION STRESS

Objective: The aim of the work was the histological study of a corrective influence of sodium 2-((4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-yl) thio) acetate on the state of rats liver under conditions of acute immobilization stress. Material and Method: As an object of research sodium 2-((4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-yl) thio) acetate was used. All substances were injected intragastrically, daily for 5 days in appropriate doses on an empty stomach from 9.00-10.00. 1 hour after the last injection, immobilization 6-hour stress was simulated. The central part of the liver was fixed for further histological examination in 10% formaldehyde solution, dehydrated in alcohols of increasing strength, poured into paraffin. Result and Discussion: The results of the study demonstrate the presence of stress-protective properties of sodium 2-((4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-yl) thio) acetate in the model of acute immobilization stress, which was reproduced for 6 hours. As can be seen from the described and presented microscopic picture, the test sample to some extent reduced the degree of stress damage to the liver. In terms of the positive effect on the histological condition of the liver parenchyma (a more pronounced structural orientation of hepatocytes was noted, their beam structure was contoured, dystrophic changes of hepatocytes are less pronounced, round cell infiltrates and foci of hepatocyte necrosis are absent), sodium 2-((4-amino-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate exhibits a stress-protective effect in the model of acute immobilization stress. We can conclude about similarity of activity of the test sample with comparison drug (Mebicar®) at studying of influence on a histologic condition of a liver parenchyma

Ecdysterone prevents negative effect of acute immobilization stress on energy metabolism of rat liver mitochondria

Ecdysterone is a naturally occurring steroid hormone, which presents in arthropods and in a number of plants as an insect defence tool. There are many studies showing that application of ecdysterone can alter mitochondrial functions of mammalian cells, however it is not clear whether its effects are direct or mediated by activation of other cellular processes. In our study, we have shown how ecdysterone acts at the mitochondrial level in normal conditions and in certain pathology. We have demonstrated that application of immobilization stress to male rats causes uncoupling of mitochondrial oxidative phosphorylation, the preliminary application of ecdysterone prevents negative effect of immobilization stress on mitochondria. In-vitro experiments with isolated mitochondria have shown that ecdysterone can increase mitochondrial coupling and hyperpolarise mitochondria but without a noticeable effect on ADP/O ratio. Molecular docking experiments revealed that ecdysterone has high binding energy with mitochondrial FOF1 ATP synthase, but further biochemical analysis have not revealed either stimulatory or inhibitory effect of ecdysterone on FOF1 ATPase activity of the enzyme. Thus, ecdysterone can directly affect mitochondrial bioenergetics, though we assume that its preventive effect on mitochondria during immobilization stress is also coupled with the activation of some other cellular processes.

Comparison of the performance of lipoperoxidation-antioxidant protection system in rats at different periods under immobilization stress effects.

Background: Under physiological conditions, the activity of the formation of active oxygen is low. The activity of these processes is intensified under stress-induced situations. This study aimed to investigate the role of free-radical oxidation (FRO) in adrenal tissues and immunocompetent organs and cells in mature white rats after 6 hours of immobilization stress. Methods: The studies were performed on 40 White male rats of the Wistar line with a bodyweight of 200 to 240 g. Two series of experiments were conducted: I series: determination of indices in intact rats (10 rats); II series: determination of indices after a 6-hour immobilization stress action on them. Animals of II series were divided into 3 groups of 10 rats in each: group 1: those undergoing acute immobilization stress, withdrawal from the experiment in 1 hour; group 2: those undergoing acute immobilization stress, withdrawal from the experiment in 25 hours; and group 3: those undergoing acute immobilization stress, withdrawal from the experiment in 49 hours. The obtained data were processed by statistical methods with the help of the "Biostat" and "Excel" software packages. Results: In groups 1, 2, and 3, the animals were simulated acute immobilization stress by fixing the animals for 6 hours in bright light. The results of the conducted studies indicate changes in lipid peroxidation and antioxidant system (LPO-AOS) in case of immobilization stress-excitation. In developing free-radical pathology at immobilization stress-excitation, the more expressed disturbance of LPO-AOS, and accordingly the intensity of lipoperoxidation in the structural membrane of all investigated organs was high at the initial stage of exposure. Conclusion: At 49 hours after immobilization, stress less pronounced influence on the lipoperoxidation process was noted. The increase in the intensity of excessive lipoperoxidation testifies to the inhibited manifestation of AOS in the organism.

Peroxiredoxin 6 Knockout Mice Demonstrate Anxiety Behavior and Attenuated Contextual Fear Memory after Receiving Acute Immobilization Stress.

Stress can elicit glucocorticoid release to promote coping mechanisms and influence learning and memory performance. Individual memory performance varies in response to stress, and the underlying mechanism is not clear yet. Peroxiredoxin 6 (PRDX6) is a multifunctional enzyme participating in both physiological and pathological conditions. Several studies have demonstrated the correlation between PRDX6 expression level and stress-related disorders. Our recent finding indicates that lack of the Prdx6 gene leads to enhanced fear memory. However, it is unknown whether PRDX6 is involved in changes in anxiety response and memory performance upon stress. The present study reveals that hippocampal PRDX6 level is downregulated 30 min after acute immobilization stress (AIS) and trace fear conditioning (TFC). In human retinal pigment epithelium (ARPE-19) cells, the PRDX6 expression level decreases after being treated with stress hormone corticosterone. Lack of PRDX6 caused elevated basal H2O2 levels in the hippocampus, basolateral amygdala, and medial prefrontal cortex, brain regions involved in anxiety response and fear memory formation. Additionally, this H2O2 level was still high in the medial prefrontal cortex of the knockout mice under AIS. Anxiety behavior of Prdx6−/− mice was enhanced after immobilization for 30 min. After exposure to AIS before a contextual test, Prdx6−/− mice displayed a contextual fear memory deficit. Our results showed that the memory performance of Prdx6−/− mice was impaired when responding to AIS, accompanied by dysregulated H2O2 levels. The present study helps better understand the function of PRDX6 in memory performance after acute stress.

Вплив на селезінку гострого іммобілізаційного стресу, спричиненого фіксацією щурів за шийну складку

Notwithstanding the long history of research, versatile studies of stress effect on living organisms are relevant to date. The stress response that arose in the process of evolution as a component of the adaptation process, in case of its unfavorable course, can trigger pathogenetic mechanisms of numerous pathologies. Investigation of the effect of stress reactions on living organisms requires the use of laboratory animals in the experimental studies, to which there is currently no alternative. In our opinion, special attention should be paid to those experimental models of stress that are easy-to-use, cost effective and are in concordance with current principles of bioethics. The purpose of the study was to study the impact of 6-hour-long cervical fold suspension experimental model of acute immobilization stress on the albino rat spleen. Material and methods. Based on the international bioethical principles, 10 male albino rats were involved in the study. The intact animals were assigned into control Group I (n=5); experimental Group II (n=5) involved animals, exposed to 6-hour-long cervical fold suspension model of acute immobilization stress. After euthanasia, macro- and microscopic examination of the spleen was made. Microspecimens were stained with hematoxylin and eosin. Results and discussion. The macroscopic analysis of the spleen revealed no visual differences in the rats of the experimental group compared to control ones. Histological study of the spleen specimens of the rat of Group II has shown sparse perivascular swellings of the central arteries, thickening of the periarterial zone, narrowing of the diameter of the germinal center due to the cell redistribution that was detected in the white pulp in the medium and large lymphoid nodules under the effect of the acute immobilization stress induced by the atraumatic cervical fold suspension for 6 hours. The above changes led to a relatively slight increase in the volume of the white pulp of the spleen by 4.23 ± 1.52%. A clear boundary between the white and red pulp was noted. In addition, disturbances in the microcirculation in the vessels of the hemomicrocirculatory bed, manifested by edema of the splenic stroma, plethora of vessels and a decrease in the number of erythrocytes in these areas in the subcapsular departments were noted. In the deeper layers of the spleen, foci of sparse perivascular diapedetic hemorrhages were found with the phenomena of blood stasis in the microcirculatory bed, leukostasis and sludge phenomenon. The described changes led to blood flow slowing in the microcirculatory bed with subsequent adhesion of erythrocytes and the formation of blood clots in the vessels of larger diameter. Thus, histologically, acute stress induced by cervical fold suspension causes minor morphological changes in the spleen of rats of the experimental group, the moderate severity of which indicates the relative resistance of splenic structures to the action of 6-hour-long immobilization. Conclusion. The findings of the study showed the relative resistance of the rat spleen to 6-hour-long stress caused by cervical fold suspension, with minor morphological changes in the white pulp and impaired hemomicrocirculation

STRESS-PROTECTIVE EFFECTS OF NEW MEDICINAL FORM WITH GLYCINE AND MAGNESIUM CITRATE

Introduction. Stress disorders are common in clinical practice, and their treatment requires selective medication choice. Among the drugs having anxiolytic and sedative effects, glycine and magnesium compounds are being intensively investigated and the options of producing sublingual tablets based on these substances seem to be promising. The aim of this study is to investigate the effects of glycine and magnesium citrate and their combination on glycine and magnesium citrate on somatic parameters (Selye's triad) under the stress conditions and to determine the most effective composition of the compounds.
 Materials and methods. The experiments were carried out on 76 white rats. The substances were administered sublingually and then the animals were kept in the small cages for 6 hours in order to simulate immobilization stress. At the end of the stress exposure, the rats were euthanized and the relative masses of the thymus and adrenal glands as well as a presence of ulcers and haemorrhages in the stomach were determined. Statistical processing was performed using the Statistica for Windows 8.0 software.
 Results and discussion. Immobilization stress resulted in a decrease in the relative weight of the thymus in the rats without significant changes in the weight of the adrenal glands and intense ulceration in the stomach. Prophylactic use of the compounds under the study and their combinations prevented the stress-induced involution of the thymus. The most pronounced protective effect was demonstrated by the combination of 100 mg glycine and 250 mg magnesium citrate and glycine itself. At the same time, the relative mass of the adrenal glands did not change significantly. The lowest incidence of ulcerative lesions was observed in the groups of animals who received the combinations of glycine (100 mg) and magnesium citrate (250-350 mg) or glycine (100 mg) separately. This scheme leads to a decrease in the number and area of gastric ulcers as compared to the control group. Magnesium citrate in doses of 250 mg and 350 mg was found not as effective in protecting the gastric mucosa.
 Conclusion. Acute immobilization stress causes involution of the thymus and gastric ulceration, but does not result in adrenal hypertrophy. According to the findings obtained by the Selye triad study, a combination of 100 mg glycine and 250 mg magnesium citrate and glycine separately in a dose of 100 mg have showed the highest prophylactic effect.

Stress-induced impairment of fear extinction recall is associated with changes in neuronal activity patterns in PVT

Treatment resistance of anxiety-related disorders often arises from an inappropriate fear expression, impairment in fear extinction, and spontaneous return of fear. Stress exposure is considered a high risk factor for neuropsychiatric disorders, but understanding of the long-term consequences of stress is limited, particularly when it comes to treatment outcome. Therefore, studying the consequences of acute stress would provide critical information on the role of stress in psychopathology. In the present study, we investigated the effect of acute immobilization stress on anxiety-like behavior and on conditioned fear memory. Our results demonstrate that prior stress exposure had no effect on anxiety-related behavior, fear acquisition, as well as fear extinction compared to non-stressed controls, but resulted in significantly higher rates of freezing during recall of extinction, indicating a consolidation failure. Further, immunohistochemical analysis of the expression of the immediate early gene c-Fos after recall of extinction revealed increased neuronal activity in the posterior paraventricular nucleus of the thalamus (PVT) in previously stressed animals compared to non-stressed controls. These results indicate, firstly, that acute stress affects long-term fear memory even after successful extinction training, and secondly, a strong involvement of the PVT in maladaptive fear responses induced by prior stress. Thus, stress-induced changes in PVT neuronal activity might be of importance for the pathophysiology of stress-sensitive anxiety-related psychiatric disorders, since exposure to an earlier acute stressor could counteract the success of therapy.

Acutely increased β-hydroxybutyrate plays a role in the prefrontal cortex to escape stressful conditions during the acute stress response

Ketone bodies can be increased in the blood under certain physiological conditions, but their role under such conditions remains to be clarified. In the present study, we found the increment and usage of β-hydroxybutyrate (BHB) in the prefrontal cortex (PFC) during acute stress. BHB levels increased in the blood and PFC after 30-min acute immobilization stress, and BHB dehydrogenase 1 increased in the PFC simultaneously, but not in the hippocampus. Moreover, increased levels of acetyl-CoA, pyruvate carboxylase, and glutamate dehydrogenase 1 were found in the PFC, implicating the metabolism of increased BHB in the brain. Thus, we checked the levels of glutamate, glutamine, and GABA and found increased levels of glutamate and glutamine in the stressed group compared with that in the control group in the PFC. Exogenous administration of BHB enhanced struggling behaviors under stressful conditions. Our results suggest that the metabolism of BHB from peripheral blood in the PFC may contribute to acute stress responses to escape stressful conditions.