Repeated Immobilization Stress Research Articles

The State of the Haemostasis System under Conditions of Immobilization Stress against the Background of Experimental Metabolic Syndrome

The state of the haemostasis system under conditions of immobilization stress against the background of metabolic syndrome (MS) in male Wistar rats was studied. Two series of experiments were conducted using single and multiple immobilization effects. It was shown that the development of MS with prolonged maintenance of rats on a high-calorie diet led to a decrease in anticoagulant-fibrinolytic and antiplatelet potential of blood. In the plasma of intact rats subjected to both single and multiple immobilization, an increase in blood clotting and a decrease in fibrinolysis were found. At the same time, the use of multiple immobilization effects in comparison with single immobilization contributed to a more pronounced increase in platelet aggregation. The combination of both single and multiple immobilization and MS in rats caused a significant decrease in fibrinolysis, anticoagulant activity of blood and increased platelet aggregation. However, in the case of repeated immobilization exposure, an even more significant increase in ADP-dependent platelet aggregation was observed. A comparative analysis of the indicators of primary and plasma haemostasis under these experimental conditions allows us to conclude that immobilization, regardless of its duration, aggravates the state of hypercoagulation in rats with MS. Moreover, repeated immobilization stress on the background of metabolic disorders leads to more pronounced hypercoagulation shifts due to an increase in platelet aggregation by 2 times compared with intact animals.

Stress alters the transcriptional activity of Leydig cells dependently on the diurnal time.

The increasing amount of data points to the circadian timing system as an essential part of processes regulating androgen homeostasis. However, the relationship between stress response, timekeeping-, and steroidogenesis-related systems is unexplored. Here, the stress-response of the testosterone-producing rat Leydig cells depending on the time of stressful events was studied. The study analyzes the effects of 3-h immobilization (IMO) applied at different periods during the day. The IMO performed once [1 time immobilization stress (1×IMO)] or repeated in 10 consecutive days [10 time repeated immobilization stress (10×IMO)]. Both types of IMO increased corticosterone and decreased testosterone blood level. However, the effect of 10×IMO occurring in the active phase on blood testosterone was less pronounced. This is related to different sensitivity to IMO-events depending on the diurnal time. Most steroidogenesis-related genes [gene encoding luteinizing hormone/choriogonadotropin receptor (Lhcgr), gene encoding cytochrome P450, family 11, subfamily a, polypeptide 1 (Cyp11a1), gene encoding hydroxy-δ-5-steroid dehydrogenase, 3 β- and steroid δ-isomerase 1 (Hsd3b1/2), and gene encoding cytochrome P450, family 17, subfamily a, polypeptide 1 (Cyp17a1)] were downregulated in the inactive phase but unchanged or even upregulated in the active phase of the day. Both types of IMO stimulated the expression of clock elements gene encoding aryl hydrocarbon receptor nuclear translocator-like (Bmal1)/aryl hydrocarbon receptor nuclear translocator-like (BMAL1), gene encoding period circadian regulator 1 (Per1)/period circadian regulator 1 (PER1) regardless of the day's stage and reduced gene encoding nuclear receptor subfamily 1, group D, member 1 (Rev-erba) in the inactive phase. The principal component analysis (PCA) confirmed a major shift, for both IMO-types, in the transcription of the genes across the passive/active stage. Further, 10×IMO changed a diurnal pattern of the glucocorticoid receptor [gene encoding nuclear receptor subfamily 3, group C, member 1 (Nr3c1)/nuclear receptor subfamily 3, group C, member 1 (GR)] expression, whereas the observed time-dependent IMO-response of the Leydig cells correlated with different corticosterone engagements. Altogether, the Leydig cell's stress response depends on the daytime of the stressful event, emphasizing the importance of the circadian system in supporting androgen homeostasis and male fertility.

A comparative study of adrenalin and fluocinolon induced oxidative stress in male wistar rats

Hormone secretion by the hypothalamic-pituitary-adrenocortical (HPA) axis is modulated by multiple factors which include the circadian rhythm, various types of stressors and glucocorticoids. Treatment with synthetic glucocorticoids as e.g. dexamethasone or dermocorticosteroids and repeated immobilization stress, decreases the total body weight gain of animals by disturbing the HPA axis function and accelerating the catabolism of the organism. Synthetic glucocorticoids are widely used as anti-inflammatory and anti-allergic drugs. Neverteheless, their administration may cause side effects in the normal functioning of several organs. Starting from the above findings and from the important physiological roles of the glucocorticoids in the metabolism, we investigated the reactions of the adrenal and thymus, the evolution of the body and organ weight and the level of the free radicals after adrenaline- and fluocinolon stress. In this study, we used electron paramagnetic resonance spectroscopy for the direct detection of free radical content in the organs o f stressed Wistar rats. We followed the changes of the blood glucose level, body weight,structural modification and whole redox state of the rats during adrenaline and Fluocinolon-acetonid N treatment, as endogenous and exogenous sources of elevated glucocoticoid levels. We found a relationship between changes of the redox state and modified homeostasis of the organism, as an effect of elevated glucocorticoid levels. The oxidative stress induced by adrenalin treatment seemed to be an inducer rather than the result of the tissue damage.

Effects of repeated immobilization stress on hypothalamic-pituitary- ovarian axis in female rats

Objective: To explore the effects of repeated immobilization stress on hypothalamic-pituitary-ovarian axis in female rats. Methods: Forty female SD rats were randomly divided into two groups: control group (n=20) and experimental group (n=20). One group was fed normally, the other group was subjected to incremental load restraint stress. Brake stress once a day in the retainer (starting at 9: 00 a.m.), braking for 2 hours on the first day, increasing load by 0.5 hours a day for two weeks. Body weight, estrous cycle, sex hormone, organ coefficient, pathology and expression of related genes were detected to explore the harm of hypothalamic-pituitary-ovarian axis. Results: Repeated immobilization stress caused weight loss, prolonged estrous cycle, and changed the organ coefficient and morphology of ovaries and uterus. QPCR technique was used to detect the related genes. It was found that the expressions of gonadotropin releasing hormone, pituitary gonadotropin releasing hormone receptor, follicle stimulating hormone and luteinizing hormone mRNA were decreased significantly, while the expressions of ovarian follicle stimulating hormone and luteinizing hormone receptor mRNA were increased significantly. The expression of estrogen receptor mRNA in ovary and uterus was decreased significantly. Conclusion: Repeated immobilization stress may disrupt the estrous cycle by interfering with the endocrine regulation of the hypothalamic-pituitary-ovarian axis, thus damaging the gonadal and reproductive endocrine function of female animals.

SAT-362 Hypothalamic Pituitary Adrenal Axis Dysregulation Alters Central and Peripheral Adaptation to Repeated Stress Exposure in Mice

Aims: The hypothalamic pituitary adrenal (HPA) axis is the key neuroendocrine mediator of the stress response and controls many aspects of physiology and behavior. We previously showed that experimentally disrupting normal HPA function in mice led to altered neural and behavioral responses to acute stress. When exposed to prolonged or repeated stress, organisms undergo adaptation in many processes of metabolism, endocrine function, and behavior. Further, many of these processes are thought to be driven by HPA secreted hormones. In this study, we aimed to test this hypothesis by disrupting normal HPA axis function and measuring metabolic, endocrine, and neural outcomes following repeated stress exposure. Methods: HPA axis function in male C57BL/6 mice was disrupted via noninvasive, oral corticosterone administration, which we have shown blunts hormonal and behavioral stress responses. Mice were then exposed to repeated immobilization stress (2h/d for 14d), during which time body weight was measured to assess metabolic adaptation to stress. Mice were euthanized and adipose tissue, adrenal glands, blood, and brain were collected for analysis. We evaluated the effects of HPA disruption on mass of white adipose tissue and adrenal glands, and determined plasma corticosterone concentrations as a measure of endocrine adaptation to stress. Using RTqPCR we investigated the effects of HPA disruption on the expression of genes related to synaptic excitability in the medial prefrontal cortex (mPFC), a brain region known to regulate behavioral and emotional responses to stress. Results: Repeated stress led to body weight loss in all mice, however body weight loss was exaggerated by HPA disruption, suggesting increased sensitivity to stress. Additionally, this decrease in body weight could not be accounted for by decreased white adipose mass alone, suggesting effects on other tissues caused by HPA disruption. Repeated stress increased adrenal weight similarly in all mice, but only elevated levels of plasma corticosterone in Control mice, demonstrating altered endocrine adaptation to stress after HPA disruption. Finally, we observed increased gene expression of the astrocytic glutamate exchanger xCT in the mPFC following repeated stress only in HPA disrupted mice, suggesting that HPA disruption affects processes of neural adaptation. Conclusions: HPA axis disruption increased sensitivity to metabolic outcomes of repeated stress exposure and altered endocrine stress adaptation. Additionally, effects on mPFC gene expression suggest altered neural adaptation to stress. These results support the hypothesis that an intact HPA axis is crucial in mediating adaptive responses to stress, and that dysfunction of this system may be linked to negative health outcomes of stress exposure. Sources of Research Support: NSF 1553067 and NIA R21AG050054 to INK.

Gene expression profile in peripheral blood mononuclear cells of postpartum depression patients

Postpartum depression (PPD) is a common mental health problem that causes maternal suffering and various negative consequences for offspring. The pathogenesis of PPD and the causes of consequences for offspring remain largely unknown. Here, we applied RNA sequencing to sequence the whole transcriptomes of peripheral blood mononuclear cells (PBMCs) from PPD patients (Edinburgh Postnatal Depression Scale [EPDS] score ≥13) and control subjects (EPDS = 0). We found that PPD was positively correlated with multiple genes involved in energy metabolism, neurodegenerative diseases and immune response, while negatively correlated with multiple genes in mismatch repair and cancer-related pathways. Remarkably, genes associated with appetite regulation and nutrient response were differentially expressed between PPD and control subjects. Then, we employed a postnatal growth retardation model by repeated immobilization stress (IS) stimulation to maternal mice. The expression of appetite regulation and nutrient response-related genes in the PBMCs of IS mice and in the hypothalamus of their offspring were also affected. In conclusion, this study provides a comprehensive characterization of the PBMCs transcriptome in PPD and suggests that maternal stress may affect appetite regulation and nutrient response in the hypothalamus of offspring mice.

Anti-stress effects of human placenta extract: possible involvement of the oxidative stress system in rats

BackgroundHuman placenta hydrolysate (hPH) has been utilized to improve menopausal, fatigue, liver function. Its high concentration of bioactive substances is known to produce including antioxidant, anti-inflammatory and anti-nociceptive activities. However, its mechanisms of stress-induced depression remain unknown.MethodsThe present study examined the effect of hPH on stress-induced depressive behaviors and biochemical parameters in rats. hPH (0.02 ml, 0.2 ml or 1 ml/rat) was injected intravenously 30 min before the daily stress session in male Sprague-Dawley rats exposed to repeated immobilization stress (4 h/day for 7 days). The depressive-like behaviors of all groups were measured by elevated plus maze (EPM) and forced swimming test (FST). After the behavior tests, brain samples of all groups were collected for the analysis of glutathione peroxidase (GPx) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) staining.ResultsTreatment with hPH produced a significant decrease of immobility time in the FST compared to the controls. Additionally, hPH treatment elicited a slightly decreasing trend in anxiety behavior on the EPM. Furthermore, hPH increased the level of GPx protein in the hippocampus, and decreased the expression of NADPH-d in the paraventricular nucleus (PVN).ConclusionThis study demonstrated that hPH has anti-stress effects via the regulation of nitric oxide (NO) synthase and antioxidant activity in the brain. These results suggest that hPH may be useful in the treatment of stress-related diseases such as chronic fatigue syndrome.

Anti-stress effects of a GSK-3β inhibitor, AR-A014418, in immobilization stress of variable duration in mice.

The present study was designed to explore the anti-stress role of AR-A014418, a selective glycogen synthase kinase-3β inhibitor (GSK-3β), on changes provoked by immobilization stress of varying duration. Acute stress of varying degree was induced by subjecting mice to immobilization stress of short duration (30 min) or long duration (120 min). Thereafter, these animals were exposed to the same stressor for 5 days to induce stress adaptation. The behavioral alterations were assessed using an actophotometer, a hole-board, and the open field and social interaction tests. The serum corticosterone levels were assessed as markers of the hypothalamic-pituitary-adrenal (HPA) axis activity. The levels of total GSK-3β and p-GSK-3β-S9 were determined in the prefrontal cortex. A single exposure to short or long immobilization stress produced behavioral and biochemical changes and the levels of p-GSK-3β-S9 decreased without affecting the total GSK-3β levels in the brain. However, repeated exposure to both short and long stress reversed the behavioral and biochemical changes along with the normalization of p-GSK-3β-S9 levels. The administration of AR-A014418, a selective GSK-3β inhibitor, diminished acute stress-induced behavioral and biochemical changes. Furthermore, AR-A014418 normalized acute stress-induced alterations in p-GSK-3β-S9 levels without changing total GSK-3β levels. Our study suggests that acute stress-induced decrease in p-GSK-3β-S9 levels in the brain contributes to the development of behavioral and biochemical alterations and the normalization of GSK-3β signaling may contribute to stress adaptive behavior in mice which have been subjected to repeated immobilization stress.

Enduring attenuation of norepinephrine synaptic availability and augmentation of the pharmacological and behavioral effects of desipramine by repeated immobilization stress

Here we provide evidence that repeated immobilization stress (RIS) in rats induces a persistent increase in noradrenergic activity in the anterior aspects of the anterolateral bed nucleus of the stria terminalis (alBNST). This increase in noradrenergic activity results from both enhanced synthesis and reuptake of norepinephrine (NE). It leads to a decrease in the synaptic availability of NE, which elicits an augmented noradrenergic response to the inhibitors of NE reuptake (NRIs), such as desipramine (DMI), an antidepressant. The enduring depression-like behavior and the augmentation of the climbing behavior seen in repeatedly stressed rats following subchronic administration of DMI in the forced swimming test (FST) might be explained by a dysregulation of noradrenergic transmission observed in alBNST. Taken together, we propose that dysregulation of noradrenergic transmission such as the one described in the present work may represent a mechanism underlying major depressive disorders (MDD) with melancholic features in humans.

Exaggerated phosphorylation of brain tau protein in CRH KO mice exposed to repeated immobilization stress

Neuroendocrine and behavioral stress responses are orchestrated by corticotropin-releasing hormone (CRH) and norepinephrine (NE) synthesizing neurons. Recent findings indicate that stress may promote development of neurofibrillary pathology in Alzheimer's disease. Therefore, we investigated relationships among stress, tau protein phosphorylation, and brain NE using wild-type (WT) and CRH-knockout (CRH KO) mice. We assessed expression of phosphorylated tau (p-tau) at the PHF-1 epitope and NE concentrations in the locus coeruleus (LC), A1/C1 and A2/C2 catecholaminergic cell groups, hippocampus, amygdala, nucleus basalis magnocellularis, and frontal cortex of unstressed, singly stressed or repeatedly stressed mice. Moreover, gene expression and protein levels of tyrosine hydroxylase (TH) and CRH receptor mRNA were determined in the LC. Plasma corticosterone levels were also measured. Exposure to a single stress increases tau phosphorylation throughout the brain in WT mice when compared to singly stressed CRH KO animals. In contrast, repeatedly stressed CRH KO mice showed exaggerated tau phosphorylation relative to WT controls. We also observed differences in extent of tau phosphorylation between investigated structures, e.g. the LC and hippocampus. Moreover, CRH deficiency leads to different responses to stress in gene expression of TH, NE concentrations, CRH receptor mRNA, and plasma corticosterone levels. Our data indicate that CRH effects on tau phosphorylation are dependent on whether stress is single or repeated, and differs between brain regions. Our findings indicate that CRH attenuates mechanisms responsible for development of stress-induced tau neuropathology, particularly in conditions of chronic stress. However, the involvement of central catecholaminergic neurons in these mechanisms remains unclear and is in need of further investigation.

Differential role of angiotensin neuropeptides in repeated exposure of immobilization stress of varying duration in mice.

The present study aimed to investigate the role of angiotensin II in repeated immobilization stress exposure of varying duration. Mice were subjected either to short (30min) or long duration (120min) immobilization stress for 5days. The behavioral changes were assessed by actophotometer, hole board, open field and social interaction tests on day 1 and day 5. The serum corticosterone levels were measured as an index of HPA axis on day 5. A single exposure of short or long duration stress produced behavioral deficits and increased corticosterone levels. However, repeated exposure of stressors was followed by restoration of behavioral and biochemical changes, suggesting the development of stress adaptation. A single administration of telmisartan (5mg/kg) exacerbated the short stress-induced decrease in behavioral activity and increase in corticosterone levels on the first day of stress exposure, suggesting the anti-stress role of angiotensin II. In contrast, the normalization of behavioral and biochemical response was observed in prolonged stress-subjected mice following telmisartan treatment on the 1st day of stress exposure, suggesting stress inducing action of angiotensin II. Furthermore, telmisartan treatment for 5days abolished the restoration of behavioral and biochemical response following 5 consecutive exposures of short immobilization stress, without altering stress adaptation in prolonged stress, suggesting that angiotensin II has stress adaptive role in short stress. It is concluded that angiotensin II acts as anti-stress agent and promotes adaptation during short stress, whereas it acts as stress promoting agent, without affecting stress adaptation during prolonged stress.

Stress Enables Reinforcement-Elicited Serotonergic Consolidation of Fear Memory

BackgroundPrior exposure to stress is a risk factor for developing posttraumatic stress disorder (PTSD) in response to trauma, yet the mechanisms by which this occurs are unclear. Using a rodent model of stress-based susceptibility to PTSD, we investigated the role of serotonin in this phenomenon. MethodsAdult mice were exposed to repeated immobilization stress or handling, and the role of serotonin in subsequent fear learning was assessed using pharmacologic manipulation and western blot detection of serotonin receptors, measurements of serotonin, high-speed optogenetic silencing, and behavior. ResultsBoth dorsal raphe serotonergic activity during aversive reinforcement and amygdala serotonin 2C receptor (5-HT2CR) activity during memory consolidation were necessary for stress enhancement of fear memory, but neither process affected fear memory in unstressed mice. Additionally, prior stress increased amygdala sensitivity to serotonin by promoting surface expression of 5-HT2CR without affecting tissue levels of serotonin in the amygdala. We also showed that the serotonin that drives stress enhancement of associative cued fear memory can arise from paired or unpaired footshock, an effect not predicted by theoretical models of associative learning. ConclusionsStress bolsters the consequences of aversive reinforcement, not by simply enhancing the neurobiological signals used to encode fear in unstressed animals, but rather by engaging distinct mechanistic pathways. These results reveal that predictions from classical associative learning models do not always hold for stressed animals and suggest that 5-HT2CR blockade may represent a promising therapeutic target for psychiatric disorders characterized by excessive fear responses such as that observed in PTSD.

Molecular changes induced by repeated restraint stress in the heart: the effect of oxytocin receptor antagonist atosiban.

Even though stress belongs to the most common lifestyle risk factors of cardiovascular diseases, there are only limited data on direct influence of stressors on the heart. The aim of the present study was to explore selected protein signaling pathways in response to repeated immobilization stress in the heart tissue. Effects of simultaneous treatment with atosiban, an oxytocin receptor antagonist, on stress-induced changes in the heart were also investigated. Male Wistar rats were exposed to repeated immobilization (2 h daily, lasting 2 weeks). The results showed increased phosphorylation of Akt kinase, enhanced levels of Bcl-2, and decreased levels of cleaved caspase-3 in the left ventricle in response to chronic stress independently of the treatment. Exposure to restraint led to the rise of HSP-90 and p53 in vehicle-treated rats only. Stress failed to modify MMP-2 activity and ultrastructure of the heart tissue. Treatment with the oxytocin/vasopressin receptor antagonist atosiban reversed stress-induced rise in HSP-90 and p53 proteins. In conclusion, our data demonstrate that repeated restraint stress induces Akt kinase activation and this is associated with elevation of anti-apoptotic proteins (Bcl-2) and down-regulation of pro-apoptotic proteins (cleaved caspase-3). These findings suggest that activation of pro-survival anti-apoptotic Akt kinase pathway plays an important role in molecular mechanisms underlying responses and adaptation of the rat heart to repeated stress exposure. The results further indicate a regulatory role of oxytocin/vasopressin in the control of stress-induced activation in HSP-90 and related proteins.

Intratesticular alpha1-adrenergic receptors mediate stress-disturbed transcription of steroidogenic stimulator NUR77 as well as steroidogenic repressors DAX1 and ARR19 in Leydig cells of adult rats

The aim of the present study was to define the role of testicular α1-adrenergic receptors (α1-ADRs) in stress-triggered adaptation of testosterone-producing Leydig cells of adult rats. Results showed that in vivo blockade of testicular α1-ADRs prevented partial recovery of circulating androgen levels registered after 10× repeated immobilization stress (10 × IMO). Moreover, α1-ADR-blockade diminished 10 × IMO-triggered recovery of Leydig cell androgen production, and abolished mitochondrial membrane potential recovery. In the same cells, 10 × IMO-induced increase in Star transcript was abolished, Lhcgr transcript decreased, while transcription of other steroidogenic proteins was not changed. α1-ADR-blockade recovered stress-induced decrease of Nur77, one of the main steroidogenic stimulator, while significantly reduced 10 × IMO-increased in the transcription of the main steroidogenic repressors, Arr19 and Dax1. In vitro experiments revealed an adrenaline-induced α1-ADR-mediated decrease in Nur77 transcription in Leydig cells. Adrenaline-induced increase of repressor Dax1 also involves ADRs in Leydig cells. Accordingly, α1-ADRs participate in some of the stress-triggered effects on the steroidogenic machinery of Leydig cells.

Immobilization stress sensitizes rat dorsal horn neurons having input from the low back.

Stress is known to promote several forms of muscle pain including non-specific low back pain. However, the question if stress alone activates nociceptive central neurons has not been studied systematically. Here, we investigated the influence of repeated immobilization stress on dorsal horn neurons and behaviour in the rat. The stress consisted of immobilization in a narrow tube for 1 h on 12 days. Single dorsal horn neurons were recorded with microelectrodes introduced into the spinal segment L2. In this segment, about 14% of the neurons responded to mechanical stimulation of the subcutaneous soft tissues of the low back in naïve rats. The neurons often behaved like wide dynamic range cells in that they had a low mechanical threshold and showed graded responses to noxious stimuli. The stress-induced changes in neuronal response behaviour were (1) appearance of new receptive fields in the deep tissues of the hindlimb, (2) increased input from deep soft tissues, but unchanged input from the skin and (3) significant increase in resting activity. Surprisingly, the pressure-pain threshold of the low back remained unchanged, although dorsal horn neurons were sensitized. In the open field test, the rats showed signs of increased anxiety. This study shows that stress alone is sufficient to sensitize dorsal horn neurons. The data may explain the enhanced pain low back patients report when they are under stress. The increased resting discharge may lead to spontaneous pain.

Regulation of nonclassical renin-angiotensin system receptor gene expression in the adrenal medulla by acute and repeated immobilization stress.

The involvement of the nonclassical renin-angiotensin system (RAS) in the adrenomedullary response to stress is unclear. Therefore, we examined basal and immobilization stress (IMO)-triggered changes in gene expression of the classical and nonclassical RAS receptors in the rat adrenal medulla, specifically the angiotensin II type 2 (AT2) and type 4 (AT4) receptors, (pro)renin receptor [(P)RR], and Mas receptor (MasR). All RAS receptors were identified, with AT2 receptor mRNA levels being the most abundant, followed by the (P)RR, AT1A receptor, AT4 receptor, and MasR. Following a single IMO, AT2 and AT4 receptor mRNA levels decreased by 90 and 50%, respectively. Their mRNA levels were also transiently decreased by repeated IMO. MasR mRNA levels displayed a 75% transient decrease as well. Conversely, (P)RR mRNA levels were increased by 50% following single or repeated IMO. Because of its abundance, the function of the (P)RR was explored in PC-12 cells. Prorenin activation of the (P)RR increased phosphorylation of extracellular signal-regulated kinase 1/2 and tyrosine hydroxylase at Ser(31), likely increasing its enzymatic activity and catecholamine biosynthesis. Together, the broad and dynamic changes in gene expression of the nonclassical RAS receptors implicate their role in the intricate response of the adrenomedullary catecholaminergic system to stress.

A systems approach identifies co-signaling molecules of early growth response 1 transcription factor in immobilization stress.

BackgroundAdaptation to stress is critical for survival. The adrenal medulla, the major source of epinephrine, plays an important role in the development of the hyperadenergic state and increased risk for stress associated disorders, such as hypertension and myocardial infarction. The transcription factor Egr1 plays a central role in acute and repeated stress, however the complexity of the response suggests that other transcription factor pathways might be playing equally important roles during acute and repeated stress. Therefore, we sought to discover such factors by applying a systems approach.ResultsUsing microarrays and network analysis we show here for the first time that the transcription factor signal transducer and activator of transcription 3 (Stat3) gene is activated in acute stress whereas the prolactin releasing hormone (Prlh11) and chromogranin B (Chgb) genes are induced in repeated immobilization stress and that along with Egr1 may be critical mediators of the stress response.ConclusionsOur results suggest possible involvement of Stat3 and Prlh1/Chgb up-regulation in the transition from short to repeated stress activation.

Comparison of the effects of single and daily repeated immobilization stress on resting activity and heterotypic sensitization of the hypothalamic–pituitary–adrenal axis

Acute exposure to severe stressors causes marked activation of the hypothalamic–pituitary–adrenal (HPA) axis that is reflected on the day after higher resting levels of HPA hormones and sensitization of the HPA response to novel (heterotypic) stressors. However, whether a single exposure to a severe stressor or daily repeated exposure to the same (homotypic) stressor modifies these responses to the same extent has not been studied. In this experiment, we studied this issue in adult male Sprague-Dawley rats daily exposed for seven days to a severe stressor such as immobilization on boards (IMO). A first exposure to 1 h IMO resulted in a marked activation of the HPA axis as reflected in plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone, and such activation was significantly reduced after the seventh IMO. On the day after the first IMO, higher resting levels of ACTH and corticosterone and sensitization of their responses to a short exposure to an open-field (OF) were observed, together with a marked hypoactivity in this environment. Repeated exposure to IMO partially reduced hypoactivity, the increase in resting levels of HPA hormones and the ACTH responsiveness to the OF on the day after the last exposure to IMO. In contrast, corticosterone response was gradually increased, suggesting partial dissociation from ACTH. These results indicate that daily repeated exposure to the same stressor partially reduced the HPA response to the homotypic stressor as well as the sensitization of HPA axis activity observed the day after chronic stress cessation.

Enhancement and inhibition of apomorphine-induced sensitization in rats exposed to immobilization stress: Relationship with adaptation to stress

Stress increases vulnerability to addiction while drugs of abuse impair coping responses and pre-dispose to depression. Pre-clinical research shows that stress exposure augments locomotor sensitization effects of drugs of abuse and impairs behavioral tolerance to repeated stress. The present study investigates relationship between behavioral tolerance to repeated immobilization stress and apomorphine-induced sensitization. Apomorphine was injected either before exposure or after the termination of immobilization, daily for 5days, to monitor drug-induced behavioral sensitization and tolerance in immobilization stress-induced anorexia. We find that apomorphine-induced sensitization is enhanced and tolerance to repeated immobilization is impaired if the drug is administered before exposure to stress episode. Conversely, apomorphine-induced sensitization is inhibited and adaptation to stress is facilitated if the drug is administered after the termination of stress episode. It shows that apomorphine, if experienced during stress, produces greater sensitization and impairs stress tolerance. Conversely, sensitization effects of apomorphine are blocked and tolerance to stress is facilitated in animals receiving drug after the termination of stress episode. It is suggested that additive effects of stress and apomorphine on mesocorticolimbic dopamine neurotransmission and 5-HT-1A influences on dopamine neurotransmission may have a role in the modulation of apomorphine sensitization and tolerance to repeated immobilization stress. The results may help develop potential pharmacotherapies when substance abuse/dependence disorder and depression occur together.

Repeated Immobilization Stress Increases Expression of β3-Adrenoceptor in the Left Ventricle and Atrium of the Rat Heart

Stress is a contributor of many cardiovascular diseases. Positive inotropic and chronotropic effects of catecholamines are regulated via β-adrenergic receptors (ARs). Many reports exist concerning changes of cardiac β1 - and β2 -ARs in stress, but only a few deal with modulation of cardiac β3 -AR. Our aim was to analyze the expression and binding sites of β1 -, β2 - and β3 -ARs and adenylyl cyclase activity in the left ventricle, and β3 -AR expression and binding in the left atrium of rats exposed to acute and chronic immobilization stress (IMO). The concentration of noradrenaline in the ventricle decreased, while adrenaline increased, especially after repeated IMO. The mRNA and protein levels, and binding sites of β3 -subtype significantly rose following chronic IMO, while all parameters for β2 -AR dropped after single and repeated exposure. Similarly, the mRNA levels and binding sites for β3 -subtype increased in the left atrium as a consequence of chronic IMO. The rise in β3 -subtypes and a drop in β2 -subtypes resulted in inhibition of adenylyl cyclase activity within the left ventricle. Taken together, among other factors, up-regulation of β3 -AR could represent an adaptation mechanism, which might be related to altered physiological function of the left ventricle and atrium during prolonged emotional stress and might serve cardioprotective function during catecholamine overload.