Increase In Plasma Corticosterone Concentration Research Articles

Gastroprotective and antidepressant-like effect of plum pectin (Prunus domestica L.) under water-immobilization stress in laboratory mice

Stress effects activate the processes of free radical oxidation in the organism, lead to hyper production of reactive radicals and oxidative stress, provoking the development of an inflammatory process in various parts of the gastrointestinal tract. Pectin polysaccharides together with the enzyme components of the endogenous antioxidant system contribute to the elimination of the imbalance between prooxidants and antioxidants in the tissues of stressed animals and have a gastroprotective and antidepressant-like effect. The aim of the research was to evaluate the gastroprotective, antioxidant and antidepressant-like effect of plum pectin orally administered to white laboratory mice before stressful exposure. Material and methods. In the experiment on white BALB/c mice weighing 20-25 g (90 males, 10 in each group), pectin isolated from fresh plum fruits in an artificial gastric environment was used. It was administered orally to mice 24 h before the onset of stress exposure or behavioral activity asessment. 50 animals were subjected to 5 h of water immersion stress. After this corticosterone concentration in blood plasma, and the activity of superoxide dismutase, catalase and glutathione peroxidase in the tissue supernatants of the gastrointestinal tract were determined, and the condition of the gastric mucosa was also assessed. Behavioral activity of experimental mice (n=30) was assessed in the open field and forced swimming tests. Results. The stress effect was accompanied by an increase in plasma corticosterone concentration (more than 3 fold), in the activity of superoxide dismutase, glutathione peroxidase in the tissues of the stomach wall and small intestine (17.9-28.6%) and destructive damage in the gastric mucosa compared with the indices of intact animals. Preliminary oral administration of plum pectin to animals at a dose of 80 mg per 1 kg of body weight helped to reduce the level of corticosterone and the number of stress-induced hemorrhages on the gastric mucosa, normalized the activity of antioxidant enzymes and also decreased the immobility time of mice in the forced swimming test. Preliminary oral administration of plum pectin to animals at a dose of 80 mg per 1 kg of body weight prevented an increase in the activity of antioxidant enzymes, corticosterone in the blood and the development of stress-induced hemorrhages on the gastric mucosa, and reduced the time of immobility of mice in the forced swimming test. Conclusion. Plum fruit pectin pre-administered into mice before stress prevents stress-induced damage in the tissues of the gastrointestinal tract, contributing to an increase in the body's resistance to the stress factor. Plum pectin has an antioxidant, gastroprotective and antidepressant-like effect and can be used as an ingredient in functional foods that reduce the risk of inflammatory diseases of the gastrointestinal tract under stress.

Effect of lithium chloride on food intake, cloacal temperature, voluntary activity, and crop-emptying rate in chicks

Infections frequently accompany with non-specific symptoms such as anorexia and hyperthermia. In addition, there may be unpleasant sensations such as visceral discomfort during infection. Lipopolysaccharide (LPS), a Gram-negative bacteria cell wall component, is known to induce the unpleasant sensation of conditioned taste aversion in mammals. However, the relationship between unpleasant sensations and changes in behavior and physiological conditions has not been investigated extensively in birds. Lithium chloride (LiCl) is a compound that induces unpleasant sensations, including visceral discomfort, although its effects on behavior and physiological conditions have also not been investigated extensively in birds. Thus, the present study was aimed to investigate the effect of an intraperitoneal (IP) injection of LiCl on conditioned visual aversion, food intake, cloacal temperature, voluntary activity, crop-emptying rate, and blood constituents in chicks (Gallus gallus). We also examined the effect of IP injections of LPS and zymosan, a cell wall component of fungus, on conditioned visual aversion formation. First, IP injection of LiCl was confirmed to induce conditioned visual aversion in chicks. An IP injection of LiCl significantly decreased food intake, voluntary activity, and crop-emptying rate but did not affect the temperature. In addition, the injection of LiCl significantly increased plasma corticosterone concentration, indicating that LiCl serves as a stressor in chicks. Finally, IP injections of LPS and zymosan were found to induce conditioned visual aversion in chicks. Collectively, these results suggest that LiCl induces conditioned aversion, anorexia, hypoactivity, and inhibition of crop-emptying in chicks. In addition, LPS and zymosan would induce unpleasant sensations in chicks.

Poly I:C and R848 facilitate nitric oxide production via inducible nitric oxide synthase in chicks

Nitric oxide (NO) is a gaseous bioactive molecule associated with many physiological functions including vasodilation and neurotransmission. NO also plays an important role in immune responses during viral infections in mammals. However, there is a paucity of knowledge regarding the involvement of NO in viral infections in birds. Therefore, the purpose of the present study was to determine if intraperitoneal (IP) injection of poly I:C and R848 (resiquimod), which are analogues of virus component, affects NO production in chicks (Gallus gallus) as a bird model. The involvement of inducible NO synthase (iNOS) in poly I:C- and R848-induced anorexia and corticosterone release was also investigated. These virus analogues significantly increased plasma NO metabolites (NOx) concentrations. IP injection of poly I:C and R848 significantly increased iNOS mRNA expression in several organs including the liver. On the other hand, poly I:C and R848 significantly decreased mRNA expressions of endothelial NOS and neural NOS in several organs, indicating that induction of iNOS might be responsible for increased NOx levels in plasma. This finding was further confirmed by using a selective iNOS inhibitor, S-methylisothiourea sulfate (SMT), which abolished the poly I:C- and R848-induced increase in plasma NOx concentration. In addition, SMT partly attenuated the poly I:C- and R848-induced increase in plasma corticosterone concentration, suggesting that corticosterone release induced by these virus analogues may be partly mediated by iNOS. Collectively, the present results suggest that viral infections facilitate NO production by inducing iNOS. The liver would play an important role in the NO production because the response in iNOS mRNA expression to poly I:C and R848 was remarkable. The present results also suggest that NO is associated with corticosterone release in birds under viral infection.

Plasma steroids and immune measures vary with restraint duration in a toad (Rhinella icterica)

Immunoenhancing effects have been widely described following acute stressors in several vertebrates, and valuable contributions have been made from studies on acute stress to understand hormonal-immune interactions. However, most studies focus on hormonal and immune responses after standardized time lapses, neglecting potential influence of duration of exposition to stressor. Herein, we investigate fluctuations of plasma hormone concentrations (corticosterone and testosterone) and immunity (neutrophil to lymphocyte ratio, phagocytosis of blood cells, and plasma bacterial killing ability) in a toad species (Rhinella icterica) in response to six different periods of exposure to restraint stress. We observed increased plasma corticosterone concentrations following restraint in all sampled times (0.5 to 48 h), with the highest values being observed during the first hour (0.5 to 1 h). Restraint-induced increases in the neutrophil to lymphocyte ratio and phagocytosis percentage were observed from the first 0.5 h, gradually increasing after that with the time of restraint. We also observed decreased testosterone plasma concentrations in response to a more prolonged restraint (24 and 48 h). No changes were observed in plasma bacterial killing ability following restraint. Together, our results demonstrate dynamic time-related hormonal and immune changes. These results point to the fact that for some species measuring hormonal and immune variables at single time points following a stressor might work better when preceded by a study of the temporal changes of the response variables to the stimuli applied. Also, time of response needs to be considered when different variables are used as proxies of stress.

Antidepressant and Anxiolytic-Like Effects of the Stem Bark Extract of Fraxinus rhynchophylla Hance and Its Components in a Mouse Model of Depressive-Like Disorder Induced by Reserpine Administration.

There is an urgent need to find antidepressants that can be administered for long periods without inducing severe side effects to replace conventional antidepressants that control monoamine levels, such as tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs), and selective serotonin reuptake inhibitors (SSRI). We sought to determine the antidepressant effects of Fraxinus rhynchophylla Hance (F. rhynchophylla Hance, FX) and its components on a reserpine-induced mouse model. One hour after oral administration of FX (30, 50, and 100 mg/kg), esculin (50 mg/kg), esculetin (50 mg/kg), fraxin (50 mg/kg), and fluoxetine (20 mg/kg), reserpine was delivered intraperitoneally to mice. Behavioral experiments were conducted to measure anxiety and depressive-like behaviors after 10 days of administration. FX and its components increased the number of entries into the center of an open field as well as distance traveled within it and decreased immobility duration in the forced swim and tail suspension tests. Reserpine-induced increases in plasma corticosterone concentrations were attenuated by the administration of FX and its components, which were also found to decrease the reserpine-induced enhancement of mRNA levels of interleukin (IL)-12 p40, IL-6, and tumor necrosis factor (TNF)-α, pro-inflammatory cytokines. Finally, the diminished expressions of hippocampal phosphorylated cAMP response element-binding protein (pCREB) and brain-derived neurotrophic factor (BDNF) by reserpine were increased by FX and its components. Our results suggest that FX and its components regulate anxiety and depressive-like behaviors through stress hormones, immune regulation, and the activation of neuroprotective mechanisms, further supporting the potential of FX and its components as antidepressants.

Prolonged Peripheral Immunosuppressive Responses as Consequences of Random Amphetamine Treatment, Amphetamine Withdrawal and Subsequent Amphetamine Challenges in Rats

Drug-induced immunosuppression may underline increased hypothalamic–pituitary–adrenal axis response to stress observed following chronic psychostimulant treatment. However, the consequences of random amphetamine (AMPH) treatment, withdrawal and AMPH challenge after withdrawal on the peripheral immunity and systemic corticosterone response are unknown. In this study, the total blood and spleen leukocyte, lymphocyte, T, B, NK, TCD4+/TCD8+ cell numbers and ratio, pro-inflammatory interferon gamma (IFN-γ), and anti-inflammatory interleukin-4 (IL-4) production, and plasma corticosterone concentration in Wistar rats were investigated after: chronic, random AMPH/SAL treatment alone (20 injections in 60 days, 1 mg/kg b.w., i.p.), AMPH/SAL withdrawal (for 20 consecutive days after random AMPH/SAL exposure) or AMPH/SAL challenge after withdrawal (single injection after the AMPH/SAL withdrawal phase). The results showed blood and spleen leukopenia, lymphopenia, lower blood production of IFN-ɤ, and increased plasma corticosterone concentration after the AMPH treatment, which were more pronounced in the AMPH after withdrawal group. In contrast, an increased number of blood NK cells and production of IL-4 after chronic, random AMPH treatment alone, were found. Blood AMPH-induced leukopenia and lymphopenia were due to decreased total number of T, B lymphocytes and, at least in part, of granulocytes and monocytes. Moreover, decreases in the number of blood TCD4+ and TCD8+ lymphocytes both in the AMPH chronic alone and withdrawal phases, were found.The major findings of this study are that AMPH treatment after the long-term withdrawal from previous random AMPH exposure, accelerates the drug-induced immunosuppressive and systemic corticosterone responses, suggesting prolonged immunosuppressive effects and an increase in incidence of infectious diseases.Graphical Prolonged peripheral immunosuppressive responses as consequences of random amphetamine…The results indicate that the chronic and random AMPH exposure alone and the acute (single injection) challenge of the drug after the withdrawal phase induced long-term immunosuppressive effects, which were similar to those occurring during the stress response, and sensitized the peripheral immunosuppressive and corticosterone responses of the rat to the disinhibitory effects of this stressor.

Effects of temperature on plasma corticosterone in a native lizard

The glucocorticoid stress response is frequently used to indicate vertebrate response to the environment. Body temperature may affect glucocorticoid concentrations, particularly in ectotherms. We conducted lab manipulations and field measurements to test the effects of body temperature on plasma corticosterone (predominant glucocorticoid in reptiles) in eastern fence lizards (Sceloporus undulatus). First, we acclimated lizards to one of 4 treatments: 22 °C, 29 °C, 33 °C, or 36 °C, and measured cloacal temperatures and plasma corticosterone concentrations at baseline and after exposure to a standardized stressor (cloth bag). Both baseline and stress-induced corticosterone concentrations were lower in lizards with lower body temperatures. Second, we acclimated lizards to 22 °C or 29 °C and exposed them to a standardized (cloth bag) stressor for 3 to 41 min. Lizards acclimated to 29 °C showed a robust increase in plasma corticosterone concentrations with restraint stress, but those at 22 °C showed no such increases in corticosterone concentrations. Third, we measured lizards upon capture from the field. There was no correlation between body temperature and baseline plasma corticosterone in field-caught lizards. These results suggest body temperature can significantly affect plasma corticosterone concentrations in reptiles, which may be of particular concern for experiments conducted under laboratory conditions but may not translate to the field.

Behavioral and physiological responses to intraperitoneal injection of zymosan in chicks

Zymosan is a cell wall component of the yeast Saccharomyces cerevisiae and produces severe inflammatory responses in mammals. When zymosan is peripherally injected in mammals, it induces several behavioral and physiological changes including anorexia and hyperthermia. However, to our knowledge, behavioral and physiological responses to zymosan have not yet been clarified in birds. Therefore, the purpose of the present study was to determine if intraperitoneal injection of zymosan affects food intake, voluntary activity, cloacal temperature, plasma corticosterone (CORT) and glucose concentrations, and splenic gene expression of cytokines in chicks (Gallus gallus). Intraperitoneal injection of zymosan (2.5 mg) significantly decreased food intake, voluntary activity, and plasma glucose concentration, and increased plasma CORT concentration. The injection of 0.5 mg zymosan significantly increased cloacal temperature, while 2.5 mg zymosan had a tendency to increase it. Finally, 2.5 mg zymosan significantly increased the splenic gene expression of interleukin-1β (IL-1β), IL-6, IL-8, interferon-γ, and tumor necrosis factor–like cytokine 1A. The present results suggest that zymosan would be one of components which induces nonspecific symptoms including anorexia, hypoactivity, hyperthermia, and stress responses, under fungus infection in chicks.

Effects of toll-like receptor-7 agonists on feeding behaviour, voluntary activity, cloacal temperature and crop emptying in chicks

ABSTRACT 1. The purpose of the present study was to determine if an intraperitoneal injection of two toll-like receptor-7 (TLR7) agonists, imiquimod and resiquimod, affect feed intake, voluntary activity, cloacal temperature, crop-emptying rate, plasma corticosterone (CORT) and glucose concentrations, and splenic gene expression of cytokines in chicks (Gallus gallus). 2. Although intraperitoneal injection of 100 µg imiquimod significantly increased splenic gene expression of interleukin-1β (IL-1β), IL-6, IL-8, and interferon-γ (IFN-γ), it did not affect feed intake, voluntary activity, cloacal temperature, crop-emptying rate or plasma constituents. 3. Intraperitoneal injection of 100 µg resiquimod significantly decreased feed intake, voluntary activity, cloacal temperature, crop-emptying rate and increased plasma corticosterone concentrations. 4. Intraperitoneal injection of resiquimod significantly increased splenic gene expression of IL-1β, IL-6, IL-8, IFN-γ, and tumour necrosis factor-like cytokine 1A. 5. The results showed that activation of TLR7 is associated with anorexia, hypoactivity, hypothermia, disturbance of feed passage in the digestive tract and the response to stress in chicks.

Embryonic thermal manipulation has short and long-term effects on the development and the physiology of the Japanese quail

In vertebrates, the embryonic environment is known to affect the development and the health of individuals. In broiler chickens, the thermal-manipulation (TM) of eggs during the incubation period was shown to improve heat tolerance at slaughter age (35 days of age) in association with several modifications at the molecular, metabolic and physiological levels. However, little is known about the Japanese quail (Coturnix japonica), a closely related avian species widely used as a laboratory animal model and farmed for its meat and eggs. Here we developed and characterized a TM procedure (39.5°C and 65% relative humidity, 12 h/d, from days 0 to 13 of incubation) in quails by analyzing its short and long-term effects on zootechnical, physiological and metabolic parameters. Heat-tolerance was tested by a heat challenge (36°C for 7h) at 35 days of age. TM significantly reduced the hatching rate of the animals and increased mortality during the first four weeks of life. At hatching, TM animals were heavier than controls, but lighter at 25 days of age for both sexes. Thirty-five days after hatching, TM decreased the surface temperature of the shank in females, suggesting a modulation of the blood flow to maintain the internal temperature. TM also increased blood partial pressure and oxygen saturation percentage at 35 days of age in females, suggesting a long-term modulation of the respiration physiology. Quails physiologically responded to the heat challenge, with a modification of several hematologic and metabolic parameters, including an increase in plasma corticosterone concentration. Several physiological parameters such as beak surface temperature and blood sodium concentration revealed that TM birds responded differently to the heat challenge compared to controls. Altogether, this first comprehensive characterization of TM in Japanese quail showed durable effects that may affect the response of TM quails to heat.

The effect of various models of cold stress on cytokine production by the cells of the mouse peritoneal cavity under conditions of blockade of opiate receptors

The study of the mechanisms of functioning of the immune system under stress does not lose its relevance for decades. An important factor in the neuroendocrine regulation of immunity during stress is the endogenous opioid system. In the present work, we evaluated the effect of various cold stress variants on the production of cytokines IL-1β and IL-10 by the cells of the mouse peritoneal cavity under conditions of blockade of opiate receptors. It was established that acute and chronic cold stress, regardless of duration, did not affect the production of IL-1β and increased the production of IL-10 by peritoneal macrophages, this effect was canceled by the introduction of naloxone. The effect of chronic cold stress on IL-10 production depended on cell activation. In all variants of stress, an increase in plasma corticosterone concentration was observed, which did not depend on the blockade of opiate receptors. The work was performed in the framework of the state task, the number of the state registration of the topic No. 01201353248.

Physiological responses to central and peripheral injections of compound 48/80 and histamine in chicks

Mast cells are a type of immune cell widely distributed in the body of vertebrates. Mast cells have many granules that contain several bioactive molecules such as histamine, and these molecules are released through degranulation when the mast cell receives certain stimuli. Because the number of mast cells increases during infection in chickens (Gallus gallus), the activity of mast cells might be related to non-specific symptoms such as anorexia under an infectious condition. Therefore, the purpose of the present study was to investigate whether intraperitoneal (IP) and intracerebroventricular (ICV) injections of compound 48/80, which induces degranulation of mast cells, affects feeding, voluntary activity, cloacal temperature, and the concentrations of plasma corticosterone (CORT) and glucose in chicks. The effect of histamine, which is found in mast cell granules, on these parameters was also investigated. IP injection of compound 48/80 significantly decreased food intake, voluntary activity, and cloacal temperature, and increased plasma CORT concentration in the chicks. While ICV injection of compound 48/80 also decreased food intake, it increased cloacal temperature and plasma glucose concentration. Both IP and ICV injections of histamine significantly decreased food intake, cloacal temperature, and plasma CORT concentration. However, only IP injection of histamine significantly decreased voluntary activity and increased plasma glucose concentration. The results suggest that degranulation of mast cells is related to non-specific symptoms in chicks, although the mechanism seems to be different between peripheral and central tissues. In addition, the effect of peripherally-injected compound 48/80 may be partly mediated by histamine.

Synaptic structure and alterations in the hippocampus in neonatal rats exposed to lipopolysaccharide

Synaptic structure integrity plays a key role in learning and memory. Previous studies have shown that there is cognitive dysfunction in septic neonates in later life. In this study, intraperitoneal injection of lipopolysaccharide (LPS) in the developing rats was used as a sepsis model to determine whether hippocampal synapses would be affected. Expression of synaptophysin (Syn), synaptosomal associated protein of 25 kD (SNAP-25), and N-methyl d-aspartate receptor (NMDAR) in the hippocampus in septic brain were significantly reduced. Consistent with this, the number of dendritic spines associated with the pyramidal neurons in the CA1 region of hippocampus at 28d after LPS administration was decreased. Additionally, the number of synapse and synaptic vesicles were reduced and appeared swollen. The number of neurons in the CA1 and CA3 of hippocampus at 14, and 28d after LPS injection remained unchanged. Coupled with the above was upregulated expression of interleukin-1β (IL-1β), IL-1 receptor 1 (IL-R1), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) at 1-3d after LPS injection. IL-1β expression was specifically detected in activated microglia. The plasma corticosterone (CORT) concentration in the LPS treatment rats was increased; but the glucocorticoid receptor (GR) expression in the hippocampus was decreased. We conclude that LPS injection in neonatal rats can cause synaptic disruption in the hippocampus which may be attributed to inflammatory response due to excess production of proinflammatory cytokines e.g., IL-1β derived from activated microglia. The significance of increased plasma CORT concentration and decreased GR expression in the hippocampus is discussed.

Effects of escitalopram and ibuprofen on a depression-like phenotype induced by chronic stress in rats

Clinical and preclinical studies have reported that co-administration of nonsteroidal anti-inflammatory drugs (NSAIDs) and antidepressant drugs are effective in patients with depression and in animal models of depression. However, several studies have suggested that NSAIDs inhibit the antidepressant effects of selective serotonin reuptake inhibitors in humans and mice. The present study investigated the effects of escitalopram (ESC) and ibuprofen (IBU), alone or in combination, on the stress-induced behavior and expression of brain-derived neurotrophic factor (BDNF) and p11, markers of depression and antidepressant action, in chronically stressed rats. Rats were subjected to chronic restraint stress (CRS) for 3 weeks and administered the following drugs: single administration of ESC or IBU or co-administration of ESC and IBU (ESC + IBU). Immobility time was measured by the forced swimming test (FST), and hippocampal BDNF and p11 levels were analyzed by quantitative real-time polymerase chain reaction and Western blotting. CRS increased immobility time on the FST. Administration of ESC, IBU, or ESC + IBU significantly attenuated the stress-induced increase in immobility time. CRS also significantly increased plasma corticosterone concentration by 169%. This effect was significantly recovered by administering ESC, IBU, or ESC + IBU. The levels of BDNF and p11 in the hippocampus decreased significantly in response to CRS. These decreases were prevented by administering ESC, IBU, or ESC + IBU. These findings suggest that both single and co-administration of ESC and IBU exerts antidepressant effects. These effects were associated with upregulation of BDNF and p11 expression.

Nitrergic neurotransmission in the paraventricular nucleus of the hypothalamus modulates autonomic, neuroendocrine and behavioral responses to acute restraint stress in rats

We investigated the involvement of nitrergic neurotransmission within the paraventricular nucleus of the hypothalamus (PVN) in modulation of local neuronal activation, autonomic and neuroendocrine responses and behavioral consequences of acute restraint stress in rats. Bilateral microinjections of the selective neuronal nitric oxide (NO) synthase (nNOS) inhibitor Nw-Propyl-L-arginine (NPLA) or the NO scavenger carboxy-PTIO into the PVN reduced arterial pressure and heart rate increases, as well as the fall in cutaneous tail temperature induced by restraint stress. PVN injection of either NPLA or carboxy-PTIO also inhibited restraint-induced increases in anxiety-related behaviors in the elevated plus-maze 24 h later. Local microinjection of NPLA or carboxy-PTIO into the PVN reduced the number of c-fos-immunoreactive neurons in the dorsal parvocellular, ventromedial, medial parvocellular and lateral magnocelllular portions of the PVN in animals subjected to restraint stress. However, neither NPLA nor carboxy-PTIO into the PVN affected restraint-induced increases in plasma corticosterone concentration. The present results indicate that PVN nitrergic neurotransmission acting via nNOS activation has a facilitatory influence on autonomic responses to acute restraint and the delayed emotional consequences of restraint stress. Our results also provide evidence of a prominent role of local nitrergic neurotransmission in PVN neuronal activation during stress.

Adrenocortical responses in Japanese quail classified by their permanence in proximity to either low or high density of conspecifics.

The density-related permanence test (DRP) is used to classify young birds (while in groups) according to their individual permanence in proximity to either a high or low density of conspecifics (HD or LD, respectively). The birds' performance in DRP was associated with underlying differences in the social responses of their individuals. Quails in homogeneous groups of LD residents responded with less compact groups and higher levels of agonistic interactions to the presence of an intruder, and showed higher levels of agonistic interactions among cagemates than the homogeneous groups of HD birds. This study deepen the characterization of DRP evaluating whether contrasting behavior during test is associated with birds' stress responses to challenging situations during rearing. Plasma corticosterone responses were individually assessed after submitting DRP categorized birds to a brief (10min) partial restraint (mechanical stressor; experiment 1), or after introducing them during 5min as intruders in homogeneous groups of 6 unknown same category (HD or LD) conspecifics (social stressor; experiment 2). Experiment 1 showed that basal corticosterone levels were similar in all groups and the partial mechanical restraint induced an increase in plasma corticosterone concentration also in all groups. However, the increase induced by the stressor was higher in the LD birds than in their HD counterparts. In experiment 2, compared to controls, social stressor showed no plasma corticosterone changes in the intruders that were introduced in an unfamiliar group of HD conspecifics. However, intruders (both HD and LD) that were visiting the LD residents showed an increased corticosterone response compared to their control counterparts. Results suggest that categorization of birds in the DRP test could have relevance for selection programs oriented to obtain birds better suited to intensive rearing conditions that includes high density of animals and exposure to unavoidable stressors.

Sex differences in hippocampal mineralocorticoid and glucocorticoid receptor mRNA expression in response to acute mate pair separation in zebra finches (Taeniopygia guttata).

Mate separation has been shown to mediate changes in physiological and behavioral processes via activation of the hypothalamo-pituitary-adrenal (HPA) axis in both mammalian and avian species. To elucidate the neural mechanisms associated with changes in the HPA axis in response to social stress, we investigated the effects of mate pair separation on circulating corticosterone concentrations as well as gene expression levels of mineralocorticoid receptor (MR), glucocorticoid receptor (GR), and corticotropin releasing hormone (CRH) in the hypothalamus and hippocampus of both male and female zebra finches, a species that forms strong pair bonds. Zebra finches (Taeniopygia guttata) were housed three to a cage (a mated pair plus a stimulus female), and were assigned to one of three new housing treatment groups: (1) male or female removed from their respective mate and placed in a cage with a new opposite sex conspecific and stimulus female (2) male or female that remained with their mate, but a new stimulus female was introduced, or (3) the subjects were handled but not separated from their mate or the stimulus female. After 48 hr in the new housing condition, we observed significant increases in plasma corticosterone concentrations in response to both mate pair and stimulus female separation. No significant differences in MR, GR, or CRH mRNA expression in the hypothalamus were observed in response to any treatment for both males and females. Females exhibited a significant up regulation in hippocampal MR, but not GR mRNA, whereas males exhibited a significant down regulation of both hippocampal MR and GR mRNA in response to mate pair separation. Thus, the hippocampus appears to play a key role in regulating sex specific responses to social stressors.

Effect of a 1800MHz electromagnetic field emitted during embryogenesis on chick development and hatchability.

The level of artificial electromagnetic field (EMF) has steadily increased with the development of human civilization. The developing chicken embryo has been considered a good model to study the effects of EMF on living organisms. The aim of the study was to determine the effect of a 1800MHz electromagnetic field during embryogenesis on the frequency of chick embryo malformations, morphometric parameters of the heart and liver and concentration of corticosterone in blood plasma, lipid and glycogen content in the liver of newly hatched chicks. A 1800MHz EMF was found to shorten the duration of embryogenesis (earlier pipping and hatching of chicks) while having no effect on the quantity and quality of chicks and on increasing the incidence of embryo malformations. Exposure of chick embryos to EMF caused decreases in relative heart weight and right ventricle wall thickness. The pipping and hatching of chicks can be accelerated by stressful impact of EMF, which is confirmed by a significant increase in plasma corticosterone concentrations and decrease in fat and glycogen in the liver of chicks exposed during embryogenesis on the electromagnetic field with a frequency of 1800MHz.

The Electrical Stimulation of the Bed Nucleus of the Stria Terminalis Causes Oxidative Stress in Skeletal Muscle of Rats.

Recent studies indicate that activation of hypothalamus-pituitary-adrenocortical axis (HPA) plays the crucial role in stress response, while several lines of evidence mark the bed nucleus of the stria terminalis (BST) as a major mediator of the HPA axis responses to stress. The purpose of this study was to investigate the influence of the corticosterone flux induced by the electrical stimulation of BST on markers of free radical damage of lipids and proteins and antioxidant enzyme activity in skeletal muscle of rats. The male Wistar rats were used and assigned to one of three groups: sham-operated (SHM; n = 6), two-week (ST2; n = 6), and four-week stimulated (ST4; n = 5) groups. Blood, soleus, and extensor digitorum longus muscles were collected. The chronic, 4-week electrical stimulation of the BST evokes increased plasma corticosterone concentration, which resulted in oxidative stress in skeletal muscles. We found higher level of lipid peroxidation markers, lower level of protein oxidation marker, and elevated antioxidant enzyme activity in both muscles. Our findings have also potential implication showing that reaction to the long-term “psychological stress” may lead to free radical damage of muscle.

Conservation of Phenotypes in the Roman High- and Low-Avoidance Rat Strains After Embryo Transfer

The Roman high- (RHA-I) and low-avoidance (RLA-I) rat strains are bi-directionally bred for their good versus non-acquisition of two-way active avoidance, respectively. They have recently been re-derived through embryo transfer (ET) to Sprague-Dawley females to generate specific pathogen free (SPF) RHA-I/RLA-I rats. Offspring were phenotyped at generations 1 (G1, born from Sprague-Dawley females), 3 and 5 (G3 and G5, born from RHA-I and RLA-I from G2-G4, respectively), and compared with generation 60 from our non-SPF colony. Phenotyping included two-way avoidance acquisition, context-conditioned fear, open-field behaviour, novelty-seeking, baseline startle, pre-pulse inhibition (PPI) and stress-induced increase in plasma corticosterone concentration. Post-ET between-strain differences in avoidance acquisition, context-conditioned freezing and novelty-induced self-grooming are conserved. Other behavioural traits (i.e. hole-board head-dipping, novel object exploration, open-field activity, startle, PPI) differentiate the strains at G3-G5 but not at G1, suggesting that the pre-/post-natal environment may have influenced these co-segregated traits at G1, though further selection pressure along the subsequent generations (G1-G5) rescues the typical strain-related differences.