Free Corticosterone Research Articles

Corticosterone Response as an Age-Specific Mediator of Nestling Body Mass in a Wild Passerine.

The environment can affect individual performance directly via resource availability or indirectly through resource allocation among competing fitness components, such as body growth and maintenance activities related to short-term survival. Corticosterone (CORT), the main glucocorticoid in birds, may be an important mediator of energy allocation to different organismal functions, but its effect on the plasticity of fitness-related traits has rarely been investigated at different ontogenetic stages. Here, we evaluated the role of baseline and stress-induced CORT on nestling development of wild great tits (Parus major) under different growth conditions and at different developmental stages. We found that nestling mass and condition were positively related to stress-induced levels of total CORT and free CORT in the middle of nestling stage but negatively related at the prefledging stage. Our results also showed that stress-induced levels of total CORT can be used as a proxy for bioavailable free CORT. No significant relationship of body mass or condition in either stage was shown with levels of baseline CORT or stress-induced CORT-binding globulin capacity. None of these age-specific relationships depend on brood size manipulation. We conclude that the effects of glucocorticoids on nestling performance are stage specific. The ability to secrete CORT may have beneficial effects on nestling development in the middle of the nestling stage, while it can be adaptive to keep CORT levels at optimal ranges before fledging to give priority to growth-related processes that are important for long-term fitness.

Assessing Stress in Arctic Lemmings: Fecal Metabolite Levels Reflect Plasma Free Corticosterone Levels.

Interest in the ecology of stress in wild populations has triggered the development of noninvasive methods for quantifying stress hormones. Measurement of fecal corticosteroid metabolites (FCMs) is one such method, but it is still unclear whether FCMs can be a reliable proxy of free plasma glucocorticoids. To assess the validity of this assumption, we carried out a robust assessment on brown lemmings (Lemmus trimucronatus) from Bylot Island, Nunavut, Canada, that were hand captured and anesthetized and related plasma glucocorticoid levels to fecal metabolite glucocorticoid levels. We examined endogenous factors that could explain interindividual variability. Blood corticosterone was measured from samples obtained on capture and 30 min later, and FCM levels were measured from animals kept in captivity for 72 h. Plasma free corticosterone increased 135-fold over baseline values 30 min after capture, which confirmed that initial handling was perceived as a stressor. We found that FCM levels were highly related with free (marginal [Formula: see text] = 0.53) but not with total ([Formula: see text] = 0.02) corticosterone levels, regardless of age, sex, and reproductive condition. FCM levels started increasing 2 h after capture and reached maximum levels 4 h after capture. No circadian rhythm in FCMs was found. Plasma total corticosterone levels were much higher in adult females compared with adult males, but this difference was much smaller when measuring free corticosterone levels and FCM levels. Our results suggest that FCM levels are good measures of stress by being closely related to plasma free corticosterone levels in brown lemmings.

Acute embryonic exposure to corticosterone alters physiology, behaviour and growth in nestlings of a wild passerine

Maternally-derived glucocorticoids can modify the normal development of young animals. To date, little is known about maternal effects that are mediated by acute embryonic exposure to glucocorticoids. In birds, elevated maternal transmission of corticosterone (CORT) to egg albumen is mainly dependent on acute stress. In this study, we increased CORT levels in the egg albumen of a wild passerine, the great tit (Parus major), breeding in favourable deciduous and less suitable coniferous habitat. Subsequently we measured the somatic growth, baseline and acute glucocorticoid responses, immunity and behaviour of prenatally manipulated offspring with respect to control siblings. We found that prenatally CORT-exposed nestlings had lower baseline CORT levels, a more rapid decline in CORT during recovery from a standardized stressor, and a reduced heterophil/lymphocyte ratio compared with controls. Although stress-induced total CORT levels remained unchanged, free CORT levels were significantly lower and the levels of corticosteroid binding globulins (CBG) significantly higher in experimental offspring. Prenatally CORT-exposed offspring begged longer after hatching than controls. Stress-induced behavioural activity of fledglings did not differ between treatments, while its association with baseline CORT levels was significant in the control group only. The body mass and tarsus length of fledglings was positively affected by manipulation in unfavourable coniferous habitat only. We conclude that maternal effects related to elevated levels of albumen CORT modify diverse aspects of offspring phenotype and potentially increase offspring performance in resource poor environments. Moreover, our results indicate that maternal glucocorticoids may suppress the effect of hormones on behavioural responses.

Adaptive response of rat pancreatic β-cells to insulin resistance induced by monocrotophos: Biochemical evidence

Our previous findings clearly suggested the role of duration of exposure to monocrotophos (MCP) in the development of insulin resistance. Rats exposed chronically to MCP developed insulin resistance with hyperinsulinemia without overt diabetes. In continuation of this vital observation, we sought to delineate the biochemical mechanisms that mediate heightened pancreatic β-cell response in the wake of MCP-induced insulin resistance in rats. Adult rats were orally administered (0.9 and 1.8mg/kgb.w/d) MCP for 180days. Terminally, MCP-treated rats exhibited glucose intolerance, hyperinsulinemia, and potentiation of glucose-induced insulin secretion along with elevated levels of circulating IGF1, free fatty acids, corticosterone, and paraoxonase activity. Biochemical analysis of islet extracts revealed increased levels of insulin, malate, pyruvate and ATP with a concomitant increase in activities of cytosolic and mitochondrial enzymes that are known to facilitate insulin secretion and enhanced shuttle activities. Interestingly, islets from MCP-treated rats exhibited increased insulin secretory potential ex vivo compared to those isolated from control rats. Further, MCP-induced islet hypertrophy was associated with increased insulin-positive cells. Our study demonstrates the impact of the biological interaction between MCP and components of metabolic homeostasis on pancreatic beta cell function/s. We speculate that the heightened pancreatic beta cell function evidenced may be mediated by increased IGF1 and paraoxonase activity, which effectively counters insulin resistance induced by chronic exposure to MCP. Our findings emphasize the need for focused research to understand the confounding environmental risk factors which may modulate heightened beta cell functions in the case of organophosphorus insecticide-induced insulin resistance. Such an approach may help us to explain the sharp increase in the prevalence of type II diabetes worldwide.

A Single Bout of Fasting (24 h) Reduces Basal Cytokine Expression and Minimally Impacts the Sterile Inflammatory Response in the White Adipose Tissue of Normal Weight F344 Rats.

Sterile inflammation occurs when inflammatory proteins are increased in blood and tissues by nonpathogenic states and is a double-edged sword depending on its cause (stress, injury, or disease), duration (transient versus chronic), and inflammatory milieu. Short-term fasting can exert a host of health benefits through unknown mechanisms. The following experiment tested if a 24 h fast would modulate basal and stress-evoked sterile inflammation in plasma and adipose. Adult male F344 rats were either randomized to ad libitum access to food or fasted for 24 h prior to 0 (control), 10, or 100, 1.5 mA-5 s intermittent, inescapable tail shocks (IS). Glucose, nonesterified free fatty acids (NEFAs), insulin, leptin, and corticosterone were measured in plasma and tumor necrosis factor- (TNF-) α, interleukin- (IL-) 1β, IL-6, and IL-10 in plasma, and subcutaneous, intraperitoneal, and visceral compartments of white adipose tissue (WAT). In control rats, a 24 h fast reduced all measured basal cytokines in plasma and visceral WAT, IL-1β and IL-6 in subcutaneous WAT, and IL-6 in intraperitoneal WAT. In stressed rats (IS), fasting reduced visceral WAT TNF-α, subcutaneous WAT IL-1β, and plasma insulin and leptin. Short-term fasting may thus prove to be a useful dietary strategy for reducing peripheral inflammatory states associated with visceral obesity and chronic stress.

Variation in corticosterone response and corticosteroid binding‐globulin during different breeding sub‐stages in Eurasian tree sparrow (Passer montanus)

In free-living animals, it has been well demonstrated that the intensity of the adrenocortical response to acute restraint stress can vary with reproductive investment during breeding. The parental care hypothesis posits that the stress response is negatively correlated with parental investment in avian species. To further test this hypothesis, we examined changes in both free and total corticosterone (CORT) at baseline and stress-induced levels (maximal CORT) and corticosteroid-binding globulin (CBG) capacities, in both sexes of a multi-brooded Eurasian tree sparrows (Passer montanus), during the nest building, the early nestling, the later egg-laying, and the later nestling stages. Our results showed Eurasian tree sparrows did not exhibit any differences between sexes in CORT and CBG levels during the egg-laying or nestling stages. Both sexes had lowered CBG capacities and females exhibited lower maximal CORT during the early compared to later nestling stages. In addition, both sexes had lower maximal free CORT levels during the nest building stage than those of the early nestling stages, and males expressed higher total maximal CORT levels than females during nest building stage. The variation in CORT response and CBG levels during different breeding sub-stages in Eurasian tree sparrow may correlate with their energetic situations and parental investments. J. Exp. Zool. 325A:75-83, 2016. © 2015 Wiley Periodicals, Inc.

Effects of Prenatal Environment on Phenotype Are Revealed by Postnatal Challenges: Embryonic Hormone Exposure, Adrenocortical Function, and Food in Seabird Chicks.

The interaction between prenatal environments and postnatal environments is an important source of phenotypic variability. We examined the ability of prenatal steroid exposure and postnatal energy restriction to explain adrenocortical function and fledging age in captive seabird chicks. We proposed and tested two hypotheses: (1) the strength of prenatal effects is attenuated by challenging postnatal environments (postnatal override) and (2) the strength of prenatal effects increases with the severity of postnatal challenges (postnatal reveal). We reared common murre (Uria aalge) chicks and measured prenatal exposure to corticosterone (CORT) and testosterone (T) from allantoic waste. Adrenocortical function was assessed after 10 d of ad lib. feeding and then after 5 and 10 d on controlled diets. Postnatal override predicts that prenatal steroids will explain more phenotypic variation before implementation of energy restriction; postnatal reveal predicts that the contribution of prenatal steroids will increase with duration and severity of energy restriction. Energy restriction increased secretion of baseline CORT and the adrenocortical response to the standardized stressor of handling and restraint. The ability of prenatal steroids to explain baseline CORT increased with duration of energy restriction, and for day 20 free baseline CORT, there was a significant interaction between kilojoules per day and prenatal CORT levels; severity of restriction strengthened the relationship between prenatal hormone levels and postnatal hormone levels. Both maximum CORT at day 20 and fledging age were best explained by diet treatment and day 15 or day 20 baseline CORT, respectively. Overall, prenatal CORT increased fledging age and baseline secretion of CORT, while prenatal T decreased them. However, prenatal effects on adrenocortical function were apparent only under the energy restriction conditions. Thus, we found some support for the postnatal reveal hypothesis; our results suggest that some prenatal effects on phenotype may be more likely to manifest in challenging postnatal environments.

Norepinephrine and corticosterone in the medial prefrontal cortex and hippocampus predict PTSD-like symptoms in mice.

This study measured changes in brain extracellular norepinephrine (NE) and free corticosterone (CORT) levels in a mouse model of post-traumatic stress disorder and related them to hyperarousal and fear memory retention. To this end, microdialysis in the medial prefrontal cortex (mPFC) and the hippocampus (HPC) of male C57BL/6NCrl mice was performed during an acoustic startleresponse (ASR) and following an electric foot shock (FS), as well as during an ASR and recall of contextual fear (CF) 1day later. Changes in ASR-stimulated NE levels in the mPFC corresponded to ASR 34days after FS. Changes in basal and ASR-stimulated extracellular NE levels in the HPC, in contrast, were related to expression of early (day 2) and late (day 34) CF after FS. The increase in extracellular NE levels correlated in a U-shape manner with arousal levels and CF, thus suggesting a non-direct relationship. Stress of different modalities/strength (ASR, FS and CF) caused a similar relative increase in free CORT levels both in the mPFC and the HPC. One day after FS, ASR-induced increases in the CORT content in the mPFC tended to correlate with the FS-potentiated ASR in a U-shape manner. Taken together, these data show that the intracerebral increase in free CORT was likely related to an immediate response to stress, whereas NE neurotransmission in the forebrain predicted arousal and CF 1month after trauma.

Somatostatin Is Essential for the Sexual Dimorphism of GH Secretion, Corticosteroid-Binding Globulin Production, and Corticosterone Levels in Mice

Distinct male and female patterns of pituitary GH secretion produce sexually differentiated hepatic gene expression profiles, thereby influencing steroid and xenobiotic metabolism. We used a fully automated system to obtain serial nocturnal blood samples every 15 minutes from cannulated wild-type (WT) and somatostatin knockout (Sst-KO) mice to determine the role of SST, the principal inhibitor of GH release, in the generation of sexually dimorphic GH pulsatility. WT males had lower mean and median GH values, less random GH secretory bursts, and longer trough periods between GH pulses than WT females. Each of these parameters was feminized in male Sst-KO mice, whereas female Sst-KO mice had higher GH levels than all other groups, but GH pulsatility was unaffected. We next performed hepatic mRNA profiling with high-density microarrays. Male Sst-KO mice exhibited a globally feminized pattern of GH-dependent mRNA levels, but female Sst-KO mice were largely unaffected. Among the differentially expressed female-predominant genes was Serpina6, which encodes corticosteroid-binding globulin (CBG). Increased CBG was associated with elevated diurnal peak plasma corticosterone in unstressed WT females and both sexes of Sst-KO mice compared with WT males. Sst-KO mice also had exaggerated ACTH and corticosterone responses to acute restraint stress. However, consistent with their lack of phenotypic signs of excess glucocorticoids, cerebrospinal fluid concentrations of free corticosterone in Sst-KO mice were not elevated. In summary, SST is necessary for the prolonged interpulse troughs that define masculinized pituitary GH secretion. SST also contributes to sexual dimorphism of the hypothalamic-pituitary-adrenal axis via GH-dependent regulation of hepatic CBG production.

The prudent parent meets old age: A high stress response in very old seabirds supports the terminal restraint hypothesis

The reproductive success of wild animals usually increases with age before declining at the end of life, but the proximate mechanisms underlying those patterns remain elusive. Young animals are expected to invest less in current reproduction due to high prospects for future reproduction (the “restraint” hypothesis). The oldest animals may also show restraint when conditions are sub-optimal where even a small increase in reproductive investment may lead to death (“terminal restraint”). Alternatively, reproduction may be constrained by lack of experience and senescence (the “constraint” hypothesis). In two species of breeding seabirds, behavioural (time to return the offspring, calmness during restraint) and physiological (metabolism, glucose and corticosterone) parameters responded similarly to stress with advancing age, implying a generalized stress response. Across those parameters, birds were “shy” (high stress response) when young or old, and “bold” (low stress response) when middle-aged. Specifically, free corticosterone, the principal avian glucocorticoid responsible for directing energy away from reproduction and towards immediate survival following stress, was highest in both young and very old stressed birds. All age groups had a similar adrenal capacity to produce corticosterone, implying that middle-aged birds were showing restraint. Because the stress response, was highest at ages when the probability of current reproduction was lowest rather than at ages when the probability of future reproduction was highest we concluded that birds restrained reproductive investment based on current conditions rather than potential future opportunities. In particular, old birds showed terminal restraint when stressed. Hormonal cues promoted investment in adult survival over reproductive output at both the start and end of life consistent with the restraint hypothesis.

Role of corticosteroid binding globulin in emotional reactivity sex differences in mice.

Sex differences exist for stress reactivity as well as for the prevalence of depression, which is more frequent in women of reproductive age and often precipitated by stressful events. In animals, the differential effect of stress on male's and female's emotional behavior has been well documented. Crosstalk between the gonadal and stress hormones, in particular between estrogens and glucocorticoids, underlie these sex differences on stress vulnerability. We have previously shown that corticosteroid binding globulin (CBG) deficiency in a mouse model (Cbg k.o.) leads, in males, to an increased despair-like behavior caused by suboptimal corticosterone stress response. Because CBG displays a sexual dimorphism and is regulated by estrogens, we have now investigated whether it plays a role in the sex differences observed for emotional reactivity in mice. By analyzing Cbg k.o. and wild-type (WT) animals of both sexes, we detected sex differences in despair-like behavior in WT mice but not in Cbg k.o. animals. We showed through ovariectomy and estradiol (E2) replacement that E2 levels explain the sex differences found in WT animals. However, the manipulation of E2 levels did not affect the emotional behavior of Cbg k.o. females. As Cbg k.o. males, Cbg k.o. females have markedly reduced corticosterone levels across the circadian cycle and also after stress. Plasma free corticosterone levels in Cbg k.o. mice measured immediately after stress were blunted in both sexes compared to WT mice. A trend for higher mean levels of ACTH in Cbg k.o. mice was found for both sexes. The turnover of a corticosterone bolus was increased in Cbg k.o. Finally, the glucocorticoid-regulated immediate early gene early growth response 1 (Egr1) showed a blunted mRNA expression in the hippocampus of Cbg k.o. mutants while mineralocorticoid and glucocorticoid receptors presented sex differences but equivalent mRNA expression between genotypes. Thus, in our experimental conditions, sex differences for despair-like behavior in WT mice are explained by estrogens levels. Also, in both sexes, the presence of CBG is required to attain optimal glucocorticoid concentrations and normal emotional reactivity, although in females this is apparent only under low E2 concentrations. These findings suggest a complex interaction of CBG and E2 on emotional reactivity in females.

Corticosterone, food intake and refueling in a long-distance migrant

Elevated baseline corticosterone levels function to mobilize energy in predictable life-history stages, such as bird migration. At the same time, baseline corticosterone has a permissive effect on the accumulation of fat stores (fueling) needed for migratory flight. Most migrants alternate flight bouts with stopovers, during which they replenish the fuel used during the preceding flight (refueling). The role of corticosterone in refueling is currently unclear. In a fasting–re-feeding experiment on northern wheatears (Oenanthe oenanthe) in autumn we found that baseline total and free corticosterone levels were negatively related with both food intake and the rate of fuel deposition after fasting. This confirms our earlier findings in wild conspecifics in spring and indicates that corticosterone does not stimulate stopover refueling. Whether the negative relationship between baseline corticosterone level and fuel deposition rate is causal is questionable, because within-individual comparison of corticosterone metabolite levels in droppings did not reveal differences between refueling and control periods. In other words, corticosterone does not appear to be down-regulated during refueling, which would be expected if it directly hampers refueling. We discuss possible correlates of corticosterone level that may explain the negative association between corticosterone and stopover refueling. Additionally, we found that fasting decreases total corticosterone level, which contrasts with previous studies. We propose that the difference is due to the other studies being conducted outside of the migration life-history stage, and provide a possible explanation for the decrease in corticosterone during fasting in migrating birds.

Rapid induction of the Growth Hormone Gene Transcription by Glucocorticoids In Vitro: Possible Involvement of Membrane Glucocorticoid Receptors and Phosphatidylinositol 3‐Kinase Activation

The regulation of transcription of the growth hormone (GH) gene by glucocorticoids was studied in MtT/S cells, a cell line derived from an oestrogen-induced mammotrophic tumour in the rat, and in the primary culture of the anterior pituitary gland of adult mice. The levels of the GH heteronuclear RNA (GH hnRNA), which are mainly determined by the transcription rate, increased by 25-fold during 24 h in response to dexamethasone (DEX; 1 μM) in MtT/S cells that were cultured in the medium containing charcoal-stripped serum for 7 days. The stimulatory effect of DEX on the GH hnRNA levels was detectable as early as 30 min. This rapid effect of DEX did not require on-going protein synthesis, whereas it was considered that DEX requires the presence of unknown cellular proteins produced independently of DEX stimulation. By contrast, on-going protein synthesis was required for DEX action when incubated for 6 h, as has been observed in the previous studies. The specific inhibitor of glucocorticoid receptor, RU486, inhibited both rapid (30 min) and delayed (6 h) the effects of glucocorticoids on GH hnRNA levels. Membrane impermeable glucocorticoid, corticosterone-bovine serum albumin conjugate (CSBSA), was found to have effects similar to those of DEX and free corticosterone (CS), suggesting that glucocorticoids regulate GH gene transcription at least in part through the membrane bound receptors. From pharmacological studies, it was suggested that phosphatidylinositol 3-kinase (PI3K) activation is involved in the rapid effects but not in the delayed effects of glucocorticoids. This also suggests that the delayed effects of glucocorticoids depend on mechanisms other than the activation of PI3-kinase. Finally, both rapid and delayed effects of CS and CSBSA were observed not only in MtT/S cells, but also in the mouse pituitary cells in primary culture. Therefore, it is possible that the membrane initiated action of glucocorticoids is involved in the regulation of GH transcription in normal pituitary cells, as well as in pituitary tumour cells.

Vitamin A status regulates glucocorticoid availability in Wistar rats: consequences on cognitive functions and hippocampal neurogenesis?

A disruption of the vitamin A signaling pathway has been involved in age-related memory decline and hippocampal plasticity alterations. Using vitamin A deficiency (VAD), a nutritional model leading to a hyposignaling of the retinoid pathway, we have recently demonstrated that retinoic acid (RA), the active metabolite of vitamin A, is efficient to reverse VAD-induced spatial memory deficits and adult hippocampal neurogenesis alterations. Besides, excess of glucocorticoids (GCs) occurring with aging is known to strongly inhibit hippocampal plasticity and functions and few studies report on the counteracting effects of RA signaling pathway on GCs action. Here, we have addressed whether the modulation of brain GCs availability could be one of the biological mechanisms involved in the effects of vitamin A status on hippocampal plasticity and functions. Thus, we have studied the effects of a vitamin A-free diet for 14 weeks and a 4-week vitamin A supplementation on plasma and hippocampal corticosterone (CORT) levels in Wistar rats. We have also investigated corticosteroid binding globulin (CBG) binding capacity and 11beta-Hydrosteroid Dehydrogenase type 1 (11β-HSD1) activity, both important modulators of CORT availability at the peripheral and hippocampal levels respectively. Interestingly, we show that the vitamin A status regulates levels of free plasma CORT and hippocampal CORT levels, by acting through a regulation of CBG binding capacity and 11β-HSD1 activity. Moreover, our results suggest that increased CORT levels in VAD rats could have some deleterious consequences on spatial memory, anxiety-like behavior and adult hippocampal neurogenesis whereas these effects could be corrected by a vitamin A supplementation. Thus, the modulation of GCs availability by vitamin A status is an important biological mechanism that should be taken into account in order to prevent age-related cognitive decline and hippocampal plasticity alterations.

Deficiency of FK506‐binding protein (FKBP) 51 alters sleep architecture and recovery sleep responses to stress in mice

FK506-binding protein 51 (FKBP51) is a co-chaperone of the glucocorticoid receptor, functionally linked to its activity via an ultra-short negative feedback loop. Thus, FKBP51 plays an important regulatory role in the hypothalamic-pituitary-adrenocortical (HPA) axis necessary for stress adaptation and recovery. Previous investigations illustrated that HPA functionality is influenced by polymorphisms in the gene encoding FKBP51, which are associated with both increased protein levels and depressive episodes. Because FKBP51 is a key molecule in stress responses, we hypothesized that its deletion impacts sleep. To study FKBP51-involved changes in sleep, polysomnograms of FKBP51 knockout (KO) mice and wild-type (WT) littermates were compared at baseline and in the recovery phase after 6-h sleep deprivation (SD) and 1-h restraint stress (RS). Using another set of animals, the 24-h profiles of hippocampal free corticosterone levels were also determined. The most dominant effect of FKBP51 deletion appeared as increased nocturnal wake, where the bout length was significantly extended while non-rapid eye movement sleep (NREMS) and rapid eye movement sleep were rather suppressed. After both SD and RS, FKBP51KO mice exhibited less recovery or rebound sleep than WTs, although slow-wave activity during NREMS was higher in KOs, particularly after SD. Sleep compositions of KOs were nearly opposite to sleep profiles observed in human depression. This might result from lower levels of free corticosterone in FKBP51KO mice, confirming reduced HPA reactivity. The results indicate that an FKBP51 deletion yields a pro-resilience sleep phenotype. FKBP51 could therefore be a therapeutic target for stress-induced mood and sleep disorders.

Effect of aqueous, ethanolic and acetonitrile Crocus sativus L. extracts on stress biomarkers in male rats

In this study, antianxiety-like behavior of aqueous, ethanolic and acetonitrile Crocus sativus L. extracts have been investigated in forced-swimming stress in rats. In addition, main metabolites crocin and safranal were quantified in all extracts using HPLC. Different doses of extracts (10, 30, 60 mg/kg) were injected intraperitoneally (i.p.) in a 9-day period, meanwhile, swimming stress was performed for 15 minutes in four sessions (days 3, 5, 7 and 9). The time performing the followings was measured: immobility, swimming and struggling. Moreover, free fatty acids, glucose, corticosterone and HSP70 were measured. The outcomes demonstrated saffron decreased stress significantly by prolonging immobility and decreasing the active behavior swimming, without much effect on struggling. The extracts also showed significant reduction in levels of the stress biomarkers. With having the highest amount of safranal and the lowest amount of crocin, comparing the other extracts, acetonitrile has been identified as the most effective extract in reducing anxiety. The saffron extracts probably proved anti-stress and sedative properties, partly due to distinct proportion and synergistic impact of the active constituents. On the other hand, crocin and safranal have anti-oxidant and anti-inflammatory powers that may aid to mediate this protective central impact. Regarding these information, saffron may have the potential to be employed in clinical practice. Key words: HPLC method, antianxiety-like behavior, Crocus sativus L. (saffron), forced-swimming stress, rat, stress biomarkers.

Corticosterone exposure during development has sustained but not lifelong effects on body size and total and free corticosterone responses in the zebra finch

Animals exposed to stress during development experience sustained morphological, physiological, neurological, and behavioral consequences. For example, elevated glucocorticoids (GCs) during development can increase GC secretion in adults. Studies have examined the sustained effects of elevated developmental GCs on total GC responses, but no study to date has examined the effect of developmental stress on corticosteroid binding globulin (CBG). CBG is a protein which binds to GCs and facilitates their transportation in blood. When bound to CBG, GCs are unavailable to interact with target tissues. Exposure to stress can decrease CBG capacity and, thus, increase free GCs (the portion of unbound GCs). We examined the long-term effects of elevated corticosterone (CORT) during development (12–28days post-hatch) on acute stress responses, negative feedback, and CBG capacity at 30, 60, and 90days post-hatch in zebra finches. Additionally, we evaluated the effect of CORT treatment on body size and condition at 28, 60, and 90days post-hatch. CORT exposed birds had higher acute stress responses at 30days post-hatch compared to control birds. However, there was no treatment effect at 60 or 90days post-hatch. CBG levels were not affected by treatment, and so free CORT estimations reflected patterns in total CORT. CORT treatment decreased growth and condition in zebra finches at 28days post-hatch, but these differences were not present at later life history stages. However, brood size had a sustained effect on body size such that birds reared in medium sized broods were larger at 28, 60, and 90days post-hatch. These results demonstrate the complexity of early environmental effects on adult phenotype and suggest that some conditions may have stronger programmatic effects than others.

Corticosteroid-binding globulin contributes to the neuroendocrine phenotype of mice selected for extremes in stress reactivity

Increasing evidence indicates an important role of steroid-binding proteins in endocrine functions, including hypothalamic-pituitary-adrenal (HPA) axis activity and regulation, as they influence bioavailability, local delivery, and cellular signal transduction of steroid hormones. In the plasma, glucocorticoids (GCs) are mainly bound to the corticosteroid-binding globulin (CBG) and to a lesser extend to albumin. Plasma CBG levels are therefore involved in the adaptive stress response, as they determine the concentration of free, biologically active GCs. In this study, we investigated whether male mice with a genetic predisposition for high-reactivity (HR), intermediate-reactivity (IR), or low-reactivity (LR) stress-induced corticosterone (CORT) secretion present different levels of free CORT and CORT-binding proteins, basally and in response to stressors of different intensity. Our results suggest a fine control interaction between plasma CBG expression and stress-induced CORT release. Although plasma CBG levels, and therefore CBG binding capacity, were higher in HR animals, CORT secretion overloaded the CBG buffering function in response to stressors, resulting in clearly higher free CORT levels in HR compared with IR and LR mice (HR>IR>LR), resembling the pattern of total CORT increase in all three lines. Both stressors, restraint or forced swimming, did not evoke fast CBG release from the liver into the bloodstream and therefore CBG binding capacity was not altered in our three mouse lines. Thus, we confirm CBG functions in maintaining a dynamic equilibrium between CBG-bound and unbound CORT, but could not verify its role in delaying the rise of plasma free CORT immediately after stress exposure.

Central glucocorticoid system dysfunction in a mouse model of extreme anxiety: clinical implications

Animal models of psychiatric disorders are useful tools for elucidating associations between behavioral symptoms and biological abnormalities and for suggesting possible treatment strategies for psychiatric diseases. Here we describe phenotypic, neuroendocrine and molecular traits of a mouse model of extreme inborn high anxiety-related behavior (HAB) from the perspective of clinical application to study central mechanisms of psychiatric abnormalities. HABs consistently show higher anxiety and depression-like behavior, increased contextual fear and inhibitory avoidance learning compared to normal anxiety-related behaviour (NAB) mice. While basal blood corticosterone (CORT) was found to be an unimportant endocrine parameter in our mouse model, HABs responded with significantly reduced CORT to stressful stimuli. The DEX-CRH test revealed much stronger suppression of the hypothalamic pituitary adrenal (HPA) axis after Dex infusion and a blunted response to CRH stimulation in HABs. Analysis of glucocorticoid receptors showed significantly higher amounts in almost all brain areas of HABs, whereas levels of free CORT in these brain regions were reduced. An increased expression of enzymes involved in CORT metabolism is likely to be critically involved in HAB mice. All together, these data suggest that the mouse model of high anxiety resembles behavioral and endocrine symptomatologies of psychiatric disorders with the focus on a dysregulation of the central glucocorticoid system. This study was supported by Max-Planck-Gesellschaft.

Modulation of the adrenocortical response to acute stress with respect to brood value, reproductive success and survival in the Eurasian hoopoe

Reproducing parents face the difficult challenge of trading-off investment in current reproduction against presumed future survival and reproduction. Glucocorticoids are supposed to mediate this trade-off because the adrenocortical response to stress disrupts normal reproductive behaviour in favour of self-maintenance and own survival. According to the brood-value hypothesis, individuals with a low survival probability until the next reproductive season have to invest in current reproduction, a process driven by a down-regulation of their adrenocortical response. If the adrenocortical response to stress effectively mediates the trade-off between current reproduction versus future survival and reproduction, we expect a negative relationship with reproductive success and a positive correlation of the adrenocortical stress response with survival. We studied the relationship between corticosterone secretion in parents and their current brood value, reproductive success and survival in a short-lived multi-brooded bird, the Eurasian hoopoe Upupa epops. The adrenocortical response to acute handling stress was correlated with the brood value within the individual (first and second broods of the year) and between individuals. Birds breeding late in the season mounted a lower total corticosterone response to acute stress than birds breeding earlier, while females showed lower levels than males. We observed a negative relationship between the adrenocortical stress response and rearing success or fledging success in females, as predicted by the brood-value hypothesis. However, we could not evidence a clear link between the adrenocortical stress response and survival. Future research testing the brood-value hypothesis and trade-offs between current reproduction and future survival should also measure free corticosterone and carefully differentiate between cross-sectional (i.e. between-individual) and individual-based experimental studies.