Measured Plasma Corticosterone Research Articles

Modulation of noradrenergic signalling reverses stress-induced changes in the hippocampus: Involvement of orexinergic systems.

Stress can be beneficial for adapting to dangerous situations in the short term but can be damaging in the long term, especially in the hippocampus. The noradrenergic and orexinergic systems play important roles in stress response. This study investigated the effect of noradrenergic activation on changes induced by chronic stress in the hippocampus and the involvement of orexinergic modulation in this process. This study examined five groups of 40 male Wistar rats (4 + 4 animals/ group): control, chronic stress, acute stress, control with noradrenergic activation, and chronic stress with noradrenergic activation. Hippocampal tissue and blood plasma were the primary specimens analyzed. The researchers measured plasma corticosterone (CORT) using a fluorometric method, examined the expression of prepro-orexin (prepro-OX), orexin receptor-1 (OXr1), and glucocorticoid receptor (GR) through RT-PCR, and quantified neuronal populations using Nissl staining. Acute and chronic stress increased plasma CORT levels and gene expression of prepro-OX, OXr1, and GR, while decreasing neuronal numbers, with chronic stress having a more pronounced effect. Yohimbine-treated and/or stressed rats exhibited elevated plasma CORT levels. Chronic stress substantially upregulated GR and increased prepro-OX and OXr1 expressions whereas yohimbine recovered those profiles in chronically stressed animals. Conversely, chronic stress reduced hippocampal neuronal populations, and chronic stress combined with yohimbine partially compensated for the neuronal numbers compared to chronic stress alone. These results suggest that noradrenergic signalling can reverse chronic stress-induced impairments in prepro-OX, OXr1, GR, and neuronal populations.

The effects of lowering barometric pressure on pain behavior and the stress hormone in mice with neuropathic pain.

Lowering barometric pressure (LP) can exacerbate neuropathic pain. However, animal studies in this field are limited to a few conditions. Furthermore, although sympathetic involvement has been reported as a possible mechanism, whether the sympathetic nervous system is involved in the hypothalamic-pituitary-adrenal (HPA) axis remains unknown. To address these issues, we investigated LP-induced hyperalgesia by focusing on the cumulative effect of LP and measuring plasma corticosterone levels as a marker of HPA axis activation in mice. Mice with chronic constriction injury (CCI) were used in this study. For behavioral tests, two types of LP stimulation were adopted: a single LP at 20 hPa (Single LP) and three consecutive LPs at 20 hPa (3LPs). Twelve mice were used for each protocol. The no-pressure-change protocol was used as the control. The mechanical sensitivity was tested before and after LP stimulation using von Frey filaments (vF). For corticosterone measurements, six CCI and six intact mice were exposed to 3LPs (CCI-3LPs and INT-3LPs), and another six CCI and six intact mice were exposed to the no-pressure-change protocol (CCI-NP and INT-NP). Blood samples were collected immediately after exposure. Plasma corticosterone levels were measured by ELISA. The number of paw elevations by vF before and after LP stimulation did not differ significantly in either the Single LP or the no-pressure-change protocol. For the 3LPs, the number of paw elevations after LP stimulation was significantly greater than before stimulation. Plasma corticosterone levels in the CCI-3LPs were significantly higher than those in CCI-NPs. In intact mice, there was no significant difference in plasma corticosterone levels between the INT-3LPs and INT-NPs. LP has a cumulative effect on neuropathic pain. Hypothalamic-pituitary-adrenal axis activation may have an important relationship with LP-induced pain in mice.

N-acetylcysteine counteracts increased brain excitatory/inhibitory balance following maternal high-fat diet and restores emotional and cognitive profiles in adult mouse offspring

IntroductionHigh-fat diet (HFD) consumption during pregnancy can shape fetal brain development, increasing susceptibility to mental disorders. Nevertheless, the mechanisms underlying these negative outcomes remain unclear.ObjectivesWe hypothesize that mHFD induces inflammation and oxidative stress (OS) in the fetal brain, disrupting excitatory/inhibitory (E/I) balance in the adult brain. This results in altered hypothalamic-pituitary-adrenal (HPA) axis reactivity, emotional regulation, and cognitive function. We tested the ability of N-acetyl-cysteine (NAC) - a powerful anti-oxidant and anti-inflammatory compound - to counteract mHFD effects.MethodsOur mHFD model consists of female C57BL/6N mice fed either HFD (fat 58%, carbohydrate 25.5%, and protein 16.4%) or control diet (CD, fat 10.5%, carbohydrate 73.1% and protein 16.4%) before and during pregnancy (13 weeks). After 5 weeks on diets, half of them received NAC (1g/kg) for 8 weeks, until delivery.Gene expression of Il-1b, Cd68, Tmem119, iNOS, and Arg1 was measured in fetal brains. Cognitive function and emotional phenotype were assessed in adult male and female offspring through the Morris Water Maze (MWM) and the Emergence test, respectively. HPA axis functionality was assessed by measuring plasma corticosterone levels by ELISA following acute stress. Gene expression of vesicular glutamate transporter 1 (Vglut1) and vesicular GABA transporter (Vgat) were assessed as markers of E/I balance.ResultsExposure to mHFD induced inflammation and OS in the fetal brain of both sexes, by increasing Il-1b and iNOS/Arg1. Additionally, Cd68 and Tmem119 were specifically increased in females. In adulthood, mHFD reduced latency to emerge from the shelter in the Emergence test in both sexes. In females, mHFD impaired cognitive function, reducing time spent in the MWM target zone, and increased HPA reactivity in response to acute stress. Furthermore, mHFD decreased Vgat expression in both sexes, resulting in an imbalanced Vglut1/Vgat ratio towards excessive excitatory input. Maternal NAC supplementation rescued this imbalance.ConclusionsOverall, these data show that mHFD increases inflammation and OS in fetal brains, with greater effects in female offspring, inducing alterations in the E/I neuronal balance with concomitant disruptions of the neuroendocrine system and the emotional and cognitive profiles during adulthood. The supplementation with NAC was effective in rescuing the E/I imbalance as well as the behavioral phenotype.Disclosure of InterestNone Declared

Offspring's own serotonin transporter genotype, independently from the maternal one, increases anxiety- and depression-like behavior and alters neuroplasticity markers in rats

IntroductionDevelopmental changes due to early life variations in the serotonin system affect stress-related behavior and neuroplasticity in adulthood. These outcomes can be caused both by offspring's own and maternal serotonergic genotype. We aimed to dissociate the contribution of the own genotype from the influences of mother genotype. MethodsSixty-six male homozygous (5-HTT−/−) and heterozygous (5-HTT+/−) serotonin transporter knockout and wild-type rats from constant 5-HTT genotype mothers crossed with varying 5-HTT genotype fathers were subjected to tests assessing anxiety- and depression-like behaviors. Additionally, we measured plasma corticosterone levels and mRNA levels of BDNF, GABA system and HPA-axis components in the prelimbic and infralimbic cortex. Finally, we assessed the effect of paternal 5-HTT genotype on these measurements in 5-HTT+/− offspring receiving their knockout allele from their mother or father. Results5-HTT−/− offspring exhibited increased anxiety- and depression-like behavior in the elevated plus maze and sucrose preference test. Furthermore, Bdnf isoform VI expression was reduced in the prelimbic cortex. Bdnf isoform IV and GABA related gene expression was also altered but did not survive false discovery rate (FDR) correction. Finally, 5-HTT+/− offspring from 5-HTT−/− fathers displayed higher levels of anxiety- and depression-like behavior and changes in GABA, BDNF and HPA-axis related gene expression not surviving FDR correction. LimitationsOnly male offspring was tested. ConclusionsOffspring's own 5-HTT genotype influences stress-related behaviors and Bdnf isoform VI expression, independently of maternal 5-HTT genotype. Paternal 5-HTT genotype separately influenced these outcomes. These findings advance our understanding of the 5-HTT genotype dependent susceptibility to stress-related disorders.

Western diet-induced obesity interferes with the HPA axis-blunting effects of palatable food in male rats

Limited intermittent consumption of palatable food reduces HPA axis responses to stress in chow-fed rats, and this effect is dependent on the rewarding properties of the palatable food. However, obesity may be a state of reduced consummatory food reward, suggesting that palatable foods may be less effective at blunting HPA axis reactivity in the context of diet-induced obesity (DIO). To test this hypothesis, adult male Long-Evans rats were given unlimited access to Western (high-fat, high-sugar) diet (WD) vs. normal chow (controls). After 8 weeks of diet exposure, rats were given limited sucrose intake (LSI) consisting of additional twice-daily access to a small amount (4 ml) of either 3% or 30% sucrose drink, or water (controls) for 2 weeks. Rats then received an acute restraint stress challenge, with collection of tail blood samples for measurement of plasma corticosterone. WD-fed rats had increased caloric intake, body weight and adiposity, as expected. Rats offered LSI (3% or 30%) readily drank the maximal amount allowed (8 ml/day) and reduced their dietary intake to compensate for the sucrose calories, such that LSI did not alter body weight regardless of diet type. In chow-fed lean rats, LSI with either 3% or 30% sucrose reduced the plasma corticosterone response to restraint stress, but this effect was absent in WD-fed DIO rats. Together, these data support the hypothesis that obesity attenuates stress blunting by palatable foods and suggest the possibility that consequently, individuals with obesity may need to consume larger amounts of palatable food to obtain adequate stress relief.

Intact Recognition Memory and Altered Hippocampal Glucocorticoid Receptor Signaling in Fkbp5-deficient Mice Following Acute Uncontrollable Stress.

The FK506 binding protein 5 (FKBP5) is a co-chaperone that regulates the activity of the glucocorticoid receptor (GR) and has been reported to mediate stress resilience. This study aimed to determine the effects of Fkbp5 deletion on acute stress-induced recognition memory impairment and hippocampal GR signaling. Wild-type and Fkbp5-knockout mice were subjected to acute uncontrollable stress induced by restraint and electrical tail shock. First, we assessed the cognitive status of mice using a novel object recognition task. Next, we measured plasma corticosterone, GR levels, and the levels of GR phosphorylation at serine 211 in the hippocampus. Wild-type mice exhibited stress-induced memory impairments, whereas Fkbp5-knockout mice did not. Plasma corticosterone and GR levels did not differ between the non-stressed wild-type and Fkbp5-knockout mice, but the levels of phosphorylated GR were lower in Fkbp5-knockout mice than in wild-type mice. Wild-type and Fkbp5-knockout mice showed increased nuclear GR levels following stress, indicating GR translocation. However, cytosolic phosphorylated GR levels were lower in the hippocampi of Fkbp5-knockout mice following stress than in those of wild-type mice. These results suggest that FKBP5 deficiency increases resilience to acute stress by altering GR signaling.

Patterns of stress response to foreign eggs by a rejecter host of an obligate avian brood parasite.

One of the most effective defenses of avian hosts against obligate brood parasites is the ejection of parasitic eggs from the nests. Despite the clear fitness benefits of this behavior, individuals within so-called "egg-rejecter" host species still show substantial variation in their propensity to eliminate foreign eggs from the nest. We argue that this variation can be further understood by studying the physiological mechanisms of host responses to brood parasitic egg stimuli: independent lines of research increasingly support the hypothesis that stress-related physiological response to parasitic eggs may trigger egg rejection. The "stress-mediated egg rejection" hypothesis requires that hosts activate the stress-response when responding to parasitic egg stimuli. We tested this prediction by asking whether hosts showed differential stress response when exposed to host-like (mimetic) or parasite-like (non-mimetic) eggs. We experimentally parasitized incubating American robins Turdus migratorius, a robust egg-rejecter host to obligate brood parasitic brown-headed cowbirds Molothrus ater, with mimetic or non-mimetic model eggs. To assess the stress response, we measured the heart rate in incubating females immediately after experimental parasitism. We also measured plasma corticosterone and, in a subset of birds, used RNA-sequencing to analyze the expression of proopiomelanocortin (POMC), a precursor of adrenocorticotropic hormone, 2 h after experimental parasitism. We found that egg type had no effect on heart rate. Two hours following experimental parasitism, plasma corticosterone did not differ between the differently-colored model egg treatments or between rejecter and accepter females within the non-mimetic treatment. However, females exposed to non-mimetic eggs showed an upregulation of POMC gene expression (before FDR correction) in the pituitary compared with females treated with mimetic eggs. Our findings suggest that in an egg-rejecter host species, non-mimetic parasitic eggs may increase the activity of the stress-related hypothalamic-pituitary-adrenal axis compared with mimetic eggs, although the temporaldynamics of this response are not yet understood.

FKBP5 inhibitors modulate alcohol drinking and trauma-related behaviors in a model of comorbid post-traumatic stress and alcohol use disorder.

Post-traumatic stress disorder (PTSD) leads to enhanced alcohol drinking and development of alcohol use disorder (AUD). Identifying shared neural mechanisms might help discover new therapies for PTSD/AUD. Here, we employed a rat model of comorbid PTSD/AUD to evaluate compounds that inhibit FK506-binding protein 51 (FKBP5), a co-chaperone modulator of glucocorticoid receptors implicated in stress-related disorders. Male and female rats received a familiar avoidance-based shock stress followed by voluntary alcohol drinking. We then assessed trauma-related behaviors through sleep bout cycles, hyperarousal, fear overgeneralization, and irritability. To evaluate the role of stress and alcohol history on the sensitivity to FKBP5 inhibitors, in two separate studies, we administered two FKBP5 inhibitors, benztropine (Study 1) or SAFit2 (Study 2). FKBP5 inhibitors were administered on the last alcohol drinking session and prior to each trauma-related behavioral assessment. We also measured plasma corticosterone to assess the actions of FKBP5 inhibitors after familiar shock stress and alcohol drinking. Benztropine reduced alcohol preference in stressed males and females, while aggressive bouts were reduced in benztropine-treated stressed females. During hyperarousal, benztropine reduced several startle responseoutcomes across stressed males and females. Corticosterone was reduced in benztropine-treated stressed males. The selective FKBP5 inhibitor, SAFit2, reduced alcohol drinking in stressed males but not females, with no differences in irritability. Importantly, SAFit2 decreased fear overgeneralization in stressed males and females. SAFit2 also reduced corticosterone across stressed males and females. Neither FKBP5 inhibitor changed sleep bout structure. These findings indicate that FKBP5 inhibitors modulate stress-related alcohol drinking and partially modulate trauma-related behaviors. This work supports the hypothesis that targeting FKBP5 may alleviate PTSD/AUD comorbidity.

Nicotine exposure through breastfeeding affects brain-derived neurotrophic factor and synaptic proteins levels in the brain of stressed adult female mice.

Nicotine has been used during pregnancy and lactation as a tobacco harm reduction strategy. However, it is unclear whether nicotine exposure during a critical development period negatively impacts stress responses in adulthood. This study investigated how nicotine, administered via breastfeeding, affects the brain-derived neurotrophic factor (BDNF), synaptic proteins levels, and anxiety-like behavior in adult female mice subjected to stress. Female Swiss mice were exposed to saline or nicotine (8mg/kg/day) through breastfeeding between their fourth and 17th postnatal days (P) via implanted osmotic mini pumps. The unpredictable chronic mild stress (UCMS) protocol was performed during their adulthood (P65) for 10 consecutive days, followed by the elevated plus maze (EPM) test 1 day after the protocol. Animals were euthanized and their blood, collected for plasma corticosterone measurements and their brain structures, dissected for BDNF and synaptic proteins analyses. We found no significant differences in corticosterone levels between groups (Saline/Non-stress, Nicotine/Non-stress, Saline/Stress, and Nicotine/Stress). The UCMS protocol hindered weight gain. Mice exposed to nicotine through breastfeeding with or without the UCMS protocol in adulthood showed higher grooming and head dipping frequency; decreased BDNF levels in cerebellum and striatum; increased postsynaptic density protein 95 (PSD-95), synapsin I, and synaptophysin levels in cerebellum; and decreased PSD-95 and synapsin I levels in brainstem. Our results indicate that nicotine exposure through breastfeeding leads to long-lasting behavioral effects and synaptic protein changes, most of which were independent of the UCMS protocol, even after a long nicotine-free period, highlighting the importance of further studies on nicotine exposure during development.

Protective effects of glucocorticoid receptor antagonist Mifepristone on fear memory extinction impairment in a rat model of PTSD

IntroductionCentral glucocorticoid receptor (GR) has been found to play an important role in the interpretation of cognitive abnormalities of posttraumatic stress disorder (PTSD), particularly focused on the extinction failure of fear memory. Potential of using GR antagonist as a pharmacological agent to prevent PTSD-related fear memory disruption is worth investigating.ObjectivesWe aimed to examine whether GR antagonist Mifepristone (RU486) administered before single prolonged stress (SPS) can prevent rats from fear memory extinction impairment.MethodsIn the present study, SPS was employed in rats to induce a rodent model of PTSD. 60 minutes before SPS, RU486 (20 mg/kg) was administered by intraperitoneal injection. Seven days after SPS, rats received a protocol of behavioral testing to measure their abilities of specific fear memory (by a cue-dependent fear conditioning paradigm) and nonspecific spatial memory (by T-maze). Neurochemically, we measured plasma corticosterone with or without dexamethasone suppression, activation ratio of GR and levels of norepinephrine, dopamine, and serotonin in amygdala, paraventricular nucleus, dorsal and ventral hippocampus.ResultsOur results found that RU486 exerted protective effects on SPS-induced fear extinction impairment. Corticosterone of SPS-RU486 rats was less suppressed by dexamethasone. GR became less activated in dorsal hippocampus of SPS-RU486 rats.ConclusionsThe findings supported the utility of GR antagonism in preventing the development of PTSD.DisclosureNo significant relationships.

Sex‐specific Consequences of Psychosocial Stress on Cardiorespiratory Control: a Comparison with Intermittent Hypoxia

Sleep apnea (SA) is a complex, multifactorial and a sex‐specific respiratory disorder; sexual dimorphism being present both in its prevalence and in the presentation of the pathology. To this day, the origins of SA remain unknown. While intermittent hypoxia (IH) is commonly used to assess the pathophysiology of SA, this systemic stress is a consequence, not a cause of SA. The psychosocial stress of social isolation (SI) and the recent COVID pandemic showed how SI increases the risk for a broad range of diseases, including hypertension and obesity, which are common comorbidities of SA. While there is growing evidence linking psychosocial stress and SA, its effect on cardiorespiratory function is yet to be established. To address this issue, we tested the hypothesis that SI is sufficient to induce sex‐specific cardiorespiratory and metabolic disturbances similar to those seen in patients with SA. We then compared the effects of SI with those observed following moderate IH.Adult (8 weeks old) rats were subjected to either three weeks of social isolation or standard housing. SI consisted of single housing without visual contact with other rats (n = 22); the control rats were housed in pairs (n = 22), both groups under normoxic conditions. The third group (n = 18) housed in pairs was exposed to intermittent hypoxia (IH: FiO2 = 0.10 – 30s, 10 cycles/hour, 8 hours/day, 7 days). Apneas were quantified by whole body plethysmography during sleep. Cardiovascular measurements were then measured by tail cuff pressure and body composition by magnetic resonance. Blood samples were obtained at the end of the protocol to measure plasma corticosterone and ACTH with a multiplex assay.Male rats subjected to SI had an apnea index 27% higher than controls, were hypertensive (+ 15mmHg) and gained 6% more weight than males in pair housing. The body fat and fluid gains of SI males were, respectively, 21% and 38% higher than their controls. Yet, food consumption did not differ between the two groups. SI augmented plasma ACTH and corticosterone. The SI protocol had no significant effect in females. IH males (but not females) were hypertensive (+ 9mmHg), and their heart rate was 54 bpm greater than controls but no significant change in the number of apneas. Moderate IH did not augment stress hormone levels. Unlike SI, IH reduced food consumption and weight gain in both sexes. IH reduced body fat by 18% and body fluids by 30% compared to controls. Body composition of IH females was not different from controls.Our results demonstrate that SI is sufficient to activate the neuroendocrine stress response and induce sex‐specific cardiorespiratory and metabolic disturbances similar to those reported in SA patients. Our observations also suggest that the cardiovascular disturbance in IH occurs before respiratory disruption, and that and the activation of the stress pathways is necessary to augment apneic events. A longer or more severe protocol should be considered. These results indicate that stress hormones play an important role in the etiology of respiratory disorders and key comorbidities such as hypertension and obesity. We propose that SI is a valuable model to investigate the origins and pathophysiology of SA.

Impact of broiler breeder growth trajectory on plasma corticosterone concentration: a comparison of analytical methods

Blood concentration of corticosterone (CORT) is a measure of welfare in feed restricted broiler breeders. The RIA and ELISA have been routinely used for measuring CORT in blood, excreta, and feather. Due to the presence of some confounding factors in the aforementioned colorimetric enzyme reaction methods, some methodological difficulties have been attributed to those assays. The correlation between broiler breeder plasma CORT concentrations, measured using ELISA and a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, was the focus of the current study. A total of 36 broiler breeder pullets were used, of which 30 were randomly assigned to one of 10 unique growth trajectories, and 6 were assigned to an unrestricted group. We designed the growth trajectories using a 3-phase Gompertz growth model with 10 levels of BW gain in the prepubertal and pubertal growth phases, ranging from the breeder-recommended target BW (CON) to 22.5% higher (CON+22.5%), in 2.5% increments. The BW trajectories were applied to each individual bird using a precision feeding (PF) system, which collected BW and feed intake data. The birds were classified based on age at first egg (AFE), and 12 birds each having the highest and lowest AFE was selected for the CORT study. Then median photostimulation BW of the candidate birds was used to define the upper (heavy BW) and lower (standard BW) extremes, and plasma CORT levels were evaluated by ELISA and LC-MS/MS methods from their blood collected at 18, 20, 22, 24, and 26 wk of age. Concentrations of plasma CORT measured using ELISA method were highly correlated (r = 0.95; P < 0.001) with values measured using LC-MS/MS method, validating interchangeably usage of both methods to measure plasma CORT in broiler breeders. Plasma CORT levels were not affected by photostimulation BW or breeders' age, indicating same welfare status between the precision fed high and low BW groups.

The anxiolytic sertraline reduces the impact of psychological stress on bladder function in mice

AimsTo determine if treatment with the selective serotonin reuptake inhibitor (SSRI) sertraline reduces the bladder dysfunction caused by water avoidance stress in mice. Main methodsAdult female mice were randomly allocated to (1) Unstressed, (2) Stressed or (3) Stress + Sertraline experimental groups. Stressed mice were subjected to water avoidance for 1 h/day for 10 days and received sertraline or vehicle in drinking water, starting 10-days prior to the first stress exposure. Age matched control/unstressed mice were house under normal conditions without stress exposure. Voiding behaviour was assessed throughout the experimental protocol. After the final stress exposure, a blood sample was taken to measure plasma corticosterone levels and bladders were removed, catheterised and intravesical pressure responses recorded during distension and in response to pharmacological agents. Key findingsPlasma corticosterone levels in sertraline-treated animals were equivalent to unstressed controls and significantly decreased compared to the stressed group. Voiding frequency was significantly increased in the stressed group, and treatment with sertraline significantly decreased voiding frequency, however, this remained elevated compared to unstressed control animals. Bladders from stressed mice displayed enhanced maximal contractile response to the muscarinic agonist carbachol and greater release of ACh in the serosal fluid, which was reduced to control levels by sertraline treatment. Spontaneous phasic contractions were not altered by stress but were significantly reduced in bladders from sertraline treated animals, relative to controls. SignificanceThese results indicate that management of voiding dysfunction caused by psychological stress may be aided by the addition of an SSRI such as sertraline.

Hypothalamic-pituitary-adrenal axis regulation and organization in urban and rural song sparrows

Urban habitats present animals with persistent disturbances and acute stressors not present in rural habitats or present at significantly lower levels. Differences in the glucocorticoid stress response could underlie colonization of these novel habitats. Despite urban habitats characterization as more stressful, previous comparisons of urban and rural birds have failed to find consistent differences in baseline and stress induced glucocorticoid levels. Another aspect of glucocorticoid regulation that could underlie an animal’s ability to inhabit novel habitats, but has yet to be well examined, is more efficient termination of the glucocorticoid stress response which would allow birds in urban habitats to recover more quickly after a disturbance. The glucocorticoid stress response is terminated by negative feedback achieved primarily through their binding of receptors in the hippocampus and hypothalamus and subsequent decreased synthesis and release from the adrenals. We investigated if male song sparrows (Melospiza melodia) in urban habitats show more efficient termination of the glucocorticoid stress response than their rural counterparts using two approaches. First, we measured glucocorticoid receptor, mineralocorticoid receptor and 11β-HSD2 (an enzyme that inactivates corticosterone) mRNA expression in negative feedback targets of the brain (the hippocampus and hypothalamus) as a proxy measure of sensitivity to negative feedback. Second, we measured plasma corticosterone levels after standardized restraint and again following a challenge with the synthetic glucocorticoid, dexamethasone, as a means of assessing how quickly birds decreased glucocorticoid synthesis and release. Though there were no differences in the hypothalamus of urban and rural song sparrows, urban birds had lower glucocorticoid receptor and 11β-HSD2 mRNA expression in the hippocampus. Further, urban and rural birds had similar reductions in corticosterone following the dexamethasone challenge, suggesting that they do not differ in how quickly they decrease glucocorticoid synthesis and release. Thus, urban and rural song sparrows display similar termination of the glucocorticoid stress response even though urban birds have decreased hippocampal glucocorticoid receptor and 11β-HSD2 abundance.

Short-term capture stress and its effects on corticosterone levels and heat shock proteins in captive American Alligators (Alligator mississippiensis)

Heat shock proteins (HSPs) are important mediators of the normal cellular function and the cellular stress response. As such, HSPs are often utilized to measure the effects of stressors on organisms in vivo. However, multiple variables can influence their expression, including time or season, confounding results. To investigate the utility of HSPs in measuring effects of stressors in a top-trophic carnivore, we captured 20 American Alligators (Alligator mississippiensis (Daudin, 1802)), placed them in burlap sacks for 2 h and collected blood samples over four time points (baseline, 1 and 2 h after placement into burlap sacks, and 24 h after initial capture) to measure plasma corticosterone (the main crocodilian glucocorticoid) and levels of HSP60, HSP70, and HSP90. Time point significantly affected plasma corticosterone levels in Alligators (p &lt; 0.0001), with levels significantly elevated at 1, 2, and 24 h, relative to baseline (all p &lt; 0.05). However, capture stress did not affect HSP60, HSP70, or HSP90 in red blood cells (all p &gt; 0.05). Our results suggest HSPs may be important biomarkers for investigating the impacts of stressors on captive and wild crocodilians, as they are not acutely elevated by capture or handling stress.

Effects of test experience, closed-arm wall color, and illumination level on behavior and plasma corticosterone response in an elevated plus maze in male C57BL/6J mice: a challenge against conventional interpretation of the test

The elevated plus maze test is a widely used test for assessing anxiety-like behavior and screening novel therapeutic agents in rodents. Previous studies have shown that a variety of internal factors and procedural variables can influence elevated plus maze behavior. Although some studies have suggested a link between behavior and plasma corticosterone levels, the relationships between them remain unclear. In this study, we investigated the effects of experience with a battery of behavioral tests, the wall color of the closed arms, and illumination level on the behavior and plasma corticosterone responses in the elevated plus maze in male C57BL/6J mice. Mice were either subjected to a series of behavioral tests, including assessments of general health and neurological function, a light/dark transition test, and an open field test, or left undisturbed until the start of the elevated plus maze test. The mice with and without test battery experience were allowed to freely explore the elevated plus maze. The other two independent groups of naïve mice were tested in mazes with closed arms with different wall colors (clear, transparent blue, white, and black) or different illumination levels (5, 100, and 800 lx). Immediately after the test, blood was collected to measure plasma corticosterone concentrations. Mice with test battery experience showed a lower percentage of open arm time and entries and, somewhat paradoxically, had lower plasma corticosterone levels than the mice with no test battery experience. Mice tested in the maze with closed arms with clear walls exhibited higher open arm exploration than mice tested in the maze with closed arms with black walls, while there were no significant differences in plasma corticosterone levels between the different wall color conditions. Illumination levels had no significant effects on any measure. Our results indicate that experience with other behavioral tests and different physical features of the maze affect elevated plus maze behaviors. Increased open arm time and entries are conventionally interpreted as decreased anxiety-like behavior, while other possible interpretations are considered: open arm exploration may reflect heightened anxiety and panic-like reaction to a novel situation under certain conditions. With the possibility of different interpretations, the present findings highlight the need to carefully consider the test conditions in designing experiments and drawing conclusions from the behavioral outcomes in the elevated plus maze test in C57BL/6J mice.

Anxiety-like behavior and neuroendocrine changes in offspring resulting from gestational post-traumatic stress disorder

Exposure to stressful environmental events during the perinatal period can increase vulnerability to psychopathologies that cause neuroendocrine changes associated with deficits in emotional behavior that can appear early in life. Post-traumatic stress disorder (PTSD) is a frequent, chronic, and disabling disorder that negatively impacts the emotional, social, and cognitive behaviors of affected individuals. Thus, we induced PTSD in pregnant rats by applying inescapable footshocks and then investigated the behavioral parameters similar to anxiety in offspring at prepubertal age, in addition to the plasma levels of maternal and offspring corticosterone and expression of glucocorticoid receptors (GR) in the offspring’s hippocampus. With the dams, maternal behavior, open field, and object recognition tests were performed. With the male and female offspring, we performed the following: quantification of ultrasonic vocalizations, elevated plus-maze test, evaluation of exploratory activity in the open field, and hole board test, as well as plasma corticosterone measurements and Western blotting for GR. Our results showed that gestational PTSD affected maternal behavior, led to anxiety-like symptoms, increased corticosterone levels, and increased GR expression in the offspring’s hippocampus. Therefore, our data can contribute to the understanding of the onset of early (childhood and juvenile/pre-pubertal phases) anxiety owing to exposure to a traumatic event during the gestation period.

Distinct binding and signaling activity of Acthar Gel compared to other melanocortin receptor agonists

Purpose To compare the binding and agonistic activity of Acthar® Gel and synthetic melanocortin receptor (MCR) agonists and examine how the activity of select agonists affects the in vivo production of corticosterone. Materials and Methods In vitro binding was determined using concentration-dependent displacement of the ligand [125I]Nle4, D-Phe7-α-melanocyte-stimulating hormone (α-MSH) on cells expressing MC1R, MC3R, MC4R, or MC5R. Functional activity was determined using a time-resolved fluorescence cyclic adenosine monophosphate (cAMP) assay in cells expressing MC1R, MC2R, MC3R, MC4R, or MC5R. In vivo corticosterone analyses were performed by measuring plasma corticosterone levels in Sprague Dawley rats. Results Acthar Gel and synthetic MCR agonists exhibited the highest binding at MC1R, lowest binding at MC5R, and moderate binding at MC3R and MC4R. Acthar Gel stimulated the production of cAMP in all 5 MCR-expressing cell lines, with MC2R displaying the lowest level of full agonist activity, 3-, 6.6-, and 10-fold lower than MC1R, MC3R, and MC4R, respectively. Acthar Gel was a partial agonist at MC5R. The synthetic MCR agonists induced full activity at all 5 MCRs, with the exception of α-MSH having no activity at MC2R. Acthar Gel treatment had less of an impact on in vivo production of corticosterone compared with synthetic ACTH1-24 depot. Conclusions Acthar Gel bound to and activated each MCR tested in this study, with partial agonist activity at MC5R and the lowest level of full agonist activity at MC2R, which distinguished it from synthetic MCR agonists. The minimal activity of Acthar Gel at MC2R corresponded to lower endogenous corticosteroid production.

Foraging behavior, contaminant exposure risk, and the stress response in wild California condors (Gymnogyps californianus)

Wild California condors (Gymnogyps californianus) are frequently exposed to lead via lead-based ammunition ingestion, and recent studies indicate significant exposure to organochlorines (e.g. dichlorodiphenyldichloroethylene (DDE) and polychlorinated biphenyls (PCBs)) for condors feeding on beach-cast marine mammals. We investigated the influence of contaminant exposure on condor glucocorticoid response through comparisons between wild and captive populations and identification of modifiers of glucocorticoid release in wild condors. We assessed the glucocorticoid response to routine trapping and handling events through measurement of plasma corticosterone and urate glucocorticoid metabolites (GCM). Comparison of peak urate GCM levels showed wild condors exhibited higher responses to handling-associated stressors (2300 ± 1400 ng/g dry wt, average ± SD, n = 27) than captive condors (910 ± 490 ng/g dry wt., n = 6, U = 28, p = 0.003). Multiple linear regression models and an information theoretic approach (AICc) identified several extrinsic variables (e.g., time captive in flight pen before sample collection) that were negatively associated with plasma corticosterone and urate GCM levels in wild condors, which explained ~25% of glucocorticoid variation. When accounting for these extrinsic variables we found that behavioral variables associated with increased lead and organochlorine exposure risk were positively associated with GCM levels, explaining an additional 15% of glucocorticoid variation among wild condors. Days absent from management area, a variable associated with reduced survival attributed to increased lead exposure risk, had a positive influence on plasma corticosterone levels (β = 53 ± 20 SE) and peak urate GCM levels (β = 1090 ± 586 SE). Years observed feeding on marine mammals, a variable positively associated with DDE and PCB exposure, positively influenced peak urate GCM (β = 1100 ± 520 SE) and the magnitude of GCM response (peak GCM - 1st urate GCM) (β = 1050 ± 500 SE). Our findings suggest that individual propensities for contaminant-associated foraging behaviors predict higher stress-induced glucocorticoid levels in wild condors, and that accounting for variables associated with trapping and handling is essential for assessing the impact of environmental stressors such as contaminants on the condor stress response. As an abnormal glucocorticoid response to stress is associated with reduced reproduction and survival in vertebrates, this work indicates the need for further investigations into the physiological impacts of sub-lethal contaminant exposures in scavenging species worldwide.

Bacopa monnieri alleviates aluminium chloride-induced anxiety by regulating plasma corticosterone level in Wistar rats.

Objectives Aluminium is present in food preparations, antacids and many medications. It causes neurodegeneration thereby resulting in a spectrum of neurological disorders such as dementia, Alzheimer's disease and anxiety. Bacopa monnieri (BM) is widely used in ayurvedic medicine to improve memory functions. Its anxiolytic property was investigated in this study by using elevated plus maze (EPM) and plasma corticosterone level. Methods Thirty rats were assigned into five groups. Control group received distilled water, and 0.5% tween 80, AlCl3 group received Aluminium Chloride (AlCl3), Protective groups (BM100+AlCl3 group and BM200+AlCl3 group) received AlCl3 and BM at two different doses, and the BM200 group received BM. The EPM experiment was performed at the end of the 4th week of oral administration of BM and AlCl3 followed by the measurement of plasma corticosterone. Results Oral administration of AlCl3 to rats increases the levels of anxiety as seen in a decrease in the percentage of entries into the open arms of EPM, an increase in grooming frequency and defecation index. However, the rats in the protective groups shown an increase in the percentage of open arm entries and rearing frequency, and decreased grooming frequency and defecation index. AlCl3 alone treated group showed a significant increase in the plasma corticosterone levels compared to the control group. Whereas the protective groups have shown a significant decrease in the plasma corticosterone levels than the AlCl3 alone treated group. Conclusions Hence the BM has potential role in reverting the anxiogenic effect of AlCl3 in the amygdala as it is evident from the plasma corticosterone levels and the EPM parameters of different groups under study.