Non-genomic effects of glucocorticoids in the neural system. Evidence, mechanisms and implications

Skin Anti-Inflammatory Potential with Reduced Side Effects of Novel Glucocorticoid Receptor Agonists

Glucocorticoids (GCs) are commonly used in the treatment of inflammatory skin diseases, although the balance between therapeutic benefits and side effects is still crucial in clinical practice. One of the major and well-known adverse effects of topical GCs is cutaneous atrophy, which seems to be related to the activation of the glucorticoid receptor (GR) genomic pathway. Dissociating anti-inflammatory activity from atrophogenicity represents an important goal to achieve, in order to avoid side effects on keratinocytes and fibroblasts, known target cells of GC action. To this end, we evaluated the biological activity and safety profile of two novel chemical compounds, DE.303 and KL.202, developed as non-transcriptionally acting GR ligands. In primary keratinocytes, both compounds demonstrated anti-inflammatory properties inhibiting NF-κB activity, downregulating inflammatory cytokine release and interfering with pivotal signaling pathways involved in the inflammatory process. Of note, these beneficial actions were not associated with GC-related atrophic effects: treatments of primary keratinocytes and fibroblasts with DE.303 and KL.202 did not induce, contrarily to dexamethasone-a known potent GC-alterations in extracellular matrix components and lipid synthesis, thus confirming their safety profile. These data provide the basis for evaluating these compounds as effective alternatives to the currently used GCs in managing inflammatory skin diseases.

Day-to-day coordination of the stress and reproductive axes: A continuous-time analysis of within-person testosterone and cortisol relationships in athletic and healthy men

Day-to-day coordination of the stress (i.e., hypothalamic-pituitary-adrenal [HPA]) and reproductive (i.e., hypothalamic-pituitary-gonadal [HPG]) axes is central to allostatic regulation, reproductive success, and survival. Reports of positive, within-person testosterone and cortisol relationships (or coupling) suggest cross-talk of a facilitative nature, but longitudinal evidence is scarce and has methodological and analytical limitations. To address this, we used a continuous-time (CT) model to investigate day-to-day, within-person coupling of testosterone and cortisol in two male cohorts. Salivary testosterone and cortisol fluctuations were monitored in 35 athletic men across two international tournaments (M = 19.3 tests) and in 41 healthy men during normal daily living (M = 27.9 tests). Bayesian CT analysis revealed a diminishing effect of each hormone on itself as time-interval length or lag increased. In both groups, cortisol had a negative lagged effect on testosterone that persisted for around three days. The cortisol effect on testosterone peaked after 0.71 and 0.51 days in athletic (standardized estimate = -0.13) and healthy men (standardized estimate = -0.11), respectively. Further estimates of non-lagged, contemporaneous correlations revealed positive testosterone and cortisol relationships (athlete r = 0.04, healthy r = 0.46). In summary, complex within-person HPA and HPG interplay emerged in two independent male cohorts. Specifically, a rising cortisol concentration was linked to a fall in testosterone concentration at later time points, but concurrently these hormones tended to rise and fall together. Our results suggest that inhibitory and facilitatory hormonal actions coexist on varying timescales, thereby expanding knowledge of HPG and HPA cross-talk in everyday life.

The relative speed of the glucocorticoid stress response varies independently of scope and is predicted by environmental variability and longevity across birds

The acute glucocorticoid response is a key mediator of the coordinated vertebrate response to unpredictable challenges. Rapid glucocorticoid increases initiate changes that allow animals to cope with stressors. The scope of the glucocorticoid response - defined here as the absolute increase in glucocorticoids - is associated with individual differences in performance and varies across species with environment and life history. In addition to varying in scope, responses can differ enormously in speed; however, relatively little is known about whether speed and absolute glucocorticoid levels covary, how selection shapes speed, or what aspects of speed are important. We used corticosterone samples collected at 5 time points from 1750 individuals of 60 species of birds to ask i) how the speed and scope of the glucocorticoid response covary and ii) whether variation in absolute or relative speed is predicted by environmental context or life history. Among species, faster absolute glucocorticoid responses were strongly associated with a larger scope. Despite this covariation, the relative speed of the glucocorticoid response (standardized within species) varied independently of absolute scope, suggesting that selection could operate on both features independently. Species with faster relative glucocorticoid responses lived in locations with more variable temperature and had shorter lifespans. Our results suggest that rapid changes associated with the speed of the glucocorticoid response, such as those occurring through non-genomic receptors, might be an important determinant of coping ability and we emphasize the need for studies designed to measure speed independently of absolute glucocorticoid levels.

Glucocorticoids and Aggression: A Tripartite Interaction

The effects of glucocorticoids on aggression can be conceptualized based on its mechanisms of action. These hormones can affect cell function non-genomically within minutes, primarily by affecting the cell membrane. Overall, such effects are activating and promote both metabolic preparations for the fight and aggressive behavior per se. Chronic increases in glucocorticoids activate genomic mechanisms and are depressing overall, including the inhibition of aggressive behavior. Finally, excessive stressors trigger epigenetic phenomena that have a large impact on brain programming and may also induce the reprogramming of neural functions. These induce qualitative changes in aggression that are deemed abnormal in animals, and psychopathological and criminal in humans. This review aims at deciphering the roles of glucocorticoids in aggression control by taking in view the three mechanisms of action often categorized as acute, chronic, and toxic stress based on the duration and the consequences of the stress response. It is argued that the tripartite way of influencing aggression can be recognized in all three animal, psychopathological, and criminal aggression and constitute a framework of mechanisms by which aggressive behavior adapts to short-term and log-term changes in the environment.

Dexamethasone attenuates the modulatory effect of the insular cortex on the baroreflex in anesthetized rat

The arterial baroreflex (BR) is an important neural mechanism for the stabilization of arterial pressure (AP). It is known that the insular cortex (IC) and other parts of the central autonomic network (CAN) are able to modulate the BR arc, altering baroreflex sensitivity (BRS). In addition, the sensitivity of the BR changes under the influence of hormones, in particular glucocorticoids (GC). It has been suggested that GC may influence BRS by altering the ability of the IC to modulate the BR. This hypothesis has been tested in experiments on rats anesthetized with urethane. It was found that microelectrostimulation of the visceral area in the left IC causes a short-term drop in AP, which is accompanied by bradycardia, and impairs BRS. The synthetic GC dexamethasone (DEX) did not significantly affect the magnitude of depressor responses but increased BRS and impaired the effect of IC stimulation on the BR. The results obtained confirm the hypothesis put forward and suggest that GC can attenuate the inhibitory effects of the IC on the BR arc, thereby enhancing the sensitivity of the BR.

Corticosterone in the ventral hippocampus differentially alters accumbal dopamine output in drug-naïve and amphetamine-withdrawn rats

Dysregulation in glucocorticoid stress and accumbal dopamine reward systems can alter reward salience to increase motivational drive in control conditions while contributing to relapse during drug withdrawal. Amphetamine withdrawal is associated with dysphoria and stress hypersensitivity that may be mediated, in part, by enhanced stress-induced corticosterone observed in the ventral hippocampus. Electrical stimulation of the ventral hippocampus enhances accumbal shell dopamine release, establishing a functional connection between these two regions. However, the effects of ventral hippocampal corticosterone on this system are unknown. To address this, a stress-relevant concentration of corticosterone (0.24ng/0.5 μL) or vehicle were infused into the ventral hippocampus of urethane-anesthetized adult male rats in control and amphetamine withdrawn conditions. Accumbal dopamine output was assessed with in vivo chronoamperometry. Corticosterone infused into the ventral hippocampus rapidly enhanced accumbal dopamine output in control conditions, but produced a biphasic reduction of accumbal dopamine output in amphetamine withdrawal. Selectively blocking glucocorticoid-, mineralocorticoid-, or cytosolic receptors prevented the effects of corticosterone. Overall, these results suggest that the ability of corticosterone to alter accumbal dopamine output requires cooperative activation of mineralocorticoid and glucocorticoid receptors in the cytosol, which is dysregulated during amphetamine withdrawal. These findings implicate ventral hippocampal corticosterone in playing an important role in driving neural systems involved in positive stress coping mechanisms in healthy conditions, whereas dysregulation of this system may contribute to relapse during withdrawal.

Cortisol rapidly increases baroreflex sensitivity of heart rate control, but does not affect cardiac modulation of startle

Cortisol, the final product of human HPA axis activation, rapidly modulates the cortical processing of afferent signals originating from the cardiovascular system. While peripheral effects have been excluded, it remains unclear whether this effect is mediated by cortical or subcortical (e.g. brainstem) CNS mechanisms. Cardiac modulation of startle (CMS) has been proposed as a method to reflect cardio-afferent signals at subcortical (potentially brainstem-) level. Using a single blind, randomized controlled design, the cortisol group (n = 16 volunteers) received 1 mg cortisol intravenously, while the control group (n = 16) received a placebo substance. The CMS procedure involved the assessment of eye blink responses to acoustic startle stimuli elicited at six different latencies to ECG-recorded R-waves (R + 0, 100, 200, 300, 400 and 500 ms). CMS was assessed at four measurement points: baseline, -16 min, +0 min, and +16 min relative to substance application. Baroreflex sensitivity (BRS) of heart rate (HR) control was measured non-invasively based on spontaneous beat-to-beat HR and systolic blood pressure changes. In the cortisol group, salivary cortisol concentration increased after IV cortisol administration, indicating effective distribution of the substance throughout the body. Furthermore, BRS increased in the cortisol group after cortisol infusion. There was no effect of cortisol on the CMS effect, however. These results suggest that low doses of cortisol do not affect baro-afferent signals, but central or efferent components of the arterial baroreflex circuit presumably via rapid, non-genomic mechanisms.

Polysaccharide-Rich Extract of Phragmites rhizome Attenuates Water Immersion Stress and Forced Swimming Fatigue in Rodent Animal Model

Our study aimed to investigate the effects of the polysaccharide-rich extract of Phragmites rhizoma (PEP) against water immersion restraint (WIR) stress and forced swimming-induced fatigue. Exposure to WIR stress significantly increased the ulcer index, bleeding score, the weight of the adrenal gland, blood glucose concentrations, total cholesterol, cortisol, and creatine kinase (CK). The weight of the spleen decreased significantly. In addition, myeloperoxidase (MPO) and thiobarbituric acid-reactive substance (TBARS) were significantly upregulated by WIR stress. The antioxidative factors such as glutathione (GSH) and superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in the stomach were decreased by WIR stress. Alterations induced by WIR stress were effectively reversed by pretreatment with PEP. The swimming endurance capacity of mice was significantly prolonged by the oral administration of PEP. Swimming-induced fatigue significantly reduced the body weight; however, the injection of PEP inhibited the decrease of body weight. The PEP-treated group had significantly lower CK levels in plasma, an indicator of muscle damage. These results indicated that PEP has anti-stress and anti-fatigue effects, which are mediated by suppressing the hyperactivation of the hypothalamus-pituitary-adrenal axis, and antagonism of the oxidative damages induced by WIR stress and prolonged swimming times.

Nongenomic glucocorticoid effects and their mechanisms of action in vertebrates

Glucocorticoids (GC) act on multiple organ systems to regulate a variety of physiological processes in vertebrates. Due to their immunosuppressive and anti-inflammatory actions, glucocorticoids are an attractive target for pharmaceutical development. Accordingly, they are one of the most widely prescribed classes of therapeutics. Through the classical mechanism of steroid action, glucocorticoids are thought to mainly affect gene transcription, both in a stimulatory and suppressive fashion, regulating de novo protein synthesis that subsequently leads to the physiological response. However, over the past three decades multiple lines of evidence demonstrate that glucocorticoids may work through rapid, nonclassical mechanisms that do not require alterations in gene transcription or translation. This review assimilates evidence across the vertebrate taxa on the diversity of nongenomic actions of glucocorticoids and the membrane-associated cellular mechanisms that may underlie rapid glucocorticoid responses to include potential binding sites characterized to date.

Intrathecal triamcinolone acetonide exerts anti-inflammatory effects on Lewis rat experimental autoimmune neuritis and direct anti-oxidative effects on Schwann cells

Background

Corticosteroids dominate in the treatment of chronic autoimmune neuropathies although long-term use is characterized by devastating side effects.

Methods

We introduce the intrathecal application of the synthetic steroid triamcinolone (TRIAM) as a novel therapeutic option in experimental autoimmune neuritis in Lewis rats

Results

After immunization with neuritogenic P2 peptide, we show a dose-dependent therapeutic effect of one intrathecal injection of 0.3 or 0.6 mg/kg TRIAM on clinical and electrophysiological parameters of neuritis with a lower degree of inflammatory infiltrates (T cells and macrophages) and demyelination in the sciatic nerve. In vitro studies in Schwann cell cultures showed an increased expression of IL-1 receptor antagonist and reduced expression of Toll-like receptor 4 after incubation with TRIAM as well as a protective effect of TRIAM against oxidative stress after H₂O₂ exposure.

Conclusion

Intrathecal TRIAM application could be a novel immunomodulatory and potentially neuroprotective option for autoimmune neuropathies with a direct effect on Schwann cells.

Basal testosterone's relationship with dictator game decision-making depends on cortisol reactivity to acute stress: A dual-hormone perspective on dominant behavior during resource allocation

The dual-hormone hypothesis proposes that testosterone's relationship with status-seeking behavior is moderated by cortisol. However, research testing this hypothesis has focused on basal cortisol; the potential moderating effect of the acute cortisol response to stress has been largely overlooked. The present research investigated the moderating role of cortisol responses to an acute stressor on basal testosterone's link with dominant, status-relevant decision-making. Also, given the multifaceted nature of the response to acute stress, cardiovascular and affective responses to the stressor were examined as alternative moderators of the testosterone-behavior relationship. Participants (N = 112; 56% female) were exposed to a social-evaluative stressor, and their stress responses were measured. Participants subsequently engaged in a one-shot dictator game, wherein they were asked to split money ($10) with a confederate counterpart. The amount of money participants decided to keep for themselves was treated as a metric of dominant status-seeking behavior. For individuals who demonstrated lower cortisol responses to the stressor, basal testosterone was positively associated with more dominant behavior (i.e., keeping more money for oneself), but for those who showed higher cortisol responses, the testosterone-behavior relationship was suppressed. Moreover, other aspects of the stress response (i.e., cardiovascular and affective responses) did not moderate the relationship between basal testosterone and dictator game behavior. These results provide unique support for the dual-hormone hypothesis using markers of stress-induced cortisol change. The findings also suggest that the antagonistic effects of stress on testosterone's role in motivating status-relevant behavior may be specific to cortisol's role in the acute stress response.

Fast Feedback Inhibition of Adrenocorticotropic Hormone Secretion by Endogenous Cortisol in Humans

BACKGROUND

Using high-frequency blood sampling, we demonstrate glucocorticoid fast feedback (FF) mediated by endogenous cortisol in 6 normal humans.

METHODS

We stimulated adrenocorticotropic hormone (ACTH) secretion by ovine corticotropin-releasing hormone (oCRH) with the experimental paradigm in which a high-frequency blood sampling was designed for plasma ACTH and cortisol determinations.

RESULTS

We saw previously unrecognized variability in the timing of key events such as onsets of ACTH and cortisol secretion, onset and offset of FF, and in FF duration. This variability mandated analyses referenced to case-wise event times rather than referenced simply to time since oCRH administration. The mean time of FF onset was 4.0 min (range 0-9; median 3) after cortisol secretion began, and the mean FF duration was 7.5 min (range 3-18; median 6.0). The FF effect was rate-sensitive and does not reflect level-sensitive cortisol feedback. In agreement with previous estimates using hydrocortisone infusions, the rate of rise of cortisol that triggered FF was approximately 44 nmol/L/min or 1.6 µg/dL/min. FF onset followed the trigger cortisol slope with an average lag of 1 min (range 0-3; median 0). Unexpectedly, this trigger cortisol slope quickly declined within the FF period.

CONCLUSIONS

This experimental design may enable new physiological studies of human FF that is mediated by endogenous cortisol, including mechanisms, reproducibility, and generalizability to other activating stimuli.

Transgenerational hypocortisolism and behavioral disruption are induced by the antidepressant fluoxetine in male zebrafish Danio rerio

The global prevalence of depression is high during childbearing. Due to the associated risks to the mother and baby, the selective serotonin reuptake inhibitor fluoxetine (FLX) is often the first line of treatment. Given that FLX readily crosses the placenta, a fetus may be susceptible to the disruptive effects of FLX during this highly plastic stage of development. Here, we demonstrate that a 6-day FLX exposure to a fetus-relevant concentration at a critical developmental stage suppresses cortisol levels in the adult zebrafish (F₀). This effect persists for three consecutive generations in the unexposed descendants (F₁ to F₃) without diminution and is more pronounced in males. We also show that the in vivo cortisol response of the interrenal (fish "adrenal") to an i.p. injection of adrenocorticotropic hormone was also reduced in the males from the F₀ and F₃ FLX lineages. Transcriptomic profiling of the whole kidney containing the interrenal cells revealed that early FLX exposure significantly modified numerous pathways closely associated with cortisol synthesis in the male adults from the F₀ and F₃ generations. We also show that the low cortisol levels are linked to significantly reduced exploratory behaviors in adult males from the F₀ to F₂ FLX lineages. This may be a cause for concern given the high prescription rates of FLX to pregnant women and the potential long-term negative impacts on humans exposed to these therapeutic drugs.

Corticosterone rapidly improves the endurance of high-intensity exercise (swimming) via nongenomic mechanisms in mice

BACKGROUND

Glucocorticoids (GCs) take a pivotal role during the stress response. Some clinical studies suggest short-term GCs intake improves exercise endurance. However, whether the rapid nongenomic effects of GCs are involved in acute exercise is still unknown. Here, we aimed to reveal the potential nongenomic effects of GCs in skeletal muscle of mice during exercise.

METHODS

Adrenalectomized mice subjected to a weight-loaded forced swim were used for detecting the changes of time to exhaustion. Corticosterone (CORT) and other drugs were injected via the coccygeal vein before swimming. After exhaustion, the injury of skeletal muscle, nitric oxide generation, blood glucose and lactic acid were determined.

RESULTS

The results demonstrated that CORT rapidly extended the time to exhaustion within 30 min (~30%), which could not be abolished by glucocorticoid receptor antagonist RU486. Pretreatment with the nitric oxide synthesis inhibitor L-NAME prior to CORT administration further increased exercise tolerance compared to the increase caused by CORT alone. Moreover, CORT contributed to protecting skeletal muscle from injury and maintaining blood glucose.

CONCLUSIONS

Considered together, our results suggest that GCs rapidly improve exercise tolerance via its nongenomic mechanism, which is associated with the inhibition of nitric oxide generation. Pretreatment of GCs may be helpful to enhance exercise tolerance during acute exercise.

Glucocorticoid hormones are both a major circadian signal and major stress signal: How this shared signal contributes to a dynamic relationship between the circadian and stress systems

Glucocorticoid hormones are a powerful mammalian systemic hormonal signal that exerts regulatory effects on almost every cell and system of the body. Glucocorticoids act in a circadian and stress-directed manner to aid in adaptation to an ever-changing environment. Circadian glucocorticoid secretion provides for a daily waxing and waning influence on target cell function. In addition, the daily circadian peak of glucocorticoid secretion serves as a timing signal that helps entrain intrinsic molecular clock phase in tissue cells distributed throughout the body. Stress-induced glucocorticoid secretion also modulates the state of these same cells in response to both physiological and psychological stressors. We review the strong functional interrelationships between glucocorticoids and the circadian system, and discuss how these interactions optimize the appropriate cellular and systems response to stress throughout the day. We also discuss clinical implications of this dual aspect of glucocorticoid signaling, especially for conditions of circadian and HPA axis dysregulation.

Cellular Mechanisms of Cortisol-Induced Changes in Mauthner-Cell Excitability in the Startle Circuit of Goldfish

Predator pressure and olfactory cues (alarm substance) have been shown to modulate Mauthner cell (M-cell) initiated startle escape responses (C-starts) in teleost fish. The regulation of such adaptive responses to potential threats is thought to involve the release of steroid hormones such as cortisol. However, the mechanism by which cortisol may regulate M-cell excitability is not known. Here, we used intrasomatic, in vivo recordings to elucidate the acute effects of cortisol on M-cell membrane properties and sound evoked post-synaptic potentials (PSPs). Cortisol tonically decreased threshold current in the M-cell within 10 min before trending towards baseline excitability over an hour later, which may indicate the involvement of non-genomic mechanisms. Consistently, current ramp injection experiments showed that cortisol increased M-cell input resistance in the depolarizing membrane, i.e., by a voltage-dependent postsynaptic mechanism. Cortisol also increases the magnitude of sound-evoked M-cell PSPs by reducing the efficacy of local feedforward inhibition (FFI). Interestingly, another pre-synaptic inhibitory network mediating prepulse inhibition (PPI) remained unaffected. Together, our results suggest that cortisol rapidly increases M-cell excitability via a post-synaptic effector mechanism, likely a chloride conductance, which, in combination with its dampening effect on FFI, will modulate information processing to reach threshold. Given the central role of the M-cell in initiating startle, these results are consistent with a role of cortisol in mediating the expression of a vital behavior.

Signaling Cascade Involved in Rapid Stimulation of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) by Dexamethasone

Impairment of mucociliary clearance with reduced airway fluid secretion leads to chronically inflamed airways. Cystic fibrosis transmembrane conductance regulator (CFTR) is crucially involved in airway fluid secretion and dexamethasone (dexa) has previously been shown to elevate CFTR activity in airway epithelial cells. However, the pathway by which dexa increases CFTR activity is largely unknown. We aimed to determine whether the increase of CFTR activity by dexa is achieved by non-genomic signaling and hypothesized that the phosphoinositide 3-kinase (PI3K) pathway is involved in CFTR stimulation. Primary rat airway epithelial cells and human bronchial submucosal gland-derived Calu-3 cells were analyzed in Ussing chambers and kinase activation was determined by Western blots. Results demonstrated a critical involvement of PI3K and protein kinase B (AKT) signaling in the dexa-induced increase of CFTR activity, while serum and glucocorticoid dependent kinase 1 (SGK1) activity was not essential. We further demonstrated a reduced neural precursor cell expressed, developmentally downregulated 4-like (NEDD4L) ubiquitin E3 ligase activity induced by dexa, possibly responsible for the elevated CFTR activity. Finally, increases of CFTR activity by dexa were demonstrated within 30 min accompanied by rapid activation of AKT. In conclusion, dexa induces a rapid stimulation of CFTR activity which depends on PI3K/AKT signaling in airway epithelial cells. Glucocorticoids might thus represent, in addition to their immunomodulatory actions, a therapeutic strategy to rapidly increase airway fluid secretion.

Effects of the combination of metyrapone and oxazepam on cocaine-induced increases in corticosterone in the medial prefrontal cortex and nucleus accumbens

We have previously demonstrated that a combination of drugs (i.e., metyrapone and oxazepam) known to attenuate HPA-axis activity effectively decreases cocaine self-administration and cue reactivity in rats. However, we did not find changes in plasma corticosterone that matched the behavioral effects we observed, indicating that a different mechanism of action must be involved. Therefore, we hypothesized that the combination of metyrapone and oxazepam attenuates cocaine taking and seeking by decreasing cocaine-induced increases in corticosterone in the brain. Male rats were implanted with guide cannulae targeting the medial prefrontal cortex or nucleus accumbens. After the rats recovered from surgery, the microdialysis session was conducted. Rats were housed in the experimental chamber and the dialysis probes inserted into the guide cannulae the night before the session. The following day, dialysate samples were collected over a five-hour session. Baseline samples were collected for the first two hours, every 20min. Samples were then collected following administration of cocaine (15mg/kg, ip). Before injections of cocaine, rats were pretreated with either vehicle or the combination of metyrapone (50mg/kg, ip) and oxazepam (10mg/kg, ip). The administration of cocaine resulted in an increase in corticosterone in the medial prefrontal cortex following vehicle pretreatment, which was not observed in the nucleus accumbens. This cocaine-induced increase in corticosterone was attenuated by metyrapone/oxazepam. Reducing cocaine-induced increases in corticosterone in the medial prefrontal cortex might represent a novel mechanism through which the combination of metyrapone/oxazepam produces its behavioral effects.

Rapid permissive action of dexamethasone on the regulation of blood pressure in a rat model of septic shock

Glucocorticoids (GCs) play a vital role in the regulation of blood pressure by their permissive effects in potentiating vasoactive responses to catecholamines through glucocorticoid receptors. GCs achieve this function by controlling vascular smooth muscle tone. Clinically, low to moderate doses of GCs are generally used in the treatment of septic shock in recent years. GCs are now known to have both genomic and non-genomic effects. While genomic effects of GCs were well studied, few non-genomic effects were reported, much less the non-genomic mechanisms. One of the most important characters of their non-genomic effects is short latency. The aim of this study was to determine whether GCs can rapidly regulate blood pressure by their permissive action on norepinephrine (NE). Adrenalectomized rats were subjected to cecal ligation and puncture to induce septic shock. The septic rats displayed a significant decrease in the blood pressure response to NE. Dexamethasone (DEX) rapidly restores this hyporeactivity to NE in adrenalectomized septic rats. Further studies showed that DEX potentiates the NE-induced shrinkage and actin cytoskeleton rearrangement of single cell from mesenteric arteries in a short time. These findings suggest that GCs probably exert their permissive actions on the pressure response to NE through rapid non-genomic mechanisms. In this article, we found that as an adjunctive therapy for septic shock, the use of GCs may involve a rapid permissive action, and non-genomic effects of GCs may be involved in these processes.

MicroRNAs 29b and 181a down-regulate the expression of the norepinephrine transporter and glucocorticoid receptors in PC12 cells

MicroRNAs are short non-coding RNAs that provide global regulation of gene expression at the post-transcriptional level. Such regulation has been found to play a role in stress-induced epigenetic responses in the brain. The norepinephrine transporter (NET) and glucocorticoid receptors are closely related to the homeostatic integration and regulation after stress. Our previous studies demonstrated that NET mRNA and protein levels in rats are regulated by chronic stress and by administration of corticosterone, which is mediated through glucocorticoid receptors. Whether miRNAs are intermediaries in the regulation of these proteins remains to be elucidated. This study was undertaken to determine possible regulatory effects of miRNAs on the expression of NET and glucocorticoid receptors in the noradrenergic neuronal cell line. Using computational target prediction, we identified several candidate miRNAs potentially targeting NET and glucocorticoid receptors. Western blot results showed that over-expression of miR-181a and miR-29b significantly repressed protein levels of NET, which is accompanied by a reduced [³ H] norepinephrine uptake, and glucocorticoid receptors in PC12 cells. Luciferase reporter assays verified that both miR-181a and miR-29b bind the 3'UTR of mRNA of NET and glucocorticoid receptors. Furthermore, exposure of PC12 cells to corticosterone markedly reduced the endogenous levels of miR-29b, which was not reversed by the application of glucocorticoid receptor antagonist mifepristone. These observations indicate that miR-181a and miR-29b can function as the negative regulators of NET and glucocorticoid receptor translation in vitro. This regulatory effect may be related to stress-induced up-regulation of the noradrenergic phenotype, a phenomenon observed in stress models and depressive patients. This study demonstrated that miR-29b and miR-181a, two short non-coding RNAs that provide global regulation of gene expression, markedly repressed protein levels of norepinephrine (NE) transporter and glucocorticoid receptor (GR), as well as NE uptake by binding the 3'UTR of their mRNAs in PC12 cells. Also, exposure of cells to corticosterone significantly reduced miR-29b levels through a GR-independent way.

Testosterone, cortisol, and human competition

Testosterone and cortisol figure prominently in the research literature having to do with human competition. In this review, we track the history of this literature, concentrating particularly on major theoretical and empirical contributions, and provide commentary on what we see as important unresolved issues. In men and women, athletic competition is typically associated with an increase in testosterone (T) and cortisol (C). Hormone changes in response to non-athletic competition are less predictable. Person (e.g., power motivation, mood, aggressiveness, social anxiety, sex, and baseline levels of T and C) and context (e.g., whether a competition is won or lost, the closeness of the competition, whether the outcome is perceived as being influenced by ability vs. chance, provocations) factors can influence hormone responses to competition. From early on, studies pointed to a positive relationship between T and dominance motivation/status striving. Recent research, however, suggests that this relationship only holds for individuals with low levels of C - this is the core idea of the dual-hormone hypothesis, and it is certain that the broadest applications of the hypothesis have not yet been realized. Individuals differ with respect to the extent to which they embrace competition, but the hormonal correlates of competitiveness remain largely unexplored. Although rapid increases in both T and C associated with competition are likely adaptive, we still know very little about the psychological benefits of these hormonal changes. Administration studies have and will continue to contribute to this inquiry. We close with a discussion of what, we think, are important methodological and mechanistic issues for future research.

Effects of basal and acute cortisol on cognitive flexibility in an emotional task switching paradigm in men

The stress hormone cortisol is assumed to influence cognitive functions. While cortisol-induced alterations of declarative memory in particular are well-investigated, considerably less is known about its influence on executive functions. Moreover, most research has been focused on slow effects, and rapid non-genomic effects have not been studied. The present study sought to investigate the impact of acute cortisol administration as well as basal cortisol levels on cognitive flexibility, a core executive function, within the non-genomic time frame. Thirty-eight healthy male participants were randomly assigned to intravenously receive either cortisol or a placebo before performing a task switching paradigm with happy and angry faces as stimuli. Cortisol levels were measured at six points during the experiment. Additionally, before the experiment, basal cortisol measures for the cortisol awakening response were collected on three consecutive weekdays immediately following awakening and 30, 45, and 60min after. First and foremost, results showed a pronounced impact of acute and basal cortisol on reaction time switch costs, particularly for angry faces. In the placebo group, low basal cortisol was associated with minimal switch costs, whereas high basal cortisol was related to maximal switch costs. In contrast, after cortisol injection, basal cortisol levels showed no impact. These results show that cognitive flexibility-enhancing effects of acute cortisol administration are only seen in men with high basal cortisol levels. This result supports the context dependency of cortisol administration and shows the relevance of taking basal cortisol levels into account.

Stress and the social brain: behavioural effects and neurobiological mechanisms

Stress often affects our social lives. When undergoing high-level or persistent stress, individuals frequently retract from social interactions and become irritable and hostile. Predisposition to antisocial behaviours - including social detachment and violence - is also modulated by early life adversity; however, the effects of early life stress depend on the timing of exposure and genetic factors. Research in animals and humans has revealed some of the structural, functional and molecular changes in the brain that underlie the effects of stress on social behaviour. Findings in this emerging field will have implications both for the clinic and for society.

Glucocorticoid Mechanisms of Functional Connectivity Changes in Stress-Related Neuropsychiatric Disorders

Stress—especially chronic, uncontrollable stress—is an important risk factor for many neuropsychiatric disorders. The underlying mechanisms are complex and multifactorial, but they involve correlated changes in structural and functional measures of neuronal connectivity within cortical microcircuits and across neuroanatomically distributed brain networks. Here, we review evidence from animal models and human neuroimaging studies implicating stress-associated changes in functional connectivity in the pathogenesis of PTSD, depression, and other neuropsychiatric conditions. Changes in fMRI measures of corticocortical connectivity across distributed networks may be caused by specific structural alterations that have been observed in the prefrontal cortex, hippocampus, and other vulnerable brain regions. These effects are mediated in part by glucocorticoids, which are released from the adrenal gland in response to a stressor and also oscillate in synchrony with diurnal rhythms. Recent work indicates that circadian glucocorticoid oscillations act to balance synapse formation and pruning after learning and during development, and chronic stress disrupts this balance. We conclude by considering how disrupted glucocorticoid oscillations may contribute to the pathophysiology of depression and PTSD in vulnerable individuals, and how circadian rhythm disturbances may affect non-psychiatric populations, including frequent travelers, shift workers, and patients undergoing treatment for autoimmune disorders.

Amplification of neuromuscular transmission by methylprednisolone involves activation of presynaptic facilitatory adenosine A2A receptors and redistribution of synaptic vesicles

The mechanisms underlying improvement of neuromuscular transmission deficits by glucocorticoids are still a matter of debate despite these compounds have been used for decades in the treatment of autoimmune myasthenic syndromes. Besides their immunosuppressive action, corticosteroids may directly facilitate transmitter release during high-frequency motor nerve activity. This effect coincides with the predominant adenosine A2A receptor tonus, which coordinates the interplay with other receptors (e.g. muscarinic) on motor nerve endings to sustain acetylcholine (ACh) release that is required to overcome tetanic neuromuscular depression in myasthenics. Using myographic recordings, measurements of evoked [(3)H]ACh release and real-time video microscopy with the FM4-64 fluorescent dye, results show that tonic activation of facilitatory A2A receptors by endogenous adenosine accumulated during 50 Hz bursts delivered to the rat phrenic nerve is essential for methylprednisolone (0.3 mM)-induced transmitter release facilitation, because its effect was prevented by the A2A receptor antagonist, ZM 241385 (10 nM). Concurrent activation of the positive feedback loop operated by pirenzepine-sensitive muscarinic M1 autoreceptors may also play a role, whereas the corticosteroid action is restrained by the activation of co-expressed inhibitory M2 and A1 receptors blocked by methoctramine (0.1 μM) and DPCPX (2.5 nM), respectively. Inhibition of FM4-64 loading (endocytosis) by methylprednisolone following a brief tetanic stimulus (50 Hz for 5 s) suggests that it may negatively modulate synaptic vesicle turnover, thus increasing the release probability of newly recycled vesicles. Interestingly, bulk endocytosis was rehabilitated when methylprednisolone was co-applied with ZM241385. Data suggest that amplification of neuromuscular transmission by methylprednisolone may involve activation of presynaptic facilitatory adenosine A2A receptors by endogenous adenosine leading to synaptic vesicle redistribution.

The influence of aripiprazole, olanzapine and enriched environment on depressant-like behavior, spatial memory dysfunction and hippocampal level of BDNF in prenatally stressed rats

BACKGROUND

Cognitive function deficits caused by impaired neurogenesis of the brain structures are considered an important pathogenic factor in many neurological and mental diseases such as schizophrenia and depression. The aim of the study was to determine the effect of the enriched environment on cognitive functions and antidepressant-like effect of prenatally stressed rats. It was important to determine the effect of aripiprazole ARI and olanzapine OLA and clarify whether the enriched environment induces increases in brain derived neurothropic factor BDNF in the hippocampus in the prenatally stressed group (PSG) and non-stressed control group (NSCG).

METHODS

The effect of chronic stress applied to pregnant rats and the use of ARI (1.5mg/kg ip) and OLA (0.5mg/kg ip) were studied in the Morris water maze (MWM), Porsolt Forced swimming test (FST) and by determining BDNF levels.

RESULTS

The results indicated that enriched environment improved spatial memory and also had an antidepressant-like effect on prenatally stressed rats. ARI improved spatial memory both in the NSCG and PSG, while OLA caused memory improvement only in the PSG. Moreover, both ARI and OLA reduced immobility time in the NSCG and PSG. In PSG rats, BDNF decrease was observed while chronic treatment with ARI and OLA increased BDNF levels in the hippocampi of NSCG and PSG rats.

CONCLUSION

It has been confirmed that enriched environment improves spatial memory of animals, removes symptoms of stress, has an antidepressant-like effect, and that new neuroleptics, such as ARI or OLA, modulate these functions (increased BDNF).

Role of corticosteroid binding globulin in the fast actions of glucocorticoids on the brain

Corticosteroid binding globulin (CBG) is a glycoprotein synthesized in liver and secreted in the blood where it binds with a high affinity but low capacity glucocorticoid hormones, cortisol in humans and corticosterone in laboratory rodents. In mammals, 95% of circulating glucocorticoids are bound to either CBG (80%) or albumin (15%) and only the 5% free fraction is able to enter the brain. During stress, the concentration of glucocorticoids rises significantly and the free fraction increases even more because CBG becomes saturated. However, glucocorticoids unbound to CBG are cleared from the blood more quickly. Our studies on mice totally devoid of CBG (Cbg k.o.) showed that during stress these mutant mice display a lower rise of glucocorticoids than the wild-type controls associated with altered emotional reactivity. These data suggested that CBG played a role in the fast actions of glucocorticoids on behavior. Further analyses demonstrated that stress-induced memory retrieval impairment, an example of the fast action of glucocorticoids on the brain is abolished in the Cbg k.o. mice. This effect of stress on memory retrieval could be restored in the Cbg k.o. mice by infusing corticosterone directly in the hippocampus. The mechanisms explaining these effects involved an increased clearance but no difference in corticosterone production. Thus, CBG seems to have an important role in maintaining in blood a glucocorticoid pool that will be able to access the brain for the fast effects of glucocorticoids.

Four-month-old infants' long-term memory for a stressful social event

Infants clearly show an early capacity for memory for inanimate emotionally neutral events. However, their memory for social stress events has received far less attention. The aim of the study was to investigate infants' memory for a stressful social event (i.e., maternal unresponsiveness during the Still-Face paradigm) after a 15-day recall interval using changes in behavioral responses and salivary post-stress cortisol reactivity as measures of memory. Thirty-seven infants were exposed to social stress two times (experimental condition); the first time when they were 4 months of age and second exposure after a 2 week interval. Infants in the control condition (N = 37) were exposed to social stress just one time, at the age corresponding to the second exposure for infants in the experimental condition (4 months plus 2 weeks). Given individual differences in infants' reactivity to social stress events, we categorized infants as increasers or decreasers based on their cortisol reactivity after their initial exposure to the stress of the maternal still-face. Infants in the experimental condition, both increasers and decreasers, showed a significant change in cortisol response after the second exposure to the maternal still-face, though change was different for each reactivity group. In contrast, age-matched infants with no prior exposure to the maternal still-face showed similar post-stress cortisol reactivity to the reactivity of the experimental infants at their first exposure. There were no behavioral differences between increasers and decreasers during the Still-Face paradigm and exposures to the social stress. Thus differences between the experimental and control groups' post-stress cortisol reactivity was associated with the experimental group having previous experience with the social stress. These findings indicate long-term memory for social stress in infants as young as 4 months of age.

Prenatal corticosteroids modify glutamatergic and GABAergic synapse genomic fabric: insights from a novel animal model of infantile spasms

Prenatal exposure to corticosteroids has long-term postnatal somatic and neurodevelopmental consequences. Animal studies indicate that corticosteroid exposure-associated alterations in the nervous system include hypothalamic function. Infants with infantile spasms, a devastating epileptic syndrome of infancy with characteristic spastic seizures, chaotic irregular waves on interictal electroencephalogram (hypsarhythmia) and mental deterioration, have decreased concentrations of adrenocorticotrophic hormone (ACTH) and cortisol in cerebrospinal fluid, strongly suggesting hypothalamic dysfunction. We have exploited this feature to develop a model of human infantile spasms by using repeated prenatal exposure to betamethasone and a postnatal trigger of developmentally relevant spasms with NMDA. The spasms triggered in prenatally primed rats are more severe compared to prenatally saline-injected ones and respond to ACTH, a treatment of choice for infantile spasms in humans. Using autoradiography and immunohistochemistry, we have identified a link between the spasms in our model and the hypothalamus, especially the arcuate nucleus. Transcriptomic analysis of the arcuate nucleus after prenatal priming with betamethasone but before trigger of spasms indicates that prenatal betamethasone exposure down-regulates genes encoding several important proteins participating in glutamatergic and GABAergic transmission. Interestingly, there were significant sex-specific alterations after prenatal betamethasone in synapse-related gene expression but no such sex differences were found in prenatally saline-injected controls. A pairwise relevance analysis revealed that, although the synapse gene expression in controls was independent of sex, these genes form topologically distinct gene fabrics in males and females and these fabrics are altered by betamethasone in a sex-specific manner. These findings may explain the sex differences with respect to both normal behaviour and the occurrence and severity of infantile spasms. Changes in transcript expression and their coordination may contribute to a molecular substrate of permanent neurodevelopmental changes (including infantile spasms) found after prenatal exposure to corticosteroids.

Resting state functional MRI connectivity predicts hypothalamus-pituitary-axis status in healthy males

Homeostasis of the human stress response system is critically maintained by a hierarchical system of neural and endocrine elements for which intact negative feedback is important to prevent maladaptation towards stress. Such feedback is efficiently probed by the established combined dexamethasone-suppression/corticotropin-releasing hormone stimulation (dex/CRH) test. Here we investigate which suprahypothalamic networks might modulate the response assessed by this neuroendocrine test. Combined resting state fMRI (rs-fMRI)/EEG was acquired in 20 healthy male volunteers along with dex/CRH profiles obtained on a different day outside the scanner. Seed-based network analysis and inter-seed cross correlation analysis for selected atlas-based limbic, paralimbic and medial prefrontal cortex seeds were correlated with stimulated cortisol and adrenocorticotropin hormone (ACTH) concentrations. Lower connectivity between a left hippocampus-based network and the right hippocampus significantly predicted stimulated cortisol concentration (R(2)=0.70, corrected pcluster=0.001). Six further significantly negative correlations were detected mainly in the left anterior cingulate cortex (ACC) and the medial prefrontal cortex (mPFC). The strongest positive correlation with stimulated hormone concentration was detected for the left subcallosal ACC (ACTH, R(2)=0.57, corrected pcluster=0.009). Inter-seed connectivity mainly pointed to hippocampal/amygdala interactions as correlates of the dex/CRH response. In conclusion, resting state functional connectivity patterns of limbic, particularly hippocampal, as well as cingulate and medial prefrontal areas can explain some of the variance of the dex/CRH test in healthy subjects. Functional connectivity analysis can be considered useful to study supra-hypothalamic control systems of the HPA axis.

Rapid cortisol signaling in response to acute stress involves changes in plasma membrane order in rainbow trout liver

The activation of genomic signaling in response to stressor-mediated cortisol elevation has been studied extensively in teleosts. However, very little is known about the rapid signaling events elicited by this steroid. We tested the hypothesis that cortisol modulates key stress-related signaling pathways in response to an acute stressor in fish liver. To this end, we investigated the effect of an acute stressor on biophysical properties of plasma membrane and on stressor-related protein phosphorylation in rainbow trout (Oncorhynchus mykiss) liver. A role for cortisol in modulating the acute cellular stress response was ascertained by blocking the stressor-induced elevation of this steroid by metyrapone. The acute stressor exposure increased plasma cortisol levels and liver membrane fluidity (measured by anisotropy of 1,6-diphenyl-1,3,5-hexatriene), but these responses were abolished by metyrapone. Atomic force microscopy further confirmed biophysical alterations in liver plasma membrane in response to stress, including changes in membrane domain topography. The changes in membrane order did not correspond to any changes in membrane fatty acid components after stress, suggesting that changes in membrane structure may be associated with cortisol incorporation into the lipid bilayer. Plasma cortisol elevation poststress correlated positively with activation of intracellular stress signaling pathways, including increased phosphorylation of extracellular signal-related kinases as well as several putative PKA and PKC but not Akt substrate proteins. Together, our results indicate that stressor-induced elevation of plasma cortisol level is associated with alterations in plasma membrane fluidity and rapid activation of stress-related signaling pathways in trout liver.

Acute and lasting effects of single mineralocorticoid antagonism on offensive aggressive behaviour in rats

Aggression is a major component of territorial behaviour. However, different mechanisms evolved to fulfil the defence function while reducing the cost derived from agonistic interactions, as a differential response to the same stimulus, depending on the outcome of past conflicts - priming, which makes the aggressive response adaptable. Aggressive behaviour is facilitated by the stress response, so, we tested the effect of a single injection of a mineralocorticoid antagonist (spironolactone) on the escalation of territorial aggression in a resident-intruder paradigm, and its modulation by social stimulus. We used naïve Wild Type Groningen - WTG - rats as residents, and naïve and previously defeated Wistar rats as intruders. The first encounter was 1h after the injection, and then repeated in 3 consecutive days. When WTG rats were confronted with naïve Wistar rats, single injections of spironolactone completely abolished the attack behaviour in the short term while enhancing it in the long term. When we used defeated Wistar rats, the spironolactone effect was not as great. The short-term reduction in aggressive behaviour was attributable to the blockade of mineralocorticoid receptors during the first encounters, while the enhancement in aggressive behaviour in the long term was suggested to be related to the imbalance between mineralocorticoid and glucocorticoid receptors during the stress response associated to the encounters.

Inhaled corticosteroids inhibit substance P receptor expression in asthmatic rat airway smooth muscle cells

Background

Neurokinins (NKs) participate in asthmatic airway inflammation, but the effects of NKs on airway smooth muscle cells (ASMCs) and those of corticosteroids on NKs are unknown.

Methods

To investigate the effect of budesonide on substance P (NK-1) receptor (NK-1R) expression in the lung and ASMCs, 45 Wistar rats were randomly divided into three groups: control, asthmatic, and budesonide treatment. Aerosolized ovalbumin was used to generate the asthmatic rat model, and budesonide was administered after ovalbumin inhalation. On day 21, bronchial responsiveness tests, bronchoalveolar lavage, and cell counting were conducted. NK-1R protein expression in the lung was investigated by immunohistochemistry and image analysis. Primary rat ASMC cultures were established, and purified ASMCs of the fourth passage were collected for mRNA and protein studies via real-time RT-PCR, immunocytochemistry, and image analysis.

Results

NK-1R mRNA and protein expression in the budesonide treatment group rat’s lung and ASMCs were less than that in the asthmatic group but greater than that in the control group.

Conclusions

NK-1R is involved in the pathogenesis of asthma and that budesonide may downregulate the expression of NK-1R in the ASMCs and airways of asthmatic rats, which may alleviate neurogenic airway inflammation.

Stress-induced memory retrieval impairments: different time-course involvement of corticosterone and glucocorticoid receptors in dorsal and ventral hippocampus

The present study was aimed at determining the relative contribution of the dorsal (DH) and ventral (VH) hippocampus in stress-induced memory retrieval impairments. Thus, we studied the temporal involvement of corticosterone and its receptors, i.e. mineralocorticoid (MR) and glucocorticoid (GR) in the DH and VH, in relation with the time-course evolution of stress-induced memory retrieval impairments. In a first experiment, double microdialysis allowed showing on the same animal that an acute stress (electric footshocks) induced an earlier corticosterone rise in the DH (15-60 min post-stress) and then in the VH (90-105 min post-stress). The return to baseline was faster in the DH (105 min) than in the VH (120 min). Memory deficits assessed by delayed alternation occurred at 15-, 60-, and 105-min delays after stress and were closely related to the kinetic of corticosterone rises within the DH and VH. In a second experiment, the GR antagonist RU-38486 and the MR antagonist RU-28318 were administered in the DH or VH 15 min before stress. RU-38486 restored memory at 60 but not at 105 min post-stress delays in the DH, whereas the opposite pattern was observed in the VH. By contrast, RU-28318 had no effect on memory impairments at both the 60- and 105-min post-stress delays, showing that MR receptors are not involved at these delays. However, RU-28318 administered in the DH restored memory when administered at a shorter post-stress delay (15 min). Overall, our data are first to evidence that stress induces a functional switch from the DH to VH via different corticosterone time-course evolutions in these areas and the sequential GR receptors involvement in the DH and then in the VH, as regards the persistence of stress-induced memory retrieval deficits over time.

Detection of the acute effects of hydrocortisone in the hippocampus using pharmacological fMRI

Impaired hippocampal function is believed to be important in the pathogenesis of depression. The hippocampus contains a high concentration of both mineralocorticoid (MR) and glucocorticoid receptors (GR), and the experimental administration of corticosteroids has been reported to mimic memory impairments seen in depression. Using pharmacological functional magnetic resonance imaging (phMRI) we investigated whether hippocampal function is altered after acute administration of hydrocortisone. Changes in BOLD signal following infusion of 100mg hydrocortisone given as a rapid intravenous bolus were measured in 14 healthy volunteers in a within-subject placebo-controlled crossover design. Subsequently, subjects completed an n-back task during an fMRI scan. Hydrocortisone infusion caused a significant, time-dependent increase in fMRI BOLD signal in hippocampus reaching a maximal effect at 11-19min. The n-back task increased BOLD signal in prefrontal and parietal cortical areas and decreased it in the hippocampus. After hydrocortisone the left hippocampal decrease in BOLD signal was attenuated with the magnitude of attenuation correlating with the increase seen after hydrocortisone infusion. No difference in behavioural task performance was observed. The results suggest acute hydrocortisone has rapid direct and modulatory influences on hippocampal function, probably acting through non-genomic GR or MR signalling. Hydrocortisone infusion phMRI may be a useful tool to investigate hippocampal corticosteroid receptor function in depression.

Dynamically changing effects of corticosteroids on human hippocampal and prefrontal processing

Stress has a powerful impact on memory. Corticosteroids, released in response to stress, are thought to mediate, at least in part, these effects by affecting neuronal plasticity in brain regions involved in memory formation, including the hippocampus and prefrontal cortex. Animal studies have delineated aspects of the underlying physiological mechanisms, revealing rapid, nongenomic effects facilitating synaptic plasticity, followed several hours later by a gene-mediated suppression of this plasticity. Here, we tested the hypothesis that corticosteroids would also rapidly upregulate and slowly downregulate brain regions critical for episodic memory formation in humans. To target rapid and slow effects of corticosteroids on neural processing associated with memory formation, we investigated 18 young, healthy men who received 20 mg hydrocortisone either 30 or 180 min before a memory encoding task in a double-blind, placebo-controlled, counter-balanced, crossover design. We used functional MRI to measure neural responses during these memory encoding sessions, which were separated by a month. Results revealed that corticosteroids' slow effects reduced both prefrontal and hippocampal responses, while no significant rapid actions of corticosteroids were observed. Thereby, this study provides initial evidence for dynamically changing corticosteroid effects on brain regions involved in memory formation in humans.

Dose-dependent effects of hydrocortisone infusion on autobiographical memory recall

The glucocorticoid hormone cortisol has been shown to impair episodic memory performance. The present study examined the effect of two doses of hydrocortisone (synthetic cortisol) administration on autobiographical memory retrieval. Healthy volunteers (n = 66) were studied on two separate visits, during which they received placebo and either moderate-dose (0.15 mg/kg IV; n = 33) or high-dose (0.45 mg/kg IV; n = 33) hydrocortisone infusion. From 75 to 150 min post-infusion subjects performed an Autobiographical Memory Test and the California Verbal Learning Test (CVLT). The high-dose hydrocortisone administration reduced the percent of specific memories recalled (p = .04), increased the percent of categorical (nonspecific) memories recalled (p < .001), and slowed response times for categorical memories (p < .001), compared with placebo performance. Under moderate-dose hydrocortisone the autobiographical memory performance did not change significantly with respect to percent of specific or categorical memories recalled or reaction times. Performance on the CVLT was not affected by hydrocortisone. These findings suggest that cortisol affects accessibility of autobiographical memories in a dose-dependent manner. Specifically, administration of hydrocortisone at doses analogous to those achieved under severe psychosocial stress impaired the specificity and speed of retrieval of autobiographical memories.

Acutely elevated cortisol in response to stressor is associated with attentional bias toward depression-related stimuli but is not associated with attentional function

Cortisol induces attentional bias toward a negative stimulus and impaired attentional function. Depressed individuals have high levels of cortisol, and exhibit an attentional bias toward a depression-related stimulus and impaired processing speed and executive attention, which are components of attentional function. Therefore, the study tested the hypotheses that an acute increase in cortisol in response to a stressor is associated with attentional bias toward a depression-related stimulus and impaired processing speed and executive attention. Thirty-six participants were administered the dot-probe task for the measurement of attentional bias toward a depression-related stimulus and the Trail Making Test A and B for the measurement of processing speed and executive attention before and after a mental arithmetic task. It was revealed that attentional bias toward a depression-related stimulus following the stressor was observed only among the responders (i.e., participants with cortisol elevation in response to a stressor). On the other hand, no differences in the performance of processing speed and executive attention were noted between the responders and non-responders. The results indicate that acutely elevated cortisol is related to attentional bias, but is not related to processing speed and executive attention. The results have an implication for the etiology of depression.

Involvement of basolateral amygdala GABAA receptors in the effect of dexamethasone on memory in rats

In this study we investigated whether GABA(A) receptors of the basolateral amygdala (BLA) interact with the effect of dexamethasone on the retrieval stage of memory. Adult male Wistar rats were bilaterally cannulated in the BLA by stereotaxic surgery. The animals were trained in step-through apparatus by induction of electric shock (1.5 mA, 3 s) and were tested for memory retrieval after 1 d. The time of latency for entering the dark compartment of the instrument and the time spent by rats in this chamber were recorded for evaluation of the animals' retrieval in passive avoidance memory. Administration of dexamethasone (0.3 and 0.9 mg/kg, subcutaneously (s.c.)), immediately after training, enhanced memory retrieval. This effect was reduced by intra-BLA microinjection of muscimol (0.125, 0.250 and 0.500 µg/rat), when administered before 0.9 mg/kg of dexamethasone. Microinjection of bicuculline (0.75 µg/rat, intra-BLA) with an ineffective dose of dexamethasone (0.1 mg/kg, s.c.) increased memory retrieval. However, the same doses of muscimol and bicuculline without dexamethasone did not affect memory processes. Our data support reports that dexamethasone enhances memory retrieval. It seems that GABA(A) receptors of the BLA mediate the effect of dexamethasone on memory retrieval in rats.

Tune it down to live it up? Rapid, nongenomic effects of cortisol on the human brain

The stress hormone cortisol acts on the brain, supporting adaptation and time-adjusted coping processes. Whereas previous research has focused on slow emerging, genomic effects of cortisol, we addressed the rapid, nongenomic cortisol effects on in vivo neuronal activity in humans. Three independent placebo-controlled studies in healthy men were conducted. We observed changes in CNS activity within 15 min after intravenous administration of a physiological dose of 4 mg of cortisol (hydrocortisone). Two of the studies demonstrated a rapid bilateral thalamic perfusion decrement using continuous arterial spin labeling. The third study revealed rapid, cortisol-induced changes in global signal strength and map dissimilarity of the electroencephalogram. Our data demonstrate that a physiological concentration of cortisol profoundly affects the functioning and perfusion of the human brain in vivo via a rapid, nongenomic mechanism. The changes in neuronal functioning suggest that cortisol acts on the thalamic relay of background as well as on task-specific sensory information, allowing focus and facilitation of adaptation to challenges.

Rapid steroid hormone actions initiated at the cell surface and the receptors that mediate them with an emphasis on recent progress in fish models

In addition to the classic genomic mechanism of steroid action mediated by activation of intracellular nuclear receptors, there is now extensive evidence that steroids also activate receptors on the cell surface to initiate rapid intracellular signaling and biological responses that are often nongenomic. Recent progress in our understanding of rapid, cell surface-initiated actions of estrogens, progestins, androgens and corticosteroids and the identities of the membrane receptors that act as their intermediaries is briefly reviewed with a special emphasis on studies in teleost fish. Two recently discovered novel proteins with seven-transmembrane domains, G protein-coupled receptor 30 (GPR30), and membrane progestin receptors (mPRs) have the ligand binding and signaling characteristics of estrogen and progestin membrane receptors, respectively, but their functional significance is disputed by some researchers. GPR30 is expressed on the cell surface of fish oocytes and mediates estrogen inhibition of oocyte maturation. mPRα is also expressed on the oocyte cell surface and is the intermediary in progestin induction of oocyte maturation in fish. Recent results suggest there is cross-talk between these two hormonal pathways and that there is reciprocal down-regulation of GPR30 and mPRα expression by estrogens and progestins at different phases of oocyte development to regulate the onset of oocyte maturation. There is also evidence in fish that mPRs are involved in progestin induction of sperm hypermotility and anti-apoptotic actions in ovarian follicle cells. Nonclassical androgen and corticosteroid actions have also been described in fish models but the membrane receptors mediating these actions have not been identified.