Central mineralocorticoid receptors are indispensable for corticosterone-induced impairment of memory retrieval in rats

Hormonal contraceptive usage influences stress hormone effects on cognition and emotion

Men and women partially differ in how they respond to stress and how stress in return affects their cognition and emotion. The influence of hormonal contraceptives (HCs) on this interaction has received little attention, which is surprising given the prevalence of HC usage. This selective review illustrates how HC usage modulates the effects of stress hormones on cognition and emotion. As three examples, we discuss stress hormone effects on episodic memory, fear conditioning and cognitive emotion regulation. The identified studies revealed that stress effects on cognitive-emotional processes in women using HCs were at times reduced or even absent when compared to men or naturally cycling women. Especially striking were the few examples of reversed effects in HC women. As underlying neuroendocrine mechanisms, we discuss influences of HCs on the neuroendocrine stress response and effects of HCs on central glucocorticoid sensitivity. The summarized findings emphasize the need for additional translational research.

Stachyose Alleviates Corticosterone-Induced Long-Term Potentiation Impairment via the Gut–Brain Axis

Stress can induce learning and memory impairment; corticosterone is often used to study the effects and mechanisms of stress in animal models. Long-term potentiation (LTP) has been widely used for tackling the mechanisms of memory. Liuwei Dihuang decoction-active fraction combination (LW-AFC) can improve stress-induced LTP and cognition impairment; stachyose is an oligosaccharide in LW-AFC. The effects and mechanisms of stachyose on stress are unknown. In this study, stachyose showed protective effects against LTP impairment by corticosterone in vivo only via intragastric administration for 7 consecutive days, but there was little effect even after direct intracerebroventricular injection; the protective effect of stachyose could be canceled by non-absorbable antibiotics (ATB) which disturbed gut flora. 16S rRNA sequencing, alpha diversity, and principal coordinate analysis (PCoA) revealed that the gut flora in corticosterone-treated mice was disturbed and stachyose could improve corticosterone-induced gut flora disturbance. Bacteroidetes were decreased and Deferribacteres were increased significantly in corticosterone-treated mice, and stachyose restored Bacteroidetes and Deferribacteres to the normal level. D-serine, a coactivator of NMDA receptors, plays an important role in synaptic plasticity and cognition. Here, corticosterone had little effect on the content of D-serine and L-serine (the precursor of D-serine), but it reduced the D-serine release-related proteins, Na⁺-independent alanine–serine–cysteine transporter-1 (ASC-1), and vesicle-associated membrane protein 2 (VAMP2) significantly in hippocampus; stachyose significantly increased ASC-1 and VAMP2 in corticosterone-treated mice, and ATB blocked stachyose’s effects on ASC-1 and VAMP2. NMDA receptors co-agonists L-serine, D-serine, and glycine significantly improved LTP impairment by corticosterone. These results indicated that stachyose might indirectly increase D-serine release through the gut–brain axis to improve LTP impairment by corticosterone in the hippocampus in vivo.

Reduced D-Serine Release May Contribute to Impairment of Long-Term Potentiation by Corticosterone in the Perforant Path-Dentate Gyrus

Long-term potentiation (LTP) is a neurobiological mechanism of cognitive function, and the N-methyl-D-aspartate (NMDA) receptors is fundamental for LTP. Previous studies showed that over activation of NMDA receptors may be a crucial cause of LTP and cognitive impairment induced by stress or corticosterone. However, other studies showed that the function of NMDA receptors is insufficient since the NMDA receptors co-agonist D-serine could improve stress-induced cognitive impairment. The purpose of this study is to clarify whether over activation of NMDA receptors or hypofunction of NMDA receptors is involved in hippocampal impairment of LTP by corticosterone and the underlying mechanisms. Results showed that hippocampal LTP and object location recognition memory were impaired in corticosterone-treated mice. Corticosterone increased the glutamate level in hippocampal tissues, neither NMDA receptors antagonist nor its subtype antagonists alleviated impairment of LTP, while enhancing the function of NMDA receptors by D-serine did alleviate impairment of LTP by corticosterone, suggesting that hypofunction of NMDA receptors might be one of the main reasons for impairment of LTP by corticosterone. Further results showed that the level of D-serine and its precursor L-serine did not change. D-serine release-related protein Na+-independent alanine-serine-cysteine transporter-1 (ASC-1) in the cell membrane was decreased and increasing D-serine release by the selective activator of ASC-1 antiporter activity alleviated impairment of LTP by corticosterone. Taken together, this study demonstrates that hypofunction of NMDA receptors may be involved in impairment of LTP by corticosterone and reduced D-serine release may be an important reason for its hypofunction, which is an important complement to existing mechanisms of corticosterone-induced LTP and cognitive impairment.

Is PTSD-Phenotype Associated with HPA-Axis Sensitivity? Feedback Inhibition and Other Modulating Factors of Glucocorticoid Signaling Dynamics

Previously, we found that basal corticosterone pulsatility significantly impacts the vulnerability for developing post-traumatic stress disorder (PTSD). Rats that exhibited PTSD-phenotype were characterized by blunted basal corticosterone pulsatility amplitude and a blunted corticosterone response to a stressor. This study sought to identify the mechanisms underlining both the loss of pulsatility and differences in downstream responses. Serial blood samples were collected manually via jugular vein cannula at 10-min intervals to evaluate suppression of corticosterone following methylprednisolone administration. The rats were exposed to predator scent stress (PSS) after 24 h, and behavioral responses were assessed 7 days post-exposure for retrospective classification into behavioral response groups. Brains were harvested for measurements of the glucocorticoid receptor, mineralocorticoid receptor, FK506-binding protein-51 and arginine vasopressin in specific brain regions to assess changes in hypothalamus–pituitary–adrenal axis (HPA) regulating factors. Methylprednisolone produced greater suppression of corticosterone in the PTSD-phenotype group. During the suppression, the PTSD-phenotype rats showed a significantly more pronounced pulsatile activity. In addition, the PTSD-phenotype group showed distinct changes in the ventral and dorsal CA1, dentate gyrus as well as in the paraventricular nucleus and supra-optic nucleus. These results demonstrate a pre-trauma vulnerability state that is characterized by an over-reactivity of the HPA and changes in its regulating factors.

Central amygdala mineralocorticoid receptors modulate alcohol self-administration

The mineralocorticoid receptor (MR) is an emerging target in the field of alcohol research. The MR is a steroid receptor in the same family as the glucocorticoid receptor, with which it shares the ligand corticosterone in addition to the MR selective ligand aldosterone. Recent studies have shown correlations between central amygdala (CeA) MR expression and alcohol drinking in rats and macaques, as well as correlations between aldosterone and alcohol craving in individuals with alcohol use disorder (AUD). Additionally, our previous work demonstrated that systemic treatment with the MR antagonist spironolactone reduced alcohol self-administration and response persistence in both male and female rats. This study examined if reductions in self-administration following MR antagonist treatment were related to dysregulation of MR-mediated corticosterone negative feedback. Female rats treated with spironolactone (50 mg/kg; IP) showed increased plasma corticosterone following self-administration, which correlated with reduced alcohol self-administration. Next, local microinjection of the MR-selective antagonist eplerenone was used to identify the brain-regional locus of MR action on alcohol self-administration. Eplerenone infusion produced dose-dependent reductions in alcohol self-administration in the CeA, but had no effect in the dorsal hippocampus. Finally, to assay the functional role of CeA MR expression in alcohol self-administration, CeA MR was knocked down by antisense oligonucleotide (ASO) infusion prior to alcohol self-administration. Rats showed a transient reduction in alcohol self-administration 1 day after ASO infusion. Together these studies demonstrate a functional role of CeA MR in modulating alcohol self-administration and make a case for studying MR antagonists as a novel treatment for AUD.

Functional polymorphisms of the mineralocorticoid receptor gene NR3C2 are associated with diminished memory decline: Results from a longitudinal general-population study

BACKGROUND

The mineralocorticoid receptor (MR) in the brain has a key role in the regulation of the central stress response and is associated with memory performance. We investigated whether the genetic polymorphisms rs5522 and rs2070951 of NR3C2 showed main and interactive effects with childhood trauma on memory decline.

METHODS

Declarative memory was longitudinally assessed in 1,318 participants from the community-dwelling Study of Health in Pomerania using the Verbal Learning and Memory Test (VLMT). In a subsample of 377 participants aged 60 and older, the Mini-Mental Status Examination (MMSE) was additionally applied. Mean follow-up time for the VLMT and MMSE were 6.4 and 10.7 years, respectively.

RESULTS

Homozygous carriers of the G allele of rs2070951 (p < .01) and of the A allele of rs5522 (p < .001) showed higher immediate recall of words as compared to carriers of C allele (rs2070951) or the G allele (rs5522). The CG haplotype was associated with decreased recall (p < .001). Likewise, in the subsample of older patients, the AA genotype of rs5522 was associated with higher MMSE scores (p < .05). CG haplotypes showed significantly reduced MMSE scores in comparison to the reference haplotype (β = -0.60; p < .01).

CONCLUSIONS

Our results indicate that the GG genotype of rs2070951 as well as the AA genotype of rs5522 are associated with diminished memory decline.

Work-Related Stress, Physio-Pathological Mechanisms, and the Influence of Environmental Genetic Factors

Work-related stress is a growing health problem in modern society. The stress response is characterized by numerous neurochemicals, neuroendocrine and immune modifications that involve various neurological systems and circuits, and regulation of the gene expression of the different receptors. In this regard, a lot of research has focused the attention on the role played by the environment in influencing gene expression, which in turn can control the stress response. In particular, genetic factors can moderate the sensitivities of specific types of neural cells or circuits mediating the imprinting of the environment on different biological systems. In this current review, we wish to analyze systematic reviews and recent experimental research on the physio-pathological mechanisms that underline stress-related responses. In particular, we analyze the relationship between genetic and epigenetic factors in the stress response.

Top-down and bottom-up control of stress-coping

In this 30th anniversary issue review, we focus on the glucocorticoid modulation of limbic-prefrontocortical circuitry during stress-coping. This action of the stress hormone is mediated by mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) that are co-expressed abundantly in these higher brain regions. Via both receptor types, the glucocorticoids demonstrate, in various contexts, rapid nongenomic and slower genomic actions that coordinate consecutive stages of information processing. MR-mediated action optimises stress-coping, whereas, in a complementary fashion, the memory storage of the selected coping strategy is promoted via GR. We highlight the involvement of adipose tissue in the allocation of energy resources to central regulation of stress reactions, point to still poorly understood neuronal ensembles in the prefrontal cortex that underlie cognitive flexibility critical for effective coping, and evaluate the role of cortisol as a pleiotropic regulator in vulnerability to, and treatment of, trauma-related psychiatric disorders.

The mineralocorticoid receptor antagonist spironolactone reduces alcohol self-administration in female and male rats

Cortisol/corticosterone and the hypothalamic-pituitary-adrenal (HPA) axis serve an important role in modulating alcohol drinking behaviors. To date most alcohol research has focused on the functional involvement of corticosterone and the glucocorticoid receptor (GR), the primary receptor for corticosterone. Recent studies have indicated that the related mineralocorticoid receptor (MR), which binds both corticosterone and aldosterone, may also play a role in alcohol drinking. Therefore, the purpose of the present study was to test the functional role of MR signaling in alcohol self-administration via pharmacological antagonism of the MR with spironolactone. Male and female Long-Evans rats were trained to self-administer a sweetened alcohol solution (15% (v/v) alcohol +2% (w/v) sucrose). The effects of spironolactone (0, 10, 25, 50 mg/kg; IP) were tested on alcohol self-administration and under "probe extinction" conditions to measure the persistence of responding in the absence of the alcohol reinforcer. Parallel experiments in sucrose self-administration trained rats were used to confirm the specificity of spironolactone effects to an alcohol reinforcer. In female rats spironolactone (50 mg/kg) reduced alcohol self-administration and persistence of alcohol responding. In male rats spironolactone (25 and 50 mg/kg) reduced alcohol self-administration, but not persistence of alcohol responding. Spironolactone reduced sucrose intake in female rats only, and locomotion in male and female rats during sucrose self-administration. There was no effect of spironolactone on persistence of sucrose responding. These studies add to growing evidence that the MR is involved in alcohol drinking, while underscoring the importance of studying both male and female animals.

Rapid Intracellular Zn2+ Dysregulation via Membrane Corticosteroid Receptor Activation Affects In Vivo CA1 LTP

Involvement of membrane mineralocorticoid (MC) and glucocorticoid (GC) receptors in synaptic Zn²⁺ dynamics remains unclear. Here, we tested whether synaptic plasticity is affected by rapid intracellular Zn²⁺ dysregulation via membrane MC and GC receptor activation, in comparison with intracellular Ca²⁺ dysregulation. In anesthetized rats, extracellular Zn²⁺ level was increased under local perfusion of the hippocampal CA1 with 500 ng/ml corticosterone. In vivo CA1 long-term potentiation (LTP) at Schaffer collateral-CA1 pyramidal cell synapses was attenuated by the pre-perfusion with corticosterone prior to tetanic stimulation, and the attenuation was canceled by co-perfusion with CaEDTA, an extracellular Zn²⁺ chelator, suggesting that corticosterone-induced increase in extracellular Zn²⁺ is involved in the subsequent attenuation of LTP. In rat brain slices, corticosterone-induced increases in extracellular and intracellular Zn²⁺ were blocked in the presence of spironolactone, a MC receptor antagonist that canceled corticosterone-induced attenuation of LTP. Mifepristone, a GC receptor antagonist, which canceled corticosterone-induced attenuation of LTP, also blocked corticosterone-induced increase in intracellular Zn²⁺, but not extracellular Zn²⁺. Moreover, corticosterone-induced decrease in phosphorylated CaMKII was restored in the presence of CaEDTA or spironolactone. These results indicate that glucocorticoid rapidly induces the increase in intracellular Zn²⁺, which occurs via membrane MC and GC receptor activations, and decreases phosphorylated CaMKII level, resulting in attenuating LTP. Membrane MC and GC receptors induce intracellular Zn²⁺ dysregulation via differential mechanisms. In contrast, glucocorticoid-induced intracellular Ca²⁺ dysregulation is not crucial for affecting LTP.

Gender dependent contribution of muscarinic receptors in memory retrieval under sub-chronic stress

Stress induces retrograde amnesia in humans and rodents. Muscarinic antagonism under normal physiological conditions causes gender dependent impairment in episodic memory retrieval. We aimed to explore the gender dependent role of muscarinic receptors in memory retrieval under sub-chronic stress condition. Male and female mice were trained for Morris water maze test and contextual fear conditioning, followed by 3 h restraint stress per day for five days. Stress was either given alone or in combination with a daily subcutaneous injection of scopolamine (1 mg/kg) or donepezil (1 mg/kg). Control mice were given saline without any stress. Sub-chronic stress (induced for five days) impaired spatial memory retrieval in males (P < 0.005) but not in females (P > 0.05). Stress induced spatial memory recall deficit in male mice was independent of muscarinic receptor activity (P > 0.05). However, stress induced contextual fear memory recall impairment was reversed by donepezil treatment in male (P < 0.005) and female (P < 0.0001) mice. These findings suggest that differential role of muscarinic activity in retrieving different types of memories under stress depends on gender of subjects.

Importance of the brain corticosteroid receptor balance in metaplasticity, cognitive performance and neuro-inflammation

Bruce McEwen's discovery of receptors for corticosterone in the rat hippocampus introduced higher brain circuits in the neuroendocrinology of stress. Subsequently, these receptors were identified as mineralocorticoid receptors (MRs) that are involved in appraisal processes, choice of coping style, encoding and retrieval. The MR-mediated actions on cognition are complemented by slower actions via glucocorticoid receptors (GRs) on contextualization, rationalization and memory storage of the experience. These sequential phases in cognitive performance depend on synaptic metaplasticity that is regulated by coordinate MR- and GR activation. The receptor activation includes recruitment of coregulators and transcription factors as determinants of context-dependent specificity in steroid action; they can be modulated by genetic variation and (early) experience. Interestingly, inflammatory responses to damage seem to be governed by a similarly balanced MR:GR-mediated action as the initiating, terminating and priming mechanisms involved in stress-adaptation. We conclude with five questions challenging the MR:GR balance hypothesis.

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: The brain mineralocorticoid receptor: a saga in three episodes

In 1968, Bruce McEwen discovered that ³H-corticosterone administered to adrenalectomised rats is retained in neurons of hippocampus rather than those of hypothalamus. This discovery signalled the expansion of endocrinology into the science of higher brain regions. With this in mind, our contribution highlights the saga of the brain mineralocorticoid receptor (MR) in three episodes. First, the precloning era dominated by the conundrum of two types of corticosterone-binding receptors in the brain, which led to the identification of the high-affinity corticosterone receptor as the 'promiscuous' MR cloned in 1987 by Jeff Arriza and Ron Evans in addition to the classical glucocorticoid receptor (GR). Then, the post-cloning period aimed to disentangle the function of the brain MR from that of the closely related GR on different levels of biological complexity. Finally, the synthesis section that highlights the two faces of brain MR: Salt and Stress. 'Salt' refers to the regulation of salt appetite, and reciprocal arousal, motivation and reward, by a network of aldosterone-selective MR-expressing neurons projecting from nucleus tractus solitarii (NTS) and circumventricular organs. 'Stress' is about the limbic-forebrain nuclear and membrane MRs, which act as a switch in the selection of the best response to cope with a stressor. For this purpose, activation of the limbic MR promotes selective attention, memory retrieval and the appraisal process, while driving emotional expressions of fear and aggression. Subsequently, rising glucocorticoid concentrations activate GRs in limbic-forebrain circuitry underlying executive functions and memory storage, which contribute in balance with MR-mediated actions to homeostasis, excitability and behavioural adaptation.

Efectos de la inactivación sistémica de los receptores GR y MR sobre el daño rápido en la recuperación de la memoria espacial inducido por corticosterona

Estudios previos de nuestro laboratorio han mostrado que la inyección de corticosterona aplicada diez minutos antes de la prueba de recobre afecta la recuperación de la memoria espacial en el laberinto de Barnes. Se ha propuesto que los efectos de esta hormona están mediados por la activación de los receptores clásicos de glucocorticoides; sin embargo la rápida aparición de los efectos permite suponer un mecanismo alternativo de tipo no genómico. El objetivo del presente estudio fue determinar la participación de los receptores de glucocorticoides GR y MR sobre el efecto rápido de la corticosterona en la recuperación de la memoria espacial en el laberinto de Barnes. Treinta y siete ratas Wistar macho fueron entrenadas en la tarea y 24h después recibieron una inyección subcutánea de antagonista GR, antagonista MR o vehículo. Cincuenta minutos después de la inyección, los animales fueron inyectados con corticosterona o vehículo y diez minutos después se evaluó la recuperación de la memoria espacial. Los resultados mostraron que la corticosterona perjudica rápidamente la recuperación de la memoria espacial a largo plazo, pues los animales inyectados presentaron mayores latencias de escape, mayor número de errores, mayor número de exploraciones y mayor distancia recorrida hasta alcanzar la meta. Este efecto sólo fue revertido con la administración del antagonista MR. Este hallazgo concuerda con estudios in vitro donde se muestra que los efectos rápidos de la corticosterona sobre la trasmisión glutamatérgica en el hipocampo están mediados por los receptores MR, posiblemente localizados en la membrana celular.

The brain mineralocorticoid receptor and stress resilience

Stress exposure activates the HPA-axis and results in the release of corticosteroids which bind to two receptor types in the brain: the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). While the role of the GR in stress reactivity has been extensively studied, the MR has received less attention. Nevertheless, pioneering in-depth studies over the past two decades have shown the importance of the brain MR in the processing of stressful information. Moreover, a membrane-bound MR mediating the rapid effects of cortisol was recently discovered. This review summarizes how the MR may play a role in stress resilience. Both preclinical and clinical studies suggest that the MR is an important stress modulator and influences basal as well as stress-induced HPA-axis activity, stress appraisal, and fear-related memories. These MR effects are mediated by both genomic and non-genomic MRs and appear to be at least partially sex-dependent. Moreover, the majority of studies indicate that high MR functionality or expression may confer resilience to traumatic stress. This has direct clinical implications. First, increasing activity or expression of brain MRs may prevent or reverse symptoms of stress-related depression. Second, individuals with a relatively low MR functionality may possess an increased stress susceptibility for depression. Nevertheless, the number of clinical MR studies is currently limited. In conclusion, the recent emergence of the MR as a putative stress resilience factor is important and may open up new avenues for the prevention and treatment of psychiatric disorders.

Glucocorticoid-induced impairment of long-term memory retrieval in female rats: influences of estrous cycle and estrogen

Using an inhibitory avoidance (IA) task, the effects of glucocorticoids on memory retrieval in intact and ovariectomized (OVX) female rats were investigated. Young adult female rats were trained in a one trial IA task (1-mA, 3-s footshock). The latency to reenter the dark compartment of the apparatus was recorded in the retention test performed 48h after training. Pre-retrieval injection of corticosterone (CORT, 1, 3, and 10mg/kg) to OVX rats impaired memory retrieval at all doses tested. Similar administration of CORT (3mg/kg) in intact female rats impaired memory retrieval in the estrus phase (when endogenous plasma levels of estrogen are low) but not in the proestrus phase (when endogenous levels of estrogen are high). Concurrent administration of CORT (3mg/kg) and 17-β-estradiol (15μg/kg) in both proestrus and estrous phases impaired memory retrieval. Our findings indicate that the effects of corticosterone on memory retrieval are modulated by the estrous cycle and 17-β-estradiol.

Mineralocorticoid receptor stimulation improves cognitive function and decreases cortisol secretion in depressed patients and healthy individuals

Memory and executive function are often impaired in patients with major depression, while cortisol secretion is increased. Mineralocorticoid receptors (MR) are abundantly expressed in the hippocampus and in the prefrontal cortex, brain areas critical for memory, executive function, and cortisol inhibition. Here, we investigated whether MR stimulation with fludrocortisone (1) improves memory and executive function and (2) decreases cortisol secretion in depressed patients and healthy individuals. Twenty-four depressed patients without medication and 24 age-, sex-, and education-matched healthy participants received fludrocortisone (0.4 mg) or placebo in a randomized, double-blind, within-subject cross-over design. We measured verbal memory, visuospatial memory, executive function, psychomotor speed, and salivary cortisol secretion during cognitive testing between 1400 and 1700 hours. For verbal memory and executive function, we found better performance after fludrocortisone compared with placebo across groups. No treatment effect on other cognitive domains emerged. Depressed patients performed worse than healthy individuals in psychomotor speed and executive function. No group effect or group × treatment interaction emerged on other cognitive domains. Fludrocortisone decreased cortisol secretion across groups and there was a significant correlation between cortisol inhibition and verbal memory performance. Our data suggest a crucial role of MR in verbal memory and executive function and demonstrate the possibility to improve cognition in depressed patients and healthy individuals through MR stimulation.

Glucocorticoid actions on synapses, circuits, and behavior: implications for the energetics of stress

Environmental stimuli that signal real or potential threats to homeostasis lead to glucocorticoid secretion by the hypothalamic-pituitary-adrenocortical (HPA) axis. Glucocorticoids promote energy redistribution and are critical for survival and adaptation. This adaptation requires the integration of multiple systems and engages key limbic-neuroendocrine circuits. Consequently, glucocorticoids have profound effects on synaptic physiology, circuit regulation of stress responsiveness, and, ultimately, behavior. While glucocorticoids initiate adaptive processes that generate energy for coping, prolonged or inappropriate glucocorticoid secretion becomes deleterious. Inappropriate processing of stressful information may lead to energetic drive that does not match environmental demand, resulting in risk factors for pathology. Thus, dysregulation of the HPA axis may promote stress-related illnesses (e.g. depression, PTSD). This review summarizes the latest developments in central glucocorticoid actions on synaptic, neuroendocrine, and behavioral regulation. Additionally, these findings will be discussed in terms of the energetic integration of stress and the importance of context-specific regulation of glucocorticoids.

Obvious and hidden anxiety and the related factors in operating room nurses employed in general hospital, Qazvin, Iran: a cross-sectional study

BACKGROUND

Health promotion and security of manpower in a society is one of the pillars to progress a society. Anxiety, is the most common psychological disorder in societies and occupations like nursing' anesthesia technicians and operation room technicians. The aim of this study was to investigate prevalence of anxiety, and its severity in Iranian nurses working in operation room. Also, we determined the most important associated factors with anxiety.

METHODS

In this cross sectional study' 152 nurses working in operating room participated. The tool to gather the data was a questionnaire, that included three parts; demographic information' obvious anxiety questions and hidden anxiety questions of Spielburger. Obtained data was analysed with SPSS 16 software.

RESULTS

The majority of participants were females (94.7%) with experience at work less than 10 years (84.9%). The average scores of participants in obvious and hidden anxiety were 41.9±39.4 (range 20 to 75) and 39.4±8.2 (range 20 to 70), respectively. Anxiety level was significantly higher in females than males (P=0.04). The most prevalent cause of anxiety, was contact with infected biological factors (23% of nurses). The less important cause was concern about retirement (42.8% of nurses).

CONCLUSION

Our results suggest that, anxiety disorders is prevalent in Iranian nurses working in public city hospitals, which warrants immediate programs for intervention to improve working situations in work place.

Reactivation of an aversive memory modulates learning strategy preference in male rats

Reminders of an aversive event adversely impact retrieval of hippocampus-dependent memories and exacerbate stress-induced levels of anxiety. Interestingly, stress and anxiety shift control over learning away from the hippocampus and toward the striatum. The aims of the current study were to determine whether spatial memory and learning strategy are impacted by reminders of a stressor. Adult male Long-Evans rats (N = 47) were subjected to an inhibitory avoidance (IA) training trial in which 32 rats were exposed (3 s) to a single inescapable electrical footshock (0.6 mA). Prior to the retention trial of a Y-maze task and the probe trials of two different learning strategy tasks, some of the rats that were exposed to the footshock (n = 17) were reminded of the stressor on an IA retrieval trial. Both groups of rats exposed to the initial stressor exhibited hypoactivity, but no impairment in spatial memory, on the Y-maze task conducted 1 week after exposure to the footshock. One month after exposure to footshock, both groups of rats exposed to the initial stressor tended to prefer a striatum-dependent learning strategy on a water T-maze task. However, 2 months after exposure to footshock, only shocked rats that were reminded of the stressor exhibited a preference for a striatum-dependent learning strategy on a visible-platform water maze task, which corresponded with lower levels of activity in an open field. The results indicate that reminders of a stressor perpetuate the deleterious effects of stress on affective and cognitive processes.

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.

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.

Mineralocorticoid and glucocorticoid receptors at the neuronal membrane, regulators of nongenomic corticosteroid signalling

The balance between corticosteroid actions induced via activation of the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) determines the brain's response to stress. While both receptors are best known for their delayed genomic role, it has become increasingly evident that they can also associate with the plasma membrane and act as mediators of rapid, nongenomic signalling. Nongenomic corticosteroid actions in the brain are required for the coordination of a rapid adaptive response to stress; membrane-associated MRs and GRs play a major role herein. However, many questions regarding the underlying mechanism are still unresolved. How do MR and GR translocate to the membrane and what are their downstream signalling partners? In this review we discuss these issues based on insights obtained from related receptors, most notably the estrogen receptor α.

Endocrinological differences between Hatano high- and low-avoidance rats during early two-way avoidance acquisition

Hatano high (HAA)- and low (LAA)-avoidance rats were selected from Sprague-Dawley rats genetically on the basis of their active avoidance behavior in a shuttle-box test. The purpose of this study was to investigate stress-related alterations of hormones corticotropin-releasing hormone (CRH), arginine-vasopressin (AVP), prolactin, and adrenocorticotropin (ACTH) in the brain and blood during early avoidance acquisition using two lines of Hatano rats. In paraventricular nucleus (PVN) of the hypothalamus, the CRH levels in HAA rats were significantly increased after shuttle-box tasks compared with before the tasks, whereas the CRH levels in LAA rats significantly decreased after shuttle-box tasks compared with before the tasks. In the HAA rats, the CRH and AVP levels in the median eminence decreased after shuttle-box tasks, whereas there were no significant differences in the levels between before and after shuttle-box tasks in LAA rats. The plasma concentrations of ACTH were significantly higher in HAA rats than in LAA rats after shuttle-box tasks. These results show that the response of CRH-ACTH was higher in HAA rats than in LAA rats. This phenotype may be an important reason for the high avoidance rates of shuttle-box tasks in HAA rats. These endocrine differences in early avoidance acquisition may be involved in regulation of their avoidance responses in the shuttle-box task.

Membrane mineralocorticoid but not glucocorticoid receptors of the dorsal hippocampus mediate the rapid effects of corticosterone on memory retrieval

This study was aimed at determining the type of the glucocorticoid membrane receptors (mineralocorticoid receptors (MRs) or glucocorticoid receptors (GRs)) in the dorsal hippocampus (dHPC) involved in the rapid effects of corticosterone or stress on memory retrieval. For that purpose, we synthesized corticosterone-3-O-carboxymethyloxime-bovine serum albumin conjugate (Cort-3CMO-BSA) conjugate (a high MW complex that cannot cross the cell membrane) totally devoid of free corticosterone, stable in physiological conditions. In a first experiment, we evidenced that an acute stress (electric footshocks) induced both a dHPC corticosterone rise measured by microdialysis and memory retrieval impairment on delayed alternation task. Both the endocrinal and cognitive effects of stress were blocked by metyrapone (a corticosterone synthesis inhibitor). In a second experiment, we showed that bilateral injections of either corticosterone or Cort-3CMO-BSA in dHPC 15 min before memory testing produced impairments similar to those resulting from acute stress. Furthermore, we showed that anisomycin (a protein synthesis inhibitor) failed to block the deleterious effect of Cort-3CMO-BSA on memory. In a third experiment, we evidenced that intra-hippocampal injection of RU-28318 (MR antagonist) but not of RU-38486 (GR antagonist) totally blocked the Cort-3CMO-BSA-induced memory retrieval deficit. In a fourth experiment, we demonstrated that RU-28318 administered 15 min before stress blocked the stress-induced memory impairments when behavioral testing occurred 15 min but not 60 min after stress. Overall, this study provides strong in vivo evidence that the dHPC membrane GRs, mediating the rapid and non-genomic effects of acute stress on memory retrieval, are of MR but not GR type.

A randomized trial on mineralocorticoid receptor blockade in men: effects on stress responses, selective attention, and memory

Corticosteroids, released in high amounts after stress, exert their effects via two different receptors in the brain: glucocorticoid receptors (GRs) and mineralocorticoid receptors (MRs). GRs have a role in normalizing stress-induced effects and promoting consolidation, while MRs are thought to be important in determining the threshold for activation of the hypothalamic-pituitary-adrenal (HPA) axis. We investigated the effects of MR blockade on HPA axis responses to stress and stress-induced changes in cognitive function. In a double-blind, placebo-controlled study, 64 healthy young men received 400 mg of the MR antagonist spironolactone or placebo. After 1.5 h, they were exposed to either a Trier Social Stress Test or a non-stressful control task. Responses to stress were evaluated by hormonal, subjective, and physiological measurements. Afterwards, selective attention, working memory, and long-term memory performance were assessed. Spironolactone increased basal salivary cortisol levels as well as cortisol levels in response to stress. Furthermore, spironolactone significantly impaired selective attention, but only in the control group. The stress group receiving spironolactone showed impaired working memory performance. By contrast, long-term memory was enhanced in this group. These data support a role of MRs in the regulation of the HPA axis under basal conditions as well as in response to stress. The increased availability of cortisol after spironolactone treatment implies enhanced GR activation, which, in combination with MR blockade, presumably resulted in a decreased MR/GR activation ratio. This condition influences both selective attention and performance in various memory tasks.

Mineralocorticoid receptors in the medial prefrontal cortex and hippocampus mediate rats' unconditioned fear behaviour

Corticosterone is released from the adrenal cortex in response to stress, and binds to glucocorticosteroid receptors (GRs) and mineralocorticosteroid receptors (MRs) in the brain. Areas such as the dorsal hippocampus (DH), ventral hippocampus (VH) and medial prefrontal cortex (mPFC) all contain MRs and have been previously implicated in fear and/or memory. The purpose of the following experiments was to examine the role of these distinct populations of MRs in rats' unconditioned fear and fear memory. The MR antagonist (RU28318) was microinfused into the DH, VH, or mPFC of rats. Ten minutes later, their unconditioned fear was tested in the elevated plus-maze and the shock-probe tests, two behavioral models of rat "anxiety." Twenty-four hours later, conditioned fear of a non-electrified probe was assessed in rats re-exposed the shock-probe apparatus. Microinfusions of RU28318 into each of the three brain areas reduced unconditioned fear in the shock-probe burying test, but only microinfusions into the VH reduced unconditioned fear in the plus-maze test. RU28318 did not affect conditioned fear of the shock-probe 24hr later. MRs in all three areas of the brain mediated unconditioned fear to a punctate, painful stimulus (probe shock). However, only MRs in the ventral hippocampus seemed to mediate unconditioned fear of the more diffuse threat of open spaces (open arms of the plus maze). In spite of the known roles of the hippocampus in spatial memory and conditioned fear memory, MRs within these sites did not appear to mediate memory of the shock-probe.

Systemic and intrahippocampal administrations of the glucocorticoid receptor antagonist RU38486 impairs fear memory reconsolidation in rats

Reconsolidation is the process by which previously consolidated memories are stabilized after retrieval. Several lines of evidence indicate that glucocorticoids modulate distinct phases of learning and memory. These effects are considered to be mediated by mineralocorticoid receptors and glucocorticoid receptors (GRs), which display a high concentration and distinct distribution in the hippocampus. The role of glucocorticoid system in fear memory reconsolidation is the subject of some controversy. Moreover, we found no studies that assessed the role of hippocampal GRs in fear memory reconsolidation. Here, we investigated the effect of GR blockade on fear memory reconsolidation in rats. Rats were trained and tested in an inhibitory avoidance task. Intrahippocampal or systemic administration of the GR antagonist RU38486 immediately following memory reactivation produced a deficit in post-retrieval long-term memory that persisted over test sessions, and memory did not re-emerge following a footshock reminder. These results indicate that hippocampal GRs are required for reconsolidation of fear-based memory.

Antidepressant-like effects of mineralocorticoid but not glucocorticoid antagonists in the lateral septum: interactions with the serotonergic system

The lateral septum (LS) is a limbic brain region that receives serotonergic projections from raphe neurons and participates in the modulation of stress responses and affective states. The present study determined whether mineralocorticoid receptors (MRs) and/or glucocorticoid receptors (GRs) located in the LS interact with the serotonergic system in the regulation of depressive-like behavior of rats subjected to the forced swimming test (FST). We also studied the effect of corticosterone release induced by the FST on MR- and GR-mRNA expression in the LS. Specifically, we studied the antidepressant-like effects of spironolactone (a MR antagonist), mifepristone (a GR antagonist), and the antidepressant clomipramine (CMI) administered directly into the LS. In addition, spironolactone and CMI actions were studied in animals with serotonergic depletion induced by dl-p-chlorophenylalanine (pCPA). Finally, adrenalectomized and Sham-operated rats were subjected to the FST to determine MR- and GR-mRNA expression in the LS at different post-FST intervals. The results showed that intraseptal injection of spironolactone, but not mifepristone induced antidepressant-like actions in the FST; this effect was blocked by pCPA treatment. CMI and spironolactone increased 5-HT concentrations in the LS of rats subjected to the FST. Increases in corticosterone release, induced by the FST, correlated with a decrease in MR-mRNA expression in the LS; no correlation was found with GR-mRNA expression. In conclusion, MRs in the lateral septum, but not GRs, participate in the regulation of depressive-like behavior of animals subjected to the FST. Both serotonin and corticosterone play an important role in MR actions in the LS.

Blockade of mineralocorticoid and glucocorticoid receptors reverses stress-induced motor impairments

AIM

Stress and glucocorticoids can influence movement performance and pathologies of the motor system. The classic notion assumes that the glucocorticoid receptor (GR) mediates the majority of stress-induced behavioral changes. Nevertheless, recent findings have attributed a more prominent role to the mineralocorticoid receptor (MR) in modulating behavior. The purpose of this study was to dissociate the impact of MR versus GR activation in movement and stress-associated motor disruption.

METHODS

Groups of male and female rats were tested in skilled reaching and open field behavior and treated peri-orally with either agonists or antagonists for MR and GR, respectively.

RESULTS

Selective acute activation of MR (aldosterone) and GR (dexamethasone) decreased movement success with a magnitude similar to stress-induced impairment in male and female animals. By contrast, antagonist treatment to block MR (RU-28318) or GR (Mifepristone, RU-486) prevented motor impairments caused by acute restraint stress or corticosterone treatment. Moreover, both antagonists reversed chronic stress- and glucocorticoid-induced motor impairments to values comparable to baseline levels. Higher success rates in treated animals were accompanied by improved performance of skilled limb movements. In addition, combined treatment with MR and GR antagonists had additive benefit on aim and advance towards the reaching target.

CONCLUSION

These observations suggest that MR or GR equally influence motor system function with partially synergistic effects. Males and females show comparable responses to MR and GR activation or blockade. The need for balanced activation of MRs and GRs in motor control requires consideration in intervention strategies to improve performance in health and disease.

Spironolactone and low-dose dexamethasone enhance extinction of contextual fear conditioning

Glucocorticoids play a role in memory formation, and they may contribute to memory changes in stress-related mental disorders, such as posttraumatic stress disorder. Cortisol may act through mineralocorticoid (MR) or glucocorticoid (GR) receptors, and the objective of the present study was to evaluate the effects of the MR antagonist spironolactone, the GR antagonist mifepristone, the MR agonist fludrocortisone, and the GR agonist dexamethasone on the extinction of contextually conditioned fear in rats. Propranolol was used as a positive control. As expected, propranolol administered before the test session increased memory extinction. Pre-test administration of spironolactone and low-dose dexamethasone also increased the extinction of an aversive memory, whereas fludrocortisone impaired extinction. High-dose dexamethasone and mifepristone were found to have no effect in this model. Post-test spironolactone treatment impaired aversive memory extinction. These results indicate that MR and GR are related to extinction of aversive memories, and MR blockade may be a promising candidate for the treatment of stress-related memory disorders.

Converging effects of acute stress on spatial and recognition memory in rodents: a review of recent behavioural and pharmacological findings

The heterogeneous effects of acute stress on learning and memory depend on numerous parameters related to the stressor, the time the stressor is experienced, and the nature of the stimuli or task examined. In the present review, we systematically summarize the rodent literature examining the effects of acute extrinsic stress on spatial and recognition memory. Converging evidence from a number of behavioural tasks suggests acute stress disrupts the retrieval of spatial and recognition memory regardless of whether the stress is experienced before or after learning. Few studies have attempted to discern whether these effects are due to specific failures in consolidation or retrieval of task relevant information. Recent studies demonstrate that diverse mechanisms related to activation of the hypothalamic-pituitary-adrenal axis and alterations in glutamatergic synaptic plasticity mediate the effects of acute stress on spatial and recognition memory. Taken together, these findings have significantly advanced our understanding of the neural mechanisms mediating learning and memory and may stimulate the search for novel therapeutics to treat stress-related psychiatric disorders.

New aspects of rapid aldosterone signaling

Aldosterone, the endogenous ligand of the mineralocorticoid receptor (MR) in humans, is a steroid hormone that regulates salt and water homeostasis. Recently, additional pathophysiological effects in the renocardiovascular system have been identified. Besides genomic effects mediated by activated MR, rapid aldosterone actions that are independent of translation and transcription have been documented. While these nongenomic actions influence electrolyte homeostasis, pH and cell volume in classical MR target organs, they also participate in pathophysiological effects in the renocardiovascular system causing endothelial dysfunction, inflammation and remodeling. The mechanisms conveying these rapid effects consist of a multitude of signaling molecules and include a cross-talk with genomic aldosterone effects as well as with angiotensin II and epidermal growth factor receptor signaling. Rapid corticosteroid signaling via the MR has also been demonstrated in the brain. Altogether, the function of nongenomic aldosterone effects seems to be to modulate other signaling cascades, depending on the surrounding milieu.

Verapamil enhances acute stress or glucocorticoid-induced deficits in retrieval of long-term memory in rats

This study was designed to investigate an interaction between acute restraint stress and corticosterone with verapamil, a blocker of L-type voltage-dependent calcium (VDC) channels on retrieval of long-term memory. Young adult male rats were trained in one trial inhibitory avoidance task (0.5 mA, 3 s footshock). On retention test given 48 h after training, the latency to re-enter dark compartment of the apparatus was recorded. In Experiment 1, verapamil pretreatment (5, 10, or 20 mg/kg) enhanced the impairing effects of acute stress (which was applied for 10 min in a Plexiglass tube 30 min before the retention test) on memory retrieval. The applied stress increased circulating corticosterone levels as assessed immediately after the retention test, indicating that stress-induced impairment of memory retrieval is mediated, in part, by increased plasma levels of glucocorticoids. Verapamil did not change this response. In Experiment 2, pretreatment of an intermediate dose of verapamil also enhanced corticosterone-induced impairment of memory retrieval. In Experiments 3 and 4, acute stress or corticosterone did not change motor activity with or without prior treatment of verapamil, suggesting that stress or glucocorticoid-induced impairment of memory retrieval is not due to any gross disturbances in motor performance of animals. These findings indicate that blockade of L-type VDC channels enhances stress or glucocorticoid-induced impairment of memory retrieval, and provide evidence for the existence of an interaction between glucocorticoids and L-type VDC channels on memory retrieval.

Emotion and cognition in high and low stress sensitive mouse strains: a combined neuroendocrine and behavioral study in BALB/c and C57BL/6J mice

Emotionally arousing experiences and stress influence cognitive processes and vice versa. Understanding the relations and interactions between these three systems forms the core of this study. We tested two inbred mouse strains (BALB/c, C57BL/6J; male; 3-month-old) for glucocorticoid stress system markers (expression of MR and GR mRNA and protein in hippocampus, amygdala, and prefrontal cortex; blood plasma corticosterone), used behavioral tasks for emotions and cognitive performance (elevated plus maze, holeboard) to assess the interdependence of these factors. We hypothesize that BALB/c mice have a stress-vulnerable neuroendocrine phenotype and that emotional expressions in BALB/c and C57BL/6J mice will differentially contribute to learning and memory. We applied factor analyses on emotional and cognitive parameters to determine the behavioral structure of BALB/c and C57BL/6J mice. Glucocorticoid stress system markers indeed show that BALB/c mice are more stress-vulnerable than C57BL/6J mice. Moreover, emotional and explorative factors differed between naïve BALB/c and C57BL/6J mice. BALB/c mice display high movement in anxiogenic zones and high risk assessment, while C57BL/6J mice show little movement in anxiogenic zones and display high vertical exploration. Furthermore, BALB/c mice are superior learners, showing learning related behavior which is highly structured and emotionally biased when exposed to a novel or changing situation. In contrast, C57BL/6J mice display a rather “chaotic” behavioral structure during learning in absence of an emotional factor. These results show that stress vulnerability coincides with more emotionality, which drives well orchestrated goal directed behavior to the benefit of cognition. Both phenotypes have their advantage depending on environmental demands.