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

Functional segregation of rostral and caudal hippocampus in associative memory

Introduction

The hippocampus plays a crucial role in episodic memory. Given its complexity, the hippocampus participates in multiple aspects of higher cognitive functions, among which are semantics-based encoding and retrieval. However, the "where," "when" and "how" of distinct aspects of memory processing in the hippocampus are still under debate.

Methods

Here, we employed a visual associative memory task that involved encoding three levels of subjective congruence to delineate the differential involvement of the rostral and caudal portions (also referred as anterior/posterior portions) of the human hippocampus during memory encoding, recognition and associative recall.

Results

Through stereo-EEG recordings in epilepsy patients we show that associative memory is reflected by rostral hippocampal activity during encoding, and caudal hippocampal activity during retrieval. In contrast, recognition memory encoding selectively activates the rostral hippocampus. The temporal dynamics of memory processing are manifested by gamma power increase, which partially overlaps with low-frequency power decrease during encoding and retrieval. Congruence levels modulate low-frequency activity prominently in the caudal hippocampus.

Discussion

These findings highlight an anatomical segregation in the hippocampus in accordance with the contributions of its partitions to associative and recognition memory.

Mineralocorticoid Receptor Antagonists and Cognitive Outcomes in Cardiovascular Disease and Beyond: A Systematic Review

Background/Objectives: Cognitive impairment is a debilitating comorbidity affecting diverse patient populations, yet the cognitive effects of therapies like mineralocorticoid receptor antagonists (MRAs) remain underexplored. Preclinical evidence suggests that MRAs, particularly spironolactone, may reduce cognitive decline by modulating aldosterone-dependent pathways and targeting hippocampal receptors. However, evidence in humans is fragmented, and no systematic review has consolidated these findings. This review evaluates the cognitive effects of MRAs, synthesizes current data, and identifies research gaps. Methods: A literature search using terms related to MRAs and cognitive outcomes was performed in PubMed and Web of Science from 1979 to 2023. A total of 143 articles were identified and 85 were screened after removing duplicates. Ultimately, 44 studies were included and were classified based on study design and population focus (preclinical, healthy controls, patients with psychiatric disorders, and cardiovascular patients). Results: Spironolactone demonstrated mixed effects on cognition. In healthy participants, it improved spatial memory under stress and prevented stress-related suppression of medial temporal activity, but impaired working memory and selective attention. In patients with psychiatric conditions, spironolactone reduced cognitive empathy deficits in major depressive disorder and improved working memory in bipolar I disorder. In cardiovascular patients, spironolactone improved cognitive scores and hippocampal memory but had no effect on non-hippocampal memory. Conclusions: Spironolactone exhibits potential cognitive benefits across diverse populations. However, its effects on cognition are mixed, highlighting the need for further research to understand its mechanisms and therapeutic potential, particularly in patients with heart failure and other related conditions.

Developmental activity-based anorexia alters hippocampal non-genomic stress response and induces structural instability and spatial memory impairment in female rats

OBJECTIVE

Anorexia nervosa (AN) is characterized by hyperactivation of the hypothalamic-pituitary-adrenal axis and cognitive deficits. However, little is known about the rapid non-genomic stress response involvement. This study investigates the molecular, structural and behavioral signatures of the anorexic phenotype induction in female rats on stress-related mechanisms in the hippocampus.

METHOD

Female adolescent rats, exposed to the combination of food restriction and wheel access, i.e., the activity-based anorexia (ABA) protocol, were sacrificed in the acute phase of the pathology (postnatal day [P]42) or following a 7-day recovery period (P49).

RESULTS

ABA rats, in addition to body weight loss and increased wheel activity, alter their pattern of activity over days, showing increased food anticipatory activity, a readout of their motivation to engage in intense physical activity. Corticosterone plasma levels were enhanced at P42 while reduced at P49 in ABA rats. In the membrane fraction of the hippocampus, we found reduced glucocorticoid receptor levels together with reduced expression of caldesmon, n-cadherin and neuroligin-1, molecular markers of cytoskeletal stability and glutamatergic homeostasis. Accordingly, structural analyses revealed reduced dendritic spine density, a reduced number of mushroom-shaped spines, together with an increased number of thin-shaped spines. These events are paralleled by impairment in spatial memory measured in the spatial order object recognition test. These effects persisted even when body weight of ABA rats was restored.

DISCUSSION

Our findings indicate that ABA induction orchestrates hippocampal maladaptive structural and functional plasticity, contributing to cognitive deficits, providing a putative mechanism that could be targeted in AN patients.

The emerging role of rapid corticosteroid actions on excitatory and inhibitory synaptic signaling in the brain

Over the past two decades, there has been increasing evidence for the importance of rapid-onset actions of corticosteroid hormones in the brain. Here, we highlight the distinct rapid corticosteroid actions that regulate excitatory and inhibitory synaptic transmission in the hypothalamus, the hippocampus, basolateral amygdala, and prefrontal cortex. The receptors that mediate rapid corticosteroid actions are located at or close to the plasma membrane, though many of the receptor characteristics remain unresolved. Rapid-onset corticosteroid effects play a role in fast neuroendocrine feedback as well as in higher brain functions, including increased aggression and anxiety, and impaired memory retrieval. The rapid non-genomic corticosteroid actions precede and complement slow-onset, long-lasting transcriptional actions of the steroids. Both rapid and slow corticosteroid actions appear to be indispensable to adapt to a continuously changing environment, and their imbalance can increase an individual's susceptibility to psychopathology.

An antibody-based molecular switch for continuous small-molecule biosensing

We present a generalizable approach for designing biosensors that can continuously detect small-molecule biomarkers in real time and without sample preparation. This is achieved by converting existing antibodies into target-responsive "antibody-switches" that enable continuous optical biosensing. To engineer these switches, antibodies are linked to a molecular competitor through a DNA scaffold, such that competitive target binding induces scaffold switching and fluorescent signaling of changing target concentrations. As a demonstration, we designed antibody-switches that achieve rapid, sample preparation-free sensing of digoxigenin and cortisol in undiluted plasma. We showed that, by substituting the molecular competitor, we can further modulate the sensitivity of our cortisol switch to achieve detection at concentrations spanning 3.3 nanomolar to 3.3 millimolar. Last, we integrated this switch with a fiber optic sensor to achieve continuous sensing of cortisol in a buffer and blood with <5-min time resolution. We believe that this modular sensor design can enable continuous biosensor development for many biomarkers.

A viewpoint on aldosterone and BMI related brain morphology in relation to treatment outcome in patients with major depression

An abundance of knowledge has been collected describing the involvement of neuroendocrine parameters in major depression. The hypothalamic-pituitary-adrenocortical (HPA) axis regulating cortisol release has been extensively studied; however, attempts to target the HPA axis pharmacologically to treat major depression have failed. This review focuses on the importance of the adrenocortical stress hormone aldosterone, which is released by adrenocorticotropic hormone and angiotensin, and the mineralocorticoid receptor (MR) in depression. Depressed patients, in particular those with atypical depression, have signs of central hyperactivation of the aldosterone sensitive MR, potentially as a consequence of a reactive aldosterone release induced by low blood pressure and as a result of low sensitivity of peripheral MR. This is reflected in reduced heart rate variability, increased salt appetite and sleep changes in this group of patients. In addition, enlarged brain ventricles, compressed corpus callosum and changes of the choroid plexus are associated with increased aldosterone (in relation to cortisol). Furthermore, subjects with these features often show obesity. These characteristics are related to a worse antidepressant treatment outcome. Alterations in choroid plexus function as a consequence of increased aldosterone levels, autonomic dysregulation, metabolic changes and/or inflammation may be involved. The characterization of this regulatory system is in its early days but may identify new targets for therapeutic interventions.

Spironolactone as a potential new pharmacotherapy for alcohol use disorder: convergent evidence from rodent and human studies

Evidence suggests that spironolactone, a nonselective mineralocorticoid receptor (MR) antagonist, modulates alcohol seeking and consumption. Therefore, spironolactone may represent a novel pharmacotherapy for alcohol use disorder (AUD). In this study, we tested the effects of spironolactone in a mouse model of alcohol drinking (drinking-in-the-dark) and in a rat model of alcohol dependence (vapor exposure). We also investigated the association between spironolactone receipt for at least 60 continuous days and change in self-reported alcohol consumption, using the Alcohol Use Disorders Identification Test-Consumption (AUDIT-C), in a pharmacoepidemiologic cohort study in the largest integrated healthcare system in the US. Spironolactone dose-dependently reduced the intake of sweetened or unsweetened alcohol solutions in male and female mice. No effects of spironolactone were observed on drinking of a sweet solution without alcohol, food or water intake, motor coordination, alcohol-induced ataxia, or blood alcohol levels. Spironolactone dose-dependently reduced operant alcohol self-administration in dependent and nondependent male and female rats. In humans, a greater reduction in alcohol consumption was observed among those who received spironolactone, compared to propensity score-matched individuals who did not receive spironolactone. The largest effects were among those who reported hazardous/heavy episodic alcohol consumption at baseline (AUDIT-C ≥ 8) and those exposed to ≥ 50 mg/day of spironolactone. These convergent findings across rodent and human studies demonstrate that spironolactone reduces alcohol use and support the hypothesis that this medication may be further studied as a novel pharmacotherapy for AUD.

Stress, memory, and implications for major depression

The stress response comprises a phylogenetically conserved set of cognitive, physiological, and behavioral responses that evolved as a survival strategy. In this context, the memory of stressful events would be adaptive as it could avoid re-exposure to an adverse event, otherwise the event would be facilitated in positively stressful or non-distressful conditions. However, the interaction between stress and memory comprises complex responses, some of them which are not yet completely understood, and which depend on several factors such as the memory system that is recruited, the nature and duration of the stressful event, as well as the timing in which this interaction takes place. In this narrative review, we briefly discuss the mechanisms of the stress response, the main memory systems, and its neural correlates. Then, we show how stress, through the action of its biochemical mediators, influences memory systems and mnemonic processes. Finally, we make use of major depressive disorder to explore the possible implications of non-adaptive interactions between stress and memory to psychiatric disorders, as well as possible roles for memory studies in the field of psychiatry.

Stress Impairs Episodic Retrieval by Disrupting Hippocampal and Cortical Mechanisms of Remembering

Despite decades of science investigating the neural underpinnings of episodic memory retrieval, a critical question remains: how does stress influence remembering and the neural mechanisms of recollection in humans? Here, we used functional magnetic resonance imaging and multivariate pattern analyses to examine the effects of acute stress during retrieval. We report that stress reduced the probability of recollecting the details of past experience, and that this impairment was driven, in part, by a disruption of the relationship between hippocampal activation, cortical reinstatement, and memory performance. Moreover, even memories expressed with high confidence were less accurate under stress, and this stress-induced decline in accuracy was explained by reduced posterior hippocampal engagement despite similar levels of category-level cortical reinstatement. Finally, stress degraded the relationship between the engagement of frontoparietal control networks and retrieval decision uncertainty. Collectively, these findings demonstrate the widespread consequences of acute stress on the neural systems of remembering.

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.

Hippocampal µ-opioid receptors on GABAergic neurons mediate stress-induced impairment of memory retrieval

Stressful life events induce abnormalities in emotional and cognitive behaviour. The endogenous opioid system plays an essential role in stress adaptation and coping strategies. In particular, the µ-opioid receptor (μR), one of the major opioid receptors, strongly influences memory processing in that alterations in μR signalling are associated with various neuropsychiatric disorders. However, it remains unclear whether μR signalling contributes to memory impairments induced by acute stress. Here, we utilized pharmacological methods and cell-type-selective/non-cell-type-selective μR depletion approaches combined with behavioural tests, biochemical analyses, and in vitro electrophysiological recordings to investigate the role of hippocampal μR signalling in memory-retrieval impairment induced by acute elevated platform (EP) stress in mice. Biochemical and molecular analyses revealed that hippocampal μRs were significantly activated during acute stress. Blockage of hippocampal μRs, non-selective deletion of μRs or selective deletion of μRs on GABAergic neurons (μR_GABA) reversed EP-stress-induced impairment of memory retrieval, with no effect on the elevation of serum corticosterone after stress. Electrophysiological results demonstrated that stress depressed hippocampal GABAergic synaptic transmission to CA1 pyramidal neurons, thereby leading to excitation/inhibition (E/I) imbalance in a μR_GABA-dependent manner. Pharmaceutically enhancing hippocampal GABA_A receptor-mediated inhibitory currents in stressed mice restored their memory retrieval, whereas inhibiting those currents in the unstressed mice mimicked the stress-induced impairment of memory retrieval. Our findings reveal a novel pathway in which endogenous opioids recruited by acute stress predominantly activate μR_GABA to depress GABAergic inhibitory effects on CA1 pyramidal neurons, which subsequently alters the E/I balance in the hippocampus and results in impairment of memory retrieval.

Cognitive dysfunction in mice lacking proper glucocorticoid receptor dimerization

Stress is a major risk factor for depression and anxiety. One of the effects of stress is the (over-) activation of the hypothalamic-pituitary-adrenal (HPA) axis and the release of stress hormones such as glucocorticoids (GCs). Chronically increased stress hormone levels have been shown to have detrimental effects on neuronal networks by inhibiting neurotrophic processes particularly in the hippocampus proper. Centrally, GCs modulate metabolic as well as behavioural processes by activating two classes of corticoid receptors, high-affinity mineralocorticoid receptors (MR) and low-affinity glucocorticoid receptors (GR). Upon activation, GR can modulate gene transcription either as a monomeric protein, or as a dimer interacting directly with DNA. GR can also modulate cellular processes via non-genomic mechanisms, for example via a GPCR-protein interaction. We evaluated the behavioral phenotype in mice with a targeted mutation in the GR in a FVB/NJ background. In GRdim/dim mice, GR proteins form poor homodimers, while the GR monomer remains intact. We evaluated the effect of poor GR dimerization on hippocampus-dependent cognition as well as on exploration and emotional behavior under baseline and chronically increased stress hormone levels. We found that GRdim/dim mice did not behave differently from GRwt/wt littermates under baseline conditions. However, after chronic elevation of stress hormone levels, GRdim/dim mice displayed a significant impairment in hippocampus-dependent memory compared to GRwt/wt mice, which correlated with differential expression of hippocampal Bdnf/TrkB and Fkbp5.

CA1 LTP Attenuated by Corticosterone is Canceled by Effusol via Rescuing Intracellular Zn2+ Dysregulation

Exposure to corticosterone attenuates hippocampal CA1 long-term potentiation (LTP) via intracellular Zn2+ dysregulation. Here we report that effusol, a phenanthrene isolated from Chinese medicine Juncus effusus, rescues CA1 LTP attenuated by corticosterone. In vivo microdialysis experiment indicated that both increases in extracellular glutamate induced under perfusion with corticosterone and high K+ are suppressed in the hippocampus by co-perfusion with effusol. Because corticosterone and high K+ also increase extracellular Zn2+ level, followed by intracellular Zn2+ dysregulation, the effect of effusol on both the increases was examined in brain slice experiments. Effusol did not suppress increase in extracellular Zn2+ in the hippocampal CA1 of brain slices bathed in corticosterone, but suppressed increase in intracellular Zn2+, which may be linked with suppressing the increase in extracellular glutamate in vivo. In vivo CA1 LTP was attenuated under perfusion with corticosterone prior to LTP induction, while the attenuation was rescued by co-perfusion with effusol, suggesting that the rescuing effect of effusol is due to suppressing the increase in intracellular Zn2+ in CA1 pyramidal cells. The present study indicates that CA1 LTP attenuated by corticosterone is canceled by effusol, which rescues intracellular Zn2+ dysregulation via suppressing extracellular glutamate accumulation. It is likely that effusol defends the hippocampal function against stress-induced cognitive decline.

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 opioid system in stress-induced memory disorders: From basic mechanisms to clinical implications in post-traumatic stress disorder and Alzheimer's disease

Cognitive and emotional impairment are a serious consequence of stress exposure and are core features of neurological and psychiatric conditions that involve memory disorders. Indeed, acute and chronic stress are high-risk factors for the onset of post-traumatic stress disorder (PTSD) and Alzheimer's disease (AD), two devastating brain disorders associated with memory dysfunction. Besides the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis, stress response also involves the activation of the opioid system in brain regions associated with stress regulation and memory processing. In this context, it is possible that stress-induced memory disorders may be attributed to alterations in the interaction between the neuroendocrine stress system and the opioid system. In this review, we: (1) describe the effects of acute and chronic stress on memory, and the modulatory role of the opioid system, (2) discuss the contribution of the opioid system to the pathophysiology of PTSD and AD, and (3) present evidence of current and potential therapies that target the opioid receptors to treat PTSD- and AD-associated symptoms.

Assessment of Improvement in Oxidative Stress Indices with Resocialization in Memory Retrieval in Y-Maze in Male Rats

Introduction:

Memory deficit is an important issue in some psychiatric diseases either as a primary symptom or as a comorbid symptom. Factors that determine the decline or improvement of memory are an important subject to reduce the severity of these diseases.

Methods and materials:

In this study, 32 male Sprague-Dawley rats were randomly divided into 4 experimental groups: social (control), isolation, resocialization for 3 days, and resocialization for 7 days. Isolation occurred for 14 days. Resocialization groups were resocialized for 3 or 7 days after isolation. In the social group, there was no intervention with normal socializing among the rats. In the isolation group, rats were isolated with no resocialization. In all 4 groups, after performing the Y-maze, the rats’ brains were removed to assess oxidative stress status in the hippocampus and prefrontal cortex.

Results:

Y-maze performance improved after 3 and 7 days of resocialization. However, oxidative stress status for malondialdehyde, glutathione and nitrite/nitrate returned to normal levels except in 2 experiments after 7 days of resocialization. In addition, in 2 experiments, just glutathione in the prefrontal cortex and nitrite/nitrate in the hippocampus after 3 days of resocialization improved.

Conclusions:

A return to normal levels in all types of antioxidant markers in the resocialization groups is not the only factor for improving memory deficits resulting from isolation. Resocialization may also be activating other regulatory mechanisms besides an antioxidant defense.

Sex-specific deficits in biochemical but not behavioral responses to delay fear conditioning in prenatal alcohol exposure mice

BACKGROUND

Studies in clinical populations and preclinical models have shown that prenatal alcohol exposure (PAE) is associated with impairments in the acquisition, consolidation and recall of information, with deficits in hippocampal formation-dependent learning and memory being a common finding. The glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and extracellular signal-regulated kinase 2 (ERK2) are key regulators of hippocampal formation development, structure and functioning and, thus, are potential mediators of PAE's effects on this brain region. In the present studies, we employed a well-characterized mouse model of PAE to identify biochemical mechanisms that may underlie activity-dependent learning and memory deficits associated with PAE.

METHODS

Mouse dams consumed either 10% (w/v) ethanol in 0.066% (w/v) saccharin (SAC) or 0.066% (w/v) SAC alone using a limited (4-h) access, drinking-in-the-dark paradigm. Male and female offspring (∼180-days of age) were trained using a delay conditioning procedure and contextual fear responses (freezing behavior) were measured 24 h later. Hippocampal formation tissue and blood were collected from three behavioral groups of animals: 20 min following conditioning (conditioning only group), 20 min following the re-exposure to the context (conditioning plus re-exposure group), and behaviorally naïve (naïve group) mice. Plasma corticosterone levels were measured by enzyme immunoassay. Immunoblotting techniques were used to measure protein levels of the GR, MR, ERK1 and ERK2 in nuclear and membrane fractions prepared from the hippocampal formation.

RESULTS

Adult SAC control male and female mice displayed similar levels of contextual fear. However, significant sex differences were observed in freezing exhibited during the conditioning session. Compared to same-sex SAC controls, male and female PAE mice demonstrated context fear deficits While plasma corticosterone concentrations were elevated in PAE males and females relative to their respective SAC naïve controls, plasma corticosterone concentrations in the conditioning only and conditioning plus re-exposure groups were similar in SAC and PAE animals. Relative to the respective naïve group, nuclear GR protein levels were increased in SAC, but not PAE, male hippocampal formation in the conditioning only group. In contrast, no difference was observed between nuclear GR levels in the naïve and conditioning plus re-exposure groups. In females, nuclear GR levels were significantly reduced by PAE but there was no effect of behavioral group or interaction between prenatal treatment and behavioral group. In males, nuclear MR levels were significantly elevated in the SAC conditioning plus re-exposure group compared to SAC naïve mice. In PAE females, nuclear MR levels were elevated in both the conditioning only and conditioning plus re-exposure groups relative to the naïve group. Levels of activated ERK2 (phospho-ERK2 expressed relative to total ERK2) protein were elevated in SAC, but not PAE, males following context re-exposure, and a significant interaction between prenatal exposure group and behavioral group was found. No main effects or interactions of behavioral group and prenatal treatment on nuclear ERK2 were found in female mice. These findings suggest a sex difference in which molecular pathways are activated during fear conditioning in mice.

CONCLUSIONS

In PAE males, the deficits in contextual fear were associated with the loss of responsiveness of hippocampal formation nuclear GR, MR and ERK2 to signals generated by fear conditioning and context re-exposure. In contrast, the contextual fear deficit in PAE female mice does not appear to be associated with activity-dependent changes in GR and MR levels or ERK2 activation during training or memory recall, although an overall reduction in nuclear GR levels may play a role. These studies add to a growing body of literature demonstrating that, at least partially, different mechanisms underlie learning, memory formation and memory recall in males and females and that these pathways are differentially affected by PAE.

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.

Obesity and episodic memory function

Obesity-related lifestyle factors, such as physical activity behavior and dietary intake, have been shown to be associated with episodic memory function. From animal work, there is considerable biological plausibility linking obesity with worse memory function. There are no published systematic reviews evaluating the effects of obesity on episodic memory function among humans, and examining whether physical activity and diet influences this obesity-memory link. Thus, the purpose of this systematic review was to evaluate the totality of research examining whether obesity is associated with episodic memory function, and whether physical activity and dietary behavior confounds this relationship. A review approach was employed, using PubMed, PsychInfo, and Sports Discus databases. Fourteen studies met our criteria. Among these 14 reviewed studies, eight were cross-sectional, four were prospective, and two employed a randomized controlled experimental design. Twelve of the 14 studies did not take into consideration dietary behavior in their analysis, and similarly, nine of the 14 studies did not take into consideration participant physical activity behavior. Among the 14 studies, ten found an inverse association of weight status on memory function, but for one of these studies, this association was attenuated after controlling for physical activity. Among the 14 evaluated studies, four did not find a direct effect of weight status on memory. Among the four null studies, one, however, found an indirect effect of BMI on episodic memory and another found a moderation effect of BMI and age on memory function. It appears that obesity may be associated with worse memory function, with the underlying mechanisms discussed herein. At this point, it is uncertain whether adiposity, itself, is influencing memory changes, or rather, whether adiposity-related lifestyle behaviors (e.g., physical inactivity and diet) are driving the obesity-memory relationship.

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.

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.

Adolescent-onset of cocaine use is associated with heightened stress-induced reinstatement of cocaine seeking

Adolescent rats take cocaine more readily than adults, are more sensitive to lower doses of the drug and work harder for it. It remains unknown if adolescent-onset of cocaine use has long-term consequences on adult relapse liability. Therefore, we tested if self-administering cocaine during adolescence impacts subsequent stress-induced reinstatement to cocaine seeking and taking, after a prolonged drug-free period. Adolescent (~P42) or adult (P88) rats self-administered cocaine (0.6 or 1.2 mg/kg/infusion) for 7 or 10 days. Then, they underwent a prolonged drug-free period (21-40 days), after which they were tested for reinstatement of cocaine-seeking (i.e. responding in the absence of cocaine) induced by the stress hormone corticosterone, the pharmacological stressor yohimbine or electric footshock. Studies employed either single extinction session (within-session extinction/reinstatement) or repeated extinction prior to reinstatement (between-session extinction/reinstatement). Finally, in a separate set of experiments, rats underwent a prolonged drug-free period (~40 days) and were then allowed to self-administer cocaine again, using progressive-ratio procedures that appraise the reinforcing efficacy of cocaine. Rats with adolescent-onset of cocaine use showed greater stress-induced reinstatement of cocaine seeking than rats with adult-onset of cocaine use. This was observed across conditions, providing external validity to these results. Groups did not differ on drug taking in progressive-ratio tests. Our studies indicate that experiencing cocaine during adolescence renders subjects particularly responsive to the subsequent effects of stress on drug seeking. This heightened propensity for reinstatement puts adolescent-onset drug users at heightened risk for relapse.

Aldosterone and the Mineralocorticoid Receptor: Risk Factors for Cardiometabolic Disorders

Preclinical studies have convincingly demonstrated a role for the mineralocorticoid receptor (MR) in adipose tissue physiology. These studies show that increased MR activation causes adipocyte dysfunction leading to decreased production of insulin-sensitizing products and increased production of inflammatory factors, creating an environment conducive to metabolic and cardiovascular disease. Accumulating data also suggest that MR activation may be an important link between obesity and metabolic syndrome. Moreover, MR activation may mediate the pathogenic consequences of metabolic syndrome. Recent attempts at reversing cardiometabolic damage in patients with type 2 diabetes using MR antagonists have shown promising results. MR antagonists are already used to treat heart failure where their use decreases mortality and morbidity over and above the use of traditional therapies alone. However, more data are needed to establish the benefits of MR antagonists in diabetes, obesity, and metabolic syndrome.

Acute stress blocks the caffeine-induced enhancement of contextual memory retrieval in mice

This study investigated in mice the dose-effect of caffeine on memory retrieval in non-stress and stress conditions. C57 Bl/6 Jico mice learned two consecutive discriminations (D1 and D2) in a four-hole board which involved either distinct contextual (CSD) or similar contextual (SSD) cues. All mice received an i.p. injection of vehicle or caffeine (8, 16 or 32mg/kg) 30min before the test session. Results showed that in non-stress conditions, the 16mg/kg caffeine dose induced a significant enhancement of D1 performance in CSD but not in SSD. Hence, we studied the effect of an acute stress (electric footshocks) administered 15min before the test session on D1 performance in caffeine-treated mice. Results showed that stress significantly decreased D1 performance in vehicle-treated controls and the memory-enhancing effect induced by the 16mg/kg caffeine dose in non-stress condition is no longer observed. Interestingly, whereas caffeine-treated mice exhibited weaker concentrations of plasma corticosterone as compared to vehicles in non-stress condition, stress significantly increased plasma corticosterone concentrations in caffeine-treated mice which reached similar level to that of controls. Overall, the acute stress blocked both the endocrinological and memory retrieval enhancing effects of caffeine.

Effect of mineralocorticoid receptor blockade on hippocampal-dependent memory in adults with obesity

OBJECTIVE

The hippocampus is crucial for paired-associate learning. Obesity is associated with increased mineralocorticoid receptor (MR) activity in peripheral and possibly central tissues, decreased hippocampal size in humans, and impaired hippocampal learning in rodents. The MR is expressed in hippocampal neurons, and MR blockade improves hippocampal learning in obese animals. The goal of the study was to determine whether MR blockade would modulate paired-associate learning in men and women with obesity.

METHODS

Men and women ages 20-61 years with BMI between 30-45 kg/m(2) were randomly assigned to placebo (n = 11; 7 women) or 50 mg spironolactone daily (n = 12; 7 women) for six weeks. At baseline and post-treatment, subjects underwent a clinical and hormonal evaluation. They also underwent a computerized task that assesses paired-associate learning and has been shown by functional magnetic resonance imaging to activate the hippocampus.

RESULTS

In an ANCOVA model that adjusted for baseline paired-associate learning, age, and race, spironolactone treatment was associated with a significant (P = 0.043) improvement in hippocampal memory as compared to placebo treatment.

CONCLUSIONS

Our findings demonstrate, for the first time, that blocking MR with chronic, low-dose spironolactone treatment improves paired-associate learning in individuals with obesity, suggesting that MR activation contributes to hippocampal memory modulation in humans.

Early social enrichment rescues adult behavioral and brain abnormalities in a mouse model of fragile X syndrome

Converging lines of evidence support the use of environmental stimulation to ameliorate the symptoms of a variety of neurodevelopmental disorders. Applying these interventions at very early ages is critical to achieve a marked reduction of the pathological phenotypes. Here we evaluated the impact of early social enrichment in Fmr1-KO mice, a genetic mouse model of fragile X syndrome (FXS), a major developmental disorder and the most frequent monogenic cause of autism. Enrichment was achieved by providing male KO pups and their WT littermates with enhanced social stimulation, housing them from birth until weaning with the mother and an additional nonlactating female. At adulthood they were tested for locomotor, social, and cognitive abilities; furthermore, dendritic alterations were assessed in the hippocampus and amygdala, two brain regions known to be involved in the control of the examined behaviors and affected by spine pathology in Fmr1-KOs. Enrichment rescued the behavioral FXS-like deficits displayed in adulthood by Fmr1-KO mice, that is, hyperactivity, reduced social interactions, and cognitive deficits. Early social enrichment also eliminated the abnormalities shown by adult KO mice in the morphology of hippocampal and amygdala dendritic spines, namely an enhanced density of immature vs mature types. Importantly, enrichment did not induce neurobehavioral changes in WT mice, thus supporting specific effects on FXS-like pathology. These findings show that early environmental stimulation has profound and long-term beneficial effects on the pathological FXS phenotype, thereby encouraging the use of nonpharmacological interventions for the treatment of this and perhaps other neurodevelopmental diseases.

Cortisol effects on flow-experience

RATIONALE

Stress affects flow-experience, but the mediating psychobiological mechanisms remain unknown. Previous studies showed an association between flow-experience and endogenous cortisol levels, suggesting an inverted, u-shaped relation between flow-experience and cortisol. However, these studies could not exclude effects of other stress factors.

OBJECTIVES

The aim of this experiment was, therefore, to test the isolated effect of cortisol on flow-experience, independent of concomitant physiological and psychological stress responses, via controlled administration of exogenous cortisol.

METHODS

Sixty-four young healthy subjects (32 males, 32 females) participated in the experiment. According to a double-blind, randomized, placebo-controlled, cross-over design, they received 20 mg oral cortisol on 1 day and placebo on the other day, respectively, with a time distance of 1 week between the experimental days. One hour after cortisol administration, participants engaged in the computer game Pacman. Pacman was delivered in five blocks of randomly differing difficulty levels. One block lasted 5 min. At the end of each block, participants rated flow-experience by the Flow Short Scale. Data was analyzed with hierarchical linear modeling. Subjects were not able to predict whether the pill they received contained cortisol or placebo.

RESULTS

Overall, results revealed a negative effect of oral 20 mg cortisol on flow-experience, with no differences between males and females.

CONCLUSIONS

This study is the first to show that exogenous cortisol in a dose corresponding to a severe stressor impairs flow-experience. The observed negative effect of high cortisol dosage on experienced flow underlines recent findings of an inverted u-shaped relationship between cortisol and flow.

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.

Early life stress and serotonin transporter gene variation interact to affect the transcription of the glucocorticoid and mineralocorticoid receptors, and the co-chaperone FKBP5, in the adult rat brain

The short allelic variant of the serotonin transporter (5-HTT) promoter-linked polymorphic region (5-HTTLPR) has been associated with the etiology of major depression by interaction with early life stress (ELS). A frequently observed endophenotype in depression is the abnormal regulation of levels of stress hormones such as glucocorticoids. It is hypothesized that altered central glucocorticoid influence on stress-related behavior and memory processes could underlie the depressogenic interaction of 5-HTTLPR and ELS. One possible mechanism could be the altered expression of the genes encoding the glucocorticoid and mineralocorticoid receptors (GR, MR) and their inhibitory regulator FK506-binding protein 51 (FKBP5) in stress-related forebrain areas. To test this notion, we exposed heterozygous (5-HTT^+/−) and homozygous (5-HTT^−/−) serotonin transporter knockout rats and their wildtype littermates (5-HTT^+/+) to daily 3 h maternal separations from postnatal day 2 to 14. In the medial prefrontal cortex (mPFC) and hippocampus of the adult male offspring, we found that GR, MR, and FKBP5 mRNA levels were affected by ELS × 5-HTT genotype interaction. Specifically, 5-HTT^+/+ rats exposed to ELS showed decreased GR and FKBP5 mRNA in the dorsal and ventral mPFC, respectively. In contrast, 5-HTT^+/− rats showed increased MR mRNA levels in the hippocampus and 5-HTT^−/− rats showed increased FKBP5 mRNA in the ventral mPFC after ELS exposure. These findings indicate that 5-HTT genotype determines the specific adaptation of GR, MR, and FKBP5 expression in response to early life adversity. Therefore, altered extra-hypothalamic glucocorticoid signaling should be considered to play a role in the depressogenic interaction of ELS and 5-HTTLPR.

Stress induced a shift from dorsal hippocampus to prefrontal cortex dependent memory retrieval: role of regional corticosterone

Most of the deleterious effects of stress on memory retrieval are due to a dysfunction of the hippocampo-prefrontal cortex interplay. The role of the stress-induced regional corticosterone increase in such dysfunction remains however unclear, since there is no published study as yet dedicated to measuring corticosterone concentrations simultaneously in both the prefrontal cortex (mPFC) and the hippocampus (dHPC) in relation with memory impairments. To that aim, we first showed in Experiment 1 that an acute stress (3 electric footschocks; 0.9 mA each) delivered before memory testing reversed the memory retrieval pattern (MRP) in a serial discrimination task in which mice learned two successive discriminations. More precisely, whereas non-stressed animals remembered accurately the first learned discrimination and not the second one, stressed mice remembered more accurately the second discrimination but not the first one. We demonstrated that local inactivation of dHPC or mPFC with the anesthetic lidocaine recruited the dHPC activity in non-stress conditions whereas the stress-induced MRP inversion recruited the mPFC activity. In a second experiment, we showed that acute stress induced a very similar time-course evolution of corticosterone rises within both the mPFC and dHPC. In a 3rd experiment, we found however that in situ injections of corticosterone either within the mPFC or the dHPC before memory testing favored the emergence of the mPFC-dependent MRP but blocked the emergence of the dHPC-dependent one. Overall, our study evidences that the simultaneous increase of corticosterone after stress in both areas induces a shift from dHPC (non-stress condition) to mPFC-dependent MRP and that corticosterone is critically involved in mediating the deleterious effects of stress on cognitive functions involving the mPFC-HPC interplay.

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.

For whom the bell (curve) tolls: cortisol rapidly affects memory retrieval by an inverted U-shaped dose-response relationship

Stress and cortisol are generally considered to impair declarative memory retrieval, although opposite results have also been reported. Dose-dependent effects and differences between genomic and non-genomic cortisol effects are possible reasons for these discrepancies. The aim of the current experiment was to assess the non-genomic effects of escalating doses of intravenous cortisol on cued recall of socially relevant information in humans. 40 participants (age range 20-30 years; 20 females) learned associations between male faces with a neutral facial expression and descriptions of either positive or negative social behaviors and were tested one week later in a cued recall paradigm. Escalating doses of cortisol (0, 3, 6, 12, 24 mg) were administered 8 min before testing according to a between-subjects design. An inverted U-shaped dose-response relationship between salivary cortisol levels and recall performance was observed, with moderate elevation of salivary cortisol resulting in the best recall performance. This is the first study in humans demonstrating that cortisol rapidly modulates declarative memory retrieval via a dose-dependent, non-genomic mechanism that follows an inverted U-shaped curve. Our result further emphasizes the importance of fast cortisol effects for human cognition.

Non-receptor-tyrosine kinases integrate fast glucocorticoid signaling in hippocampal neurons

Despite numerous descriptions of rapid effects of corticosterone on neuronal function, the intracellular mechanisms responsible for these changes remain elusive. The present comprehensive analysis reveals that signaling from a membrane-located G protein-coupled receptor activates PKC, Akt/PKB, and PKA, which subsequently trigger the phosphorylation of the tyrosine kinases Pyk2, Src, and Abl. These changes induce rapid cytoskeletal rearrangements (increased PSD-95 co-clustering) within the post-synaptic density; these events are accompanied by increased surface NMDA receptor expression, reflecting corticosterone-induced inhibition of NMDA receptor endocytosis. Notably, none of these signaling mechanisms require de novo protein synthesis. The observed up-regulation of ERK1/2 (downstream of NMDA receptor signaling) together with the fact that c-Abl integrates cytoplasmic and nuclear functions introduces a potential mechanism through which rapid signaling initiated at the plasma membrane may eventually determine the long term integrated response to corticosterone by impacting on the transcriptional machinery that is regulated by classical, nuclear mineralocorticoid, and glucocorticoid receptors.

Blocking mineralocorticoid receptors impairs, blocking glucocorticoid receptors enhances memory retrieval in humans

Memory retrieval is impaired at very low as well as very high cortisol levels, but not at intermediate levels. This inverted-U-shaped relationship between cortisol levels and memory retrieval may originate from different roles of the mineralocorticoid (MR) and glucocorticoid receptor (GR) that bind cortisol with distinctly different affinity. Here, we examined the role of MRs and GRs in human memory retrieval using specific receptor antagonists. In two double-blind within-subject, cross-over designed studies, young healthy men were asked to retrieve emotional and neutral texts and pictures (learnt 3 days earlier) between 0745 and 0915 hours in the morning, either after administration of 400 mg of the MR blocker spironolactone vs placebo (200 mg at 2300 hours and 200 mg at 0400 hours, Study I) or after administration of the GR blocker mifepristone vs placebo (200 mg at 2300 hours, Study II). Blockade of MRs impaired free recall of both texts and pictures particularly for emotional material. In contrast, blockade of GRs resulted in better memory retrieval for pictures, with the effect being more pronounced for neutral than emotional materials. These findings indicate indeed opposing roles of MRs and GRs in memory retrieval, with optimal retrieval at intermediate cortisol levels likely mediated by high MR but concurrently low GR activation.

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.

Critical role of plasma corticosteroid-binding-globulin during stress to promote glucocorticoid delivery to the brain: impact on memory retrieval

We aimed at demonstrating that corticosteroid binding globulin (CBG), a plasma glycoprotein binding glucocorticoids with high affinity in blood, endorses a major role under stress conditions by regulating free glucocorticoid access to the brain and thereby influences glucocorticoid-dependent behaviors. Hence, we compared CBG-deficient mice (Cbg-/-) and their controls (Cbg+/+) in a specific memory task, i.e. the delayed alternation behavior, requiring memory retrieval both under stress and nonstress conditions and previously shown to be dependent on hippocampal glucocorticoid levels. Our results evidence that Cbg-/- mice, unlike controls, remain insensitive to stress applied before memory retrieval. Furthermore, under stress conditions, we observed a blunted surge of corticosterone (CORT) in plasma and no free CORT rise in the hippocampus of Cbg-/-. Moreover, intrahippocampal infusion of CORT through implanted cannulae was used to mimic stress CORT rise before memory retrieval. This infusion of CORT reproduced memory retrieval impairments in Cbg-/- as in Cbg+/+ controls. Finally, we provide evidence that Cbg-/- mice exhibit a normal adrenal response to stress and ACTH. Given that CBG deficiency is known to markedly impact on CORT clearance from plasma, our current article demonstrates that Cbg-/- insensitivity in memory retrieval after stress results from the blunted CORT response due to increased CORT clearance. Overall, our data suggest that the impact of CBG genetic deficiency on various behavioral patterns reported previously stems from a smaller CORT reservoir in blood. Inasmuch as CBG discloses interindividual variations, such a parameter ought to be taken into account when studying stress-induced glucocorticoid action in brain.

Cognitive dysfunction in psychiatric disorders: characteristics, causes and the quest for improved therapy

Studies of psychiatric disorders have traditionally focused on emotional symptoms such as depression, anxiety and hallucinations. However, poorly controlled cognitive deficits are equally prominent and severely compromise quality of life, including social and professional integration. Consequently, intensive efforts are being made to characterize the cellular and cerebral circuits underpinning cognitive function, define the nature and causes of cognitive impairment in psychiatric disorders and identify more effective treatments. Successful development will depend on rigorous validation in animal models as well as in patients, including measures of real-world cognitive functioning. This article critically discusses these issues, highlighting the challenges and opportunities for improving cognition in individuals suffering from psychiatric disorders.