Corticosteroids and the brain

Orphan G Protein Coupled Receptors in Affective Disorders

G protein coupled receptors (GPCRs) are the main mediators of signal transduction in the central nervous system. Therefore, it is not surprising that many GPCRs have long been investigated for their role in the development of anxiety and mood disorders, as well as in the mechanism of action of antidepressant therapies. Importantly, the endogenous ligands for a large group of GPCRs have not yet been identified and are therefore known as orphan GPCRs (oGPCRs). Nonetheless, growing evidence from animal studies, together with genome wide association studies (GWAS) and post-mortem transcriptomic analysis in patients, pointed at many oGPCRs as potential pharmacological targets. Among these discoveries, we summarize in this review how emotional behaviors are modulated by the following oGPCRs: ADGRB2 (BAI2), ADGRG1 (GPR56), GPR3, GPR26, GPR37, GPR50, GPR52, GPR61, GPR62, GPR88, GPR135, GPR158, and GPRC5B.

Stress & executive functioning: A review considering moderating factors

A multitude of studies investigating the effects of stress on cognition has produced an inconsistent picture on whether - and under which conditions - stress has advantageous or disadvantageous effects on executive functions (EF). This review provides a short introduction to the concept of stress and its neurobiology, before discussing the need to consider moderating factors in the association between stress and EF. Three core domains are described and discussed in relation to the interplay between stress and cognition: the influence of different paradigms on physiological stress reactivity, individual differences in demographic and biological factors, and task-related features of cognitive tasks. Although some moderating variables such as the endocrine stress response have frequently been considered in single studies, no attempt of a holistic overview has been made so far. Therefore, we propose a more nuanced and systematic framework to study the effects of stress on executive functioning, comprising a holistic overview from the induction of stress, via biological mechanisms and interactions with individual differences, to the influence of stress on cognitive performance.

The neuroprotective effect of Riparin IV on oxidative stress and neuroinflammation related to chronic stress-induced cognitive impairment

BACKGROUND

Cognitive impairment is identified as one of the diagnostic criteria for major depressive disorder and can extensively affect the quality of life of patients. Based on these findings, this study aimed to investigate the possible effects of Riparin IV (Rip IV) on cognitive impairment induced by chronic administration of corticosterone in mice.

METHODS

Female Swiss mice were divided into four groups: control (Control), corticosterone (Cort), Riparin IV (Cort + Rip IV), and Fluvoxamine (Cort + Flu). Three groups were administered corticosterone (20 mg/kg) subcutaneously during the 22-day study, while the control group received only vehicle. After the 14th day, the groups were administered medications: Riparin IV (Rip IV), fluvoxamine (Flu), or distilled water, by gavage, 1 h after the subcutaneous injections. After treatment, mice underwent behavioral testing, and brain areas were removed for oxidative stress and cytokine content assays.

RESULTS

The results revealed that Cort-treated mice developed a cognitive impairment and exhibited a neuroinflammatory profile with an oxidative load and Th1/Th2 cytokine imbalance. Rip IV treatment significantly ameliorated the cognitive deficit induced by Cort and displayed a neuroprotective effect.

CONCLUSION

The antidepressant-like ability of Rip IV treatment against chronic Cort-induced stress may be due to its potential to mitigate inflammatory damage and oxidative stress. The antioxidant and anti-inflammatory effect observed indicates Rip IV as a possible drug for antidepressant treatment of non-responsive patients with severe and cognitive symptoms.

Postnatal steroid therapy is associated with autism spectrum disorder in children and adolescents of very low birth weight infants

BACKGROUND

This study evaluates the association between major neonatal morbidities and autism spectrum disorder (ASD) in children and adolescents born of very low birth weight (VLBW).

METHODS

Historical cohort study using the Israel national VLBW infant database linked with the Maccabi Healthcare Services (MHS) medical records. The study cohort comprised 4963 VLBW subjects born from 1999 to 2012, >1 year of age. Multivariable logistic regression analyses were used to assess factors associated with ASD.

RESULTS

The diagnosis of ASD was confirmed in 113 children (2.3%). Infants with major neonatal morbidities had higher rates of ASD; however, in the multivariable analyses these were not significantly associated with ASD: severe intraventricular hemorrhage (OR 1.21 [95% CI 0.60-2.45]), post-hemorrhagic hydrocephalus (OR 1.77 [0.73-4.29]), periventricular leukomalacia (OR 1.02 [0.42-2.51]), severe retinopathy of prematurity (OR 1.91 [0.995-3.67]), and bronchopulmonary dysplasia (OR 1.44 [0.84-2.45]). Postnatal steroid therapy when included separately was associated with an OR of 1.97 [1.18-3.29] for ASD. This association remained significant when postnatal steroid therapy was included with each of the neonatal morbidities (ORs ranging from 1.91 to 2.11).

CONCLUSIONS

This study suggests a significant association between postnatal steroid therapy and ASD in VLBW infants. This possible association should be considered in future studies evaluating potential risk factors for ASD in preterm infants.

The timing-dependent effects of stress-induced cortisol release on evaluative conditioning

The neuro-physiological response to stress has far-reaching implications for learning and memory processes. Here, we examined whether and how the stress-induced release of cortisol, following the socially-evaluated cold pressor test, influenced the acquisition of preferences in an evaluative conditioning (EC) procedure. We found that when the stressor preceded the evaluation phase, cortisol responders showed decreased evaluative conditioning effects. By contrast, impairing effects of a stressor-induced cortisol release before encoding were not found. Moreover, explicit memory was not found to be affected by the stressor or its timing. Implications of the timing-dependent effects of stress-induced cortisol release on EC and the relation between stress and associative memory are discussed.

Rhythmicity matters: Circadian and ultradian patterns of HPA axis activity

Oscillations are a fundamental feature of neural and endocrine systems. The hypothalamic-pituitary-adrenal (HPA) axis dynamically controls corticosteroid secretion in basal conditions and in response to stress. Across the 24-h day, HPA axis activity oscillates with both an ultradian and circadian rhythm. These rhythms have been shown to be important for regulating metabolism, inflammation, mood, cognition and stress responsiveness. Here we will discuss the neural and endocrine mechanisms driving these rhythms, the physiological importance of these rhythms and health consequences when they are disrupted.

Neurophysiological and cognitive changes in pregnancy

The hormonal fluctuations in pregnancy drive a wide range of adaptive changes in the maternal brain. These range from specific neurophysiological changes in the patterns of activity of individual neuronal populations, through to complete modification of circuit characteristics leading to fundamental changes in behavior. From a neurologic perspective, the key hormone changes are those of the sex steroids, estradiol and progesterone, secreted first from the ovary and then from the placenta, the adrenal glucocorticoid cortisol, as well as the anterior pituitary peptide hormone prolactin and its pregnancy-specific homolog placental lactogen. All of these hormones are markedly elevated during pregnancy and cross the blood-brain barrier to exert actions on neuronal populations through receptors expressed in specific regions. Many of the hormone-induced changes are in autonomic or homeostatic systems. For example, patterns of oxytocin and prolactin secretion are dramatically altered to support novel physiological functions. Appetite is increased and feedback responses to metabolic hormones such as leptin and insulin are suppressed to promote a positive energy balance. Fundamental physiological systems such as glucose homeostasis and thermoregulation are modified to optimize conditions for fetal development. In addition to these largely autonomic changes, there are also changes in mood, behavior, and higher processes such as cognition. This chapter summarizes the hormonal changes associated with pregnancy and reviews how these changes impact on brain function, drawing on examples from animal research, as well as available information about human pregnancy.

Efficacy of a Second Brain Biopsy for Intracranial Lesions after Initial Negativity

Background and Purpose

The rationale for performing a second brain biopsy after initial negativity is not well evaluated in the literature. This study was designed to 1) assess the efficacy of a second brain biopsy when the first biopsy was nondiagnostic, 2) identify possible factors associated with an increased diagnostic rate in the second biopsy, and 3) analyze additional morbidity induced by the second biopsy.

Methods

We performed a retrospective cohort study from 2009 to 2019, during which 1,919 patients underwent a brain biopsy, including 30 who were biopsied twice (1.6%). The specific histological diagnosis rate, diagnosis-associated factors, and complication rate were assessed for the 30 twice-biopsied patients.

Results

The second biopsy allowed a specific histological diagnosis in 86.7% of the patients who had initially undergone a nondiagnostic brain biopsy [odds ratio (OR)=7.5, 95% confidence interval (CI)=3.0–18.7, p<0.001]. The multivariate analysis showed that only prebiopsy corticosteroid administration (OR=2.6, 95% CI=1.1–6.0, p=0.01) was an important factor in predicting a nondiagnostic biopsy. None of the patients developed a symptomatic complication after the first biopsy, while two (6.0%) patients experienced a transient complication after the second biopsy (p=0.49).

Conclusions

Performing a second brain biopsy in patients who have an initial nondiagnostic biopsy is effective in most cases. We advocate that a second biopsy be systematically considered in the diagnosis algorithm of these patients after it has been verified that molecular testing cannot help to obtain a diagnosis. Corticosteroid administration can lead to nondiagnostic biopsies and should be avoided when possible during the prebiopsy period.

Effects of Dexamethasone on Remodeling of the Hippocampal Synaptic Filamentous Actin Cytoskeleton in a Model of Pilocarpine-induced Status Epilepticus

The filamentous actin (F-actin) cytoskeleton is progressively damaged after status epilepticus (SE), which is related to delayed neuronal death, aberrant recurrent circuits and epileptogenesis. Glucocorticoids regulate dendritic spine remodeling by acting on glucocorticoid receptors and the dynamics of the F-actin cytoskeleton. Our previous study showed that administration of dexamethasone (DEX) in the latent period of the pilocarpine epileptic model reduces damage to the hippocampal filamentous actin cytoskeleton and the loss of hippocampal neurons and aids in maintaining the synaptic structures, but it is not sufficient to stop epileptogenesis. In this work, we focused on the role of glucocorticoids in regulating the hippocampal F-actin cytoskeleton during SE. We examined the abundance of synaptic F-actin, analyzed the hippocampal F-actin/G-actin (F/G) ratio and pCofilin, and evaluated the number of hippocampal neurons and pre/postsynaptic markers in pilocarpine-induced status epilepticus mice with or without administration of dexamethasone (DEX). We found that the latency of Stage 3 seizures increased, the mortality decreased, the damage to the synaptic F-actin cytoskeleton in the hippocampal subfields was significantly attenuated, and a greater number of postsynaptic structures were retained in the hippocampal subfields after treatment with DEX. These results indicate that treatment with dexamethasone stabilizes the synaptic F-actin cytoskeleton and reduces the damage to the brain due to SE. This approach is expected to be beneficial in alleviating delayed neuron damage and the process of epileptogenesis.

The ergogenic impact of the glucocorticoid prednisolone does not translate into increased running motivation in mice

Glucocorticoids, such as prednisolone, are considered sport doping agents owing to their ergogenic properties. These are accounted for by peripheral mechanisms associated with energetic and anti-inflammatory processes. However, because glucocorticoids target brain tissues, it is likely that these ergogenic impacts are associated with central effects. One of these might be reward motivation, which relies on glucocorticoid receptor-expressing mesocorticolimbic dopaminergic neurons. In keeping with this possibility, this study has explored in mice whether repeated prednisolone administration (5 or 15 μg/ml of drinking water for 10 days) affected intrinsic motivation for running, a strong reinforcer in rodents. Running motivation was assessed by means of a cued-reward motivated instrumental task wherein wheel-running was conditioned by prior nose poke responses under fixed (FR), and then progressive (PR), ratio reinforcement schedules. Sub-chronic ingestion of prednisolone decreased the running distance covered during each rewarded sequence under FR schedules. This finding did not extend to wheel-running performances in mice provided free (i.e. unconditioned) wheel-running opportunities. Running motivation, as estimated under a PR reinforcement schedule, was found to be decreased (lowest concentration) or to remain unaffected (highest concentration) by prednisolone concentration. Lastly, an inter-individual analysis of the respective effects of prednisolone on muscular endurance (as assessed in the wire grid-hanging test) and on running motivation indicated that the former was not predictive of the latter. This observation suggests that prednisolone ergogenic impacts might occur without any concomitant increase in intrinsic exercise motivation.

Stress experience and hormone feedback tune distinct components of hypothalamic CRH neuron activity

Stress leaves a lasting impression on an organism and reshapes future responses. However, the influence of past experience and stress hormones on the activity of neural stress circuits remains unclear. Hypothalamic corticotropin-releasing hormone (CRH) neurons orchestrate behavioral and endocrine responses to stress and are themselves highly sensitive to corticosteroid (CORT) stress hormones. Here, using in vivo optical recordings, we find that CRH neurons are rapidly activated in response to stress. CRH neuron activity robustly habituates to repeated presentations of the same, but not novel stressors. CORT feedback has little effect on CRH neuron responses to acute stress, or on habituation to repeated stressors. Rather, CORT preferentially inhibits tonic CRH neuron activity in the absence of stress stimuli. These findings reveal how stress experience and stress hormones modulate distinct components of CRH neuronal activity to mediate stress-induced adaptations.

Stress activates corticotropin-releasing hormone (CRH) neurons in the hypothalamus, but how their activity is regulated during and after stress is unclear. Here, the authors show that stress habituation and corticosteroid feedback tune different components of CRH neuron activity.

The effects of psychosocial stress on intergroup resource allocation

Stress changes our social behavior. Traditionally, stress has been associated with “fight-or-flight” – the tendency to attack an aggressor, or escape the stressor. But stress may also promote the opposite pattern, i.e., “tend-and-befriend” – increased prosociality toward others. It is currently unclear which situational or physiological factors promote one or the other. Here, we hypothesized that stress stimulates both tendencies, but that fight-or-flight is primarily directed against a potentially hostile outgroup, moderated by rapid-acting catecholamines, while tend-and-befriend is mainly shown towards a supportive ingroup, regulated by cortisol. To test this hypothesis, we measured stress-related neurohormonal modulators and sex hormones in male and female participants who were exposed to a psychosocial stressor, and subsequently played an intergroup social dilemma game in which they could reveal prosocial motives towards an ingroup (ingroup-love) and hostility towards an outgroup (outgroup-hate). We found no significant effects of stress on social preferences, but stress-related heart-rate increases predicted outgroup-hostile behavior. Furthermore, when controlling for testosterone, cortisol was associated with increased ingroup-love. Other-regarding behavior was overall higher in male than female participants. Our mixed results are of interest to scholars of the effects of stress on prosocial and aggressive behavior, but call for refinement in future replications.

Corticosterone Injection Impairs Follicular Development, Ovulation and Steroidogenesis Capacity in Mice Ovary

Simple Summary

Researchers have hitherto established hundreds of animal stress models. However, these models have some limitations due to the complexity in operation and large differences between individual animals. In particular, there are few stress models that are specifically applied in mammalian ovaries. In this study, using intraperitoneal injection of cortisol/corticosterone (CORT), we successfully established a stress model that acts on the ovarian function. Our data showed that CORT inhibits ovarian and follicular development and blocks ovulation. The establishment of this model might provide a living platform for studying ovarian stress in future research.

Abstract

The aim of this study is to establish an ovarian stress model, and to investigate the effects of stress on follicular development. Our data showed that continuous intraperitoneal injection of CORT successfully created a stressful environment in the ovary. To assess the effects of CORT on ovarian functions, 80 three-week-old ICR (Institute of Cancer Research) female mice were randomly divided into control group and treatment group. All mice were injected intraperitoneally with pregnant horse serum gonadotropin (PMSG). At the same time, the treatment group were injected with CORT (1 mg/mouse) at intervals of 8 h; while the control group was injected with same volume of methyl sulfoxide (DMSO). Blood, ovaries, or ovarian granulosa cell samples were collected at 24 h, 48 h, and 55 h after PMSG injection. The results showed that, compared with the control group, CORT-injected mice revealed a significant decrease in ovulation rates, ovarian weight, ovarian index, the number of secondary follicles and mature follicles, levels of estrogen and progesterone, and mRNA expression of steroid synthase-related genes. Collectively, our findings clearly demonstrated that CORT injection could represent an effective practice to simulate stresses that inhibit ovarian functions by reducing follicular development and ovulation.

Biochemical Mechanisms and Translational Relevance of Hippocampal Vulnerability to Distant Focal Brain Injury: The Price of Stress Response

Focal brain injuries (in particular, stroke and traumatic brain injury) induce with high probability the development of delayed (months, years) cognitive and depressive disturbances which are frequently comorbid. The association of these complications with hippocampal alterations (in spite of the lack of a primary injury of this structure), as well as the lack of a clear dependence between the probability of depression and dementia development and primary damage severity and localization served as the basis for a new hypothesis on the distant hippocampal damage as a key link in the pathogenesis of cognitive and psychiatric disturbances. According to this hypothesis, the excess of corticosteroids secreted after a focal brain damage, in particular in patients with abnormal stress-response due to hypothalamic-pituitary-adrenal axis (HPAA) dysfunction, interacts with corticosteroid receptors in the hippocampus inducing signaling pathways which stimulate neuroinflammation and subsequent events including disturbances in neurogenesis and hippocampal neurodegeneration. In this article, the molecular and cellular mechanisms associated with the regulatory role of the HPAA and multiple functions of brain corticosteroid receptors in the hippocampus are analyzed. Functional and structural damage to the hippocampus, a brain region selectively vulnerable to external factors and responding to them by increased cytokine secretion, forms the basis for cognitive function disturbances and psychopathology development. This concept is confirmed by our own experimental data, results of other groups and by prospective clinical studies of post-stroke complications. Clinically relevant biochemical approaches to predict the risks and probability of post-stroke/post-trauma cognitive and depressive disturbances are suggested using the evaluation of biochemical markers of patients' individual stress-response. Pathogenetically justified ways for preventing these consequences of focal brain damage are proposed by targeting key molecular mechanisms underlying hippocampal dysfunction.

Polystyrene nanoplastics disrupt glucose metabolism and cortisol levels with a possible link to behavioural changes in larval zebrafish

Plastic nanoparticles originating from weathering plastic waste are emerging contaminants in aquatic environments, with unknown modes of action in aquatic organisms. Recent studies suggest that internalised nanoplastics may disrupt processes related to energy metabolism. Such disruption can be crucial for organisms during development and may ultimately lead to changes in behaviour. Here, we investigated the link between polystyrene nanoplastic (PSNP)-induced signalling events and behavioural changes. Larval zebrafish exhibited PSNP accumulation in the pancreas, which coincided with a decreased glucose level. By using hyperglycemic and glucocorticoid receptor (Gr) mutant larvae, we demonstrate that the PSNP-induced disruption in glucose homoeostasis coincided with increased cortisol secretion and hyperactivity in challenge phases. Our work sheds new light on a potential mechanism underlying nanoplastics toxicity in fish, suggesting that the adverse effect of PSNPs are at least in part mediated by Gr activation in response to disrupted glucose homeostasis, ultimately leading to aberrant locomotor activity.

Corticosterone inhibits the expression of cannabinoid receptor-1 and cannabinoid receptor agonist-induced decrease in cell viability in glioblastoma cells

The endocannabinoid system regulates physiological and pathological conditions, including inflammation and cancer. Recently, emotional and physical stressors were observed to be involved in impairing the endocannabinoid system, which was concomitant with an increase in serum corticosteroids. However, the influence of corticosteroids on the endocannabinoid system has yet to be completely elucidated. The present study investigated the effects of corticosterone, one of the corticosteroids, on the endocannabinoid system in malignant glioblastoma cells in vitro. U-87 MG cells derived from malignant glioblastoma were subjected to corticosterone stimulation and their viability, signal transduction, and endocannabinoid-related gene expression were examined. Corticosterone decreased the mRNA and protein expressions of cyclooxygenase-2. Of note, although endocannabinoids decreased cell viability, corticosterone inhibited the cannabinoid receptor agonist-induced decrease in cell viability by downregulating the mRNA and protein expressions of cannabinoid receptor 1 (CB1) in glioblastoma cells. These results suggest that corticosteroids modify the endocannabinoid system in glioblastoma cells, and a reduction in the beneficial anti-tumor effects of endocannabinoids through downregulation of the CB1 receptor by corticosterone may promote the malignant phenotype of glioblastoma.

The effects of different rearing conditions on sexual maturation and maternal care in heterozygous mineralocorticoid receptor knockout mice

Sexual and social development is affected by a complex interplay between genetic makeup and the early-life rearing environment. While many rodent studies focused primarily on the detrimental effects of early-life stress, human literature suggests that genetic susceptibility may not be restricted to negative environments; it may also enhance the beneficial effects of positive rearing conditions. To examine this interaction in a controlled setting, heterozygous mineralocorticoid receptor knockout (MR^+/-) mice and control litter mates were exposed to a limited nesting/bedding (LN, impoverished), standard nesting (SN, control) or communal nesting (CN, enriched) paradigm from postnatal day 2-9 (P2-P9). Offspring was monitored for puberty onset between P24-P36 and, in females, maternal care-giving (i.e. as F1) during adulthood, after which basal corticosterone was measured. Different home-cage environments resulted in profound differences in received maternal care and offspring body weight. In male offspring, LN resulted in delayed puberty onset that was mediated by body weight and unpredictability of maternal care received during early development. In female offspring, rearing condition did not significantly alter sexual maturation and had little effect on their own maternal care-giving behavior. Genotype did affect maternal care: female MR^+/- offspring exhibited a less active nursing style and upregulated fragmentation during adulthood, irrespective of early life conditions. Basal corticosterone levels were highest in MR^+/- mice with a background of LN. Overall, we found a gene-by-environment interaction with respect to basal corticosterone levels, but not for sexual maturation or maternal behavior.

Dexamethasone ameliorates the damage of hippocampal filamentous actin cytoskeleton but is not sufficient to cease epileptogenesis in pilocarpine induced epileptic mice

Rogressive deconstruction of filament actin (F-actin) in hippocampal neurons in the epileptic brain have been associated with epileptogenesis. Previous clinical studies suggest that glucocorticoids treatment plays beneficial roles in refractory epilepsy. Glucocorticoids treatment affects dendritic spine morphology by regulating local glucocorticoid receptors and F-actin cytoskeleton dynamics. However, how glucocorticoids regulate epileptogenesis by controlling F-actin cytoskeleton is not clear yet. Here we study the function of glucocorticoids in epileptogenesis by examining F-actin abundance, hippocampal neuron number, and synaptic markers in pilocarpine-induced epileptic mice in the presence or absence of dexamethasone (DEX) treatment. We found that spontaneous seizure duration was significantly reduced; F-actin damage in hippocampal subfields was remarkably attenuated; loss of pyramidal cells was dramatically decreased; more intact synaptic structures indicated by pre- and postsynaptic markers were preserved in multiple hippocampal regions after DEX treatment. However, the number of ZNT3 positive particles in the molecular layer in the hippocampus of pilocarpine epileptic mice was not altered after DEX treatment. Although not sufficient to cease epileptogenesis, our results suggest that dexamethasone treatment ameliorates the damage of epileptic brain by stabilizing F-actin cytoskeleton in the pilocarpine epileptic mice.

Influence of glucocorticoid and mineralocorticoid receptor stimulation on task switching

The influence of stress on executive functions has been demonstrated in numerous studies and is potentially mediated by the stress-induced cortisol release. Yet, the impact of cortisol on cognitive flexibility and task switching in particular remains equivocal. In this study, we investigated the influence of pharmacological glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) stimulation, two corticosteroid receptor types known to be responsible for cortisol effects on the brain. We conducted two experiments, each with 80 healthy participants (40 women and 40 men), and tested the effect of the unspecific MR/GR agonist hydrocortisone (Experiment I) and the more specific MR agonist fludrocortisone (Experiment II) on switch costs and task rule congruency in a bivalent, cued task switching paradigm. The results did not confirm our hypotheses; we found no significant effects of our manipulations on task switching capacity, although general switching and congruency effects were observed. We discuss the absence of MR/GR-mediated effects and propose alternative mechanisms that could explain stress induced effects on task switching.

Corticosterone mediated functional and structural plasticity in corticotropin-releasing hormone neurons

Corticosteroid stress hormones drive a multitude of adaptations in the brain. Hypothalamic corticotropin-releasing hormone (CRH) neurons control the circulating levels of corticosteroid stress hormones in the body and are themselves highly sensitive to corticosteroids. CRH neurons have been shown to undergo various adaptions in response to acute stress hormone elevations. However, their structural and physiological changes under chronically elevated corticosterone are less clear. To address this, we determined the structural and functional changes in CRH neurons in the paraventricular nucleus of the hypothalamus following 14 days of corticosterone treatment. We find that prolonged corticosterone elevation reduces CRH neuron intrinsic excitability as measured by summation of subthreshold postsynaptic depolarisations and spiking output. We find that under normal conditions, CRH neurons have a relatively compact and simple dendritic arbor, with a low density of somatic and dendritic spines. Interestingly, the axon originated from a proximal dendrite close to the soma in approximately half of the CRH neurons reconstructed. While prolonged elevation in corticosterone levels did not result in any changes to gross dendritic morphology, it induced a significant reduction in both somatic and dendritic spine density. Together these data reveal the morphological features of hypothalamic CRH neurons and highlight their capacity to undergo functional and morphological plasticity in response to chronic corticosterone elevations. This article is part of the Special Issue entitled 'Hypothalamic Control of Homeostasis'.

Corticosteroid Action in the Brain: The Potential of Selective Receptor Modulation

Glucocorticoid hormones have important effects on brain function in the context of acute and chronic stress. Many of these are mediated by the glucocorticoid receptor (GR). GR has transcriptional activity which is highly context-specific and differs between tissues and even between cell types. The outcome of GR-mediated transcription depends on the interactome of associated coregulators. Selective GR modulators (SGRMs) are a class of GR ligands that can be used to activate only a subset of GR-coregulator interactions, thereby giving the possibility to induce a unique combination of agonistic and antagonistic GR properties. We describe SGRM action in animal models of brain function and pathology, and argue for their utility as molecular filters, to characterize context-specific GR interactome and transcriptional activity that are responsible for particular glucocorticoid-driven effects in cognitive processes such as memory consolidation. The ultimate objective of this approach is to identify molecular processes that are responsible for adaptive and maladaptive effects of glucocorticoids in the brain.

Functional Neurochemistry of the Ventral and Dorsal Hippocampus: Stress, Depression, Dementia and Remote Hippocampal Damage

The hippocampus is not a homogeneous brain area, and the complex organization of this structure underlies its relevance and functional pleiotropism. The new data related to the involvement of the ventral hippocampus in the cognitive function, behavior, stress response and its association with brain pathology, in particular, depression, are analyzed with a focus on neuroplasticity, specializations of the intrinsic neuronal network, corticosteroid signaling through mineralocorticoid and glucocorticoid receptors and neuroinflammation in the hippocampus. The data on the septo-temporal hippicampal gradient are analyzed with particular emphasis on the ventral hippocampus, a region where most important alteration underlying depressive disorders occur. According to the recent data, the existing simple paradigm "learning (dorsal hippocampus) versus emotions (ventral hippocampus)" should be substantially revised and specified. A new hypothesis is suggested on the principal involvement of stress response mechanisms (including interaction of released glucocorticoids with hippocampal receptors and subsequent inflammatory events) in the remote hippocampal damage underlying delayed dementia and depression induced by focal brain damage (e.g. post-stroke and post-traumatic). The translational validity of this hypothesis comprising new approaches in preventing post-stroke and post-trauma depression and dementia can be confirmed in experimental and clinical studies.