Glucocorticoids, hippocampal corticosteroid receptor gene expression and antidepressant treatment: relationship with spatial learning in young and aged rats

Aging or chronic stress impairs working memory and modulates GABA and glutamate gene expression in prelimbic cortex

The glucocorticoid (GC) hypothesis posits that effects of stress and dysregulated hypothalamic-pituitary-adrenal axis activity accumulate over the lifespan and contribute to impairment of neural function and cognition in advanced aging. The validity of the GC hypothesis is bolstered by a wealth of studies that investigate aging of the hippocampus and decline of associated mnemonic functions. The prefrontal cortex (PFC) mediates working memory which also decreases with age. While the PFC is susceptible to stress and GCs, few studies have formally assessed the application of the GC hypothesis to PFC aging and working memory. Using parallel behavioral and molecular approaches, we compared the effects of normal aging versus chronic variable stress (CVS) on working memory and expression of genes that encode for effectors of glutamate and GABA signaling in male F344 rats. Using an operant delayed match-to-sample test of PFC-dependent working memory, we determined that normal aging and CVS each significantly impaired mnemonic accuracy and reduced the total number of completed trials. We then determined that normal aging increased expression of Slc6a11, which encodes for GAT-3 GABA transporter expressed by astrocytes, in the prelimbic (PrL) subregion of the PFC. CVS increased PrL expression of genes associated with glutamatergic synapses: Grin2b that encodes the GluN2B subunit of NMDA receptor, Grm4 that encodes for metabotropic glutamate receptor 4 (mGluR4), and Plcb1 that encodes for phospholipase C beta 1, an intracellular signaling enzyme that transduces signaling of Group I mGluRs. Beyond the identification of specific genes that were differentially expressed between the PrL in normal aging or CVS, examination of Log2 fold-changes for all expressed glutamate and GABA genes revealed a positive association between molecular phenotypes of aging and CVS in the PrL but no association in the infralimbic subregion. Consistent with predictions of the GC hypothesis, PFC-dependent working memory and PrL glutamate/GABA gene expression demonstrate comparable sensitivity to aging and chronic stress. However, changes in expression of specific genes affiliated with regulation of extracellular GABA in normal aging vs. genes encoding for effectors of glutamatergic signaling during CVS suggest the presence of unique manifestations of imbalanced inhibitory and excitatory signaling in the PFC.

Routinely accessible parameters of mineralocorticoid receptor function, depression subtypes and response prediction: a post-hoc analysis from the early medication change trial in major depressive disorder

OBJECTIVES

Previous studies indicated a relationship between aldosterone, the mineralocorticoid receptor (MR), and antidepressant treatment outcome. Physiological indicators of MR function (blood pressure and electrolytes) are easily accessible and may therefore serve as useful predictors. Thus, our aim was to investigate the predictive value of peripheral MR-related markers for antidepressant treatment outcomes.

METHODS

826 MDD patients who had participated in the randomised-controlled Early Medication Change (EMC) trial were analysed. Depression severity and MR-related markers were assessed weekly. In 562 patients, genetic variation of five MR-related genes was determined.

RESULTS

Patients with blood pressure <120mmHg showed higher depression severity (p = 0.005) than patients with blood pressure ≥120mmHg. Patients with a melancholic subtype had significantly lower blood pressures (p = 0.004). Na⁺/K⁺ ratio was positively and K⁺-concentration was negatively correlated to depression severity and to relative changes in HAMD from baseline to day 14, and 56 respectively (p < 0.001). For none of the MR-related genes, genetic variation was associated with treatment outcomes.

CONCLUSIONS

We confirmed early observations of an altered peripheral MR sensitivity, reflected by lower blood pressure, low K⁺ or high Na⁺/K⁺ ratio in patients with more severe depression. These routinely collected biomarkers may potentially be useful for risk stratification in an early stage of treatment. Trial Registration: clinicaltrials.gov Identifier: NCT00974155; https://www.clinicaltrials.gov/ct2/results?term=NCT00974155.

Corticosterone and Glucocorticoid Receptor in the Cortex of Rats during Aging-The Effects of Long-Term Food Restriction

Numerous beneficial effects of food restriction on aging and age-related pathologies are well documented. It is also well-established that both short- and long-term food restriction regimens induce elevated circulating levels of glucocorticoids, stress-induced hormones produced by adrenal glands that can also exert deleterious effects on the brain. In the present study, we examined the effect of long-term food restriction on the glucocorticoid hormone/glucocorticoid receptor (GR) system in the cortex during aging, in 18- and 24-month-old rats. Corticosterone level was increased in the cortex of aged ad libitum-fed rats. Food restriction induced its further increase, accompanied with an increase in the level of 11β-hydroxysteroid dehydrogenase type 1. However, alterations in the level of GR phosphorylated at Ser²³² were not detected in animals on food restriction, in line with unaltered CDK5 level, the decrease of Hsp90, and an increase in a negative regulator of GR function, FKBP51. Moreover, our data revealed that reduced food intake prevented age-related increase in the levels of NFκB, gfap, and bax, confirming its anti-inflammatory and anti-apoptotic effects. Along with an increase in the levels of c-fos, our study provides additional evidences that food restriction affects cortical responsiveness to glucocorticoids during aging.

Differential effects of reduced mineralocorticoid receptor activation by unilateral adrenalectomy vs mineralocorticoid antagonist treatment in patients with primary aldosteronism - Implications for depression and anxiety

The mineralocorticoid receptor (MR) and its ligand aldosterone have been found to play a major role in the pathophysiology of depression. Both could be targets of therapeutic interventions. We analyzed laboratory data and questionnaires evaluating anxiety (using GAD-7 questionnaire) and depression (using PHQD questionnaire) of up to 210 patients with primary aldosteronism (PA) (82 females, 54.7 ± 12.0yrs; 128 males, 48.7 ± 12.8yrs) before and one year after initiation of specific treatment of PA by either adrenalectomy (ADX) or treatment with mineralocorticoid receptor antagonists (MRA). After ADX normalization of aldosterone excess was observed. This was associated with a significant reduction of depressive symptoms, but no significant change in GAD-7 score. MRA treatment was accompanied with persistent high aldosterone levels, but led to a significant improvement of anxiety, but no significant changes in PHQD scores. These data suggest different mechanistic pathways for depression and anxiety mediated via the MR. For treatment of depression a reduction of aldosterone levels might be relevant at CNS locations specific for aldosterone, whereas MRA targets MR more broadly, including areas, where cortisol is the main ligand. MRA may be useful in treatment of anxiety related behavior.

The potential pathophysiological role of aldosterone and the mineralocorticoid receptor in anxiety and depression - Lessons from primary aldosteronism

High levels of aldosterone appear to be related to depressive and anxiety related behavior as demonstrated in therapy refractory depression and primary aldosteronism (PA). We analyzed data from a large register of patients with PA in order to clarify mediators and moderators of this influence. Up to 624 subjects were analyzed, however not all subjects had a complete dataset. Due to the known gender differences in subjects with PA we performed the analyses adjusted for gender. We compared subjects with (PHQ-9 ≥ 5) vs. no depressive symptomatology. 56% of men and 61% of women met this depression criterion. In women aldosterone concentration was significantly higher in depressed patients and renin levels were significantly increased with higher anxiety scores. This was not found in men. Depressive symptoms in men and women were significantly associated to BMI (men: dep vs non-dep: 29.6 vs. 28.4, p < 0.05; women: 26.9 vs. 24.5) and body weight (p < 0.05). Neither blood pressure nor electrolytes were different between depression groups. The relationship of these parameters to anxiety was less pronounced and partially unexpected: only in men higher anxiety (GAD ≥ 5) was related to lower systolic blood pressure. In conclusion, higher aldosterone appears to be associated with depressive symptoms in women, but less so in men with PA. BMI appears to be strongly and independently associated with depressive symptoms in patients with PA, independent of gender. Further studies are required to clarify the causal relationship.

Constitutive differences in glucocorticoid responsiveness are related to divergent spatial information processing abilities

The stress response facilitates survival through adaptation and is intimately related to cognitive processes. The Morris water maze task probes spatial learning and memory in rodents and glucocorticoids (i.e. corticosterone (CORT) in rats) have been suggested to elicit a facilitating action on memory formation. Moreover, the early aging period (around 16-18 months of age) is susceptible to stress- and glucocorticoid-mediated acceleration of cognitive decline. In this study, we tested three lines of rats selectively bred according to their individual differences in CORT responsiveness to repeated stress exposure during juvenility. We investigated whether endogenous differences in glucocorticoid responses influenced spatial learning, long-term memory, and reversal learning abilities in a Morris water maze task at early aging. Additionally, we assessed the quality of the different swimming strategies of the rats. Our results indicate that rats with differential CORT responsiveness exhibit similar spatial learning abilities but different long-term memory retention and reversal learning. Specifically, the high CORT responding line had a better long-term spatial memory, while the low CORT responding line was impaired for both long-term retention and reversal learning. Our modeling analysis of performance strategies revealed further important line-related differences. Therefore, our findings support the view that individuals with high CORT responsiveness would form stronger long-term memories to navigate in stressful environments. Conversely, individuals with low CORT responsiveness would be impaired at different phases of spatial learning and memory.

Stress-Induced Neurodegeneration: The Potential for Coping as Neuroprotective Therapy

Stress responses are essential for survival, but become detrimental to health and cognition with chronic activation. Chronic hypothalamic-pituitary-adrenal axis release of glucocorticoids induces hypothalamic-pituitary-adrenal axis dysfunction and neuronal loss, decreases learning and memory, and modifies glucocorticoid receptor/mineralocorticoid receptor expression. Elderly who report increased stress are nearly 3 times more likely to develop Alzheimer's disease, have decreased global cognition and faster cognitive decline than those reporting no stress. Patients with mild cognitive impairment are more sensitive to stress compared to healthy elderly and those with Alzheimer's disease. Stress may also transduce neurodegeneration via the gut microbiome. Coping styles determine hippocampal mineralocorticoid receptor expression in mice, indicating that coping modifies cortisol's effect on the brain. Identifying neuroprotective coping strategies that lessen the burden of stress may prevent or slow cognitive decline. Treatments and education designed to reduce stress should be recognized as neuroprotective.

Cortisol, moderated by age, is associated with antidepressant treatment outcome and memory improvement in Major Depressive Disorder: A retrospective analysis

BACKGROUND

Studies testing the relationship between cortisol levels, depression, and antidepressant treatment response have yielded divergent results suggesting the possibility of moderators of a cortisol effect. Several studies indicate that age may moderate the relationship between cortisol and depression. In patients with Major Depressive Disorder (MDD), we studied the interactive effects of age and cortisol in association with MDD diagnostic status and mood and memory response to antidepressant treatment.

METHODS

Serum cortisol levels in 66 unmedicated patients with MDD and 75 matched healthy controls (HC) were measured at baseline and retrospectively analyzed. Logistic regression was used to determine an association of age, cortisol and their interaction with MDD diagnosis in the pooled sample of MDD and HC participants. Thirty-four of the MDD participants (age range: 19-65 years; median: 36) underwent treatment with a selective serotonin reuptake inhibitor (SSRl) for 8 weeks. Clinician and self-ratings of depression symptoms, as well as tests of verbal and visual delayed recall were obtained at baseline and post treatment. Moderation analyses determined the effect of age on the relationship between baseline cortisol and treatment outcome.

RESULTS

Cortisol, moderated by age, was associated with MDD diagnosis (p < .05), treatment-associated reduction of depression symptoms (p < .001) and improvement of delayed recall (p < .001). Modeling the Cortisol × Age interaction suggested that for participants below the median age of our sample, lower cortisol levels were associated with a lower rate of MDD diagnosis and higher antidepressant effects. On the contrary, in those above the median sample age, lower cortisol was associated with a higher rate of MDD and less improvement in depression symptoms and memory performance.

CONCLUSIONS

Our results add to the body of literature suggesting that age might be an important factor in moderating the relationship between peripheral cortisol levels, depression, cognition, and prognosis. These results indicate that previous disparities in the literature linking peripheral cortisol levels with depression characteristics and treatment response may critically relate, at least in part, to the age of the participants studied.

Vitamin A deficiency impairs contextual fear memory in rats: Abnormalities in the glucocorticoid pathway

Vitamin A and its active metabolite, retinoic acid (RA), play a key role in the maintenance of cognitive functions in the adult brain. Depletion of RA using the vitamin A deficiency (VAD) model in Wistar rats leads to spatial memory deficits in relation to elevated intrahippocampal basal corticosterone (CORT) levels and increased hippocampal 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity. All of these effects are normalised by vitamin A supplementation. However, it is unknown whether vitamin A status also modulates contextual fear conditioning (CFC) in a glucocorticoid-associated fear memory task dependent on the functional integrity of the hippocampus. In the present study, we investigated the impact of VAD and vitamin A supplementation in adult male rats on fear memory processing, plasma CORT levels, hippocampal retinoid receptors and 11β-HSD1 expression following a novelty-induced stress. We also examined whether vitamin A supplementation or a single injection of UE2316, a selective 11β-HSD1 inhibitor, known to modulate local glucocorticoid levels, had any beneficial effects on contextual fear memory and biochemical parameters in VAD rats. We provide evidence that VAD rats exhibit a decreased fear conditioning response during training with a poor contextual fear memory 24 hours later. These VAD-induced cognitive impairments are associated with elevated plasma CORT levels under basal conditions, as well as following a stressful event, with saturated CORT release, altered hippocampal retinoid receptors and 11β-HSD1 expression. Vitamin A supplementation normalises VAD-induced fear conditioning training deficits and all biochemical effects, although it cannot prevent fear memory deficits. Moreover, a single injection of UE2316 not only impairs contextual fear memory, but also reduces plasma CORT levels, regardless of the vitamin A status and decreases slightly hippocampal 11β-HSD1 activity in VAD rats following stress. The present study highlights the importance of vitamin A status with respect to modulating fear memory conditioning in relation to plasma CORT levels and hippocampal 11β-HSD1.

Recurrent stress across life may improve cognitive performance in individual rats, suggesting the induction of resilience

Depressive symptoms are often accompanied by cognitive impairments and recurrent depressive episodes are discussed as a potential risk for dementia. Especially, stressful life events are considered a potent risk factor for depression. Here, we induced recurrent stress-induced depressive episodes over the life span of rats, followed by cognitive assessment in the symptom-free period. Rats exposed to stress-induced depressive episodes learned faster than control rats. A high degree of stress-induced depressive-like behavior early in the paradigm was a predictor of improved cognitive performance, suggesting induction of resilience. Subsequently, exposure to lorazepam prior to stress-induced depressive episodes and cognitive testing in a nonaversive environment prevented the positive effect. This indicates a beneficial effect of the stress-associated situation, with the existence of individual coping abilities. Altogether, stress may in some have a beneficial effect, yet for those individuals unable to tackle these aversive events, consecutive unpleasant episodes may lead to worse cognitive performance later in life.

Stress-induced corticosterone secretion covaries with working memory in aging

A substantial literature details the relationship between age-related changes to the hypothalamic-pituitary-adrenal axis and deterioration of mnemonic functions that depend on the hippocampus. The relationship between adrenocortical status and other forms of memory that depend on the prefrontal cortex is less well understood in the context of advanced age. Here, we characterized performance of young adult and aged F344 rats on a prefrontal cortex-dependent working memory task and subsequently measured corticosterone (CORT) levels over the diurnal cycle and during exposure to an acute stressor. Our analyses revealed that aged rats with better working memory mounted a greater CORT response during acute stress exposure than either young adults or age-matched rats with impaired working memory. We also observed that age-related elevation of basal CORT levels is not associated with working memory performance. Jointly, these data reveal that the hypothalamic-pituitary-adrenal axis-mediated response to acute stress is positively associated with working memory in aging.

Enteric Microbiota⁻Gut⁻Brain Axis from the Perspective of Nuclear Receptors

Nuclear receptors (NRs) play a key role in regulating virtually all body functions, thus maintaining a healthy operating body with all its complex systems. Recently, gut microbiota emerged as major factor contributing to the health of the whole organism. Enteric bacteria have multiple ways to influence their host and several of them involve communication with the brain. Mounting evidence of cooperation between gut flora and NRs is already available. However, the full potential of the microbiota interconnection with NRs remains to be uncovered. Herewith, we present the current state of knowledge on the multifaceted roles of NRs in the enteric microbiota–gut–brain axis.

Design, synthesis and in vivo study of novel pyrrolidine-based 11β-HSD1 inhibitors for age-related cognitive dysfunction

Recent findings suggest that treatment with 11β-HSD1 inhibitors provides a novel approach to deal with age-related cognitive dysfunctions, including Alzheimer's disease. In this work we report potent 11β-HSD1 inhibitors featuring unexplored pyrrolidine-based polycyclic substituents. A selected candidate administered to 12-month-old SAMP8 mice for four weeks prevented memory deficits and displayed a neuroprotective action. This is the first time that 11β-HSD1 inhibitors have been studied in this broadly-used mouse model of accelerated senescence and late-onset Alzheimer's disease.

Forebrain-Specific Transgene Rescue of 11β-HSD1 Associates with Impaired Spatial Memory and Reduced Hippocampal Brain-Derived Neurotrophic Factor mRNA Levels in Aged 11β-HSD1 Deficient Mice

Mice lacking the intracellular glucocorticoid-regenerating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) are protected from age-related spatial memory deficits. 11β-HSD1 is expressed predominantly in the brain, liver and adipose tissue. Reduced glucocorticoid levels in the brain in the absence of 11β-HSD1 may underlie the improved memory in aged 11β-HSD1 deficient mice. However, the improved glucose tolerance, insulin sensitisation and cardioprotective lipid profile associated with reduced peripheral glucocorticoid regeneration may potentially contribute to the cognitive phenotype of aged 11β-HSD1 deficient mice. In the present study, transgenic mice with forebrain-specific overexpression of 11β-HSD1 (Tg) were intercrossed with global 11β-HSD1 knockout mice (HSD1KO) to examine the influence of forebrain and peripheral 11β-HSD1 activity on spatial memory in aged mice. Transgene-mediated delivery of 11β-HSD1 to the hippocampus and cortex of aged HSD1KO mice reversed the improved spatial memory retention in the Y-maze but not spatial learning in the watermaze. Brain-derived neurotrophic factor (BDNF) mRNA levels in the hippocampus of aged HSD1KO mice were increased compared to aged wild-type mice. Rescue of forebrain 11β-HSD1 reduced BDNF mRNA in aged HSD1KO mice to levels comparable to aged wild-type mice. These findings indicate that 11β-HSD1 regenerated glucocorticoids in the forebrain and decreased levels of BDNF mRNA in the hippocampus play a role in spatial memory deficits in aged wild-type mice, although 11β-HSD1 activity in peripheral tissues may also contribute to spatial learning impairments in aged mice.

Mineralocorticoid receptor stimulation effects on spatial memory in healthy young adults: A study using the virtual Morris Water Maze task

OBJECTIVES

Stress hormones such as cortisol are known to influence a wide range of cognitive functions, including hippocampal based spatial memory. In the brain, cortisol acts via two different receptors: the glucocorticoid (GR) and the mineralocorticoid receptor (MR). As the MR has a high density in the hippocampus, we examined the effects of pharmacological MR stimulation on spatial memory.

METHODS

Eighty healthy participants (40 women, 40 men, mean age=23.9years±SD=3.3) completed the virtual Morris Water Maze (vMWM) task to test spatial encoding and spatial memory retrieval after receiving 0.4mg fludrocortisone, a MR agonist, or placebo.

RESULTS

There was no effect of MR stimulation on spatial encoding during the vMWM task. However, participants who received fludrocortisone exhibited improved spatial memory retrieval performance. There was neither a main effect of sex nor a sex-by-treatment interaction.

CONCLUSION

In young healthy participants, MR stimulation improved hippocampal based spatial memory retrieval in a virtual Morris Water Maze task. Our study not only confirms the importance of MR function in spatial memory, but suggests beneficial effects of acute MR stimulation on spatial memory retrieval in humans.

The Role of Fludrocortisone in Cognition and Mood in Patients with Primary Adrenal Insufficiency (Addison's Disease)

BACKGROUND

Primary adrenal insufficiency (AI) requires hormone replacement therapy with fludrocortisone and hydrocortisone stimulating glucocorticoid (GR) and mineralocorticoid receptors (MR). Evidence from animal and human studies shows that MR function is crucial for cognitive function and mood. Regarding patients with AI, very little is known about the role of MR in cognitive function and mood.

METHODS

A repeated-measures within-subject design was used to determine whether cognitive function and mood are related to MR occupation in patients with AI. Intraindividually, patients were examined twice, with 1 week between testing days: once with fludrocortisone (high MR occupation) and once without fludrocortisone (low MR occupation). All patients kept their stable regimen of hydrocortisone. The assessment of cognitive function included executive function, attention, and verbal, visuospatial and working memory. Additionally, mood and blood pressure were measured.

RESULTS

Verbal memory improved significantly during high MR occupation (after fludrocortisone intake) compared to low MR occupation [without fludrocortisone, t(29) = -2.1, p = 0.046]. There were trend level differences in the Number-Combination test [t(29) = -1.9, p = 0.074] and in the Stroop interference task [t(29) = -1.9, p = 0.068]. No significant differences in visuospatial and working memory were found. Furthermore, the current mood state was better during high MR occupation compared to low MR occupation [t(29) = -2.4, p = 0.023] as was diastolic blood pressure [F(2, 29) = 3.6, p = 0.07].

CONCLUSIONS

Cognitive function and mood in patients with AI depend in part on MR occupation. Because the medium effect size indicates a potential clinical significance, further studies should systematically examine which dosages of fludrocortisone are associated with optimal cognitive function and mood in AI patients.

Decreased Npas4 and Arc mRNA Levels in the Hippocampus of Aged Memory-Impaired Wild-Type But Not Memory Preserved 11β-HSD1 Deficient Mice

Mice deficient in the glucocorticoid-regenerating enzyme 11β-HSD1 resist age-related spatial memory impairment. To investigate the mechanisms and pathways involved, we used microarrays to identify differentially expressed hippocampal genes that associate with cognitive ageing and 11β-HSD1. Aged wild-type mice were separated into memory-impaired and unimpaired relative to young controls according to their performance in the Y-maze. All individual aged 11β-HSD1-deficient mice showed intact spatial memory. The majority of differentially expressed hippocampal genes were increased with ageing (e.g. immune/inflammatory response genes) with no genotype differences. However, the neuronal-specific transcription factor, Npas4, and immediate early gene, Arc, were reduced (relative to young) in the hippocampus of memory-impaired but not unimpaired aged wild-type or aged 11β-HSD1-deficient mice. A quantitative reverse transcriptase-polymerase chain reaction and in situ hybridisation confirmed reduced Npas4 and Arc mRNA expression in memory-impaired aged wild-type mice. These findings suggest that 11β-HSD1 may contribute to the decline in Npas4 and Arc mRNA levels associated with memory impairment during ageing, and that decreased activity of synaptic plasticity pathways involving Npas4 and Arc may, in part, underlie the memory deficits seen in cognitively-impaired aged wild-type mice.

Zuogui Jiangtang Jieyu Formulation Prevents Hyperglycaemia and Depressive-Like Behaviour in Rats by Reducing the Glucocorticoid Level in Plasma and Hippocampus

Aim. To determine whether Zuogui Jiangtang Jieyu prescription (ZGJTJY) has hypoglycemic and antidepressant effects which are mediated by corticosterone through adjustment of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and glucocorticoid (GR) levels. Materials and Methods. The diabetes-related depression rats were randomly divided into four groups: the model group, metformin (1.8 mg/kg) combined with fluoxetine (10.8 mg/kg) group, and ZGJTJY high and low dose groups. Four weeks after modeling, blood glucose, behavior, and cognitive function of depression were detected. The expressions of 11β-HSD1 and GR in hippocampus were measured by western blotting and immunohistochemical experiments. Results. We found that (1) the treatment with ZGJTJY (10.26 g/kg) increases the motor activities and improves cognition ability. (2) ZGJTJY (10.26 g/kg) significantly relieves the disorder in blood and the relative indexes. (3) ZGJTJY (10.26 g/kg) can reduce hippocampal corticosterone expression levels and further improve hippocampus pathological changes. (4) ZGJTJY increased the expression of GR accompanied with decreasing 11β-HSD1 in hippocampus. Conclusions. ZGJTJY inhibits the expression of 11β-HSD1 and increases GR in hippocampus and subsequently modulates blood glucose levels, and therefore it is potential property that ZGJTJY could be of benefit for the treatment of behavior and cognitive function of diabetes-related depression.

Lactobacillus fermentum NS9 restores the antibiotic induced physiological and psychological abnormalities in rats

Gut microbiota play a vital role in maintaining the health of the host. Many factors affect gut microbiota; application of broad range antibiotics disturb microbiota, while probiotic application protects the microbiota. To investigate how probiotics alter the physiological and psychological changes induced by antibiotics, we tested the performance of ampicillin-treated rats in the presence or absence of Lactobacillus fermentum strain NS9, in elevated plus maze and Morris water maze. The results showed that NS9 normalised the composition of gut microbiota and alleviated the ampicillin-induced inflammation in the colon. The levels of the mineralocorticoid and N-methyl-D-aspartate receptors were also elevated in the hippocampus of the ampillicin+NS9 treated group. NS9 administration also reduced the anxiety-like behaviour and alleviated the ampicillin-induced impairment in memory retention. These findings suggest that NS9 is beneficial to the host, because it restores the physiological and psychological abnormalities induced by ampicillin. Our results highlight how gut contents regulate the brain, and shed light on the clinical applications of probiotics to treat the side effect of antibiotics and mental disorders.

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.

Diurnal and stress-induced intra-hippocampal corticosterone rise attenuated in 11β-HSD1-deficient mice: a microdialysis study in young and aged mice

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) locally regenerates active glucocorticoids from their inert forms thereby amplifying intracellular levels within target tissues including the brain. We previously showed greater increases in intra-hippocampal corticosterone (CORT) levels upon Y-maze testing in aged wild-type than in 11β-HSD1(-/-) mice coinciding with impaired and intact spatial memory, respectively. Here we examined whether ageing influences 11β-HSD1 regulation of CORT in the dorsal hippocampus under basal conditions during the diurnal cycle and following stress. Intra-hippocampal CORT levels measured by in vivo microdialysis in freely behaving wild-type mice displayed a diurnal variation with peak levels in the evening that were significantly elevated with ageing. In contrast, the diurnal rise in intra-hippocampal CORT levels was greatly diminished in 11β-HSD1(-/-) mice and there was no rise with ageing; basal intra-hippocampal CORT levels were similar to wild-type controls. Furthermore, a short (3 min) swim stress induced a longer lasting increase in intra-hippocampal CORT levels in wild-type mice than in 11β-HSD1(-/-) mice despite no genotypic differences in elevation of plasma CORT. These data indicate that 11β-HSD1 activity contributes substantially to diurnal and stress-induced increases in hippocampal CORT levels. This contribution is even greater with ageing. Thus, 11β-HSD1 inhibition may be an attractive target for treating cognitive impairments associated with stress or ageing.

Antidepressant- and anxiolytic-like activities of an oil extract of propolis in rats

PURPOSE

Propolis biological effects are mainly attributed to its polyphenolic constituents such as flavonoids and phenolic acids that were recently described in the chemical composition of an extract of propolis obtained with edible vegetal oil (OEP) by our group. The aim of this study was to evaluate the effect of OEP on the behavior of rats.

MATERIALS AND METHODS

An in vivo open field (OF), elevated Plus-maze (EPM), and forced swimming (FS) tests were performed to evaluate locomotor activity, anxiolytic- and antidepressant effects of the extract. Besides, oxidative stress levels were measured in rat blood samples after the behavioral assays by evaluation of the Trolox equivalent antioxidant capacity (TEAC) and nitric oxide levels.

RESULTS

OEP increased locomotion in the OF test (50mg/kg) and central locomotion and open arm entries in the OF and EPM tests (10-50mg/kg) and decreased the immobility time in the FS test (10-50mg/kg). Moreover, OEP reduced nitric oxide levels in response to swim stress induced in rats.

CONCLUSION

OEP exerted stimulant, anxiolytic and antidepressant effects on the Central Nervous System and antioxidant activity in rats, highlighting propolis as a potential therapeutic compound for behavior impairment of anxiety and depression.

A double-hit model of stress dysregulation in rats: implications for limbic corticosteroid receptors and anxious behavior under amitriptyline treatment

Adversity during early life can lead to diverging endocrine and behavioral responses to stress in adulthood. In our laboratory, we evaluated the long-term effects of early life adversity and its interaction with chronic stress during adulthood. We propose this as a model of vulnerability to dysregulation of the stress response. We hypothesized that rats subjected to both protocols would show differential expression of corticosteroid receptors measured as number of neurons immunoreactive for glucocorticoid receptors (GR) or mineralocorticoid receptors (MR), in limbic areas related to the control of anxiety-like behavior. We also evaluated the effect of amitriptyline expecting to prevent the outcomes of the model. Male Wistar rats were separated from the mother (MS) for 4.5 h every day for the first 3 weeks of life. From postnatal day 50, rats were subjected to chronic variable stress (CVS) during 24 d (five types of stressor at different times of day). During the stress protocol, the rats were administered amitriptyline (10 mg/kg i.p.) daily. MS evoked lower MR expression in the central amygdaloid nucleus and this was reversed by amitriptyline. Furthermore, CVS increased MR immunoreactivity in the hippocampal area CA2 and increased anxious behavior; both effects were prevented by the antidepressant. When MS was combined with CVS during adulthood, there was a reduction of locomotor activity, with no corrective effect of amitriptyline. The differential effects among groups could mean that MS would promote an alternative phenotype that is expressed when facing CVS (a double hit) later in life.

Vitamin A status regulates glucocorticoid availability in Wistar rats: consequences on cognitive functions and hippocampal neurogenesis?

A disruption of the vitamin A signaling pathway has been involved in age-related memory decline and hippocampal plasticity alterations. Using vitamin A deficiency (VAD), a nutritional model leading to a hyposignaling of the retinoid pathway, we have recently demonstrated that retinoic acid (RA), the active metabolite of vitamin A, is efficient to reverse VAD-induced spatial memory deficits and adult hippocampal neurogenesis alterations. Besides, excess of glucocorticoids (GCs) occurring with aging is known to strongly inhibit hippocampal plasticity and functions and few studies report on the counteracting effects of RA signaling pathway on GCs action. Here, we have addressed whether the modulation of brain GCs availability could be one of the biological mechanisms involved in the effects of vitamin A status on hippocampal plasticity and functions. Thus, we have studied the effects of a vitamin A-free diet for 14 weeks and a 4-week vitamin A supplementation on plasma and hippocampal corticosterone (CORT) levels in Wistar rats. We have also investigated corticosteroid binding globulin (CBG) binding capacity and 11beta-Hydrosteroid Dehydrogenase type 1 (11β-HSD1) activity, both important modulators of CORT availability at the peripheral and hippocampal levels respectively. Interestingly, we show that the vitamin A status regulates levels of free plasma CORT and hippocampal CORT levels, by acting through a regulation of CBG binding capacity and 11β-HSD1 activity. Moreover, our results suggest that increased CORT levels in VAD rats could have some deleterious consequences on spatial memory, anxiety-like behavior and adult hippocampal neurogenesis whereas these effects could be corrected by a vitamin A supplementation. Thus, the modulation of GCs availability by vitamin A status is an important biological mechanism that should be taken into account in order to prevent age-related cognitive decline and hippocampal plasticity alterations.

Gender differences in anxiety and depressive symptoms in patients with primary hyperaldosteronism: a cross-sectional study

OBJECTIVE

The renin-angiotensin-aldosterone-system (RAAS) has gained increasing attention in the investigation of the pathogenesis of depression. Primary hyperaldosteronism (PA) is associated with a marked aldosterone excess. Prior studies on PA describe an increased prevalence of anxiety and sub-threshold depressive symptoms in these patients.

METHODS

In a cross-sectional exploratory study we investigated 132 patients with PA. Twenty-seven patients were studied before initiation of specific treatment (U = untreated), 56 were studied 5.4 years after initiation of mineralocorticoid antagonist treatment (MRA) and 49 patients were studied 4.3 years after unilateral adrenalectomy (ADX). GAD-7 and PHQD self-rating questionnaires were used to assess symptoms for anxiety and depression.

RESULTS

No significant difference was found between the three investigated groups. A higher prevalence for depression and anxiety compared to the normal population was found. Women of all groups had higher mean values compared to men, for depression in untreated patients this difference was found to be significant. Correlations between the psychopathology and hormones were only found for renin. Plasma renin concentration correlated significantly with anxious symptoms of untreated females.

CONCLUSIONS

This study supports the RAAS to be involved in the pathogenesis of depression as patients with PA seem to be more depressive and anxious compared to the normal population. Gender differences in the regulation of the RAAS seem to be apparent, as females were more affected by the dysregulation than males.

Corticosterone targets distinct steps of synaptic transmission via concentration specific activation of mineralocorticoid and glucocorticoid receptors

Hippocampal neurons are affected by chronic stress and have a high density of cytoplasmic mineralocorticoid and glucocorticoid receptors (MR and GR). Detailed studies on the genomic effects of the stress hormone corticosterone at physiologically relevant concentrations on different steps in synaptic transmission are limited. In this study, we tried to delineate how activation of MR and GR by different concentrations of corticosterone affects synaptic transmission at various levels. The effect of 3-h corticosterone (25, 50, and 100 nM) treatment on depolarization-mediated calcium influx, vesicular release and properties of miniature excitatory post-synaptic currents (mEPSCs) were studied in cultured hippocampal neurons. Activation of MR with 25 nM corticosterone treatment resulted in enhanced depolarization-mediated calcium influx via a transcription-dependent process and increased frequency of mEPSCs with larger amplitude. On the other hand, activation of GR upon 100 nM corticosterone treatment resulted in increase in the rate of vesicular release via the genomic actions of GR. Furthermore, GR activation led to significant increase in the frequency of mEPSCs with larger amplitude and faster decay. Our studies indicate that differential activation of the dual receptor system of MR and GR by corticosterone targets the steps in synaptic transmission differently.

Long-term effects of maternal separation on chronic stress response suppressed by amitriptyline treatment

Abstract The early-life environment has many long-term effects on mammals. Maternal interaction and early stressful events may affect regulation of the HPA axis during adulthood, leading to differential glucocorticoid secretion in response to stressful situations. These adverse experiences during postnatal development may even sensitize specific neurocircuits to subsequent stressors. Later in life, the overreaction of the HPA axis to stress can constitute a risk factor for metabolic and mental diseases. As tricyclic antidepressants are known to correct glucocorticoid hypersecretion during depression, we treated maternally separated animals with amitriptyline, at a lower dose than habitually used in depression models, to prevent the response to chronic stress during adulthood. Male Wistar rats were separated from the mother for 4.5 h every day for the first 3 weeks of life. From postnatal day 50, animals were subjected to chronic variable stress during 24 d (five types of stressors at different times of day). During the stress, protocol rats were orally administered amitriptyline (5 mg/kg) daily. We observed that maternal separation caused a reduction in plasma ACTH levels (p < 0.05), but evoked hypersecretion of corticosterone (p < 0.05) when it was combined with stress in adulthood. This rise was completely prevented by antidepressant treatment with amitriptyline.

Novel antidepressant-like activity of propolis extract mediated by enhanced glucocorticoid receptor function in the hippocampus

Propolis is a natural product made by honeybees that has been widely used in folk medicine with a broad spectrum of biological activities. To investigate the antidepressant-like activity of propolis extract, CD-1 mice were administered an ethanol extract of propolis (50, 100, or 200 mg/kg, p.o.) prior to the behavioral test. The propolis extract-treated group showed a dose-dependent decrease in immobility time in the FST and tail suspension test without altering locomotor activity. Propolis extract decreased the limbic hypothalamic-pituitary-adrenal axis response to the FST as indicated by an attenuated corticosterone response and decreased in c-fos immunoreactive neurons in the hippocampal dentate gyrus. Western blot analysis revealed a reduction in hippocampal glucocorticoid receptor (GR) expression following the FST, which was reversed by propolis extract. Propolis extract also increased pGR(S220)/(S234) ratio by a differential phosphorylation in S220 and S234. FST-induced downregulation of cAMP-responsive element binding protein phosphorylation at S133 (pCREB) was restored by propolis extract, showing a strong and positive relationship between pCREB and pGR(S220)/(S234) ratio. These findings suggest that the propolis extract potentiates antidepressant-like activity by enhancing GR function which is one of the therapeutic mechanisms of antidepressant; thus, propolis extract may provide a novel therapy for depression.

Local amplification of glucocorticoids in the aging brain and impaired spatial memory

The hippocampus is a prime target for glucocorticoids (GCs) and a brain structure particularly vulnerable to aging. Prolonged exposure to excess GCs compromises hippocampal electrophysiology, structure, and function. Blood GC levels tend to increase with aging and correlate with impaired spatial memory in aging rodents and humans. The magnitude of GC action within tissues depends not only on levels of steroid hormone that enter the cells from the periphery and the density of intracellular receptors but also on the local metabolism of GCs by 11β-hydroxysteroid dehydrogenases (11β-HSD). The predominant isozyme in the adult brain, 11β-HSD1, locally regenerates active GCs from inert 11-keto forms thus amplifying GC levels within specific target cells including in the hippocampus and cortex. Aging associates with elevated hippocampal and neocortical 11β-HSD1 and impaired spatial learning while deficiency of 11β-HSD1 in knockout (KO) mice prevents the emergence of cognitive decline with age. Furthermore, short-term pharmacological inhibition of 11β-HSD1 in already aged mice reverses spatial memory impairments. Here, we review research findings that support a key role for GCs with special emphasis on their intracellular regulation by 11β-HSD1 in the emergence of spatial memory deficits with aging, and discuss the use of 11β-HSD1 inhibitors as a promising novel treatment in ameliorating/improving age-related memory impairments.

11beta-hydroxysteroid dehydrogenase type 1 deficiency prevents memory deficits with aging by switching from glucocorticoid receptor to mineralocorticoid receptor-mediated cognitive control

Local brain amplification of glucocorticoids (GCs) by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) plays a pivotal role in age-related memory deficits. 11β-HSD1 deficient mice are protected from spatial memory impairments with aging, but the underlying mechanisms are unknown. To determine which brain receptors [high-affinity mineralocorticoid receptors (MRs) or low-affinity glucocorticoid receptors (GRs)] are involved, spatial memory was measured in aged 11β-HSD1(-/-) mice before and during intracerebroventricular infusion (10 d) of spironolactone (MR antagonist) or RU486 (GR antagonist). Aged C57BL/6J control mice showed impaired spatial memory in the Y-maze; this improved with GR blockade, while MR blockade had no effect. In contrast, aged 11β-HSD1(-/-) mice showed intact spatial memory that became impaired with MR blockade, but not GR blockade. Hippocampal MR and GR mRNA expression and plasma corticosterone levels were not significantly altered with spironolactone or RU486 in either genotype. These data support the notion that 11β-HSD1 deficiency in aging mice leads to lower intracellular GC concentrations in brain, particularly in the hippocampus, which activate predominantly MRs to enhance memory, while in aging C57BL/6J controls, the increased intracellular GCs saturate MRs and activate predominantly GRs, thus impairing memory, an effect reversed by GR blockade.

Cognitive correlates of hypothalamic-pituitary-adrenal axis in major depression

Depressive disorder has become a major health problem and is ranked among the leading causes of disability worldwide. Depression-related cognitive impairment contributes to loss of economic productivity and psychosocial functioning and calls for more efficient treatment strategies. Although the pathogenesis of cognitive impairments in patients with major depressive disorder (MDD) is still insufficiently understood, increasing evidence implicates hypothalamus-pituitary-adrenal (HPA) axis as an important neurobiological determinant of cognitive impairment in depression. In this article, major findings of both HPA axis function abnormalities and cognitive impairments in depressed patients are summarized, focusing on their inter-relationship. Novel approaches in pharmacotherapy and psychotherapy have emerged which will be discussed with regard to their ability to reinstate normal HPA axis function in MDD and to treat cognitive impairments in MDD.

Effects of co-administration of amitriptyline and fluoxetine on inhibitory avoidance in mice

We have previously observed that, while the impairing effects of amitriptyline on inhibitory avoidance in mice are consistently observed, those of acute fluoxetine are negligible. Two experiments were designed to investigate whether a regular dose of fluoxetine potentiates the effect of a low dose of amitriptyline that is ineffective when administered alone. Male and female CD1 mice were administered i.p. 30 min before training, as follows. In the first experiment, they were injected with saline, one of three doses of amitriptyline (2.5, 5, 10mg/kg), one dose of fluoxetine (15 mg/kg), or a combination of amitriptyline (2.5mg/kg) and fluoxetine (15 mg/kg). In the second experiment, the mice were injected with saline, amitriptyline (2.5mg/kg), one of three doses of fluoxetine (10, 15, 20mg/kg), or a combination of 2.5mg/kg of amitriptyline and one of the three mentioned doses of fluoxetine. Drug doses were selected based on previous experiments in our laboratory reported in other publications. The behavioural procedure used to test the effects of these treatments was step-through inhibitory avoidance. The joint administration of amitriptyline 2.5mg/kg and fluoxetine 15 mg/kg had a clear impairing effect on inhibitory avoidance as observed in the two experiments. The dose of 2.5mg/kg of amitriptyline, given alone, was ineffective. Doses of 5mg/kg, or higher, of amitriptyline impaired inhibitory avoidance. The only effect detected when fluoxetine was administered separately was in the males of the experiment 1, which exhibited less avoidance than controls. Our preclinical research throws light on the benefits of the combined administration of antidepressants.

Hydrocortisone responsiveness in Gulf War veterans with PTSD: effects on ACTH, declarative memory hippocampal [(18)F]FDG uptake on PET

Neuroendocrine, cognitive and hippocampal alterations have been described in Gulf War (GW) veterans, but their inter-relationships and significance for posttraumatic stress disorder (PTSD) have not been described. Hydrocortisone (Hcort) was administered to GW veterans with (PTSD+ n=12) and without (PTSD- n=8) chronic PTSD in a randomized, placebo-controlled, double-blind challenge. Changes in plasma ACTH, memory, and hippocampal [(18)F]FDG uptake on positron emission tomography were assessed. The low-dose dexamethasone suppression test was also administered. The PTSD+ group showed greater cortisol and ACTH suppression, reflecting greater peripheral glucocorticoid receptor (GR) responsiveness, and did not show an Hcort-induced decrement in delayed recall or retention. The groups had comparable relative regional hippocampal [(18)F]FDG uptake at baseline, but only the PTSD- group had an Hcort-associated decrease in hippocampal [(18)F]FDG uptake. Asymmetry in hippocampal hemispheric volumes differed between PTSD+ and PTSD- groups. This asymmetry was associated with cortisol, ACTH, retention and functional hippocampal asymmetry before, but not after, Hcort administration. Differences in brain metabolic responses between GW veterans with and without PTSD may reflect differences in peripheral and central GR responsiveness.

Modulation of the mineralocorticoid receptor as add-on treatment in depression: a randomized, double-blind, placebo-controlled proof-of-concept study

Preclinical and clinical studies have suggested a role of the mineralocorticoid receptor (MR) in the response to antidepressants. We tested in a proof-of-concept study whether adding fludrocortisone (an MR agonist) or spironolactone (an MR antagonist) accelerates onset of action and improves efficacy of escitalopram in patients with major depression. We included 64 in- and outpatients with major depression (Hamilton Depression Scale-17 score>18) in a double-blind, randomized, placebo-controlled trial. Patients were randomized in a 2:2:1 fashion to fludrocortisone (0.2 mg/d, n=24) or spironolactone (100 mg/d, n=27) or placebo (n=13) for the first 3 weeks during a 5-week treatment with escitalopram. No differences in mean HAMD change scores and in time to response emerged between treatments. However, among the responders, patients treated with fludrocortisone responded faster (Breslow test, p=0.05). The mean number of days to response was 16.0+/-2.6 days vs. placebo 22.2+/-2.0 vs. spironolactone 22.6+/-2.3 (F=3.78, p=0.03). In the whole group, plasma cortisol increased during spironolactone and decreased during fludrocortisone treatment (F=2.4, p=0.04). In patients treated with fludrocortisone, non-responders had elevated cortisol values compared to responders throughout the study period (F=5.1, p=0.04). Stimulation of MR with fludrocortisone as adjunct to escitalopram accelerated the response in the group of responders while no effect emerged in the sample as a whole. A larger randomized controlled trial is warranted.

Neurobehavioral toxicity study of dibutyl phthalate on rats following in utero and lactational exposure

To investigate the neurobehavioral effects of dibutyl phthalate (DBP), an important endocrine disruptor known for reproductive toxicity, on rodent offspring following in utero and lactational exposure, pregnant Wistar rats were treated with DBP (0, 0.037, 0.111, 0.333 and 1% in the diet) from gestation day (GD) 6 to postnatal day (PND) 28, and selected developmental and neurobehavioral parameters of the offspring were measured. There were no significant effects of DBP on body weight gain of the dams during GD 6-20 or on the pups' ages of pinna detachment, incisor eruption or eye opening. Exposure to 1% DBP prolonged gestation period, decreased body weight in both male and female pups, depressed surface righting (PND 7) in male pups, shortened forepaw grip time (PND 10), enhanced spatial learning and reference memory (PND 35) in male pups. Exposure to 0.037% DBP also shortened forepaw grip time (PND 10), but inhibited spatial learning and reference memory in male pups. Sex x treatment effects were found in forepaw grip time (PND 10), spatial learning and reference memory, and the male pups appeared to be more susceptible than the females. However, all levels of DBP exposure did not significantly alter surface righting (PND 4), air righting (PND 16), negative geotaxis (PND 4 or 7), cliff avoidance (PND 7) or open field behavior (PND 28) in either sex. Overall, the dose level of DBP in the present study produced a few adverse effects on the neurobehavioral parameters, and it may alter cognitive abilities of the male rodent.

Repeated antidepressant therapy increases cyclic GMP signaling in rat hippocampus

Cyclic adenosine monophosphpate (cAMP) signaling is thought to be involved in the pathophysiology of major depressive disorder and antidepressant action; however, relatively little is known about the possible role of cyclic guanosine monophosphate (cGMP) signaling. Accumulating evidence suggests that crosstalk occurs between cAMP and cGMP pathways. There is a need to clarify the trajectory of cAMP and cGMP concentrations, their synthesis by cyclases, and degradation by phosphodiesterases (PDEs) to understand the role of cyclic mononucleotide signaling in the effect of chronic antidepressant therapy. We used quantitative real-time PCR and enzyme immunoassay to systematically investigate the expression of intracellular signaling cascade elements in the hippocampus of rats chronically treated with the antidepressants fluoxetine and amitriptyline. We found increased cGMP levels, which were consistent with our findings of decreased PDE gene expression. Immunoassay results showed unchanged cAMP levels. We conclude that increased cGMP signaling might underlie the efficacy of chronic antidepressant treatment.

Relationship between antidepressants and IGF-1 system in the brain: possible role in cognition

Antidepressants facilitate neuroplasticity by stimulating trophic factors. This study evaluated the effect of fluoxetine (FLX) treatment on insulin-like growth factor-1 (IGF-1) in the rat brain and its role in the effect of FLX on cognition. IGF-1 receptor (IGF-1R) protein expression and IGF-1 mRNA levels were assessed in rat frontal cortex (FC) and hippocampus, in FLX-treated [15 mg/kg, orally; 3 (acute) or 21 (repeated) days] male Wistar rats. Rats were subjected to the Morris Water Maze test. Acute FLX administration decreased IGF-1 mRNA levels in the FC and hippocampus and increased IGF-1R levels in the FC. Repeated FLX increased both mRNA and IGF-1R levels in the FC. Repeated, but not acute, FLX treatment decreased IGF-1 mRNA in the hippocampus. FLX did not affect cognitive performance. Thus, repeated FLX treatment leads to upregulation of IGF-1 system is FC. It is possible that FLX affect FC neuroplasticity through activation of the IGF-1 system.