Ana Raquel Marcelino Mesquita

Chronic Stress Causes Frontostriatal Reorganization and Affects Decision-Making

Brain Rewiring After Stress Chronic stress, mainly through the release of corticosteroids, affects executive behavior through sequential structural modulation of brain networks. Stress-induced deficits in spatial reference, working memory, and behavioral flexibility are associated with synaptic and dendritic reorganization in both the hippocampus and the medial prefrontal cortex. However, the effects of chronic stress on action selection strategies are unclear. Dias-Ferreira et al. (p. 621) examined whether chronic stress affects the ability of animals to select the appropriate actions based on the consequences of their choice, and found that rats exposed to chronic unpredictable stress rapidly shift toward using habitual strategies. The shift in behavioral strategies observed in chronically stressed animals corresponded to dramatic and divergent changes in connectivity in the associative and sensorimotor corticostriatal circuits underlying these behaviors. Chronic stress alters brain neural circuits and affects the ability of animals to perform actions based on their consequences. The ability to shift between different behavioral strategies is necessary for appropriate decision-making. Here, we show that chronic stress biases decision-making strategies, affecting the ability of stressed animals to perform actions on the basis of their consequences. Using two different operant tasks, we revealed that, in making choices, rats subjected to chronic stress became insensitive to changes in outcome value and resistant to changes in action-outcome contingency. Furthermore, chronic stress caused opposing structural changes in the associative and sensorimotor corticostriatal circuits underlying these different behavioral strategies, with atrophy of medial prefrontal cortex and the associative striatum and hypertrophy of the sensorimotor striatum. These data suggest that the relative advantage of circuits coursing through sensorimotor striatum observed after chronic stress leads to a bias in behavioral strategies toward habit.

A trans-dimensional approach to the behavioral aspects of depression

Depression, a complex mood disorder, displays high comorbidity with anxiety and cognitive disorders. To establish the extent of inter-dependence between these behavioral domains, we here undertook a systematic analysis to establish interactions between mood [assessed with the forced-swimming (FST) and sucrose consumption tests (SCT)], anxiety [elevated-plus maze (EPM) and novelty suppressed feeding (NSF) tests] and cognition (spatial memory and behavioral flexibility tests) in rats exposed to unpredictable chronic-mild-stress (uCMS). Expectedly, uCMS induced depressive-like behavior, a hyperanxious phenotype and cognitive impairment; with the exception of the measure of anxiety in the EPM, these effects were attenuated by antidepressants (imipramine, fluoxetine). Measures of mood by the FST and SCT were strongly correlated, whereas no significant correlations were found between the different measures of anxiety (EPM and NSF); likewise, measures of cognition by spatial memory and behavioral flexibility tests were poorly correlated. Inter-domain analysis revealed significant correlations between mood (FST and SCT) and anxiety-like behavior (NSF, but not EPM). Furthermore, significant correlations were found between cognitive performance (reverse learning task) and mood (FST and SCT) and anxiety-like behavior (NSF). These results demonstrate interactions between different behavioral domains that crosscut the disciplines of psychiatry and neurology.

Lithium blocks stress-induced changes in depressive-like behavior and hippocampal cell fate: The role of glycogen-synthase-kinase-3β

Mood disorders are the most common psychiatric disorders. Although the mechanisms implicated in the genesis of mood disorders are still unclear, stress is known to predispose to depression, and recently, studies have related hippocampal neurogenesis and apoptosis to depression. In the present study we first examined the balance between cell birth-death in the hippocampus and subventricular zone (SVZ) of pre-pubertal and adult rats subjected to chronic-mild-stress (CMS). CMS led to increased corticosterone secretion and induced depressive-like symptoms (assessed in the forced-swimming test); these endocrine and behavioral effects were paralleled by decreased hippocampal, but not SVZ, cell proliferation/differentiation and by increased apoptotic rate. In order to determine if lithium, a known mood stabilizer with antidepressant properties, could prevent the stress-induced events, we analyzed the same parameters in a group of rats treated with lithium during the stress exposure period (CMS+Li) and observed that the hormonal, behavioral and cell turnover effects of CMS were abrogated in these animals. Subsequently, to search for possible pathways through which CMS and lithium influence behavior, cell fate and synaptic plasticity, we analyzed the expression of glycogen-synthase-kinase-3beta (GSK-3beta), as well as some of its downstream targets (B-cell-CLL/lymphoma2-associated athanonege (BAG-1) and synapsin-I). CMS increased GSK-3beta and decreased synapsin-I and BAG-1 expression in the hippocampus. Interestingly, co-administration of lithium precluded the CMS-induced effects in GSK-3beta, synapsin-I and BAG-1 expression. Our observation that specific inhibition of this kinase with AR-A014418 blocked the effects of CMS in depressive-like behavior and in BAG-1 and synapsin-I expression confirmed the involvement of the GSK-3beta pathway in stress-induced effects. In summary, these results reveal that lithium, by regulating the activity of GSK-3beta, prevents the deleterious effects of stress on behavior and cellular functions.

The impact of age on emotional and cognitive behaviours triggered by experimental neuropathy in rats

ABSTRACT Chronic pain syndromes encompass several clinical entities that frequently affect the individuals’ emotional and cognitive behaviours which, in turn, can also alter pain perception. Additionally, both pain perception and motivational‐affective behaviours change with increasing age. In order to evaluate the influence of age upon the interaction between chronic pain and affective/cognitive behaviours, 3‐, 10‐ and 22‐month‐old rats with 1 month neuropathy (spared nerve injury, SNI model) were compared with age‐matched sham‐operated controls in the open field (OF; locomotor and exploratory behaviours), elevated plus‐maze (EPM; anxiety‐like behaviour), forced swimming (FST; depressive‐like behaviour), working memory water maze (WM; spatial short‐term memory), Morris water maze (MWM; spatial reference memory) and spatial reversal (behavioural flexibility) tests. Locomotor and exploratory activities decreased steadily with age and were further reduced by SNI. Aging was associated with increased anxiety‐like behaviour, which was potentiated by SNI in both 3‐ and 22‐month‐old rats. The performance in the FST was affected by SNI but only in mid‐aged animals. Cognitive performances in the MWM and spatial reversal tests deteriorated with age; however, the SNI lesion was only detrimental in the reversal task to mid‐aged animals. Our data demonstrate that the influence of neuropathic pain on affective and cognitive behaviours is age dependent and varies with the behavioural domain that is tested. Importantly, mid‐aged animals seem to be more susceptible to depression and cognitive deterioration associated to chronic pain than young and old groups.

IL-10 modulates depressive-like behavior

The role of pro-inflammatory cytokines in psychiatric disorders has been the focus of great research attention in recent years. Paradoxically, the same is not true for anti-inflammatory cytokines. In the present study, we assessed the behavioral profile of animals with altered expression of the anti-inflammatory cytokine IL-10. We performed a battery of tests to assess anxiety, depressive-like and cognitive behaviors in mice overexpressing IL-10 (PMT10) and IL-10(-/-) animals; in the later mice we also tested the behavioral effect of IL-10 administration. In the forced-swimming test, IL-10(-/-) females displayed increased depressive-like behavior; importantly, this phenotype was reverted by the injection of IL-10. Moreover, mice overexpressing IL-10 presented a decreased depressive-like behavior. Despite the presence of a similar trend, male animals did not reach significant differences in depressive-like behavior. Assessment in the open-field showed that the absence of IL-10 decreased the percentage of time spent in the center of the arena in both male and female mice, while male animals overexpressing IL-10 revealed an opposite behavior. For both sexes, imbalance in IL-10 levels did not affect spatial reference memory. In conclusion, variations in IL-10 expression are associated with an altered depressive-like behavior, but do not influence cognitive performance. Interestingly, IL-10 imbalance produced more profound behavioral changes in females than in male animals. This is in accordance with clinical data demonstrating an increased susceptibility of women to mood disorders, suggesting an interplay between anti-inflammatory cytokines and sexual steroids.

Neurodevelopment milestone abnormalities in rats exposed to stress in early life

Manipulation of the corticosteroid milieu by interfering with the mother-newborn relationship has received much attention because of its potential bearing on psychopathology later in life. In the present study, infant rats that were deprived of maternal contact between the 2nd and the 15th postnatal days (MS2-15) for 6 h/day were subjected to a systematic assessment of neurodevelopmental milestones between postnatal days 2 and 21. The analyses included measurements of physical growth and maturation and evaluation of neurological reflexes. Although some somatic milestones (e.g. eye opening) were anticipated, MS2-15 animals showed retardation in the acquisition of postural reflex, air righting and surface righting reflexes, and in the wire suspension test; the latter two abnormalities were only found in males. A gender effect was also observed in negative geotaxis, with retardation being observed in females but not males. To better understand the delay of neurological maturation in MS2-15 rats, we determined the levels of various monoamines in different regions of the brain stem, including the vestibular area, the substantia nigra, ventral tegmental area and dorsal raphe nuclei. In the vestibular region of MS2-15 rats the levels of 5-HT were reduced, while 5-HT turnover was increased. There was also a significant increase of the 5-HT turnover in MS2-15 animals in the raphe nuclei, mainly due to increased 5-hydroxyindoleacetic acid (5-HIAA) levels, and an increase of 3,4-dihydroxyphenylacetic acid (DOPAC) levels in the ventral tegmental area (VTA) of stressed females. No significant differences were found in the immunohistochemical sections for tyrosine and tryptophan hydroxylase in these regions of the brain stem. In conclusion, the present results show that postnatal stress induces signs of neurological pathology that may contribute to the genesis of behavioral abnormalities later in life.

Induction of a Hyperanxious State by Antenatal Dexamethasone: A Case for Less Detrimental Natural Corticosteroids

BACKGROUND Synthetic glucocorticoids are commonly prescribed during pregnancy, despite a lack of systematic investigations of their potential impact on the developing brain and neurological and behavioral performance. METHODS Neuroendocrine parameters and behavior in the adult offspring of pregnant Wistar rats treated antenatally with either dexamethasone (DEX) or corticosterone (CORT) were monitored; DEX (.1 mg/kg and 1 mg/kg) and CORT (25 mg/kg) were given to pregnant rat dams on gestation days 18 and 19. RESULTS Despite normal basal levels of corticosterone, the adult offspring of mothers given DEX or CORT displayed abnormal responses in the dexamethasone-suppression test. Neither treatment influenced spatial memory performance, but both DEX and CORT facilitated development of depression-like behavior following chronic stress. The latter finding demonstrates that high-dose antenatal corticotherapy can impair the organisms resilience to stress in adulthood. Interestingly, comparison of the progeny of CORT-treated and DEX-treated mothers revealed that the latter were more anxious. CONCLUSIONS Since DEX and CORT differ in their affinity for glucocorticoid and mineralocorticoid receptors and corticosteroid-binding globulin, our findings emphasize the need to consider the pharmacologic properties of antenatal corticotherapies and demonstrate the potential long-term benefits of ligands that can bind to both receptors.

Interleukin-10: A Key Cytokine in Depression?

An increasing body of evidence implicates proinflammatory cytokines in psychiatric disorders, namely, in depression. Of notice, recent studies showed that anti-inflammatory cytokines, such as IL-10, also modulate depressive-like behavior. In this article, we propose that the anti-inflammatory cytokine IL-10 is a putative link between two of the most widely reported phenomenon observed in depressed patients: the disruption of the hypothalamic-pituitary-adrenal axis and the imbalanced production of cytokines. If so, IL-10 might represent a novel target for antidepressant therapy.

Role of human umbilical cord mesenchymal progenitors conditioned media in neuronal/glial cell densities, viability, and proliferation.

It has been recently reported that mesenchymal progenitor/stem cells isolated from the Whartons Jelly (WJ) of umbilical cords (UC) ameliorate the condition of animals suffering from central nervous system (CNS)-related conditions. However, little is known on the mechanisms that regulate these actions. Therefore, the objective of the present work was to determine how the conditioned media (CM) of a population of mesenchymal progenitors present in the UC WJ, known as human umbilical cord perivascular cells (HUCPVCs), regulate processes such as cell viability, survival, and proliferation of postnatal hippocampal neurons and glial cells. For this purpose primary hippocampal and cortical cultures of neurons and glial cells, respectively, were incubated with CM from HUCPVCs. Results revealed that HUCPVCs CM increase glial cell viability and proliferation. Furthermore, it was observed that glial cell cultures exhibited higher numbers of GFAP-positive cells (astrocytes) and O4-positive cells (oligodendrocytes) when incubated with the CM. Additionally, it was also observed that the growth factors presents in the CM did not induce an increase on the microglial cells number. For hippocampal neurons similar results were obtained, as cultures exposed to HUCPVCs CM disclosed higher numbers of MAP-2-positive cells. Moreover it was also observed that the cell viability and proliferation in this primary hippocampal cell culture system was also higher, when compared to control cultures. From these results it was possible to conclude that HUCPVCs release neuroregulatory factors that have a direct impact on the densities, viability, and proliferation of glial cells and hippocampal primary cultures.

Increased expression of ferritin, an iron-storage protein, in specific regions of the parahippocampal cortex of epileptic rats

Summary:  Purpose: Iron accumulation in the brain has been associated with neurodegenerative disorders, including epilepsy. In our previous SAGE study, we showed that ferritin, an iron‐storage protein, was one of the genes (Ferritin‐H) that showed overexpression before the chronic epileptic phase. In this study we used ferritin as indicator for disturbed iron homeostasis to acquire insight into whether this could play a role in the pathogenesis of temporal lobe epilepsy.