Sex and cell-specific gene expression in corticolimbic brain regions associated with psychiatric disorders revealed by bulk and single-nuclei RNA sequencing.

BACKGROUND: There are sex-specific differences in the prevalence, symptomology and course of psychiatric disorders. However, preclinical models have primarily used males, such that the molecular mechanisms underlying sex-specific differences in psychiatric disorders are not well established. METHODS: In this study, we compared transcriptome-wide gene expression profiles in male and female rats within the corticolimbic system, including the cingulate cortex, nucleus accumbens medial shell (NAcS), ventral dentate gyrus and the basolateral amygdala (n = 22-24 per group/region). FINDINGS: We found over 3000 differentially expressed genes (DEGs) in the NAcS between males and females. Of these DEGs in the NAcS, 303 showed sex-dependent conservation DEGs in humans and were significantly enriched for gene ontology terms related to blood vessel morphogenesis and regulation of cell migration. Single nuclei RNA sequencing in the NAcS of male and female rats identified widespread sex-dependent expression, with genes upregulated in females showing a notable enrichment for synaptic function. Female upregulated genes in astrocytes, Drd3+MSNs and oligodendrocyte were also enriched in several psychiatric genome-wide association studies (GWAS). INTERPRETATION: Our data provide comprehensive evidence of sex- and cell-specific molecular profiles in the NAcS. Importantly these differences associate with anxiety, bipolar disorder, schizophrenia, and cross-disorder, suggesting an intrinsic molecular basis for sex-based differences in psychiatric disorders that strongly implicates the NAcS. FUNDING: This work was supported by funding from the Hope for Depression Research Foundation (MJM).

Examining attachment, cortisol secretion, and cognitive neurodevelopment in preschoolers and its predictive value for telomere length at age seven.

Background: Secure attachment reflects caregiver-child relationship in which the caregiver is responsive when support and comforting are needed by the child. This pattern of bond has an important buffering role in the response to stress by the reduction of the negative experience and its associated physiological response. Disruption of the physiological stress system is thought to be a central mechanism by which early care impacts children. Early life stress causes cellular and molecular changes in brain regions associated with cognitive functions that are fundamental for early learning. Methods: The association between attachment, cortisol response before and after the Strange Situation Experiment, and neurodevelopment was examined in a sample of 107 preschoolers at age three. Also, the predictive effect of cortisol reactivity and attachment on telomere length at age seven was investigated in a followed-up sample of 77 children. Results: Children with insecure attachment had higher cortisol secretion and poorer neurodevelopmental skills at age three. A significant cortisol change was observed across the experiment with non-significant interaction with attachment. The attachment and neurodevelopment association was not mediated by cortisol secretion. Preschoolers' attachment and cortisol did not associate nor interacted to predict telomere length at age seven. Conclusion: These findings add evidence to the detrimental effects of insecure attachment as an aggravator of the physiological response to stress and poorer neurodevelopment during the preschool period. Although attachment and cortisol were not predictive of telomere length, intervention policies that promote secure attachment are more likely to positively echo on several health domains.

Integrative multi-omics landscape of fluoxetine action across 27 brain regions reveals global increase in energy metabolism and region-specific chromatin remodelling.

Depression and anxiety are major global health burdens. Although SSRIs targeting the serotonergic system are prescribed over 200 million times annually, they have variable therapeutic efficacy and side effects, and mechanisms of action remain incompletely understood. Here, we comprehensively characterise the molecular landscape of gene regulatory changes associated with fluoxetine, a widely-used SSRI. We performed multimodal analysis of SSRI response in 27 mammalian brain regions using 310 bulk RNA-seq and H3K27ac ChIP-seq datasets, followed by in-depth characterisation of two hippocampal regions using single-cell RNA-seq (20 datasets). Remarkably, fluoxetine induced profound region-specific shifts in gene expression and chromatin state, including in the nucleus accumbens shell, locus coeruleus and septal areas, as well as in more well-studied regions such as the raphe and hippocampal dentate gyrus. Expression changes were strongly enriched at GWAS loci for depression and antidepressant drug response, stressing the relevance to human phenotypes. We observed differential expression at dozens of signalling receptors and pathways, many of which are previously unknown. Single-cell analysis revealed stark differences in fluoxetine response between the dorsal and ventral hippocampal dentate gyri, particularly in oligodendrocytes, mossy cells and inhibitory neurons. Across diverse brain regions, integrative omics analysis consistently suggested increased energy metabolism via oxidative phosphorylation and mitochondrial changes, which we corroborated in vitro; this may thus constitute a shared mechanism of action of fluoxetine. Similarly, we observed pervasive chromatin remodelling signatures across the brain. Our study reveals unexpected regional and cell type-specific heterogeneity in SSRI action, highlights under-studied brain regions that may play a major role in antidepressant response, and provides a rich resource of candidate cell types, genes, gene regulatory elements and pathways for mechanistic analysis and identifying new therapeutic targets for depression and anxiety.

Contribution of the Opioid System to the Antidepressant Effects of Fluoxetine.

BACKGROUND: Selective serotonin reuptake inhibitors such as fluoxetine have a limited treatment efficacy. The mechanism by which some patients respond to fluoxetine while others do not remains poorly understood, limiting treatment effectiveness. We have found the opioid system to be involved in the responsiveness to fluoxetine treatment in a mouse model for anxiety- and depressive-like behavior. METHODS: We analyzed gene expression changes in the dentate gyrus of mice chronically treated with corticosterone and fluoxetine. After identifying a subset of genes of interest, we studied their expression patterns in relation to treatment responsiveness. We further characterized their expression through in situ hybridization and the analysis of a single-cell RNA sequencing dataset. Finally, we behaviorally tested mu and delta opioid receptor knockout mice in the novelty suppressed feeding test and the forced swim test after chronic corticosterone and fluoxetine treatment. RESULTS: Chronic fluoxetine treatment upregulates proenkephalin expression in the dentate gyrus, and this upregulation is associated with treatment responsiveness. The expression of several of the most significantly upregulated genes, including proenkephalin, is localized to an anatomically and transcriptionally specialized subgroup of mature granule cells in the dentate gyrus. We have also found that the delta opioid receptor contributes to some, but not all, of the behavioral effects of fluoxetine. CONCLUSIONS: These data indicate that the opioid system is involved in the antidepressant effects of fluoxetine, and this effect may be mediated through the upregulation of proenkephalin in a subpopulation of mature granule cells.

Cognitive Development and Brain Gray Matter Susceptibility to Prenatal Adversities: Moderation by the Prefrontal Cortex Brain-Derived Neurotrophic Factor Gene Co-expression Network.

Background: Previous studies focused on the relationship between prenatal conditions and neurodevelopmental outcomes later in life, but few have explored the interplay between gene co-expression networks and prenatal adversity conditions on cognitive development trajectories and gray matter density. Methods: We analyzed the moderation effects of an expression polygenic score (ePRS) for the Brain-derived Neurotrophic Factor gene network (BDNF ePRS) on the association between prenatal adversity and child cognitive development. A score based on genes co-expressed with the prefrontal cortex (PFC) BDNF was created, using the effect size of the association between the individual single nucleotide polymorphisms (SNP) and the BDNF expression in the PFC. Cognitive development trajectories of 157 young children from the Maternal Adversity, Vulnerability and Neurodevelopment (MAVAN) cohort were assessed longitudinally in 4-time points (6, 12, 18, and 36 months) using the Bayley-II mental scales. Results: Linear mixed-effects modeling indicated that BDNF ePRS moderates the effects of prenatal adversity on cognitive growth. In children with high BDNF ePRS, higher prenatal adversity was associated with slower cognitive development in comparison with those exposed to lower prenatal adversity. Parallel-Independent Component Analysis (pICA) suggested that associations of expression-based SNPs and gray matter density significantly differed between low and high prenatal adversity groups. The brain IC included areas involved in visual association processes (Brodmann area 19 and 18), reallocation of attention, and integration of information across the supramodal cortex (Brodmann area 10). Conclusion: Cognitive development trajectories and brain gray matter seem to be influenced by the interplay of prenatal environmental conditions and the expression of an important BDNF gene network that guides the growth and plasticity of neurons and synapses.

Life-course effects of early life adversity exposure on eating behavior and metabolism.

Environmental variations in early life influence brain development, making individuals more vulnerable to psychiatric and metabolic disorders. Early life stress (ELS) has a strong impact on the development of eating behavior. However, eating is a complex behavior, determined by an interaction between signals of energy homeostasis, neuronal circuits involved in its regulation, and circuits related to rewarding properties of the food. Although mechanisms underlying ELS-induced altered feeding behavior are not completely understood, evidence suggest that the effects of ELS on metabolic, mood, and emotional disorders, as well as reward system dysfunctions can contribute directly or indirectly to altered feeding behavior. The focus of this chapter is to discuss the effects of ELS on eating behavior and metabolism, considering different factors that control appetite such as energy homeostasis, hedonic properties of the food, emotional and cognitive status. After highlighting classic studies on the association between ELS and eating behavior alterations, we discuss how exposure to adversity can interact with genetics characteristics to predict variable outcomes.

Chronic high-fat diet affects food-motivated behavior and hedonic systems in the nucleus accumbens of male rats.

Environmental variations can influence eating and motivated behaviors, as well as the brain's feeding circuits to predisposing overweight and obesity. The identification of mechanisms through which a long-term consumption of caloric-dense palatable foods and its association with early life stress can cause neuroadaptations and possible modify motivational behaviors are relevant to elucidate the mechanisms associated with obesity. Here, we investigated the long-term effects of a chronic high-fat diet (HFD), and its interaction with early social isolation on hedonic feeding responses in adult rats. Rats were subjected, or not, to social isolation between postnatal days 21-28 and were fed a control diet or HFD, for 10 weeks post weaning. Hedonic feeding behavior was evaluated during adulthood and parameters related to the dopaminergic, cannabinoid, and opioid systems were measured in the nucleus accumbens. Animals with chronic HFD intake were less motivated to obtain sweet palatable foods. This reduced motivation did not appear to be associated with less pleasure upon tasting sweet food, as no alteration in reactivity to sweet taste was observed. Interestingly, the animals receiving HFD presented decreased immunocontents of the D1 and CB1 receptors, while the stressed group displayed a reduction in dopamine turnover. In summary, chronic HFD causes a significant motivational impairment for sweet palatable foods; these changes may be associated with a decreased dopaminergic and cannabinoid neurotransmission in the nucleus accumbens. In contrast, a brief social isolation during the prepubertal period was unable to alter the behavioral parameters studied but caused a decreased dopaminergic turnover in the nucleus accumbens of adult rats. These findings highlight the importance of long-term HFD exposure on the modulation of hedonic feeding behavior and related neurochemical systems.

Neurometabolic effects of sweetened solution intake during adolescence related to depressive-like phenotype in rats.

OBJECTIVE: Exposure to artificial sweeteners, such as aspartame, during childhood and adolescence has been increasing in recent years. However, the safe use of aspartame has been questioned owing to its potentially harmful effects on the developing brain. The aim of this study was to test whether the chronic consumption of aspartame during adolescence leads to a depressive-like phenotype and to investigate the possible mechanisms underlying these behavioral changes. METHODS: Adolescent male and female rats were given unlimited access to either water, solutions of aspartame, or sucrose in their home cages from postnatal day 21 to 55. RESULTS: Forced swim test revealed that both chronic aspartame and sucrose intake induced depressive-like behaviord, which was more pronounced in males. Additionally, repeated aspartame intake was associated with increased cerebrospinal fluid (CSF) aspartate levels, decreased hippocampal neurogenesis, and reduced activation of the hippocampal leptin signaling pathways in males. In females, we observed a main effect of aspartame: reducing PI3K/AKT one of the brain-derived neurotrophic factor pathways; aspartame also increased CSF aspartate levels and decreased the immunocontent of the GluN2A subunit of the N-methyl-d-aspartic acid receptor. CONCLUSION: The findings revealed that repeated aspartame intake during adolescence is associated with a depressive-like phenotype and changes in brain plasticity. Interestingly, males appear to be more vulnerable to the adverse neurometabolic effects of aspartame than females, demonstrating a sexually dimorphic response. The present results highlighted the importance of understanding the effects caused by the constant use of this artificial sweetener in sensitive periods of development and contribute to regulation of its safe use.

Amygdala 5-HTT Gene Network Moderates the Effects of Postnatal Adversity on Attention Problems: Anatomo-Functional Correlation and Epigenetic Changes.

Variations in serotoninergic signaling have been related to behavioral outcomes. Alterations in the genome, such as DNA methylation and histone modifications, are affected by serotonin neurotransmission. The amygdala is an important brain region involved in emotional responses and impulsivity, which receives serotoninergic input. In addition, studies suggest that the serotonin transporter gene network may interact with the environment and influence the risk for psychiatric disorders. We propose to investigate whether/how interactions between the exposure to early life adversity and serotonin transporter gene network in the amygdala associate with behavioral disorders. We constructed a co-expression-based polygenic risk score (ePRS) reflecting variations in the function of the serotonin transporter gene network in the amygdala and investigated its interaction with postnatal adversity on attention problems in two independent cohorts from Canada and Singapore. We also described how interactions between ePRS-5-HTT and postnatal adversity exposure predict brain gray matter density and variation in DNA methylation across the genome. We observed that the expression-based polygenic risk score, reflecting the function of the amygdala 5-HTT gene network, interacts with postnatal adversity, to predict attention and hyperactivity problems across both cohorts. Also, both postnatal adversity score and amygdala ePRS-5-HTT score, as well as their interaction, were observed to be associated with variation in DNA methylation across the genome. Variations in gray matter density in brain regions linked to attentional processes were also correlated to our ePRS score. These results confirm that the amygdala 5-HTT gene network is strongly associated with ADHD-related behaviors, brain cortical density, and epigenetic changes in the context of adversity in young children.

Sex-dependent effect on mitochondrial and oxidative stress parameters in the hypothalamus induced by prepubertal stress and access to high fat diet.

OBJECTIVE: Some factors related to lifestyle, including stress and high-fat diet (HFD) consumption, are associated with higher prevalence of obesity. These factors can lead to an imbalance between ROS production and antioxidant defenses and to mitochondrial dysfunctions, which, in turn, could cause metabolic impairments, favoring the development of obesity. However, little is known about the interplay between these factors, particularly at early ages, and whether long-term sex-specific changes may occur. Here, we evaluated whether social isolation during the prepubertal period only, associated or not with chronic HFD, can exert long-term effects on oxidative status parameters and on mitochondrial function in the whole hypothalamus, in a sex-specific manner. METHODS: Wistar male and female rats were divided into two groups (receiving standard chow or standard chow + HFD), that were subdivided into exposed or not to social isolation during the prepubertal period. Oxidative status parameters, and mitochondrial function were evaluated in the hypothalamus in the adult age. RESULTS: Regarding antioxidant enzymes activities, HFD decreased GPx activity in the hypothalamus, while increasing SOD activity in females. Females also presented increased total thiols; however, non-protein thiols were lower. Main effects of stress and HFD were observed in TBARS levels in males, with both factors decreasing this parameter. Additionally, HFD increased complex IV activity, and decreased mitochondrial mass in females. Complex I-III activity was higher in males compared to females. CONCLUSION: Stress during the prepubertal period and chronic consumption of HFD had persistent sex-specific effects on oxidative status, as well as on its consequences for the cell and for mitochondrial function. HFD had more detrimental effects on females, inducing oxidative imbalance, which resulted in damage to the mitochondria. This HFD-induced imbalance may be related to the development of obesity.

Neonatal handling impairs intradimensional shift and alters plasticity markers in the medial prefrontal cortex of adult rats.

Stress response can be modulated by neonatal/childhood events. Neonatal handling (NH) is an animal model in which the animals are subjected to brief separations from the dam during the first days of life, and it leads to lower emotionality and behavioral changes in adulthood. The aim of this study was to observe if early events, such as (NH), may program associative learning and behavioral flexibility in adult male rats and if these changes could be related to altered neurochemistry in the medial prefrontal cortex (mPFC). We evaluated proteins related to synaptic plasticity (brain-derived neurotrophic factor [BDNF] and synaptophysin [SYP]) as well as Na+/K+-ATPase activity. Additionally, we evaluated proteins related to the dopaminergic system (tyrosine hydroxylase [TH] and phosphorylated TH [pTH]), since this system appears to be affected in some neonatal interventions. Neonatally handled animals exhibited impairment in simple discrimination and intradimensional shift but not in reversal or compound discrimination; in addition, no alteration in switching from an egocentric spatial to a cued strategy was observed. These effects were accompanied by a decrease in SYP levels and Na+/K+-ATPase activity, suggesting reduced synaptic function. These results indicate that NH increases attention to irrelevant stimuli and/or impairs associative learning, and this is accompanied by neurochemical alterations in the (mPFC).

Impact of High-Fat Diet and Early Stress on Depressive-Like Behavior and Hippocampal Plasticity in Adult Male Rats.

During development, the brain goes through fundamental processes, including organization of neural networks and plasticity. Environmental interventions may change initial brain programming, leading to long-lasting effects and altering the susceptibility to psychopathologies, including depression disorder. It is known that depression is a psychiatric disorder with a high prevalence worldwide, including high rates among adolescents. In this study, we evaluated whether social isolation in the prepubertal period and chronic use of high-fat diet (HFD) may induce depressive-like behavior in male adult rats. We also investigated hippocampal plasticity markers and neurotransmitter systems. We found both social isolation and HFD induced a depressive-like behavior in the forced swimming task. Moreover, chronic HFD reduced synaptic markers in hippocampus, demonstrated by reductions in ßIII-tubulin (neuronal marker), PSD-95, SNAP-25, and neurotrophin-3. The HFD group also presented decreased glutamatergic and GABAergic receptors subunits. On the other hand, stress affected hippocampal brain-derived neurotrophic factor (BDNF) signaling pathways, and increased expression of subunit of the NMDA receptor (NR2A). Both factors (stress and diet) decreased GR in the hippocampus without affecting plasma corticosterone at basal levels. Interactions between early stress and HFD access were observed only in the BNDF receptor (tropomyosin receptor kinase B; TrkB) and synaptophysin. In summary, these findings showed that a brief social isolation and chronic HFD, during a sensitive developmental period, cause depressive-like behavior in adulthood. The mechanisms underlying these behavioral effects may involve changes in the levels of synaptic proteins in hippocampus: HFD consumption appears to affect synaptic markers, while social isolation affected BDNF signaling more significantly.

Short post-weaning social isolation induces long-term changes in the dopaminergic system and increases susceptibility to psychostimulants in female rats.

Childhood and adolescence are sensitive periods of development, marked by high brain maturation and plasticity. Exposure to early life stress, such as social isolation, is able to prompt changes in sensitive brain circuitries, essentially in the mesolimbic dopaminergic system and increase the risk for addictive behaviors later in life. Post-weaning social isolation can stimulate the consumption of rewarding substances, like drugs of abuse and palatable foods. However, most studies analyze long periods of social isolation and very little is known about the effects of a brief social isolation in a sensitive period of development and its association with palatable food on the reward system sensitization. Furthermore, females are more susceptible to the reinforcing effect of drugs than males. Therefore, the aim of this study was to analyze the effects of a short post-weaning social isolation combined with a free access to a chronic high sugar diet (HSD) on the dopaminergic system, oxidative status and behavioral response to an amphetamine-like drug in adulthood. We used female Wistar rats that were socially isolated from post-natal days (PD) 21 to 35 and received free access to a HSD until PD 60. On PD 65, animals were submitted to a challenge with diethylpropion (DEP), an amphetamine-like drug and different responses were analyzed: locomotor activity, immmunocontent of dopamine related proteins, and the oxidative status in the striatum, before and after the DEP challenge. We showed that a short post-weaning social isolation (SI) increased the locomotor response to DEP, when compared with previous saline administration. Social isolation also increased dopamine transporter, tyrosine hydroxylase, and decreased dopamine D2 receptor immunocontent. Additionally, SI increased the overall oxidative status parameters after the challenge with DEP. Interestingly, the exposure to a HSD prevented the SI effects on locomotor response, but did not interfere in the dopaminergic parameters evaluated, despite having modified some oxidative parameters. This study showed for the first time that a short post-weaning social isolation was able to induce long-term changes in the striatal dopaminergic system and increased the response to psychostimulants. These results emphasize the importance of stressful experiences during a short period of development on programming susceptibility to psychostimulants later in life.

Neuroprotector effect of stem cells from human exfoliated deciduous teeth transplanted after traumatic spinal cord injury involves inhibition of early neuronal apoptosis.

Stem cells from human exfoliated deciduous teeth (SHED) transplants have been investigated as a possible treatment strategy for spinal cord injuries (SCI) due to their potential for promoting functional recovery. The aim of present study was to investigate the effects of SHED on neuronal death after an experimental model of SCI. METHODS: Wistar rats were spinalized using NYU impactor®. Animals were randomly distributed into 4 groups: Control (Naive) or Surgical control, Sham (laminectomy with no SCI); SCI (laminectomy followed by SCI, treated with vehicle); SHED (SCI treated with intraspinal transplantation of 3×105 SHED, 1h after SCI). Functional evaluations and morphological analysis were performed to confirm the spinal injury and the benefit of SHED transplantation on behavior, tissue protection and motor neuron survival. Flow cytometry of neurons, astrocytes, macrophages/microglia and T cells of spinal cord tissue were run at six, twenty-four, forty-eight and seventy-two hours after lesion. Six hours after SCI, ELISA and Western Blot were run to assess pro- and anti-apoptotic factors. The SHED group showed a significant functional improvement in comparison to the SCI animals, as from the first week until the end of the experiment. This behavioral protection was associated with less tissue impairment and greater motor neuron preservation. SHED reduced neuronal loss over time, as well as the overexpression of pro-apoptotic factor TNF-α, while maintained basal levels of the anti-apoptotic BCL-XL six hours after lesion. Data here presented show that SHED transplantation one hour after SCI interferes with the balance between pro- and anti-apoptotic factors and reduces early neuronal apoptosis, what contributes to tissue and motor neuron preservation and hind limbs functional recovery.

Neonatal interventions differently affect maternal care quality and have sexually dimorphic developmental effects on corticosterone secretion.

Neonatal handling (H) and maternal separation (MS) both induce changes in maternal care, but the contribution of these changes to the behavioral and neurochemical outcomes of the offspring remains unclear, as studies often find opposite results concerning the frequency of maternal behaviors, particularly in the MS paradigm. In this study, behavior displayed by H, MS and non-handled (NH) Wistar rat dams were observed during the first 10days after birth. A tentative assessment of the quality of maternal care was made, using a previously reported score that reflects behavior fragmentation and inconsistency. Central oxytocin levels and hippocampal synaptic plasticity markers were also evaluated in dams, immediately after litter weaning. In adulthood, male and female offspring were subjected to a contextual stress-induced corticosterone challenge to provide further information on the impact of early interventions on neuroendocrine parameters. We found that while both H and MS interventions induced an increase in the amount of pup-directed behavior, MS dams displayed a more fragmented and inconsistent pattern of care, reflecting poorer maternal care quality. Interestingly, an increase in oxytocin levels was observed only in H dams. While H offspring did not differ from NH, MS males and females showed marked differences in corticosterone secretion compared to controls. Our results suggest that briefly removing the pups from the nest alters maternal care quantity but not quality and increases central oxytocin, while long separations appear to increase low quality maternal care and change neuroendocrine responses in adult offspring in a sex-specific manner.

Early life adversities or high fat diet intake reduce cognitive function and alter BDNF signaling in adult rats: Interplay of these factors changes these effects.

Environmental factors, like early exposure to stressors or high caloric diets, can alter the early programming of central nervous system, leading to long-term effects on cognitive function, increased vulnerability to cognitive decline and development of psychopathologies later in life. The interaction between these factors and their combined effects on brain structure and function are still not completely understood. In this study, we evaluated long-term effects of social isolation in the prepubertal period, with or without chronic high fat diet access, on memory and on neurochemical markers in the prefrontal cortex of rats. We observed that early social isolation led to impairment in short-term and working memory in adulthood, and to reductions of Na(+),K(+)-ATPase activity and the immunocontent of phospho-AKT, in prefrontal cortex. Chronic exposure to a high fat diet impaired short-term memory (object recognition), and decreased BDNF levels in that same brain area. Remarkably, the association of social isolation with chronic high fat diet rescued the memory impairment on the object recognition test, as well as the changes in BDNF levels, Na(+),K(+)-ATPase activity, MAPK, AKT and phospho-AKT to levels similar to the control-chow group. In summary, these findings showed that a brief social isolation period and access to a high fat diet during a sensitive developmental period might cause memory deficits in adulthood. On the other hand, the interplay between isolation and high fat diet access caused a different brain programming, preventing some of the effects observed when these factors are separately applied.

Neonatal handling causes impulsive behavior and decreased pharmacological response to methylphenidate in male adult wistar rats.

Neonatal handling has an impact on adult behavior of experimental animals and is associated with rapid and increased palatable food ingestion, impaired behavioral flexibility, and fearless behavior to novel environments. These symptoms are characteristic features of impulsive trait, being controlled by the medial prefrontal cortex (mPFC). Impulsive behavior is a key component of many psychiatric disorders such as attention deficit hyperactivity disorder (ADHD), manic behavior, and schizophrenia. Others have reported a methylphenidate (MPH)-induced enhancement of mPFC functioning and improvements in behavioral core symptoms of ADHD patients. The aims of the present study were: (i) to find in vivo evidence for an association between neonatal handling and the development of impulsive behavior in adult Wistar rats and (ii) to test whether neonatal handling could have an impact on monoamine levels in the mPFC and the pharmacological response to MPH in vivo. Therefore, experimental animals (litters) were classified as: "non-handled" and "handled" (10[Formula: see text]min/day, postnatal days 1-10). After puberty, they were exposed to either a larger and delayed or smaller and immediate reward (tolerance to delay of reward task). Acute MPH (3[Formula: see text]mg/Kg. i.p.) was used to suppress and/or regulate impulsive behavior. Our results show that only neonatally handled male adult Wistar rats exhibit impulsive behavior with no significant differences in monoamine levels in the medial prefrontal cortex, together with a decreased response to MPH. On this basis, we postulate that early life interventions may have long-term effects on inhibitory control mechanisms and affect the later response to pharmacological agents during adulthood.

Isolation during the prepubertal period associated with chronic access to palatable diets: effects on plasma lipid profile and liver oxidative stress.

Pre-puberty is a critical period for the final maturation of the neural circuits that control energy homeostasis, as external stimuli such as exposure to diets and stress may influence the adaptive responses with long-term repercussions. Our aim is to investigate the effects of isolation stress during early life and of chronic access to palatable diets, rich in sugar or fat, on the metabolic profile (glycemia, plasma lipids, leptin and cholinesterase activity) and oxidative stress parameters in the livers of adult male rats. We observed changes mainly in animals that received the high-fat diet (increased body weight and abdominal fat in adults, as well as increased plasma glucose, and cholinesterase activity), and most of these effects were further increased by exposure to stress. High-fat diet also affected the rats' lipid profile (increased cholesterol, LDL-cholesterol and triglycerides); these effects were more marked in stressed animals. Additionally, exposure to stress led to an oxidative imbalance in the liver, by increasing production of reactive species, as well as the activity of antioxidant enzymes (superoxide dismutase and catalase); these effects were accentuated with the high-fat diet (which also caused a severe reduction in glutathione peroxidase activity). Taken together, these results show that the pre-pubertal period constitutes a critical window for stressful interventions during development, leading to alterations in metabolic parameters and increased oxidative stress during adulthood that may be more pronounced in animals that receive a high-fat diet.

Stress during the pre-pubertal period leads to long-term diet-dependent changes in anxiety-like behavior and in oxidative stress parameters in male adult rats.

Social isolation during early development is one of the most potent stressors that can cause alterations in the processes of brain maturation, leading to behavioral and neurochemical changes that may persist to adulthood. Exposure to palatable diets during development can also affect neural circuits with long-term consequences. The aims of the present study were to investigate the long-term effects of isolation stress during the pre-pubertal period on the exploratory and anxiety-like behavior, the oxidative stress parameters and the respiratory chain enzymes activities in the hippocampus of adult male rats under chronic palatable diets. The results showed that isolated rats receiving either normal or high-fat diet during the pre-pubertal period presented an anxiolytic-like behavior. The animals exposed to stress and treated with high-carbohydrate diet, rich in disaccharides, on the other hand, presented the opposite pattern of behavior. Stress in the pre-pubertal period also leads to decreased activity of the antioxidant enzymes and the mitochondrial respiratory chain complexes II and IV and decreased total thiol content. These effects were reversed by high-fat diet when it was associated with stress. The effects of a sub-acute pre-pubertal isolation stress on anxiety-like behavior and on hippocampal oxidative imbalance during adulthood appear to be modulated by different types of diets, and probably different mechanisms are involved.

Effect of chronic administration of tamoxifen and/or estradiol on feeding behavior, palatable food and metabolic parameters in ovariectomized rats.

Tamoxifen (TAM) is a selective estrogen receptor modulator (SERM) used in the treatment of breast cancer; however many women complain of weight gain during TAM treatment. The anorectic effects of estradiol (E) and TAM are well known, although the effects of E on the consumption of palatable food are controversial and there is no information regarding the effects of TAM on palatable food consumption. The aim of this study was to investigate the effects of chronic treatment with estradiol and/or tamoxifen on feeding behavior in ovariectomized rats exposed to standard chow and palatable foods (Froot Loops® or chocolate). Additionally, parameters such as body weight, uterine weight, lipid profile and plasma glucose were also measured. Wistar rats were ovariectomized (OVX) and subsequently injected (ip.) for 40 days with: E, TAM, E+TAM or vehicle (OVX and SHAM - controls). Behavioral tests were initiated 25 days after the start of treatment. Froot Loops® consumption was evaluated in a novel environment for 3 min. Standard chow intake was evaluated for two days and chocolate intake for 7 days in the home cage in a free choice model (chocolate or standard chow). Rats injected with E, TAM and E+TAM groups showed a reduction in body weight and standard chow intake, compared with control groups. With regard to palatable food intake, the E, TAM and E+TAM groups demonstrated increased consumption of Froot Loops®, compared with the SHAM and OVX groups. In contrast, all groups increased their consumption of chocolate, compared with standard chow; however the E group consumed more chocolate than the OVX, TAM and E+TAM groups. Despite these differences in chocolate consumption, all groups showed the same caloric intake during the chocolate exposure period; however the TAM and E+TAM groups presented decreased body weight. Treatment with estradiol and tamoxifen showed a favorable lipid profile with low levels of TC, LDL, LDL/HDL ratio and lower levels of plasma glucose. The E group presented high levels of TG and HDL, when compared with the TAM and E+TAM groups. Taken together, results suggest that TAM acted in an estrogen-like manner on the majority of parameters analyzed. However, tamoxifen acts in a different manner depending on the type of palatable food and the exposure. In addition, the TAM group demonstrated weight loss, compared with other groups independently of the type of food presented (palatable food or standard chow), showing a low caloric efficiency.