Early life stress decreases hippocampal BDNF content and exacerbates recognition memory deficits induced by repeated D-amphetamine exposure

Differential regulation of innate immune system in frontal cortex and hippocampus in a "double-hit" neurodevelopmental model in rats

Neurodevelopmental disorders (NDs) are neuropsychiatric conditions affecting central nervous system development, characterized by cognitive and behavioural alterations. Inflammation has been recently linked to NDs. Animal models are essential for understanding their pathophysiology and identifying therapeutic targets. Double-hit models can reproduce neurodevelopmental and neuroinflammatory impairments. Sixty-seven newborn rats were assigned to four groups: Control, Maternal deprivation (MD, 24-h-deprivation), Isolation (Iso, 5 weeks), and Maternal deprivation ​+ ​Isolation (MD ​+ ​Iso, also known as double-hit). Cognitive dysfunction was assessed using behavioural tests. Inflammasome, MAPKs, and TLRs inflammatory elements expression in the frontal cortex (FC) and hippocampus (HP) was analysed through western blot and qRT-PCR. Oxidative/nitrosative (O/N) evaluation and corticosterone levels were measured in plasma samples. Double-hit group was affected in executive and working memory. Most inflammasomes and TLRs inflammatory responses were increased in FC compared to the control group, whilst MAPKs were downregulated. Conversely, hippocampal inflammasome and inflammatory components were reduced after the double-hit exposure, while MAPKs were elevated. Our findings reveal differential regulation of innate immune system components in FC and HP in the double-hit group. Further investigations on MAPKs are necessary to understand their role in regulating HP neuroinflammatory status, potentially linking our MAPKs results to cognitive impairments through their proliferative and anti-inflammatory activity.

Methamphetamine: Mechanism of Action and Chinese Herbal Medicine Treatment for Its Addiction

With the proliferation of synthetic drugs, research on the mechanism of action of addictive drugs and treatment methods is of great significance. Among them, methamphetamine (METH) is the most representative amphetamine synthetic drug, and the treatment of METH addiction has become an urgent medical and social problem. In recent years, the therapeutic effects of Chinese herbal medicines on METH addiction have gained widespread attention because of their non-addictiveness, multiple targets, low side effects, low cost, and other characteristics. Previous studies have identified a variety of Chinese herbal medicines with effects on METH addiction. Based on the research on METH in recent years, this article summarizes the mechanism of action of METH as the starting point and briefly reviews the Chinese herbal medicine-based treatment of METH.

Early-life stress elicits peripheral and brain immune activation differently in wild type and 5xFAD mice in a sex-specific manner

BACKGROUND

The risk of developing Alzheimer's disease (AD) is modulated by genetic and environmental factors. Early-life stress (ELS) exposure during critical periods of brain development can impact later brain function and health, including increasing the risk of developing AD. Microglial dysfunction and neuroinflammation have been implicated as playing a role in AD pathology and may be modulated by ELS. To complicate matters further, sex-specific effects have been noted in response to ELS and in the incidence and progression of AD.

METHODS

Here, we subjected male and female mice with either a wild type or 5xFAD familial AD-model background to maternal separation (MS) from postnatal day 2 to 14 to induce ELS.

RESULTS

We detected hippocampal neuroinflammatory alterations already at postnatal day 15. By 4 months of age, MS mice presented increased immobility time in the forced swim test and a lower discrimination index in the novel object recognition memory test compared to controls. We found altered Bdnf and Arc expression in the hippocampus and increased microglial activation in the prefrontal cortex due to MS in a sex-dependent manner. In 5xFAD mice specifically, MS exacerbated amyloid-beta deposition, particularly in females. In the periphery, the immune cell population was altered by MS exposure.

CONCLUSION

Overall, our results demonstrate that MS has both short- and long-term effects on brain regions related to memory and on the inflammatory system, both in the brain and periphery. These ELS-related effects that are detectable even in adulthood may exacerbate pathology and increase the risk of developing AD via sex-specific mechanisms.

Effects of early life adversities upon memory processes and cognition in rodent models

Exposure to stressors in early postnatal life induces long-lasting modifications in brainfunction.Thisplasticity,an essential characteristic of the brain that enables adaptation to the environment, may also induce impairments in some psychophysiological functions, including learning and memory. Early life stress (ELS) has long-term effects on thehypothalamic-pituitary-adrenal axisresponse to stressors, and has been reported to lead toneuroinflammation,altered levelsof neurotrophic factors, modifications inneurogenesis andsynaptic plasticity,with changes in neurotransmitter systems and network functioning. In this review, we focus on early postnatal stress in animal models and their effects on learning and memory.Many studies have reported ELS-induced impairments in different types of memories, including spatial memory, fear memory, recognition (both for objects and social) memory, working memory and reversal learning. Studies are not always in agreement, however, no effects, or sometimes facilitation, being reported, depending on the nature and intensity of the early intervention, as well as the age when the outcome was evaluated and the sex of the animals. When considering processes occurring after consolidation, related with memory maintenance or modification, there are a very reduced number of reports. Future studies addressing the mechanisms underlying memory changes for ELS should shed some light on the understanding of the different effects induced by stressors of different types and intensities on cognitive functions.

Epigenetic Mechanism of 5-HT/NE/DA Triple Reuptake Inhibitor on Adult Depression Susceptibility in Early Stress Mice

Major depressive disorder (MDD) is a chronic, remitting and debilitating disease and the etiology of MDD is highly complicated that involves genetic and environmental interactions. Despite many pharmacotherapeutic options, many patients remain poorly treated and the development of effective treatments remains a high priority in the field. LPM570065 is a potent 5-hydroxytryptamine (5-HT), norepinephrine (NE) and dopamine (DA) triple reuptake inhibitor and both preclinical and clinical results demonstrate significant efficacy against MDD. This study extends previous findings to examine the effects and underlying mechanisms of LPM570065 on stress vulnerability using a “two-hit” stress mouse model. The “two-hit” stress model used adult mice that had experienced early life maternal separation (MS) stress for social defeat stress (SDS) and then they were evaluated in three behavioral assays: sucrose preference test, tail suspension test and forced swimming test. For the mechanistic studies, methylation-specific differentially expressed genes in mouse hippocampal tissue and ventral tegmental area (VTA) were analyzed by whole-genome transcriptome analysis along with next-generation bisulfite sequencing analysis, followed by RT-PCR and pyrophosphate sequencing to confirm gene expression and methylation. LPM570065 significantly reversed depressive-like behaviors in the mice in the sucrose preference test, the tail suspension test, and the forced swimming test. Morphologically, LPM570065 increased the density of dendritic spines in hippocampal CA1 neurons. Hypermethylation and downregulation of oxytocin receptor (Oxtr) in the hippocampal tissues along with increased protein expression of Dnmt1 and Dnmt3a in mice that experienced the “two-hit” stress compared to those that only experienced adulthood social defeat stress, and LPM570065 could reverse these changes. Combined, these results suggest that methylation specificity of the gene Oxtr in the hippocampus may play an important role in early life stress-induced susceptibility to depression and that the5-HT/NE/DA triple reuptake inhibitor LPM570065 may reduce depression susceptibility via the reversal of the methylation of the gene Oxtr.

Impairment of cost-benefit decision making in morphine-dependent rats is partly mediated via the alteration of BDNF and p-CREB levels in the nucleus accumbens

The ability to choose goals based on decision usefulness or the time required to reach the goals chosen are important aspects of decision making. There is considerable evidence in the literature indicating the fact that drug abuse affects different aspects of cognition. In the current study, we assessed the effects of morphine dependence and its withdrawal on cost-benefit decision making and furthermore the involvement of BDNF and p-CREB in the nucleus accumbens, a key brain area involved in decision making was measured. Different groups of male Wistar rats were trained in an effort-based and/or delay-based form of cost-benefit T-maze decision-making task. Thereafter, the animals were morphine dependent and the percentage of the high reward preference was evaluated. After behavioral tests, the BDNF level, and p-CREB/CREB ratio were measured by Western blot analysis. The results showed that during effort-based but not delay-based decision making, BDNF and p-CREB levels increased. During effort-based decision making in morphine dependent rats, BDNF decreased but there was no significant change in p-CREB. Besides, during delay-based decision making in the morphine dependent group, both BDNF and p-CREB did not show any significant change. These findings revealed that BDNF and p-CREB/CREB ratio in the NAc are essential factors for effort-based but not delay-based decision making. In addition, impairment of effort-based decision making in morphine dependent rats is related to the decrease of BDNF level but not p-CREB/CREB ratio in the NAc. However, delay-based decision making defects in morphine dependent rats did not associate with the change in BDNF and p-CREB levels in the NAc.

Sex-dependent effects of paternal deprivation and chronic variable stress on novel object recognition in adult California mice (Peromyscus californicus)

Early-life stress exposure can confer vulnerability for development of psychiatric illnesses and impaired cognition in adulthood. It is well-known that early-life stress can dysregulate the hypothalamic-pituitary-adrenal (HPA) axis in a sex-dependent manner. Specifically, uniparental rodent models of prolonged disrupted mother-offspring relationships (e.g., maternal separation) have demonstrated greater alterations in stress responsivity in adult males, compared to females. Also, chronic early-life stressors (e.g., limited bedding model) impair cognitive function in males more than females. However, the sex-dependent effects of early-life stress and later-life chronic HPA axis activation on cognition have not been well-characterized. Here, we utilized the biparental California mouse (Peromyscus californicus) to model the early-life adversity of paternal deprivation (PD). Fathers either remained in the nest (biparental care) or were permanently removed (PD) on postnatal day (PND) 1. Adult offspring were exposed to daily handling (control) or chronic variable stress (CVS; three stressors for seven days). Twenty-four hours after the final stressor, the novel object recognition (NOR) task commenced, followed by serum collection for corticosterone (CORT) analysis. Independent of sex or rearing, CVS increased CORT. Exploration during acquisition for the NOR task was increased as a result of CVS and PD. During NOR testing, non-stressed females exhibited greater difference scores (i.e., increased recognition memory), compared to non-stressed males. However, the addition of CVS diminished difference scores in females - an effect not observed in CVS-exposed males. Overall, these data suggest that neonatal paternal experience, sex, and chronic stress contribute to exploratory behavior, cognition, and stress hormone concentrations in a biparental species.

Early-life adversity and neurological disease: age-old questions and novel answers

Neurological illnesses, including cognitive impairment, memory decline and dementia, affect over 50 million people worldwide, imposing a substantial burden on individuals and society. These disorders arise from a combination of genetic, environmental and experiential factors, with the latter two factors having the greatest impact during sensitive periods in development. In this Review, we focus on the contribution of adverse early-life experiences to aberrant brain maturation, which might underlie vulnerability to cognitive brain disorders. Specifically, we draw on recent robust discoveries from diverse disciplines, encompassing human studies and experimental models. These discoveries suggest that early-life adversity, especially in the perinatal period, influences the maturation of brain circuits involved in cognition. Importantly, new findings suggest that fragmented and unpredictable environmental and parental signals comprise a novel potent type of adversity, which contributes to subsequent vulnerabilities to cognitive illnesses via mechanisms involving disordered maturation of brain 'wiring'.

Maternal separation in rodents: a journey from gut to brain and nutritional perspectives

The developmental period constitutes a critical window of sensitivity to stress. Indeed, early-life adversity increases the risk to develop psychiatric diseases, but also gastrointestinal disorders such as the irritable bowel syndrome at adulthood. In the past decade, there has been huge interest in the gut-brain axis, especially as regards stress-related emotional behaviours. Animal models of early-life adversity, in particular, maternal separation (MS) in rodents, demonstrate lasting deleterious effects on both the gut and the brain. Here, we review the effects of MS on both systems with a focus on stress-related behaviours. In addition, we discuss more recent findings showing the impact of gut-directed interventions, including nutrition with pre- and probiotics, illustrating the role played by gut microbiota in mediating the long-term effects of MS. Overall, preclinical studies suggest that nutritional approaches with pro- and prebiotics may constitute safe and efficient strategies to attenuate the effects of early-life stress on the gut-brain axis. Further research is required to understand the complex mechanisms underlying gut-brain interaction dysfunctions after early-life stress as well as to determine the beneficial impact of gut-directed strategies in a context of early-life adversity in human subjects.

Preventing epigenetic traces of caregiver maltreatment: A role for HDAC inhibition

Reorganization of the brain's epigenetic landscape occurs alongside early adversity in both human and non-human animals. Whether this reorganization is simply incidental to or is a causal mechanism of the behavioral abnormalities that result from early adversity is important to understand. Using the scarcity-adversity model of low nesting resources in Long Evans rats, our lab has previously reported specific epigenetic and behavioral trajectories occurring in response to early disruption of the caregiving environment. To further probe that relationship, the current work investigates the ability of the epigenome-modifying drug sodium butyrate to prevent maltreatment-induced methylation changes when administered alongside maltreatment. Following exposure to the scarcity-adversity model, during which drug was administered prior to each caregiving session, methylation of Brain-derived Neurotrophic Factor (Bdnf) IX DNA was examined in the Prefrontal Cortex (PFC) of male and female pups at postnatal day (PN) 8. As our previous work reports, increased methylation at this exon of Bdnf in the PFC is a stable epigenetic change across the lifespan that occurs in response to early maltreatment, thus giving us a suitable starting point to investigate pharmacological prevention of maltreatment-induced epigenetic marks. Here we also examined off-target effects of sodium butyrate by assessing methylation in another region of Bdnf (exon IV) not affected in the infant brain as well as global levels of methylation in the brain region of interest. Results indicate that a 400 mg/kg (but not 300 mg/kg) dose of sodium butyrate is effective in preventing the maltreatment-induced rise in methylation at Bdnf exon IX in the PFC of male (but not female) infant pups. Administration of sodium butyrate did not affect the methylation status of Bdnf IV or overall levels of global methylation in the PFC, suggesting potential specificity of this drug. These data provide us an avenue forward for investigating whether the relationship between adversity-induced epigenetic outcomes in our model can be manipulated to improve behavioral outcomes.

Social Environment and Epigenetics

Our social environment, from the microscopic to the macro-social, affects us for the entirety of our lives. One integral line of research to examine how interpersonal and societal environments can get "under the skin" is through the lens of epigenetics. Epigenetic mechanisms are adaptations made to our genome in response to our environment which include tags placed on and removed from the DNA itself to how our DNA is packaged, affecting how our genes are read, transcribed, and interact. These tags are affected by social environments and can persist over time; this may aid us in responding to experiences and exposures, both the enriched and the disadvantageous. From memory formation to immune function, the experience-dependent plasticity of epigenetic modifications to micro- and macro-social environments may contribute to the process of learning from comfort, pain, and stress to better survive in whatever circumstances life has in store.

Effects of maternal separation and antidepressant drug on epigenetic regulation of the brain-derived neurotrophic factor exon I promoter in the adult rat hippocampus

AIM

Early life stress can induce epigenetic changes through genetic and environmental interactions and is a risk factor for depression. Brain-derived neurotrophic factor (BDNF) has been implicated in the pathophysiology of depression and antidepressant drug action. We investigated epigenetic changes at the BDNF exon I promoter in the hippocampus of adult rats subjected to maternal separation (MS) during early life and treated with an antidepressant drug as adults.

METHODS

Rat pups were subjected to MS from postnatal day 1 to 21 and received chronic escitalopram (ESC) as adults. We assessed the effects of MS and ESC on BDNF exon I and DNA methyltransferases (DNMT) mRNA levels (quantitative reverse-transcription polymerase chain reaction), acetylated histone H3, and MeCP2 binding to the BDNF promoter I (chromatin immunoprecipitation followed by real-time polymerase chain reaction), and BDNF protein levels (enzyme-linked immunosorbent assay).

RESULTS

The levels of BDNF protein, exon I mRNA, histone H3 acetylation, and DNMT1 and DNMT3a mRNA were altered in the MS group compared with the control group. Significant decreases were observed in the BDNF protein, exon I mRNA, and histone H3 acetylation levels and there were significant increases in DNMT1 and DNMT3a mRNA levels. The comparison between the MS + ESC and MS groups revealed significant increases in BDNF protein, exon I mRNA, and histone H3 acetylation levels and significant decreases in MeCP2 and DNMT1 and DNMT3a mRNA levels.

CONCLUSION

These findings indicate that MS induced epigenetic changes at the BDNF exon I promoter and these changes were prevented by antidepressant drug treatment during adulthood.

Increased cocaine-induced conditioned place preference during periadolescence in maternally separated male BALB/c mice: the role of cortical BDNF, microRNA-212, and MeCP2

RATIONALE

Early life stress is a major risk factor for cocaine addiction; however, the underlying molecular mechanisms remain relatively unexplored. MicroRNA-212 (miR-212) and methyl CpG binding protein 2 (MeCP2) have recently emerged as key regulators of brain-derived neurotrophic factor (BDNF) signaling during the acquisition and maintenance of cocaine-seeking behaviors.

OBJECTIVES

We therefore investigated the effect of maternal separation (MS) on cocaine-induced conditioned place preference (CPP) during periadolescence and how this influences miR-212, Mecp2, and Bdnf expressions in the prefrontal cortex.

METHODS

Male BALB/c mice subjected to MS (3 h/day) from postnatal day 2 to 15 or normal animal facility rearing (AFR) were tested for CPP at postnatal day 45, or not exposed to experimental manipulations (drug-naïve animals). Cultured primary cortical neurons were used to determine miR-212 expression changes following depolarization by KCL treatment.

RESULTS

MS increased cocaine-induced CPP and decreased Bdnf exon IV expression, which correlated with higher CPP scores in such animals. An experience-dependent decrease in miR-212 expression was observed following CPP test. This effect was mimicked in primary cortical neurons in vitro, under activity-dependent conditions. In contrast, increased Mecp2 expression was found after CPP test, suggesting an opposing relationship between miR-212 and Mecp2 expression following cocaine place preference acquisition. However, these effects were not present in mice exposed to MS.

CONCLUSIONS

Together, our results suggest that early life stress can enhance the motivational salience for cocaine-paired cues during periadolescence, and that altered expression of miR-212, Mecp2, and Bdnf in the prefrontal cortex is involved in this process.

Early life stress increases stress vulnerability through BDNF gene epigenetic changes in the rat hippocampus

Early life stress (ELS) exerts long-lasting epigenetic influences on the brain and makes an individual susceptible to later depression. It is poorly understood whether ELS and subsequent adult chronic stress modulate epigenetic mechanisms. We examined the epigenetic mechanisms of the BDNF gene in the hippocampus, which may underlie stress vulnerability to postnatal maternal separation (MS) and adult restraint stress (RS). Rat pups were separated from their dams (3 h/day from P1-P21). When the pups reached adulthood (8 weeks old), we introduced RS (2 h/day for 3 weeks) followed by escitalopram treatment. We showed that both the MS and RS groups expressed reduced levels of total and exon IV BDNF mRNA. Furthermore, RS potentiated MS-induced decreases in these expression levels. Similarly, both the MS and RS groups showed decreased levels of acetylated histone H3 and H4 at BDNF promoter IV, and RS exacerbated MS-induced decreases of H3 and H4 acetylation. Both the MS and RS groups had increased MeCP2 levels at BDNF promoter IV, as well as increased HDAC5 mRNA, and the combination of MS and RS exerted a greater effect on these parameters than did RS alone. In the forced swimming test, the immobility time of the MS + RS group was significantly higher than that of the RS group. Additionally, chronic escitalopram treatment recovered these alterations. Our results suggest that postnatal MS and subsequent adult RS modulate epigenetic changes in the BDNF gene, and that these changes may be related to behavioral phenotype. These epigenetic mechanisms are involved in escitalopram action.

Long-term effects of early life stress exposure: Role of epigenetic mechanisms

Stress is an adaptive response to demands of the environment and thus essential for survival. Exposure to stress during the first years of life has been shown to have profound effects on the growth and development of an adult individual. There are evidences demonstrating that stressful experiences during gestation or in early life can lead to enhanced susceptibility to mental disorders. Early-life stress triggers hypothalamic-pituitary-adrenocortical (HPA) axis activation and the associated neurochemical reactions following glucocorticoid release are accompanied by a rapid physiological response. An excessive response may affect the developing brain resulting in neurobehavioral and neurochemical changes later in life. This article reviews the data from experimental studies aimed to investigate hormonal, functional, molecular and epigenetic mechanisms involved in the stress response during early-life programming. We think these studies might prove useful for the identification of novel pharmacological targets for more effective treatments of mental disorders.

The Effects of BDNF Val66Met Gene Polymorphism on Serum BDNF and Cognitive Function in Methamphetamine-Dependent Patients and Normal Controls: A Case-Control Study

Studies suggest that a functional polymorphism of the brain-derived neurotrophic factor gene (BDNF Val66Met) may contribute to methamphetamine dependence. We hypothesized that this polymorphism had a role in cognitive deficits in methamphetamine-dependent patients and in the relationship of serum BDNF with cognitive impairments. We conducted a case-control study by assessing 194 methamphetamine-dependent patients and 378 healthy volunteers without history of drug use on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and the presence of the BDNF Val66Met polymorphism and serum BDNF levels. We showed no significant differences in genotype and allele distributions between the methamphetamine-dependent patients and controls. Some aspects of cognitive function significantly differed in the 2 groups. The serum BDNF levels in methamphetamine-dependent patients were significantly higher than those of the healthy controls. In the patients, partial correlation analysis showed a significant positive correlation between serum BDNF and the delayed memory index score. The RBANS scores showed statistically significant BDNF level × genotype interaction. Further regression analyses showed a significant positive association between BDNF levels and the RBANS total score, immediate memory or attention index among Val homozygote patients, whereas a significant negative association of BDNF levels with the RBANS total score, visuospatial/constructional, or language index was found among Met/Val heterozygous patients. We demonstrated significant impairment on some aspects of cognitive function and increased BDNF levels in methamphetamine-dependent patients as well as genotypic differences in the relationships between BDNF levels and RBANS scores on the BDNF Val66Met polymorphism only in these patients.

Involvement of Nitric Oxide, Neurotrophins and HPA Axis in Neurobehavioural Alterations Induced by Prenatal Stress

Several studies suggest that negative emotions during pregnancy generate adverse effects on the cognitive, behavioural and emotional development of the descendants. The psychoneuroendocrine pathways involve the transplacentary passage of maternal glucocorticoids in order to influence directly on fetal growth and brain development.Nitric oxide is a gaseous neurotransmitter that plays an important role in the control of neural activity by diffusing into neurons and participates in learning and memory processes. It has been demonstrated that nitric oxide is involved in the regulation of corticosterone secretion. Thus, it has been found that the neuronal isoform of nitric oxide synthase (nNOS) is an endogenous inhibitor of glucocorticoid receptor (GR) in the hippocampus and that nNOS in the hippocampus may participate in the modulation of hypothalamic-pituitary-adrenal axis activity via GR.Neurotrophins are a family of secreted growth factors consisting of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT3) and NT4. Although initially described in the nervous system, they regulate processes such as cell survival, proliferation and differentiation in several other compartments. It has been demonstrated that the NO-citrulline cycle acts together with BDNF in maintaining the progress of neural differentiation.In the present chapter, we explore the interrelation between nitric oxide, glucocorticoids and neurotrophins in brain areas that are key structures in learning and memory processes. The participation of this interrelation in the behavioural and cognitive alterations induced in the offspring by maternal stress is also addressed.

Long-lasting recognition memory impairment and alterations in brain levels of cytokines and BDNF induced by maternal deprivation: effects of valproic acid and topiramate

Exposure to stressful events early in life may have permanent deleterious consequences on nervous system function and increase the susceptibility to psychiatric conditions later in life. Maternal deprivation, commonly used as a source of neonatal stress, impairs memory in adult rats and reduces hippocampal brain-derived neurotrophic factor (BDNF) levels. Inflammatory cytokines, such as interleukins (IL) and tumor necrosis factor-α (TNF-α) have been shown to be increased in the peripheral blood of patients with psychiatric disorders. The aim of the present study was to investigate the effects of maternal separation on the levels of IL-10 and TNF-α, and BDNF in the hippocampus and prefrontal cortex of adult rats. We also evaluated the potential ameliorating properties of topiramate and valproic acid on memory deficits and cytokine and BDNF changes associated with maternal deprivation. The results indicated that, in addition to inducing memory deficits, maternal deprivation increased the levels of IL-10 in the hippocampus, and TNF-α in the hippocampus and in the cortex, and decreased hippocampal levels of BDNF, in adult life. Neither valproic acid nor topiramate were able to ameliorate memory deficits or the reduction in BDNF induced by maternal separation. The highest dose of topiramate was able to reduce IL-10 in the hippocampus and TNF-α in the prefrontal cortex, while valproate only reduced IL-10 levels in the hippocampus. These findings may have implications for a better understanding of the mechanisms associated with alterations observed in adult life induced by early stressful events, and for the proposal of novel therapeutic strategies.

Increase in brain-derived neurotrophic factor expression in early crack cocaine withdrawal

Recent reports suggest that brain-derived neurotrophic factor (BDNF) could be a biomarker for relapse, drug craving and withdrawal severity. In particular, elevated BDNF levels among former cocaine users have been associated with higher rates of relapse in 90 d. However, no data are available on BDNF levels at baseline and during crack cocaine withdrawal. This study evaluated BDNF among crack cocaine users during inpatient treatment, before and after withdrawal, vs. healthy controls. Clinical correlates with changes in BDNF levels were also assessed. Serum BDNF was evaluated in 49 male crack users on the first and last days of hospitalization and in 97 healthy controls. Serum BDNF was assayed using a sandwich ELISA kit. BDNF levels were significantly lower upon admission when compared to controls, even after adjustment for age, length of inpatient treatment, number of crack rocks used in the last 30 d, years of crack use and interaction between the latter two variables. At discharge, BDNF levels between patients and controls were similar. Number of crack rocks used in the last 30 d and years of crack use were inversely correlated with the outcome. Our findings show that BDNF levels increase during early crack cocaine withdrawal, at an inverse correlation with number of crack rocks used in the last 30 d and years of crack use.

Serum concentrations of brain-derived neurotrophic factor in patients with gender identity disorder

Gender Identity Disorder (GID) is characterized by a strong and persistent cross-gender identification that affects different aspects of behavior. Brain-derived neurotrophic factor (BDNF) plays a critical role in neurodevelopment and neuroplasticity. Altered BDNF-signaling is thought to contribute to the pathogenesis of psychiatric disordersand is related to traumatic life events. To examine serum BDNF levels, we compared one group of DSM-IV GID patients (n = 45) and one healthy control group (n = 66). Serum BDNF levels were significantly decreased in GID patients (p = 0.013). This data support the hypothesis that the reduction found in serum BDNF levels in GID patients may be related to the psychological abuse that transsexuals are exposed during their life.

Sex and litter effects on anxiety and DNA methylation levels of stress and neurotrophin genes in adolescent rats

Maternal care variations associate with DNA methylation of the glucocorticoid receptor gene, Nr3c1, in hippocampus at a nerve-growth factor-inducible protein 1 binding site. Epigenetic regulation of brain-derived neurotrophin factor is affected by early stress. These systems contribute to anxiety and fear. Early stress has sex-dependent effects perhaps reflecting sex differences in maternal care. Altering litter gender composition affects maternal behavior and DNA methylation levels of another gene in hippocampus and nucleus accumbens (NAc). We now test if DNA methylation levels of Nr3c1, Egr1, and Bdnf differ by litter composition or sex. Rats from mixed- or single-sex litters were tested for anxiety and fear on postnatal day 35. Brain tissues were collected and analyzed using direct sequencing methods. Females showed hypermethylation of Nr3c1 of hippocampal DNA and litter composition modified sex effects on methylation of Egr1 in NAc. Few differences were seen for Bdnf. LGC modified some sex differences in behavior.

Early life manipulations alter learning and memory in rats

Much research shows that early life manipulations have enduring behavioral, neural, and hormonal effects. However, findings of learning and memory performance vary widely across studies. We reviewed studies in which pre-weaning rat pups were exposed to stressors and tested on learning and memory tasks in adulthood. Tasks were classified as aversive conditioning, inhibitory learning, or spatial/relational memory. Variables of duration, type, and timing of neonatal manipulation and sex and strain of animals were examined to determine if any predict enhanced or impaired performance. Brief separations enhanced and prolonged separations impaired performance on spatial/relational tasks. Performance was impaired in aversive conditioning and enhanced in inhibitory learning tasks regardless of manipulation duration. Opposing effects on performance for spatial/relational memory also depended upon timing of manipulation. Enhanced performance was likely if the manipulation occurred during postnatal week 3 but performance was impaired if it was confined to the first two postnatal weeks. Thus, the relationship between early life experiences and adulthood learning and memory performance is multifaceted and decidedly task-dependent.

Maternal deprivation and adolescent cannabinoid exposure impact hippocampal astrocytes, CB1 receptors and brain-derived neurotrophic factor in a sexually dimorphic fashion

We have recently reported that early maternal deprivation (MD) for 24 h [postnatal day (PND) 9-10] and/or an adolescent chronic treatment with the cannabinoid agonist CP-55,940 (CP) [0.4 mg/kg, PND 28-42] in Wistar rats induced, in adulthood, diverse sex-dependent long-term behavioral and physiological modifications. Here we show the results obtained from investigating the immunohistochemical analysis of CB1 cannabinoid receptors, glial fibrillary acidic protein (GFAP) positive (+) cells and brain-derived neurotrophic factor (BDNF) expression in the hippocampus of the same animals. MD induced, in males, a significant increase in the number of GFAP+ cells in CA1 and CA3 areas and in the polymorphic layer of the dentate gyrus (DG), an effect that was attenuated by CP in the two latter regions. Adolescent cannabinoid exposure induced, in control non-deprived males, a significant increase in the number of GFAP+ cells in the polymorphic layer of the DG. MD induced a decrease in CB1 expression in both sexes, and this effect was reversed in males by the cannabinoid treatment. In turn, the drug "per se" induced, in males, a general decrease in CB1 immunoreactivity, and the opposite effect was observed in females. Cannabinoid exposure tended to reduce BDNF expression in CA1 and CA3 of females, whereas MD counteracted this trend and induced an increase of BDNF in females. As a whole, the present results show sex-dependent long-term effects of both MD and juvenile cannabinoid exposure as well as functional interactions between the two treatments.

Memory impairment induced by amphetamine derivatives in laboratory animals and in humans: a review

The 20th century brought with it the so-called club drugs (the most notorious being amphetamine derivatives), which are used by young adults at all-night dance parties. Methamphet­amine and 3,4-methylenedioxymethamphetamine (MDMA or ecstasy) are synthetic drugs with stimulant and psychoactive properties that belong to the amphetamine family. Here, we have reviewed the literature about the cognitive impairment induced by these two amphetamine derivatives and the preclinical and clinical outcomes. Although there is controversial evidence about the effect of methamphetamine and MDMA on learning and memory in laboratory animals, results from published papers demonstrate that amphetamines cause long-term impairment of cognitive functions. A large number of pharmacological receptors have been studied and screened as targets of amphetamine-induced cognitive dysfunction, and extensive research efforts have been invested to provide evidence about the molecular mechanisms behind these cognitive deficits. In humans, there is a considerable body of evidence indicating that methamphetamine and MDMA seriously disrupt memory and learning processes. Although an association between the impairments of memory performance and a history of recreational amphetamine ingestion has also been corroborated, a number of methodological difficulties continue to hamper research in this field, the most important being the concomitant use of other illicit drugs.

Early life stress exacerbates cognitive dysfunction induced by d-amphetamine: amelioration by valproic acid

It has been demonstrated that experiences taking place early in life have a profound influence on brain development, interacting with the genetic background and determining differences in the vulnerability to the onset of bipolar disorder when the individual is exposed to a second adverse event later in life. Here, we investigated the effects of exposure to an early adverse life event (maternal deprivation) and to a later adverse life event [D-amphetamine (AMPH)] on cognition in an animal model of mania. We have previously demonstrated that that repeated AMPH exposure produces severe and persistent cognitive impairment, which was more pronounced when the animals were maternal deprived, suggesting that the early adverse life event could be potentiating the effects of the exposure to the second adverse life event later in life. Here, we show that valproic acid ameliorated the cognitive deficits induced by AMPH, but it was not effective when the animals were exposed to both stressors: maternal deprivation and AMPH treatment.