Anxiogenic-like effect of chronic corticosterone in the light-dark emergence task in mice

Individual and joint effects of prenatal PM2.5 and maternal stress on child temperament

Prenatal fine particulate matter (PM2.5) and maternal psychological functioning have been associated with child cognitive outcomes, though their independent and joint impacts on earlier behavioral outcomes remains less studied. We used data from 382 mother-child pairs from a prospective birth cohort in Mexico City. Temperament was measured at 24 months using the Carey Toddler Temperament Scale (TTS). Exploratory factor analysis (EFA) was used to update the factor structure of the TTS. During pregnancy, mothers completed the Crisis in Family Systems-Revised, Edinburgh Depression Scale, pregnancy-specific anxiety scale, and the Perceived Stress Scale. Pregnancy PM2.5 was assessed using estimates from a satellite-based exposure model. We assessed the association between prenatal maternal stress and PM2.5 on temperament, in both independent and joint models. Quantile g-computation was used to estimate the joint associations. Models were adjusted for maternal age, SES, education, child sex, and child age. In EFA, we identified three temperament factors related to effortful control, extraversion, and negative affect. Our main results showed that higher levels of PM2.5 and several of the maternal psychological functioning measures were related to both effortful control and negative affect in the child, both individually and as a mixture. For instance, a one quartile increase in the prenatal mixture was associated with higher negative affect scores in the child (0.34, 95% CI: 0.16, 0.53). We observed modification of these associations by maternal SES, with associations seen only among lower SES participants for both effortful control (-0.45, 95% CI: -0.70, -0.20) and negative affect outcomes (0.60, 95% CI: 0.35, 0.85). Prenatal PM2.5 and maternal psychological functioning measures were associated with toddler temperament outcomes, providing evidence for impacts of chemical and non-chemical stressors on early child health.

Association between prenatal and childhood PM2.5 exposure and preadolescent anxiety and depressive symptoms

Background

Fine particulate matter (PM2.5) exposure has been linked to anxiety and depression in adults; however, there is limited research in the younger populations, in which symptoms often first arise.

Methods

We examined the association between early-life PM2.5 exposure and symptoms of anxiety and depression in a cohort of 8-11-year-olds in Mexico City. Anxiety and depressive symptoms were assessed using the Spanish versions of the Revised Children's Manifest Anxiety Scale and Children's Depression Inventory. Daily PM2.5 was estimated using a satellite-based exposure model and averaged over several early and recent exposure windows. Linear and logistic regression models were used to estimate the change in symptoms with each 5-µg/m3 increase in PM2.5. Models were adjusted for child's age, child's sex, maternal age, maternal socioeconomic status, season of conception, and temperature.

Results

Average anxiety and depressive symptom T-scores were 51.0 (range 33-73) and 53.4 (range 44-90), respectively. We observed consistent findings for exposures around the fourth year of life, as this was present for both continuous and dichotomized anxiety symptoms, in both independent exposure models and distributed lag modeling approaches. This window was also observed for elevated depressive symptoms. An additional consistent finding was for PM2.5 exposure during early pregnancy in relation to both clinically elevated anxiety and depressive symptoms, this was seen in both traditional and distributed lag modeling approaches.

Conclusion

Both early life and recent PM2.5 exposure were associated with higher mental health symptoms in the child highlighting the role of PM2.5 in the etiology of these conditions.

Caffeine Administration Mitigates Chronic Stress-Induced Behavioral Deficits, Neurochemical Alterations, and Glial Disruptions in Rats

Prolonged exposure to stress has detrimental effects on health, and the consumption of caffeine, mostly contained in energy drinks, has become a widely adopted stress coping strategy. Currently, there is limited information regarding the effects of caffeine intake on chronic stress exposure. Thus, this study investigated the effects of caffeine administration on chronic stress-induced behavioral deficits, neurochemical alterations, and glial disruptions in experimental rats. Thirty male Wistar rats were randomly assigned to five groups (n = 6): non-stress control, stress control, and caffeine groups of doses 12.5, 25, and 50 mg/kg. The stress control and caffeine groups were subjected to an unpredictable chronic mild stress (UCMS) protocol daily for 14 days. The rats were evaluated for phenotypic and neurobehavioral assessments. Thereafter, the rat brains were processed for biochemical and immunohistochemical assays. Caffeine administration was found to ameliorate behavioral dysfunctions in rats exposed to UCMS. The UCMS-induced changes in brain levels of monoamines, cholinesterases, and some oxidative stress biomarkers were reversed by caffeine. Caffeine administration also produced mild protective effects against UCMS-induced changes in GFAP and Iba-1 expression in stress-specific brain regions. These results showed that low and moderate doses of caffeine reversed most of the stress-induced changes, suggesting its ameliorative potential against chronic stress-induced alterations.

Commensal Escherichia coli Strains of Bovine Origin Competitively Mitigated Escherichia coli O157:H7 in a Gnotobiotic Murine Intestinal Colonization Model with or without Physiological Stress

Cattle are a primary reservoir of enterohemorrhagic Escherichia coli (EHEC) O157:H7. Currently, there are no effective methods of eliminating this important zoonotic pathogen from cattle, and colonization resistance in relation to EHEC O157:H7 in cattle is poorly understood. We developed a gnotobiotic EHEC O157:H7 murine model to examine aspects of the cattle pathogen-microbiota interaction, and to investigate competitive suppression of EHEC O157:H7 by 18 phylogenetically distinct commensal E. coli strains of bovine origin. As stress has been suggested to influence enteric colonization by EHEC O157:H7 in cattle, corticosterone administration (±) to incite a physiological stress response was included as an experimental variable. Colonization of the intestinal tract (IT) of mice by the bovine EHEC O157:H7 strain, FRIK-2001, mimicked characteristics of bovine IT colonization. In this regard, FRIK-2001 successfully colonized the IT and temporally incited minimal impacts on the host relative to other EHEC O157:H7 strains, including on the renal metabolome. The presence of the commensal E. coli strains decreased EHEC O157:H7 densities in the cecum, proximal colon, and distal colon. Moreover, histopathologic changes and inflammation markers were reduced in the distal colon of mice inoculated with commensal E. coli strains (both propagated separately and communally). Although stress induction affected the behavior of mice, it did not influence EHEC O157:H7 densities or disease. These findings support the use of a gnotobiotic murine model of enteric bovine EHEC O157:H7 colonization to better understand pathogen-host-microbiota interactions toward the development of effective on-farm mitigations for EHEC O157:H7 in cattle, including the identification of bacteria capable of competitively colonizing the IT.

Exploring the Impact of Social Media on Anxiety Among University Students in the United Kingdom: Qualitative Study

BACKGROUND

The rapid surge in social media platforms has significant implications for users' mental health, particularly anxiety. In the case of social media, the impact on mental well-being has been highlighted by multiple stakeholders as a cause for concern. However, there has been limited research into how the association between social media and anxiety arises, specifically among university students-the generation that has seen the introduction and evolution of social media, and currently lives through the medium. Extant systematic literature reviews within this area of research have not yet focused on university students or anxiety, rather predominantly investigating adolescents or generalized mental health symptoms and disorders. Furthermore, there is little to no qualitative data exploring the association between social media and anxiety among university students.

OBJECTIVE

The purpose of this study is to conduct a systematic literature review of the existing literature and a qualitative study that aims to develop foundational knowledge around the association of social media and anxiety among university students and enhance extant knowledge and theory.

METHODS

A total of 29 semistructured interviews were conducted, comprising 19 male students (65.5%) and 10 female students (34.5%) with a mean age of 21.5 years. All students were undergraduates from 6 universities across the United Kingdom, with most students studying in London (89.7%). Participants were enrolled through a homogenous purposive sampling technique via social media channels, word of mouth, and university faculties. Recruitment was suspended at the point of data saturation. Participants were eligible for the study if they were university students in the United Kingdom and users of social media.

RESULTS

Thematic analysis resulted in 8 second-order themes: 3 mediating factors that decrease anxiety levels and 5 factors that increase anxiety levels. Social media decreased anxiety through positive experiences, social connectivity, and escapism. Social media increased anxiety through stress, comparison, fear of missing out, negative experiences, and procrastination.

CONCLUSIONS

This qualitative study sheds critical light on how university students perceive how social media affects their anxiety levels. Students revealed that social media did impact their anxiety levels and considered it an important factor in their mental health. Thus, it is essential to educate stakeholders, including students, university counselors, and health care professionals, about the potential impact of social media on students' anxiety levels. Since anxiety is a multifactorial condition, pinpointing the main stressors in a person's life, such as social media use, may help manage these patients more effectively. The current research highlights that there are also many benefits to social media, and uncovering these may help in producing more holistic management plans for anxiety, reflective of the students' social media usage.

Chronic corticosterone improves perseverative behavior in mice during sequential reversal learning

BACKGROUND

Stressful life events can both trigger development of psychiatric disorders and promote positive behavioral changes in response to adversities. The relationship between stress and cognitive flexibility is complex, and conflicting effects of stress manifest in both humans and laboratory animals.

OBJECTIVE

To mirror the clinical situation where stressful life events impair mental health or promote behavioral change, we examined the post-exposure effects of stress on cognitive flexibility in mice.

METHODS

We tested female C57BL/6JOlaHsd mice in the touchscreen-based sequential reversal learning test. Corticosterone (CORT) was used as a model of stress and was administered in the drinking water for two weeks before reversal learning. Control animals received drinking water without CORT. Behaviors in supplementary tests were included to exclude non-specific confounding effects of CORT and improve interpretation of the results.

RESULTS

CORT-treated mice were similar to controls on all touchscreen parameters before reversal. During the low accuracy phase of reversal learning, CORT reduced perseveration index, a measure of perseverative responding, but did not affect acquisition of the new reward contingency. This effect was not related to non-specific deficits in chamber activity. CORT increased anxiety-like behavior in the elevated zero maze test and repetitive digging in the marble burying test, reduced locomotor activity, but did not affect spontaneous alternation behavior.

CONCLUSION

CORT improved cognitive flexibility in the reversal learning test by extinguishing prepotent responses that were no longer rewarded, an effect possibly related to a stress-mediated increase in sensitivity to negative feedback that should be confirmed in a larger study.

Enteric Escherichia coli O157:H7 in Cattle, and the Use of Mice as a Model to Elucidate Key Aspects of the Host-Pathogen-Microbiota Interaction: A Review

Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 is responsible for foodborne disease outbreaks, typically associated with the consumption of undercooked foods contaminated with cattle manure containing the bacterium. At present, effective mitigations do not exist. Many of the factors regulating enteric colonization by E. coli O157:H7 in cattle, and how cattle respond to the bacterium are unknown. In this regard, intestinal colonization locations, shedding patterns, interactions with the enteric microbiota, and host immune responses to infection are current knowledge gaps. As disturbances to host homeostasis are believed to play an important role in the enteric survival of the bacterium, it is important to consider the potential importance of stress during cattle production. Husbandry logistics, cost, and the high genetic, physiological, and microbial heterogeneity in cattle has greatly hampered the ability of researchers to elucidate key aspects of the host-pathogen-microbiota interaction. Although mice have not been extensively used as a cattle model, the utilization of murine models has the potential to identify mechanisms to facilitate hypothesis formulation and efficacy testing in cattle. Murine models have been effectively used to mechanistically examine colonization of the intestine, host responses to infection, and to interactively ascertain how host physiological status (e.g., due to physiological stress) and the enteric microbiota influences colonization and disease. In addition to reviewing the relevant literature on intestinal colonization and pathogenesis, including existing knowledge gaps, the review provides information on how murine models can be used to elucidate mechanisms toward the development of rationale-based mitigations for E. coli O157:H7 in cattle.

Beneficial effects of prolonged 2-phenylethyl alcohol inhalation on chronic distress-induced anxio-depressive-like phenotype in female mice

Chronic distress-induced hypothalamic-pituitary-adrenal axis deregulations have been associated with the development of neuropsychiatric disorders such as anxiety and depression. Currently available drugs treating such pathological conditions have limited efficacy and diverse side effects, revealing the need of new safer strategies. Aromatic plant-based compounds are largely used in herbal medicine due to their therapeutic properties on mood, physiology, and general well-being. The purpose of this study was to investigate the effects of 2-phenylethyl alcohol (PEA), one of the pharmacologically active constituents of rose essential oil, on chronic corticosterone (CORT)-induced behavioral and neurobiological changes in female mice. Animals followed a prolonged PEA inhalation exposure (30 min per day) for 15 consecutive days prior to behavioral evaluation with open-field, forced swim and novelty-suppressed feeding tests. CORT treatment induced an anxio-depressive-like phenotype, evidenced by a reduced locomotor activity in the open-field, and an increased latency to feed in the novelty-suppressed feeding paradigms. To elucidate the neural correlates of our behavioral results, immunohistochemistry was further performed to provide a global map of neural activity based on cerebral cFos expression. The altered feeding behavior was accompanied by a significant decrease in the number of cFos-positive cells in the olfactory bulb, and altered functional brain connectivity as shown by cross-correlation-based network analysis. CORT-induced behavioral and neurobiological alterations were reversed by prolonged PEA inhalation, suggesting a therapeutic action that allows regulating the activity of neural circuits involved in sensory, emotional and feeding behaviors. These findings might contribute to better understand the therapeutic potential of PEA on anxio-depressive symptoms.

Psycho-Behavioural Changes in Dogs Treated with Corticosteroids: A Clinical Behaviour Perspective

Simple Summary

Corticosteroids hormones are central to stress responses and, along with other hormones and neurotransmitters, contribute to the onset of physiological and behavioural changes aimed at helping the animal cope with anticipated demand. Both the human and animal literature suggest that exposure to systemic exogenous corticosteroid treatments can be associated with negative emotional states. In this paper, the potential behavioural effects of exogenous corticosteroid treatment on dogs and other species are discussed to show why consideration should be given to this matter when prescribing these drugs.

Abstract

Arousal and distress are often important factors in problematic behaviours, and endogenous corticosteroids are important mediators in the associated stress responses. Exogenous corticosteroid treatments have been reported to change behaviour in human patients and laboratory animals, with similar changes also noted in pet dogs. These behaviours not only potentially adversely impact the welfare of the dogs, but also the quality of life of their owners. Indeed, corticosteroids can bias sensitivity towards aversion in dogs. A decrease in behaviours associated with positive affective states, such as play and exploratory behaviours, together with an increase in aggression and barking have also been described in dogs. According to the available literature, human patients with pre-existing psychiatric disorders are more at risk of developing behavioural side effects due to corticosteroid treatments. It is reasonable to consider that the same may happen in dogs with pre-existing behavioural problems. In this paper, the possible behavioural side effects of exogenous corticosteroids are summarised to help inform and support veterinarians prescribing these drugs.

Hydrangea macrophylla and Thunberginol C Attenuate Stress-Induced Anxiety in Mice

Stress is an important neurological input for successful life. However, chronic stress and stress hormones could be a cause of various neurological disorders including anxiety disorders. Therefore, there have been many efforts to find effective materials for curing stress-induced neurological disorders. In this study, we examined the effect of Hydrangea macrophylla (HM) on corticosterone-induced neurotoxicity, stress-induced anxiety in mice and suggested a possible active ingredient of HM. HM protected cortical neurons against neurotoxicity of corticosterone (CORT), a stress hormone. HM also blocked CORT-induced hippocampal synaptic deficit via regulating Akt signaling. Oral administration of HM improved chronic restraint stress-induced anxiety in Elevated Plus maze test along with reduction of plasma corticosterone and TNF-α levels. Moreover, HM reduced stress-induced neuroinflammation and oxidative stress. Thunberginol C, an active ingredient of HM, also prevented CORT-induced neuronal cell death and restraint stress-induced anxiety. Moreover, thunberginol C reduced plasma TNF-α level and neuroinflammation and oxidative stress. Collectively, HM could be a good candidate for preventing stress-induced neurological disorders and thunberginol C may be an active ingredient of HM for this purpose.

Inter-individual variability in habituation of anxiety-related responses within three mouse inbred strains

Inter-individual variability in behavioral and physiological response has become a well-established phenomenon in animal models of anxiety and other disorders. Such variability is even demonstrated within mouse inbred strains. A recent study showed that adaptive and non-adaptive anxiety phenotypes (measured as habituation and/or sensitization of anxiety responses) may differ within cohorts of 129 mice. This variability was expressed across both anxiety- and activity-related behavioral dimensions. These findings were based however on re-analysis of previously published data. The present study therefore aimed to empirically validate these findings in 129 mice. In addition, we assessed such inter-individuality in two other strains: BALB/c and C57BL/6. Males of three mouse inbred strains (BALB/c, C57BL/6 and 129S2) were behaviorally characterized through repeated exposure to a mild aversive stimulus (modified Hole Board, 4 consecutive trials). Behavioral observations were supplemented with assessment of circulating corticosterone levels. Clustering the individual response trajectories of behavioral and endocrine responses yielded two multidimensional response types of different adaptive value. Interestingly, these response types were displayed by individuals of all three strains. The response types differed significantly on anxiety and activity related behavioral dimensions but not on corticosterone concentrations. This study empirically confirms that adaptive capacities may differ within 129 cohorts. In addition, it extends this inter-individual variability in behavioral profiles to BALB/c and C57BL/6. Whether these two sub-types constitute differential anxiety phenotypes may differ per strain and requires further study.

Nomophobia in Lebanon: Scale validation and association with psychological aspects

Objectives

Nomophobia, an abbreviation of “No mobile phone phobia”, is characterized by the illogical fear of being detached from the mobile phone or unable to use it. Research have provided evidence of an association between increased cellular phone use and multiple health issues, such as anxiety, depression, insomnia, and others. To our knowledge, there are no Lebanese studies about nomophobia, despite the high incorporation rate of mobile phones in Lebanon and the likelihood of suffering from anxiety, depression, and other conditions due to nomophobic attitudes. The study objectives were to validate and confirm psychometric properties of the Nomophobia Questionnaire (NMP-Q) and examine the associations between particular psychological conditions (anxiety, depression, stress, insomnia and impulsivity) and nomophobia among a representative sample of Lebanese people.

Methods

This cross-sectional study was carried out between January and July 2019. It enrolled 2260 residents of the community randomly selected from Lebanon’s Mohafazat. Two villages per sub-district and households from each village were chosen using a random sampling technique. A questionnaire was distributed randomly to the households. SPSS version 25 was used to perform the statistical analysis. A multinomial regression was computed taking the nomophobia categories as the dependent variable (and taking the absence of nomophobia as the reference category) and all variables that showed a significant association in the bivariate analysis as independent variables.

Results

A total of 2260 (80.71%) out of 2800 questionnaires distributed was collected back. The mean age of the participants was 27.98 ± 9.66 years (58.8% females). Moreover, the mean nomophobia score was 71.56 ± 26.92 (median = 71; minimum = 14; maximum = 140). The results showed that 46 (2.0%) had no nomophobia, 769 (34.1%) mild nomophobia [95% CI 0.322–0.361], 1089 (48.3%) moderate nomophobia [95% CI 0.463–0.504] and 349 (15.5%) severe nomophobia [95% CI 0.140–0.170]. Items of the nomophobia scale converged over a solution of three factors that had an Eigenvalue over 1 (Factor 1 = emotions associated to losing connectedness, Factor 2 = not being able to communicate, Factor 3 = not being able to access information; total variance explained = 66.65%, and Cronbach’s alpha = 0.948). The results of a multinomial regression, taking the nomophobia score as the dependent variable, showed that higher age was significantly associated with lower odds of having mild (aOR = 0.97), moderate (aOR = 0.93) and severe (aOR = 0.97) nomophobia respectively. Higher anxiety (aOR = 1.09) and higher insomnia (aOR = 1.04) were significantly associated with higher odds of having severe nomophobia.

Conclusion

The results suggest a positive correlation between nomophobia and psychological conditions. There is a need for longitudinal and prospective studies that furnish information with regards of the impact of time on the variables measured, in order to better understand the nature, causes, and attributes of nomophobia.

Effects of test experience, closed-arm wall color, and illumination level on behavior and plasma corticosterone response in an elevated plus maze in male C57BL/6J mice: a challenge against conventional interpretation of the test

The elevated plus maze test is a widely used test for assessing anxiety-like behavior and screening novel therapeutic agents in rodents. Previous studies have shown that a variety of internal factors and procedural variables can influence elevated plus maze behavior. Although some studies have suggested a link between behavior and plasma corticosterone levels, the relationships between them remain unclear. In this study, we investigated the effects of experience with a battery of behavioral tests, the wall color of the closed arms, and illumination level on the behavior and plasma corticosterone responses in the elevated plus maze in male C57BL/6J mice. Mice were either subjected to a series of behavioral tests, including assessments of general health and neurological function, a light/dark transition test, and an open field test, or left undisturbed until the start of the elevated plus maze test. The mice with and without test battery experience were allowed to freely explore the elevated plus maze. The other two independent groups of naïve mice were tested in mazes with closed arms with different wall colors (clear, transparent blue, white, and black) or different illumination levels (5, 100, and 800 lx). Immediately after the test, blood was collected to measure plasma corticosterone concentrations. Mice with test battery experience showed a lower percentage of open arm time and entries and, somewhat paradoxically, had lower plasma corticosterone levels than the mice with no test battery experience. Mice tested in the maze with closed arms with clear walls exhibited higher open arm exploration than mice tested in the maze with closed arms with black walls, while there were no significant differences in plasma corticosterone levels between the different wall color conditions. Illumination levels had no significant effects on any measure. Our results indicate that experience with other behavioral tests and different physical features of the maze affect elevated plus maze behaviors. Increased open arm time and entries are conventionally interpreted as decreased anxiety-like behavior, while other possible interpretations are considered: open arm exploration may reflect heightened anxiety and panic-like reaction to a novel situation under certain conditions. With the possibility of different interpretations, the present findings highlight the need to carefully consider the test conditions in designing experiments and drawing conclusions from the behavioral outcomes in the elevated plus maze test in C57BL/6J mice.

Dentate gyrus activin signaling mediates the antidepressant response

Antidepressants that target monoaminergic systems, such as selective serotonin reuptake inhibitors (SSRIs), are widely used to treat neuropsychiatric disorders including major depressive disorder, several anxiety disorders, and obsessive-compulsive disorder. However, these treatments are not ideal because only a subset of patients achieve remission. The reasons why some individuals remit to antidepressant treatments while others do not are unknown. Here, we developed a paradigm to assess antidepressant treatment resistance in mice. Exposure of male C57BL/6J mice to either chronic corticosterone administration or chronic social defeat stress induces maladaptive affective behaviors. Subsequent chronic treatment with the SSRI fluoxetine reverses these maladaptive affective behavioral changes in some, but not all, of the mice, permitting stratification into persistent responders and non-responders to fluoxetine. We found several differences in expression of Activin signaling-related genes between responders and non-responders in the dentate gyrus (DG), a region that is critical for the beneficial behavioral effects of fluoxetine. Enhancement of Activin signaling in the DG converted behavioral non-responders into responders to fluoxetine treatment more effectively than commonly used second-line antidepressant treatments, while inhibition of Activin signaling in the DG converted responders into non-responders. Taken together, these results demonstrate that the behavioral response to fluoxetine can be bidirectionally modified via targeted manipulations of the DG and suggest that molecular- and neural circuit-based modulations of DG may provide a new therapeutic avenue for more effective antidepressant treatments.

Identification of a prefrontal cortex-to-amygdala pathway for chronic stress-induced anxiety

Dysregulated prefrontal control over amygdala is engaged in the pathogenesis of psychiatric diseases including depression and anxiety disorders. Here we show that, in a rodent anxiety model induced by chronic restraint stress (CRS), the dysregulation occurs in basolateral amygdala projection neurons receiving mono-directional inputs from dorsomedial prefrontal cortex (dmPFC→BLA PNs) rather than those reciprocally connected with dmPFC (dmPFC↔BLA PNs). Specifically, CRS shifts the dmPFC-driven excitatory-inhibitory balance towards excitation in the former, but not latter population. Such specificity is preferential to connections made by dmPFC, caused by enhanced presynaptic glutamate release, and highly correlated with the increased anxiety-like behavior in stressed mice. Importantly, low-frequency optogenetic stimulation of dmPFC afferents in BLA normalizes the enhanced prefrontal glutamate release onto dmPFC→BLA PNs and lastingly attenuates CRS-induced increase of anxiety-like behavior. Our findings thus reveal a target cell-based dysregulation of mPFC-to-amygdala transmission for stress-induced anxiety.

Sex Differences in the Phosphoproteomic Profiles of APP/PS1 Mice after Chronic Unpredictable Mild Stress

Approximately two-thirds of those suffering with Alzheimer's disease (AD) are women, however, the biological mechanisms underlying this sex divergence of AD prevalence remain unknown. Previous research has shown sex-specific biochemical differences that bias female mice toward pro-AD signaling on the phosphoproteomic level via corticotropin releasing factor (CRF) receptor 1 activation after CRF overexpression. Here we aimed to determine if chronic stress would induce a similar response in AD mouse models. We stressed 4-month-old APP/PS1 mice using a chronic unpredictable mild stress (CUMS) paradigm for up to 1 month. Following CUMS and behavioral assessments, we quantified whole protein and phosphoprotein levels in the cortex of stressed and non-stressed APP/PS1 mice using mass spectrometry-based proteomics. While there were no statistically significant differences at the total protein and peptide abundance levels, we found 909 and 841 statistically significant phosphopeptides between stressed and unstressed females and males, respectively, using a false discovery rate of 5%. Of these significant phosphopeptides, only 301 were the same in males and females. These results indicate that while both males and females undergo protein phosphorylation changes following stress, the peptides that are phosphorylated differ between sexes. We then used Metacore analysis to determine which biological pathways were affected. We found that several pathways were changed differently between male and female mice including NMDA receptor trafficking, cytoskeleton organization, and tau pathology. The differing biological pathways affected between males and females in response to chronic stress may help us to better understand why women are at a higher risk of AD.

Kir6.1 Heterozygous Mice Exhibit Aberrant Amygdala-Dependent Cued Fear Memory

ATP-sensitive K⁺ (K_ATP) channels are predominantly expressed in the brain and consist of four identical inward-rectifier potassium ion channel subunits (Kir6.1 or Kir6.2) and four identical high-affinity sulfonylurea receptor subunits (SUR1, SUR2A, or SUR2B). We previously observed that chronic corticosterone-treated (CORT) mice exhibited enhanced anxiety-like behaviors and cued fear memory. In the present study, the protein and mRNA expression levels of Kir6.1, but not Kir6.2, were decreased in the lateral amygdala (LA) of CORT mice. Heterozygous Kir6.1-null (Kir6.1^+/-) mice also showed enhanced tone (cued) fear memory and long-term potentiation (LTP) in the cortico-LA pathway compared to those in wild-type mice. However, LTP was not enhanced in the hippocampal CA1 regions of Kir6.1^+/- mice. Consistent with increased cued fear memory, both Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-regulated kinase (ERK) activities were significantly elevated in the LAs of Kir6.1^+/- mice after tone stimulation. Our results indicate that increased CaMKII and ERK activities may induce LTP in the LA in Kir6.1^+/- mice, leading to aberrant cued fear memory. The changes in neural plasticity in the LA of Kir6.1^+/- mice were associated with anxiety-like behaviors and may be related to the pathogenic mechanisms of anxiety disorders in human patients.

Effects of chronic intermittent ethanol exposure during early and late adolescence on anxiety-like behaviors and behavioral flexibility in adulthood

Although both humans and laboratory rodents demonstrate cognitive and affective alterations associated with adolescent alcohol exposure, it is still unknown whether the consequences of early initiation of alcohol use differ from those of later binge drinking within the adolescent developmental period. The present study was designed to assess the effects of early and late AIE on (1) anxiety-like behavior under social (modified social interaction test) and non-social test circumstances (modified light/dark box test, elevated plus maze), and (2) behavioral flexibility, indexed via set shifting in males and females. Early-mid adolescent intermittent exposure (early AIE) occurred between postnatal days (P) 25 and 45, whereas late adolescent intermittent exposure (late AIE) was conducted between P45 and P65, with behavioral testing initiated not earlier than 25 days after repeated exposure to ethanol (4.0 g/kg intragastrically, every other day for a total of 11 exposures). Anxiety-like behavior on the EPM was evident in males and females following early AIE, whereas only males demonstrated non-social anxiety on the EPM following late AIE. Social anxiety-like alterations and deficits in behavioral flexibility were evident only in males following early AIE. Taken together, the results of the present study demonstrate a particular vulnerability of young adolescent males to long-lasting detrimental effects of repeated ethanol and an insensitivity of older adolescent females to the intermittent ethanol exposure paradigm.

Chronic mild corticosterone exposure during adolescence enhances behaviors and upregulates neuroplasticity-related proteins in rat hippocampus

Adolescence is a critical period with ongoing maturational processes in stress-sensitive systems. It remains unknown how adolescent individuals would be affected by chronic exposure to corticosterone (the major stress hormone in rodents, CORT) at the doses that are usually not detrimental in adults. In this study, male Sprague-Dawley rats were injected with CORT (5 mg/kg) or vehicle for 21 days during adolescence (postnatal day (PND) 29-49) or adulthood (PND 71-91) and then subjected to behavioral testing or sacrifice for neurobiological analyses. Shortly after treatment cessation, different from CORT-treated adults showing increased anxiety-like behaviors, CORT-treated adolescents exhibited enhanced prepulse inhibition and spatial learning. They also showed increased expression of hippocampal neuroplasticity-related proteins, including BDNF, nectin3, and AMPA receptor subunits. These effects became undetectable after a four-week washout period when CORT-treated adolescents exhibited improved reversal learning. Together, these findings demonstrate that chronic CORT exposure at the dose of 5 mg/kg endows adolescent individuals with enhanced cognitive capacities, possibly supported by increased hippocampal neuroplasticity. This study also highlights mild elevation of CORT levels during adolescence as a potential approach of promoting adaptive behaviors.

Anxiety and exploratory behavior in the African striped mouse, Rhabdomys, taxa are partially modified by the physical rearing environment

The environment may modulate genetic influences on behavioral expression. We investigated whether the physical rearing environment modulates anxiety and exploratory behavior in four populations, representing three species, of the striped mouse Rhabdomys. One population originated from an arid, open habitat and the others from grassy, covered habitats, and two species occurred in sympatry. We raised captive individuals of all populations in treatments that simulated cover or no cover for two generations and investigated the behavior of resulting adults in an open-field, light-dark and startle response tests. We expected that, when raised without cover, the arid population would be less anxious and more exploratory than grassland populations, but found the opposite in the open-field test only. We also expected that all individuals would be anxious and less exploratory when raised under cover, which was the case for anxiety in a light-dark test, but individuals from the no cover treatment were more anxious in the open-field test. Only one population × treatment interaction was detected in which the arid population was least exploratory. Therefore, the physical rearing environment had less of an influence than phylogeny on the development of anxiety and exploration in Rhabdomys.

iPlasticity: Induced juvenile-like plasticity in the adult brain as a mechanism of antidepressants

The network hypothesis of depression proposes that mood disorders reflect problems in information processing within particular neural networks. Antidepressants (AD), including selective serotonin reuptake inhibitors (SSRI), function by gradually improving information processing within these networks. AD have been shown to induce a state of juvenile-like plasticity comparable to that observed during developmental critical periods: Such critical-period-like plasticity allows brain networks to better adapt to extrinsic and intrinsic signals. We have coined this drug-induced state of juvenile-like plasticity 'iPlasticity.' A combination of iPlasticity induced by chronic SSRI treatment together with training, rehabilitation, or psychotherapy improves symptoms of neuropsychiatric disorders and issues underlying the developmentally or genetically malfunctioning networks. We have proposed that iPlasticity might be a critical component of AD action. We have demonstrated that iPlasticity occurs in the visual cortex, fear erasure network, extinction of aggression caused by social isolation, and spatial reversal memory in rodent models. Chronic SSRI treatment is known to promote neurogenesis and to cause dematuration of granule cells in the dentate gyrus and of interneurons, especially parvalbumin interneurons enwrapped by perineuronal nets in the prefrontal cortex, visual cortex, and amygdala. Brain-derived neurotrophic factor (BDNF), via its receptor tropomyosin kinase receptor B, is involved in the processes of synaptic plasticity, including neurogenesis, neuronal differentiation, weight of synapses, and gene regulation of synaptic formation. BDNF can be activated by both chronic SSRI treatment and neuronal activity. Accordingly, the BDNF/tropomyosin kinase receptor B pathway is critical for iPlasticity, but further analyses will be needed to provide mechanical insight into the processes of iPlasticity.

Aberrant Amygdala-dependent Fear Memory in Corticosterone-treated Mice

Anxiety disorder is a major psychiatric disorder characterized by fear, worry, and excessive rumination. However, the molecular mechanisms underlying neural plasticity and anxiety remain unclear. Here, we utilized a mouse model of anxiety-like behaviors induced by the chronic administration of corticosterone (CORT) to determine the exact mechanism of each region of the fear circuits in the anxiety disorders. Chronic CORT-treated mice showed a significant increase in anxiety-related behaviors as assessed by the elevated plus maze, light-dark, open-field, and marble-burying tasks. In addition, chronic CORT-treated mice exhibited abnormal amygdala-dependent tone-induced fear memory but normal hippocampus-dependent contextual memory. Consistent with amygdala hyperactivation, chronic CORT-treated mice showed significantly increased numbers of c-Fos-positive cells in the basolateral amygdala (BLA) after tone stimulation. Long-term potentiation (LTP) was markedly enhanced in the BLA of chronic CORT-treated mice compared to that of vehicle-treated mice. Immunoblot analyses revealed that autophosphorylation of Ca²⁺/calmodulin-dependent protein kinase (CaMK) IIα at threonine 286 and phosphorylation of cyclic-adenosine-monophosphate response-element-binding protein (CREB) at serine 133 were markedly increased in the BLA of chronic CORT-treated mice after tone stimulation. The protein and mRNA levels of brain-derived neurotrophic factor (BDNF) also significantly increased. Our findings suggest that increased CaMKII activity and synaptic plasticity in the BLA likely account for the aberrant amygdala-dependent fear memory in chronic CORT-treated mice.

Adolescent Cannabinoid Exposure Induces a Persistent Sub-Cortical Hyper-Dopaminergic State and Associated Molecular Adaptations in the Prefrontal Cortex

Considerable evidence suggests that adolescent exposure to delta-9-tetrahydrocanabinol (THC), the psychoactive component in marijuana, increases the risk of developing schizophrenia-related symptoms in early adulthood. In the present study, we used a combination of behavioral and molecular analyses with in vivo neuronal electrophysiology to compare the long-term effects of adolescent versus adulthood THC exposure in rats. We report that adolescent, but not adult, THC exposure induces long-term neuropsychiatric-like phenotypes similar to those observed in clinical populations. Thus, adolescent THC exposure induced behavioral abnormalities resembling positive and negative schizophrenia-related endophenotypes and a state of neuronal hyperactivity in the mesocorticolimbic dopamine (DA) pathway. Furthermore, we observed profound alterations in several prefrontal cortical molecular pathways consistent with sub-cortical DAergic dysregulation. Our findings demonstrate a profound dissociation in relative risk profiles for adolescent versus adulthood exposure to THC in terms of neuronal, behavioral, and molecular markers resembling neuropsychiatric pathology.

Neuroanatomical pathways underlying the effects of hypothalamo-hypophysial-adrenal hormones on exploratory activity

When injected via the intracerebroventricular route, corticosterone-releasing hormone (CRH) reduced exploration in the elevated plus-maze, the center region of the open-field, and the large chamber in the defensive withdrawal test. The anxiogenic action of CRH in the elevated plus-maze also occurred when infused in the basolateral amygdala, ventral hippocampus, lateral septum, bed nucleus of the stria terminalis, nucleus accumbens, periaqueductal grey, and medial frontal cortex. The anxiogenic action of CRH in the defensive withdrawal test was reproduced when injected in the locus coeruleus, while the amygdala, hippocampus, lateral septum, nucleus accumbens, and lateral globus pallidus contribute to center zone exploration in the open-field. In addition to elevated plus-maze and open-field tests, the amygdala appears as a target region for CRH-mediated anxiety in the elevated T-maze. Thus, the amygdala is the principal brain region identified with these three tests, and further research must identify the neural circuits underlying this form of anxiety.

Emotions and Steroid Secretion in Aging Men: A Multi-Study Report

Although aging increases the risk of cognitive and socioemotional deterioration, it has also been shown to be accompanied by an increase in experienced positive emotions and a decrease in negative emotions. Steroid hormones and age-related alterations in secretion patterns have been suggested to play a crucial role in these age-related changes in emotional experience. Importantly, previous studies identified effects of neuroactive hormones on age-related alterations in emotional experience, which vary by sex and depression levels. Therefore, in three independent cross-sectional studies including a total of 776 men, we examined age-related differences in emotional experience and subsequently the moderation effect of steroid hormones. Sample one consisted of 271 self-reporting healthy (SRH) men aged between 40 and 75 years, while sample two comprised 121 men in the identical age range but only including vitally exhausted (VE) men. Sample three included 384 men aged between 25 and 78 years who reported having fathered (FA) at least one child. For the SRH men, age was negatively associated with anxiety symptoms and aggression, while negative trends emerged for depressive symptoms. In VE men, age was negatively associated with depressive symptoms and positively associated with aggression and positive emotions. For FA men, anxiety symptoms and aggression were negatively associated with age. Age trends of steroid hormones and identified moderation effects are reported. However, with adjustment for multiple comparisons, most of the significant associations fade and the reported associations need to be regarded as exploratory starting points for the further investigation of age-related alterations in emotional experience and their relation to steroid secretion. Overall, the results indicate that salivary cortisol might be a moderator of the association between age and symptoms of anxiety for SRH and VE men, while salivary testosterone seems to moderate the association between age and symptoms of anxiety or depression in VE and FA men, respectively. Both hair cortisol and progesterone seem to influence age-related alterations in anger experience. Age-related alterations in the hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-gonadal (HPG) axis emerge as promising avenues to further investigate the decrease in experienced negative emotions in aging men.

Adolescent THC Exposure Causes Enduring Prefrontal Cortical Disruption of GABAergic Inhibition and Dysregulation of Sub-Cortical Dopamine Function

Chronic adolescent marijuana use has been linked to the later development of psychiatric diseases such as schizophrenia. GABAergic hypofunction in the prefrontal cortex (PFC) is a cardinal pathological feature of schizophrenia and may be a mechanism by which the PFC loses its ability to regulate sub-cortical dopamine (DA) resulting in schizophrenia-like neuropsychopathology. In the present study, we exposed adolescent rats to Δ-9-tetra-hydrocannabinol (THC), the psychoactive component in marijuana. At adulthood, we characterized the functionality of PFC GABAergic neurotransmission and its regulation of sub-cortical DA function using molecular, behavioral and in-vivo electrophysiological analyses. Our findings revealed a persistent attenuation of PFC GABAergic function combined with a hyperactive neuronal state in PFC neurons and associated disruptions in cortical gamma oscillatory activity. These PFC abnormalities were accompanied by hyperactive DAergic neuronal activity in the ventral tegmental area (VTA) and behavioral and cognitive abnormalities similar to those observed in psychiatric disorders. Remarkably, these neuronal and behavioral effects were reversed by pharmacological activation of GABA_A receptors in the PFC. Together, these results identify a mechanistic link between dysregulated frontal cortical GABAergic inhibition and sub-cortical DAergic dysregulation, characteristic of well-established neuropsychiatric endophenotypes.

Beneficial effect of aspirin against interferon-α-2b-induced depressive behavior in Sprague Dawley rats

Accumulating data advocates that inflammatory mediators may contribute to depression in experimental models as well as in humans. Nonetheless, whether anti-inflammatory treatments can prevent depression still remains controversial. To substantiate our hypothesis, we used an interferon-α-2b model of depression using Sprague Dawley rats. Interferon-α-2b is a cytokine which activates immune response and also produces depression. The animals were treated for 21 days with aspirin (10 mg/kg, per oral (p.o.)) dexamethasone (1 mg/kg p.o.) and amitriptyline (10 mg/kg p.o.). Amitriptyline was used as reference standard, and given concurrently with aspirin and dexamethasone to examine any synergy. Interferon-α-2b (6000 IU/kg, intraperitoneal (i.p.)) was administered in all the above groups daily, except normal control. Tests performed included sucrose preference test, behavioural tests like forced swim test, elevated plus maze, light dark box and locomotor activity along with biochemical estimations like serum cortisol and brain neurotransmitters. The rats in the group treated with Interferon-α-2b produced depressive behaviour in rats. We found that animals treated with aspirin decreased immobility time in forced swim test, increased sucrose preference, decreased serum cortisol and increased brain serotonin levels signifying antidepressant action. In contrast, there was no effect in groups treated with dexamethasone. Our results suggest that aspirin can serve as a potential antidepressant both individually and as adjuvant agent in the treatment of depression. Inhibition of the cyclo-oxygenase-2 levels and prostaglandins concentration or any other potential physiological and biochemical mechanisms may be involved in antidepressant effect.

Genome-wide Methyl-Seq analysis of blood-brain targets of glucocorticoid exposure

Chronic exposure to glucocorticoids (GCs) can lead to psychiatric complications through epigenetic mechanisms such as DNA methylation (DNAm). We sought to determine whether epigenetic changes in a peripheral tissue can serve as a surrogate for those in a relatively inaccessible tissue such as the brain. DNA extracted from the hippocampus and blood of mice treated with GCs or vehicle solution was assayed using a genome-wide DNAm platform (Methyl-Seq) to identify differentially methylated regions (DMRs) induced by GC treatment. We observed that ∼70% of the DMRs in both tissues lost methylation following GC treatment. Of the 3,095 DMRs that mapped to the same genes in both tissues, 1,853 DMRs underwent DNAm changes in the same direction. Interestingly, only 209 DMRs (<7%) overlapped in genomic coordinates between the 2 tissues, suggesting tissue-specific differences in GC-targeted loci. Pathway analysis showed that the DMR-associated genes were members of pathways involved in metabolism, immune function, and neurodevelopment. Also, changes in cell type composition of blood and brain were examined by fluorescence-activated cell sorting. Separation of the cortex into neuronal and non-neuronal fractions and the leukocytes into T-cells, B-cells, and neutrophils showed that GC-induced methylation changes primarily occurred in neurons and T-cells, with the blood tissue also undergoing a shift in the proportion of constituent cell types while the proportion of neurons and glia in the brain remained stable. From the current pilot study, we found that despite tissue-specific epigenetic changes and cellular heterogeneity, blood can serve as a surrogate for GC-induced changes in the brain.

Further validation of the affective bias test for predicting antidepressant and pro-depressant risk: effects of pharmacological and social manipulations in male and female rats

RATIONALE

Affective biases are hypothesised to contribute to the cause and treatment of mood disorders. We have previously found that affective biases, associated with learning and memory, are observed following acute treatments with a range of antidepressant and pro-depressant manipulations.

OBJECTIVE

This study aimed to test if similar biases are observed in male and female Sprague Dawley (SD) rats. We also test whether the stress hormone, corticosterone, induces a negative bias in the affective bias test (ABT) consistent with its putative role in the development of depression. We then use a meta-analysis to compare our findings with data published for the Lister Hooded rats.

METHODS

The ABT uses a within-subject study design where animals learn to associate distinct digging substrates, encountered on different days, with the same value food reward. Exposure to one substrate is paired with a treatment manipulation (drug or environmental) and the other with a control condition. A preference test is used to test if the treatment has induced a positive or negative bias.

RESULTS

Consistent with previous data, both male and female SD rats exhibit similar positive affective biases following treatment with the antidepressant, venlafaxine, and social play and negative affective biases following FG 7142 (benzodiazepine inverse agonist) and social stress. Acute treatment with corticosterone induced a negative bias.

CONCLUSIONS

These data add to the translational validity of the ABT and suggest that corticosterone can induce a negative affective bias following acute treatment, an effect which may contribute to its long-term effects on mood.

Epigenetic regulation of G protein coupled receptor signaling and its implications in psychiatric disorders

G protein-coupled receptors (GPCRs) act as a relay center through which extracellular signals, in the form of neurotransmitters or therapeutics, are converted into an intracellular response, which ultimately shapes the overall response at the tissue and behavioral level. Remarkably in similar ways, epigenetic mechanisms also modulate the expression pattern of a large number of genes in response to the dynamic environment inside and outside of the body, and consequently overall response. Emerging evidences from the pharmacogenomics and preclinical studies clearly suggest that these two distinct mechanisms criss-cross each other in several neurological disorders. At one hand such cross-talks between two distinct mechanisms make disease etiology more challenging to understand, while on the other hand if dealt appropriately, such situations might provide an opportunity to find novel druggable target and strategy for the treatment of complex diseases. In this review article, we have summarized and highlighted the main findings that tie epigenetic mechanisms to GPCR mediated signaling in the pathophysiology of central nervous system (CNS) disorders, including depression, addiction and pain.

Rhythmical Photic Stimulation at Alpha Frequencies Produces Antidepressant-Like Effects in a Mouse Model of Depression

Current therapies for depression consist primarily of pharmacological agents, including antidepressants, and/or psychiatric counseling, such as psychotherapy. However, light therapy has recently begun to be considered as an effective tool for the treatment of the neuropsychiatric behaviors and symptoms of a variety of brain disorders or diseases, including depression. One methodology employed in light therapy involves flickering photic stimulation within a specific frequency range. The present study investigated whether flickering and flashing photic stimulation with light emitting diodes (LEDs) could improve depression-like behaviors in a corticosterone (CORT)-induced mouse model of depression. Additionally, the effects of the flickering and flashing lights on depressive behavior were compared with those of fluoxetine. Rhythmical flickering photic stimulation at alpha frequencies from 9–11 Hz clearly improved performance on behavioral tasks assessing anxiety, locomotor activity, social interaction, and despair. In contrast, fluoxetine treatment did not strongly improve behavioral performance during the same period compared with flickering photic stimulation. The present findings demonstrated that LED-derived flickering photic stimulation more rapidly improved behavioral outcomes in a CORT-induced mouse model of depression compared with fluoxetine. Thus, the present study suggests that rhythmical photic stimulation at alpha frequencies may aid in the improvement of the quality of life of patients with depression.

In-depth behavioral characterization of the corticosterone mouse model and the critical involvement of housing conditions

Depression and anxiety are disabling and highly prevalent psychiatric disorders. To better understand the neurobiological basis of mood and anxiety disorders, relevant animal models are needed. The corticosterone mouse model is frequently used to study depression. Chronic stress and accompanying glucocorticoid elevation causes pathological changes in the central nervous system, which are related to psychiatric symptoms. Exogenous administration of corticosterone is therefore often used to induce depressive-like behavior in mice and in some cases also features of anxiety-like behavior are shown. However, a thorough characterization of this model has never been conducted and housing conditions of the used subjects often differ between the implemented protocols. We chronically administered a subcutaneous corticosterone bolus injection to single- and group-housed mice, and we subsequently evaluated the face validity of this model by performing a battery of behavioral tests (forced swim test, mouse-tail suspension test, saccharin intake test, novelty-suppressed feeding test, elevated plus maze, light/dark paradigm and open field test). Our results show that corticosterone treatment has a substantial overall effect on depressive-like behavior. Increases in anxiety-like behavior on the other hand are mainly seen in single housed animals, independent of treatment. The current study therefore does not only show a detailed behavioral characterization of the corticosterone mouse model, but furthermore also elucidates the critical influence of housing conditions on the behavioral outcome in this model.

The Omega-3 Polyunsaturated Fatty Acid Docosahexaenoic Acid (DHA) Reverses Corticosterone-Induced Changes in Cortical Neurons

BACKGROUND

Chronic exposure to the glucocorticoid hormone corticosterone exerts cellular stress-induced toxic effects that have been associated with neurodegenerative and psychiatric disorders. Docosahexaenoic acid is a polyunsaturated fatty acid that has been shown to be of benefit in stress-related disorders, putatively through protective action in neurons.

METHODS

We investigated the protective effect of docosahexaenoic acid against glucocorticoid hormone corticosterone-induced cellular changes in cortical cell cultures containing both astrocytes and neurons.

RESULTS

We found that glucocorticoid hormone corticosterone (100, 150, 200 μM) at different time points (48 and 72 hours) induced a dose- and time-dependent reduction in cellular viability as assessed by methyl thiazolyl tetrazolium. Moreover, glucocorticoid hormone corticosterone (200 μM, 72 hours) decreased the percentage composition of neurons while increasing the percentage of astrocytes as assessed by βIII-tubulin and glial fibrillary acidic protein immunostaining, respectively. In contrast, docosahexaenoic acid treatment (6 μM) increased docosahexaenoic acid content and attenuated glucocorticoid hormone corticosterone (200 μM)-induced cell death (72 hours) in cortical cultures. This translates into a capacity for docosahexaenoic acid to prevent neuronal death as well as astrocyte overgrowth following chronic exposure to glucocorticoid hormone corticosterone. Furthermore, docosahexaenoic acid (6 μM) reversed glucocorticoid hormone corticosterone-induced neuronal apoptosis as assessed by terminal deoxynucleotidyl transferase-mediated nick-end labeling and attenuated glucocorticoid hormone corticosterone-induced reductions in brain derived neurotrophic factor mRNA expression in these cultures. Finally, docosahexaenoic acid inhibited glucocorticoid hormone corticosterone-induced downregulation of glucocorticoid receptor expression on βIII- tubulin-positive neurons.

CONCLUSIONS

This work supports the view that docosahexaenoic acid may be beneficial in ameliorating stress-related cellular changes in the brain and may be of value in psychiatric disorders.

Enriched environment decreases microglia and brain macrophages inflammatory phenotypes through adiponectin-dependent mechanisms: Relevance to depressive-like behavior

Regulation of neuroinflammation by glial cells plays a major role in the pathophysiology of major depression. While astrocyte involvement has been well described, the role of microglia is still elusive. Recently, we have shown that Adiponectin (ApN) plays a crucial role in the anxiolytic/antidepressant neurogenesis-independent effects of enriched environment (EE) in mice; however its mechanisms of action within the brain remain unknown. Here, we show that in a murine model of depression induced by chronic corticosterone administration, the hippocampus and the hypothalamus display increased levels of inflammatory cytokines mRNA, which is reversed by EE housing. By combining flow cytometry, cell sorting and q-PCR, we show that microglia from depressive-like mice adopt a pro-inflammatory phenotype characterized by higher expression levels of IL-1β, IL-6, TNF-α and IκB-α mRNAs. EE housing blocks pro-inflammatory cytokine gene induction and promotes arginase 1 mRNA expression in brain-sorted microglia, indicating that EE favors an anti-inflammatory activation state. We show that microglia and brain-macrophages from corticosterone-treated mice adopt differential expression profiles for CCR2, MHC class II and IL-4recα surface markers depending on whether the mice are kept in standard environment or EE. Interestingly, the effects of EE were abolished when cells are isolated from ApN knock-out mouse brains. When injected intra-cerebroventricularly, ApN, whose level is specifically increased in cerebrospinal fluid of depressive mice raised in EE, rescues microglia phenotype, reduces pro-inflammatory cytokine production by microglia and blocks depressive-like behavior in corticosterone-treated mice. Our data suggest that EE-induced ApN increase within the brain regulates microglia and brain macrophages phenotype and activation state, thus reducing neuroinflammation and depressive-like behaviors in mice.

Depressive-like behaviours and decreased dendritic branching in the medial prefrontal cortex of mice with tumors: A novel validated model of cancer-induced depression

Depression is commonly comorbid in cancer patients and has detrimental effects on disease progression. Evidence suggests that biological mechanisms may induce the onset of cancer-induced depression (CID). The present investigation aims to establish a validated preclinical animal model of CID. Female BALB/c mice were allocated to four groups: control (n=12), chronic oral exposure to corticosterone (CORT) (n=12), CORT exposure followed by chronic low dose fluoxetine (FLX) treatment (n=12), and subcutaneous inoculation of 4T1 mammary carcinoma cells (n=13). Anhedonia was evaluated using the sucrose preference test (SPT), and behavioural despair was evaluated using the forced swim test (FST) and tail suspension test (TST). Sholl analyses were used to examine the dendritic morphology of Golgi-Cox impregnated neurons from the medial prefrontal cortex (mPFC). CORT exposure and tumor burden were both associated with decreased sucrose preference, increased FST immobility, and decreased basilar and apical dendritic branching of neurons in the mPFC. CORT-induced behavioural and dendritic morphological changes were reversible by FLX. No differences in TST immobility were observed between groups. On the secondary TST outcome measure, CORT exposure and tumor burden were associated with a trend towards decreased power of movement. CORT exposure induced a positive control model of a depressive-like state, with FLX treatment confirming the predictive validity of the model. This verified the sensitivity of behavioural and histological tests, which were used to assess the CID model. The induction of a depressive-like state in this model represents the first successfully validated animal model of CID.

Somatostatin, neuronal vulnerability and behavioral emotionality

Somatostatin (SST) deficits are common pathological features in depression and other neurological disorders with mood disturbances, but little is known about the contribution of SST deficits to mood symptoms or causes of these deficits. Here we show that mice lacking SST (Sst(KO)) exhibit elevated behavioral emotionality, high basal plasma corticosterone and reduced gene expression of Bdnf, Cortistatin and Gad67, together recapitulating behavioral, neuroendocrine and molecular features of human depression. Studies in Sst(KO) and heterozygous (Sst(HZ)) mice show that elevated corticosterone is not sufficient to reproduce the behavioral phenotype, suggesting a putative role for Sst cell-specific molecular changes. Using laser capture microdissection, we show that cortical SST-positive interneurons display significantly greater transcriptome deregulations after chronic stress compared with pyramidal neurons. Protein translation through eukaryotic initiation factor 2 (EIF2) signaling, a pathway previously implicated in neurodegenerative diseases, was most affected and suppressed in stress-exposed SST neurons. We then show that activating EIF2 signaling through EIF2 kinase inhibition mitigated stress-induced behavioral emotionality in mice. Taken together, our data suggest that (1) low SST has a causal role in mood-related phenotypes, (2) deregulated EIF2-mediated protein translation may represent a mechanism for vulnerability of SST neurons and (3) that global EIF2 signaling has antidepressant/anxiolytic potential.

Glucagon-like peptide-2-induced memory improvement and anxiolytic effects in mice

We investigated the effectiveness of glucagon-like peptide-2 (GLP-2) on memory impairment in lipopolysaccharide (LPS)-treated mice, and anxiety-like behavior in adrenocorticotropic hormone (ACTH)-treated mice. In the Y-maze test, LPS (10 µg/mouse, i.c.v.) significantly decreased spontaneous alternation, which was prevented by pretreatment with GLP-2 (0.01-0.3 µg/mouse, i.c.v.). The GLP-2 treatment just before the Y-maze test also improved LPS-induced memory impairment. Continuous treatment with GLP-2 (3 µg/mouse, i.c.v.) had no effect on the open-field test in saline-treated or ACTH-treated mice. Chronic ACTH treatment did not cause anxiogenic effects in the elevated plus-maze test. GLP-2 showed weak anxiolytic-like effects in the elevated plus-maze test in ACTH-treated, but not saline-treated mice. Moreover, GLP-2 increased 5-HT, but not 5-HIAA and tryptophan hydroxylase 2 levels in the amygdala of ACTH-treated mice. Pharmacological depletion of 5-HT prevented the anxiolytic effects of GLP-2. These results suggest that GLP-2 protected and improved memory function in LPS-treated mice, and also had anxiolytic effects due to changes in the 5-HT system.

Inverse effects of lipopolysaccharides on anxiety in pregnant mice and their offspring

This study aimed to evaluate the effects of the bacterial lipopolysaccharide (LPS) exposure during early pregnancy on anxiety-related behaviour of both pregnant female mice and their male offspring. Pregnant NMRI mice were treated with subcutaneous injections of LPS (30, 60, 120, 240 and 480 μg/kg) on the tenth gestational day of pregnancy. Pro-inflammatory cytokines, such as TNF-α, IL-1β, IL-6 and corticosterone levels, were measured in maternal serum 1.5h following the LPS injections. Baseline anxiety levels of pregnant mice (1.5h after LPS administration) and their male offspring (at postnatal days 60-70) were investigated with the elevated plus maze (EPM) test. In addition, anxiety levels in the offspring were measured after 2h restraint stress or TNF-α (10 μg/kg) administration. Our results demonstrate that LPS administration induces anxiety-like behaviour and a significant increase in cytokines and corticosterone levels in maternal serum. However, in male offspring, prenatal LPS administration has no significant effects on serum cytokines and corticosterone secretion with an exception of the lowest LPS dose that slightly reduced corticosterone levels. Interestingly, prenatal LPS treatment seemed to decrease the baseline anxiety levels, while pretreatment with restraint stress or TNF-α abolished this anxiolytic effects. In summary, our results suggest that prenatal exposure to LPS during early pregnancy may result in reduced baseline anxiety in adult male offspring.

Effects of negative stressors on DNA methylation in the brain: implications for mood and anxiety disorders

Stress is a major contributor to anxiety and mood disorders. The recent discovery of epigenetic changes in the brain resulting from stress has enhanced our understanding of the mechanism by which stress is able to promote these disorders. Although epigenetics encompasses chemical modifications that occur at both DNA and histones, much attention has been focused on stress-induced DNA methylation changes on behavior. Here, we review the effect of stress-induced DNA methylation changes on physiological mechanisms that govern behavior and cognition, dysregulation of which can be harmful to mental health. A literature review was performed in the areas of DNA methylation, stress, and their impact on the brain and psychiatric illness. Key findings center on genes involved in the hypothalamic-pituitary-adrenal axis, neurotransmission and neuroplasticity. Using animal models of different stress paradigms and clinical studies, we detail how DNA methylation changes to these genes can alter physiological mechanisms that influence behavior. Appropriate levels of gene expression in the brain play an important role in mental health. This dynamic control can be disrupted by stress-induced changes to DNA methylation patterns. Advancement in other areas of epigenetics, such as histone modifications and the discovery of the novel DNA epigenetic mark, 5-hydroxymethylcytosine, could provide additional avenues to consider when determining the epigenetic effects of stress on the brain.

Stress hormone exposure reduces mGluR5 expression in the nucleus accumbens: functional implications for interoceptive sensitivity to alcohol

Escalations in alcohol drinking associated with experiencing stressful life events and chronic life stressors may be related to altered sensitivity to the interoceptive/subjective effects of alcohol. Indeed, through the use of drug discrimination methods, rats show decreased sensitivity to the discriminative stimulus (interoceptive) effects of alcohol following exposure to the stress hormone corticosterone (CORT). This exposure produces heightened elevations in plasma CORT levels (eg, as may be experienced by an individual during stressful episodes). We hypothesized that decreased sensitivity to alcohol may be related, in part, to changes in metabotropic glutamate receptors-subtype 5 (mGluR5) in the nucleus accumbens, as these receptors in this brain region are known to regulate the discriminative stimulus effects of alcohol. In the accumbens, we found reduced mGluR5 expression (immunohistochemistry and Western blot) and decreased neural activation (as measured by c-Fos immunohistochemistry) in response to a moderate alcohol dose (1 g/kg) following CORT exposure (7 days). The functional role of these CORT-induced adaptations in relation to the discriminative stimulus effects of alcohol was confirmed, as both the systemic administration of 3-Cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB) an mGluR5 positive allosteric modulator and the intra-accumbens administration of (R,S)-2-Amino-2-(2-chloro-5-hydroxyphenyl)acetic acid sodium salt (CHPG) an mGluR5 agonist restored sensitivity to alcohol in discrimination-trained rats. These results suggest that activation of mGluR5 may alleviate the functional impact of the CORT-induced downregulation of mGluR5 in relation to sensitivity to alcohol. Understanding the contribution of such neuroadaptations to the interoceptive effects of alcohol may enrich our understanding of potential changes in subjective sensitivity to alcohol during stressful episodes.

Mechanisms underlying the antidepressant response and treatment resistance

Depression is a complex and heterogeneous disorder affecting millions of Americans. There are several different medications and other treatments that are available and effective for many patients with depression. However, a substantial percentage of patients fail to achieve remission with these currently available interventions, and relapse rates are high. Therefore, it is necessary to determine both the mechanisms underlying the antidepressant response and the differences between responders and non-responders to treatment. Delineation of these mechanisms largely relies on experiments that utilize animal models. Therefore, this review provides an overview of the various mouse models that are currently used to assess the antidepressant response, such as chronic mild stress, social defeat, and chronic corticosterone. We discuss how these mouse models can be used to advance our understanding of the differences between responders and non-responders to antidepressant treatment. We also provide an overview of experimental treatment modalities that are used for treatment-resistant depression, such as deep brain stimulation and ketamine administration. We will then review the various genetic polymorphisms and transgenic mice that display resistance to antidepressant treatment. Finally, we synthesize the published data to describe a potential neural circuit underlying the antidepressant response and treatment resistance.

Mood disorders in Huntington's disease: from behavior to cellular and molecular mechanisms

Huntington's disease (HD) is a neurodegenerative disorder that is best known for its effect on motor control. Mood disturbances such as depression, anxiety, and irritability also have a high prevalence in patients with HD, and often start before the onset of motor symptoms. Various rodent models of HD recapitulate the anxiety/depressive behavior seen in patients. HD is caused by an expanded polyglutamine stretch in the N-terminal part of a 350 kDa protein called huntingtin (HTT). HTT is ubiquitously expressed and is implicated in several cellular functions including control of transcription, vesicular trafficking, ciliogenesis, and mitosis. This review summarizes progress in efforts to understand the cellular and molecular mechanisms underlying behavioral disorders in patients with HD. Dysfunctional HTT affects cellular pathways that are involved in mood disorders or in the response to antidepressants, including BDNF/TrkB and serotonergic signaling. Moreover, HTT affects adult hippocampal neurogenesis, a physiological phenomenon that is implicated in some of the behavioral effects of antidepressants and is linked to the control of anxiety. These findings are consistent with the emerging role of wild-type HTT as a crucial component of neuronal development and physiology. Thus, the pathogenic polyQ expansion in HTT could lead to mood disorders not only by the gain of a new toxic function but also by the perturbation of its normal function.

Glucocorticoid receptor deletion from the dorsal raphé nucleus of mice reduces dysphoria-like behavior and impairs hypothalamic-pituitary-adrenocortical axis feedback inhibition

Glucocorticoids can cause depression and anxiety. Mechanisms for glucocorticoid effects on mood are largely undefined. The dorsal raphé nucleus (DRN) produces the majority of serotonin in the brain, and expresses glucocorticoid receptors (GR). Because we previously showed that antidepressants used to treat depression and anxiety decrease DRN GR expression, we hypothesized that deleting DRN GR would have anxiolytic- and antidepressant-like effects. We also hypothesized that DRN GR deletion would disinhibit activity of the hypothalamic-pituitary-adrenal (HPA) axis. Adeno-associated virus pseudotype AAV2/9 expressing either Cre recombinase (DRNGRKO mice) or GFP (DRN-GFP mice) was injected into the DRN of floxed GR mice to test these hypotheses. Three weeks after injection, mice underwent 21 days of social defeat or control handling and were tested for anxiety-like behavior (open-field test, elevated-plus maze), depression-like behavior [sucrose preference, forced-swim test (FST), tail-suspension test (TST)], social interaction, and circadian and stress-induced HPA activity. DRN GR deletion decreased anxiety-like behavior in control but not in defeated mice. DRN GR deletion decreased FST and tended to decrease TST despair-like behavior in both control and defeated mice, but did not affect sucrose preference. Exploration of social (a novel mouse) as well as neutral (an empty box) targets was increased in DRNGRKO mice, suggesting that DRN GR deletion also promotes active coping. DRN GR deletion increased stress-induced HPA activity without strongly altering circadian HPA activity. We have shown a novel role for DRN GR to mediate anxiety- and despair-like behavior and to regulate HPA negative feedback during acute stress.

Circadian modulation of anxiety: a role for somatostatin in the amygdala

Pharmacological evidence suggests that the neuropeptide somatostatin (SST) exerts anxiolytic action via the amygdala, but findings concerning the putative role of endogenous SST in the regulation of emotional responses are contradictory. We hypothesized that an endogenous regulation of SST expression over the course of the day may determine its function and tested both SST gene expression and the behavior of SST knock out (SST^-/-) mice in different aversive tests in relation to circadian rhythm. In an open field and a light/dark avoidance test, SST^-/- mice showed significant hyperactivity and anxiety-like behavior during the second, but not during the first half of the active phase, failing to show the circadian modulation of behavior that was evident in their wild type littermates. Behavioral differences occurred independently of changes of intrinsically motivated activity in the home cage. A circadian regulation of SST mRNA and protein expression that was evident in the basolateral complex of the amygdala of wild type mice may provide a neuronal substrate for the observed behavior. However, fear memory towards auditory cue or the conditioning context displayed neither a time- nor genotype-dependent modulation. Together this indicates that SST, in a circadian manner and putatively via its regulation of expression in the amygdala, modulates behavior responding to mildly aversive conditions in mice.

Brain region-specific reduction in c-Fos expression associated with an anxiolytic effect of yokukansan in rats

ETHNOPHARMACOLOGICAL RELEVANCE

A traditional Japanese (Kampo) medicine, yokukansan, has long been used to treat neurosis, insomnia, and night crying and irritability in children. Recently, this medicine has reported to improve the behavioral and psychological symptoms of dementia that often become problematic in patients with Alzheimer's disease and other forms of dementia.

AIM OF THE STUDY

Several animal studies have reported that yokukansan has an anxiolytic effect. However, the underlying mechanisms are not yet understood. In the present study, we investigated the effects in rats of single and repeated administrations of yokukansan on anxiety-like behaviors, stress responses, and the brain regions involved.

MATERIALS AND METHODS

Yokukansan dissolved in water (100 or 300 mg/kg) was administered orally to F344/N male rats 1h before each test or for two weeks before the tests began. Locomotor activity and anxiety-related behavior in the open-field test and the elevated plus-maze test, serum corticosterone levels, and restraint stress-induced c-Fos expression in various brain regions as a marker of neuronal activation were evaluated in both the vehicle-treated and yokukansan-treated rats.

RESULTS

A single administration of yokukansan had no effect on locomotor activity or anxiety-like behavior; however, repeated administration decreased anxiety-like behavior in a dose-dependent manner. Neither single nor repeated administration of yokukansan had an effect on the basal or stress-induced levels of serum corticosterone. For c-Fos expression, restraint stress increased the number of c-Fos-positive cells in the subdivisions of the prefrontal cortex, amygdala, and hypothalamus. Repeated administration of yokukansan decreased the stress-induced c-Fos expression in the prelimbic cortex and the basolateral and medial amygdaloid nuclei.

CONCLUSIONS

The present study indicates that repeated oral administration of yokukansan has an anxiolytic effect and that this effect may be associated with attenuated neuronal activity in the medial prefrontal cortex and amygdala.