Biology subjects

Samuels, B. A.

Publications and source records attributed to Samuels, B. A..

12 recordsLinked to original sources

bioRxiv2025

Male and Female Mice Are Similarly Susceptible to Chronic Nondiscriminatory Social Defeat Stress Despite Differences in Attack Frequency from Aggressor

RationaleMood disorders are often precipitated by chronic stress and can result in an inability to adapt to the environment and increased vulnerability to challenging experiences. While diagnoses of mood disorders are diagnosed twice as frequently in women than in men, most preclinical chronic social defeat stress mouse models exclude females due to decreased aggression toward female intruders. ObjectivesWe previously reported that the chronic non-discriminatory social defeat stress (CNSDS) paradigm is effective in both sexes, allowing for comparisons between male and female mice. We aimed to improve the screening protocol to identify CD-1 aggressors for use in CNSDS and the method for determining susceptibility to CNSDS. Finally, we aimed to determine whether susceptibility to CNSDS correlated with impaired performance in a satiety- based outcome devaluation task. MethodsWe analyzed CNSDS screening and social defeat sessions to determine appropriate parameters for selecting CD-1 aggressors and investigated aggressions toward male and female intruder mice. We also investigated CNSDS effects on a reward valuation task. ResultsWe observed that despite receiving fewer attacks, female mice are equally susceptible to CNSDS as males and that CNSDS abolished satiety-based outcome devaluation in susceptible male and female mice, but not in resilient male and female mice. ConclusionsThese data suggest that CNSDS-defined susceptible and resilient phenotypes extend to reward behaviors.

neuroscience↗

bioRxiv2025

The 16p11.2 microdeletion influences how early-life microbiota perturbations affect hippocampal development and behavior throughout the lifespan

Neurodevelopmental disorders (NDDs) arise from interactions between genetic factors and environmental exposures, with infancy representing a critical period of vulnerability. This exploratory, preclinical study investigated whether the 16p11.2 microdeletion (16pDel), a NDD-associated genetic variant, exacerbates the effects of early-life therapeutic antibiotic exposure on the gut microbiome, hippocampal development, and behavior. Cefdinir, selected for its epidemiological association with NDD risk, acutely perturbed the gut microbiome, causing sustained reductions in Lachnospiraceae. These changes were followed by alterations in sociability, risk assessment, and associative learning. Notably, only cefdinir-exposed 16pDel mice exhibited altered hippocampal stem cell dynamics and gene expression, demonstrating genotype-dependent susceptibility. Increased intestinal permeability and alterations in arginine biosynthesis and glycerophospholipid metabolism implicate gut barrier dysfunction as a contributing factor. Our findings suggest that genetic composition can exacerbate neurodevelopmental consequences of early-life microbiome perturbations, identify metabolic pathways for potential interventions, and support cautious antibiotic use during infancy, especially in genetically vulnerable populations.

neuroscience↗

bioRxiv2025

Chronic social instability stress differentially affects the behavior and the transcriptome of the anterodorsal bed nucleus of the stria terminalis between male and female mice

Abstract Stress is comprised of systemic/physiological and processive/social factors, with social stressors requiring higher limbic processing. Sex is an important aspect of stress research as men and women show differing responses to stress and mood disorder development. We investigated how social stress affects the bed nucleus of the stria terminalis (BNST) and how sex may contribute. We used a chronic social instability stress (CSIS) paradigm to stress male and female mice for approximately 7 weeks. Afterwards, one cohort was used for avoidance behavior testing using the open field test, the elevated plus maze, the light/dark box emergence test, and the novelty suppressed feeding test. A second cohort was used for bulk RNA-sequencing of the anterodorsal (ad)BNST. A third cohort of CRH Cre+/Ai14 reporter mice were used for patch clamp electrophysiology in the adBNST. CSIS caused the females to be less avoidant, while the males became more avoidant. Low estrogen state in the females caused them to be less avoidant than in a high estrogen state. In the adBNST, we found major transcriptomic differences between the males and females. Males increased expression in more genes related to the RNA and protein processing whereas the females upregulated genes related to synaptic transmission. The transcriptome in the males is more sensitive to the stress than the females. Finally, CSIS caused adBNST CRH neurons to be hyperpolarized and have lower input resistance in males. In summary, social stress is differentially regulated between males and females, which may relate to the development of stress-related behavioral changes.

neuroscience↗

bioRxiv2024

Chronic variable mild stress alters the transcriptome and signaling properties of the anterodorsal bed nuceleus of the stria terminalis in a sex-dependent manner

Chronic stress is a physiological state marked by dysregulation of the hypo-pituitary-adrenal axis and high circulating levels of stress hormones, such as corticosterone in mice or cortisol in humans. This dysregulated state may result in the development of mood disorders but the process by which this occurs is still unknown. The bed nucleus of the stria terminalis (BNST) serves as an integration center for stress signaling and is therefore likely an important area for the development of mood disorders. This project utilized a chronic variable mild stress (CVMS) paradigm to persistently stress mice for 6 weeks followed by RNA-Sequencing of the anterodorsal (ad) BNST and electrophysiology of corticotropin releasing hormone-expressing cells in the adBNST. Our results show significant sex-biases in the transcriptome of the adBNST as well as effects of CVMS on the transcriptome of the adBNST specifically in males. Female biased genes are related to synaptic transmission while male biased genes are related to RNA processing. Stress sensitive genes in males are related to synaptic transmission and synapse formation. Additionally, electrophysiology data showed that CVMS suppressed the M-current in males but not females. However, CVMS increased the strength of excitatory post-synaptic currents in females but not males. This suggests significant differences in how males and females process chronic stress. It also suggests that the BNST is more sensitive to chronic stress in males than in females.

neuroscience↗

bioRxiv2024

The Interaction Of Diet-Induced Obesity And Chronic Stress In A Mouse Model Of Menopause

Menopause is characterized by the cessation of ovarian hormone production. During postmenopause, cisgender women face increased risks of obesity, cognitive decline, and mood disorder. Mood disorders are associated with exposure to chronic stress. We investigated the combined effects of a high-fat diet (HFD) and chronic stress exposure in a mouse model of menopause using 4-vinylcyclohexene diepoxide (VCD), a selective ovotoxicant that gradually depletes ovarian follicles and hormones. Starting at 6 months, 82 female WT C57BL/6J mice received saline or VCD (130 mg/kg i.p.) 5 days per week for 3 weeks. One month after injection, mice were fed either low-fat diet (LFD) or HFD for 8 weeks followed by 6 weeks of chronic variable mild stress (CVMS). Post-CVMS, mice were either processed for gene expression of the anterodorsal BNST or behavior tests to assess cognitive and anxiety-related behaviors. Plasma samples were collected to analyze metabolic hormones and corticosterone levels. VCD-treated HFD-fed mice had higher fat and body mass, and elevated fasting glucose levels compared to controls and more pronounced avoidance behaviors and cognitive impairments. LFD-fed, VCD-treated mice exhibited less exploration of novel objects and open spaces compared to OIL and HFD counterparts. VCD elevated corticosterone levels on LFD and increased BNST Pacap gene expression on HFD. These findings highlight cognitive repercussions of estrogen deficiency and suggest a potential protective effect of a HFD against some of the adverse outcomes associated with menopause. Our study emphasizes the importance of considering dietary and hormonal interactions in the development of therapeutic strategies.

neuroscience↗

bioRxiv2024

Pharmacological Enhancement of Adult Hippocampal Neurogenesis Improves Behavioral Pattern Separation in Young and Aged Mice

BACKGROUNDImpairments in behavioral pattern separation (BPS)--the ability to distinguish between similar contexts or experiences--contribute to memory interference and overgeneralization seen in many neuropsychiatric conditions, including depression, anxiety, PTSD, dementia, and age-related cognitive decline. While BPS relies on the dentate gyrus and is sensitive to changes in adult hippocampal neurogenesis (AHN), its significance as a pharmacological target has not been tested. METHODSIn this study, we applied a human neural stem cell high-throughput screening cascade to identify compounds that increase human neurogenesis. One compound with a favorable profile, RO6871135, was then tested in BPS in mice. RESULTSChronic treatment with RO6871135, 7.5 mg/kg increased AHN and improved BPS in a fear discrimination task in both young and aged mice. RO6871135 treatment also lowered innate anxiety-like behavior, which was more apparent in mice exposed to chronic corticosterone. Ablation of AHN by hippocampal irradiation supported a neurogenesis-dependent mechanism for RO6871135-induced improvements in BPS. To identify possible mechanisms of action, in vitro and in vivo kinase inhibition and chemical proteomics assays were performed. These tests indicated that RO6871135 inhibited CDK8, CDK11, CaMK2a, CaMK2b, MAP2K6, and GSK3b. An analog compound also demonstrated high affinity for CDK8, CaMK2a, and GSK3b. CONCLUSIONSThese studies demonstrate a method for empirical identification and preclinical testing of novel neurogenic compounds that can improve BPS, and points to possible novel mechanisms that can be interrogated for the development of new therapies to improve specific endophenotypes such as impaired BPS.

animal behavior and cognition↗

bioRxiv2023

Chemogenetic activation of corticotropin-releasing factor-expressing neurons in the anterior bed nucleus of the stria terminalis reduces effortful motivation behaviors

Corticotropin-releasing factor (CRF) in the anterior bed nucleus of the stria terminalis (aBNST) is associated with chronic stress and avoidance behavior. However, CRF+ BNST neurons project to reward- and motivation-related brain regions, suggesting a potential role in motivated behavior. We used chemogenetics to selectively activate CRF+ aBNST neurons in male and female CRF-ires-Cre mice during an effort-related choice task and a concurrent choice task. In both tasks, mice were given the option either to exert effort for high value rewards or to choose freely available low value rewards. Acute chemogenetic activation of CRF+ aBNST neurons reduced barrier climbing for a high value reward in the effort-related choice task in both males and females. Furthermore, acute activation of CRF+ aBNST neurons also reduced effortful lever pressing in high-performing males in the concurrent choice task. These data suggest a novel role for CRF+ aBNST neurons in effort-based decision and motivated behavior.

neuroscience↗

bioRxiv2019

Chronic corticosterone administration induces negative valence and impairs positive valence behaviors in mice

Behavioral approaches utilizing rodents to study mood disorders have focused primarily on negative valence behaviors associated with potential threat (anxiety). However, for disorders such as depression, positive valence behaviors that assess reward processing may be more translationally-valid and predictive of antidepressant treatment outcome. Chronic corticosterone (CORT) administration is a well-validated pharmacological stressor that increases negative valence behaviors (David et al., 2009; Gourley et al., 2008a,b; Gourley et al., 2012; Olausson et al., 2013). However, whether chronic stress paradigms such as CORT administration also lead to deficits in positive valence behaviors remains unclear. We treated male C57BL/6J mice with chronic CORT and assessed both negative and positive valence behaviors. We found that CORT induced negative valence behaviors associated with anxiety in the open field and NSF. Interestingly, CORT also impaired instrumental acquisition, reduced sensitivity to a devalued outcome, reduced breakpoint in progressive ratio, and impaired performance in probabilistic reversal learning. Taken together, these results demonstrate that chronic CORT administration at the same dosage both induces negative valence behaviors associated with anxiety and impairs positive valence behaviors associated with reward processing. These data suggest that CORT administration is a useful experimental system for preclinical approaches to studying stress-induced mood disorders.\n\nSignificance StatementChronic exposure to stress can precipitate mood disorders such as anxiety and depression. However, most studies focus on the effects of chronic stress on increasing negative affect behaviors. Elucidating how chronic stress impacts translationally-valid positive valence behaviors is less studied. Here, we show that chronic pharmacological stress induces negative affect behaviors associates with anxiety and impairs reward-related, positive valence behaviors in mice.

neuroscience↗

bioRxiv2019

Corticotropin-Releasing Hormone Signaling in the Oval Bed Nucleus of the Stria Terminalis Mediates Chronic Stress-Induced Negative Valence Behaviors Associated with Anxiety

The bed nucleus of stria terminalis (BNST) is a forebrain region highly sensitive to stress that expresses corticotropin-releasing hormone (CRH) neuropeptide at high levels and regulates negative valence behaviors associated with anxiety. However, how chronic stress modulates CRH signaling and neuronal activity in BNST remains unknown. We subjected C57BL6/J mice to a 6-week chronic variable mild stress (CVMS) paradigm and investigated the effects on behavior, BNST cellular neurophysiology, and BNST CRH signaling. We also utilized pharmacological infusions and optogenetics to decipher and mimic the effects of CVMS on BNST cellular neurophysiology and behavior. CVMS elevated plasma corticosterone levels, induced negative valence behaviors associated with anxiety, diminished M-currents (voltage-gated K+ currents that stabilize membrane potential and regulate neuronal excitability), and increased mEPSC amplitude in ovBNST. Additionally, the number of c-fos+, CRH+, and CRH activator pituitary adenylate cyclase-activating polypeptide (PACAP)+ cells were increased while CRH inhibitor striatal-enriched protein tyrosine phosphatase (STEP)+ cells were decreased in ovBNST. These expression data were confirmed with qPCR. CVMS also activated PKA in BNST and the electrophysiological and behavioral effects of CVMS were reversed by ovBNST infusion of the PKA-selective antagonist H89. Moreover, optogenetic activation of ovBNST directly induced negative valence behaviors associated with anxiety, mimicking the effects of CVMS. CVMS mediates effects on negative valence behaviors associated with anxiety by activating CRH signaling components and cellular excitability in ovBNST Our findings decipher an important CRH-associated stress molecular signature in BNST and advance our understanding of the neural circuitry underlying stress-induced disorders.

neuroscience↗

bioRxiv2019

Social Instability is an Effective Chronic Stress Paradigm for both Male and Female Mice

Despite stress-associated disorders having a higher incidence rate in females, preclinical research mainly focuses on males. Chronic stress paradigms, such as chronic social defeat and chronic corticosterone administration, were mainly designed and validated in males and subsequent attempts to use these paradigms in females has demonstrated sex differences in the behavioral and HPA axis response to stress. Here, we developed a social stress paradigm, social instability stress (SIS), which exposes adult mice to unstable social hierarchies for 7 weeks. SIS effectively induces negative valence behaviors and hypothalamus-pituitary-adrenal (HPA) axis activation in both males and females. Importantly, while there were effects of estrous cycle on behavior, this variability did not impact the overall effects of SIS on behavior, suggesting estrous does not need to be tracked while utilizing SIS. Furthermore, the effects of SIS on negative valence behaviors were also reversed following chronic antidepressant treatment with fluoxetine (FLX) in both males and females. SIS also reduced adult hippocampal neurogenesis in female mice, while chronic FLX treatment increased adult hippocampal neurogenesis in both males and females. Overall, these data demonstrate that the SIS paradigm is an ethologically valid approach that effectively induces chronic stress in both adult male and adult female mice.

neuroscience↗

bioRxiv2018

Dentate Gyrus Activin Signaling Mediates the Antidepressant Treatment 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 different 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. Treatment of mice with either chronic corticosterone or chronic social defeat stress effectively induces increased negative valence behaviors. Subsequent chronic treatment with the SSRI fluoxetine reverses these behavioral changes in some, but not all, of the mice, permitting stratification into persistent responders and non-responders to fluoxetine. We found several significant differences in expression of Activin signaling-related genes between responders and non-responders to fluoxetine in the dentate gyrus, a region that we recently reported is critical for the beneficial behavioral effects of fluoxetine. Furthermore, enhancement of Activin signaling in the dentate gyrus converted behavioral non-responders into responders to fluoxetine treatment more effectively than commonly used adjunctive antidepressant treatments, while inhibition of Activin signaling in the dentate gyrus converted responders into non-responders. Taken together, these results demonstrate that the behavioral response to FLX can be bidirectionally modified via targeted manipulations of the dentate gyrus and suggest that molecular- and neural circuit-based modulations of dentate gyrus may provide a new therapeutic avenue for more effective antidepressant treatments or adjunctive therapies.

neuroscience↗

bioRxiv2018

Fluoxetine effects on behavior and adult hippocampal neurogenesis in female C57BL/6J mice across the estrous cycle

Some mood disorders, such as major depressive disorder, are more prevalent in women than in men. However, historically preclinical studies in rodents have a lower inclusion rate of females than males, possibly due to the fact that behavior can be affected by the estrous cycle. Several studies have demonstrated that chronic antidepressant treatment can decrease anxiety-like behaviors and increase adult hippocampal neurogenesis in male rodents. However, very few studies have conclusively looked at the effects of antidepressants on behavior and neurogenesis across the estrous cycle in naturally cycling female rodents. Here we analyze the effects of chronic treatment with the selective serotonin reuptake inhibitor (SSRI) fluoxetine (Prozac) on behavior and adult hippocampal neurogenesis in naturally cycling C57BL/6J females across all four phases of the estrous cycle. Interestingly, we find that the effects of fluoxetine on both behavior and adult hippocampal neurogenesis are driven by mice specifically in the estrus or diestrus phases of the estrous cycle. Taken together our data is the first to illustrate the impact of fluoxetine on brain and behavior across all four stages of the murine estrous cycle.\n\nHighlightsO_LIChronic fluoxetine reduces anxiety-like behaviors in naturally cycling female mice\nC_LIO_LIChronic fluoxetine increases adult hippocampal neurogenesis in naturally cycling female mice\nC_LIO_LIThe effects of chronic fluoxetine on behavior and adult hippocampal neurogenesis are driven by the estrus and diestrus phases of the estrous cycle\nC_LI

neuroscience↗