Trends of reproductive hormones in male rats during psychosocial stress: role of glucocorticoid metabolism in behavioral dominance

Dopamine D2 receptors in the dorsomedial prefrontal cortex modulate social hierarchy in male mice

Social hierarchy greatly influences behavior and health. Both human and animal studies have signaled the medial prefrontal cortex (mPFC) as specifically related to social hierarchy. Dopamine D1 receptors (D1Rs) and D2 receptors (D2Rs) are abundantly expressed in the mPFC, modulating its functions. However, it is unclear how DR-expressing neurons in the mPFC regulate social hierarchy. Here, using a confrontation tube test, we found that most adult C57BL/6J male mice could establish a linear social rank after 1 week of cohabitation. Lower rank individuals showed social anxiety together with decreased serum testosterone levels. D2R expression was significantly downregulated in the dorsal part of mPFC (dmPFC) in lower rank individuals, whereas D1R expression showed no significant difference among the rank groups in the whole mPFC. Virus knockdown of D2Rs in the dmPFC led to mice being particularly prone to lose the contests in the confrontation tube test. Finally, simultaneous D2R activation in the subordinates and D2R inhibition in the dominants in a pair switched their dominant-subordinate relationship. The above results indicate that D2Rs in the dmPFC play an important role in social dominance. Our findings provide novel insights into the divergent functions of prefrontal D1Rs and D2Rs in social dominance, which may contribute to ameliorating social dysfunctions along with abnormal social hierarchy.

Preclinical Models of Chronic Stress: Adaptation or Pathology?

The experience of prolonged stress changes how individuals interact with their environment and process interoceptive cues, with the end goal of optimizing survival and well-being in the face of a now-hostile world. The chronic stress response includes numerous changes consistent with limiting further damage to the organism, including development of passive or active behavioral strategies and metabolic adjustments to alter energy mobilization. These changes are consistent with symptoms of pathology in humans, and as a result, chronic stress has been used as a translational model for diseases such as depression. While it is of heuristic value to understand symptoms of pathology, we argue that the chronic stress response represents a defense mechanism that is, at its core, adaptive in nature. Transition to pathology occurs only after the adaptive capacity of an organism is exhausted. We offer this perspective as a means of framing interpretations of chronic stress studies in animal models and how these data relate to adaptation as opposed to pathology.

Constitutive depletion of brain serotonin differentially affects rats' social and cognitive abilities

Central serotonin appears a promising transdiagnostic marker of psychiatric disorders and a modulator of some of their key behavioral symptoms. In adult male Tph2 -/- rats, constitutively lacking central serotonin, we tested individual's cognitive, social and non-social abilities and characterized group's social organization under classical and ethological testing conditions. Using unsupervised machine learning, we identified the functions most dependent on serotonin. Although serotonin depletion did not affect cognitive performances in classical testing, in the home-cage it induced compulsive aggression and sexual behavior, hyperactive and hypervigilant stereotyped behavior, reduced self-care and exacerbated corticosterone levels. This profile recalled symptoms of impulse control and anxiety disorders. Serotonin appeared essential for behavioral adaptation to dynamic social environments. Our animal model challenges the essential role of serotonin in decision-making, flexibility, impulsivity, and risk-taking. These findings highlight the importance of studying everyday life functions within the dynamic social living environment to model complexity in animal models.

Social deficits in BTBR T+ Itpr3tf/J mice vary with ecological validity of the test

Translational value of mouse models of neuropsychiatric disorders depends heavily on the accuracy with which they replicate symptoms observed in the human population. In mouse models of autism spectrum disorder (ASD) these include, among others, social affiliation, and communication deficits as well as impairments in understanding and perception of others. Most studies addressing these issues in the BTBR T+ Itpr3tf/J mouse, an idiopathic model of ASD, were based on short dyadic interactions of often non-familiar partners placed in a novel environment. In such stressful and variable conditions, the reproducibility of the phenotype was low. Here, we compared physical conditions and the degree of habituation of mice at the time of testing in the three chambered social affiliation task, as well as parameters used to measure social deficits and found that both the level of stress and human bias profoundly affect the results of the test. To minimize these effects, we tested social preference and network dynamics in mice group-housed in the Eco-HAB system. This automated recording allowed for long-lasting monitoring of differences in social repertoire (including interest in social stimuli) in BTBR T+ Itpr3tf/J and normosocial c57BL/6J mice. With these observations we further validate the BTBR T+ Itpr3tf/J mouse as a model for ASD, but at the same time emphasize the need for more ecological testing of social behavior within all constructs of the Systems for Social Processes domain (as defined by the Research Domain Criteria framework).

Nucleus accumbens dichotomically controls social dominance in male mice

Social dominance versus social submissiveness is a basic behavioral trait of social animals such as human beings and laboratory mice. The brain regions associated with this behavior have been intensely investigated, and early neuroimaging research on human subjects implies that the nucleus accumbens (NAc) might be involved in encoding social dominance. However, the underlying circuitry and synaptic mechanism are largely unknown. In this study, by introducing lesions to both NAc subregions, the shell and core, a causal relationship is established between social dominance and both NAc subregions. A further electrophysiology investigation on the circuitry of these two subregions revealed that the postsynaptic strength of excitatory synapses onto the medium spiny neurons that express the D1 dopamine receptors in the shell is negatively correlated, and the postsynaptic strength of excitatory synapses onto the medium spiny neurons that express the D2 dopamine receptors in the core is positively correlated, with social dominance. Correspondingly, a DREADD investigation revealed that the activities of these respective medium spiny neurons suppress and promote social dominance. These findings identify a neural substrate for social dominance, implying the potential for a therapeutic strategy for treating related psychiatric disorders.

Light Environment Effect in the Sperm and Ribonucleic Acid Quality and Body Weight of Male Mus musculus

BACKGROUND: The mice are categorized as the nocturnal animal meaning that most of the activity conducted in dark environment. However, the treatment of mice as the object studied in the laboratory often experiences the lack attention especially the treat to light exposure to mice during the investigation period which potentially affect the result. AIM: The present study aims to investigate the effect of light environment in the sperm quality, RNA quality, and body weight of male Mus musculus. METHODS: We compared in the mice the desired parameter onto the sample of 16 mice which kept in light and dark cages for 6 weeks. RESULTS: The results indicated that there was a significant difference in the number of sperm, concentration, and purity of RNA between the mice exposed in dark and light environment. The average number of sperm from the ones kept in the dark was found twice as much as those in the light condition. The average RNA concentration in the dark was higher than in the light place but the RNA purity in the dark was lower than the light place. However, the motility and morphology of sperm was not showing any significancy different in both conditions. CONCLUSION: The result proved that the natural light of cages for treating the mice in the laboratory influences the amount of sperm and the quality RNA. Therefore, the control of the light room in the experimental laboratory needs to be considered, especially during the further experiment which related to the quality of sperm, RNA, and body weight of mice.

Gonadal steroid hormone receptors in the medial amygdala contribute to experience-dependent changes in stress vulnerability

Social experience can generate neural plasticity that changes how individuals respond to stress. Winning aggressive encounters alters how animals respond to future challenges and leads to increased plasma testosterone concentrations and androgen receptor (AR) expression in the social behavior neural network. In this project, our aim was to identify neuroendocrine mechanisms that account for changes in stress-related behavior following the establishment of dominance relationships over a two-week period. We used a Syrian hamster model in which acute social defeat stress increases anxiety-like responses in a conditioned defeat test in males and in a social avoidance test in females. First, we administered flutamide, an AR antagonist, via intraperitoneal injections daily during the establishment of dominance relationships in male hamsters. We found that pharmacological blockade of AR prevented a reduction in conditioned defeat in dominant males and blocked an upregulation of AR in the posterior dorsal medial amygdala (MePD) and posterior ventral medial amygdala (MePV), but not in the ventral lateral septum. Next, we administered flutamide into the posterior aspects of the medial amygdala (MeP) prior to acute social defeat stress or prior to conditioned defeat testing in males. We found that pharmacological blockade of AR in the MeP prior to social defeat, but not prior to testing, increased the conditioned defeat response in dominant males and did not alter behavior in subordinates. Finally, we developed a procedure to establish dominance relationships in female hamsters and investigated status-dependent changes in plasma steroid hormone concentrations, estrogen receptor alpha (ERα) immunoreactivity, and defeat-induced social avoidance. We found that dominant female hamsters showed reduced social avoidance regardless of social defeat exposure as well as increased ERα expression in the MePD, but no status-dependent changes in the concentration of plasma steroid hormones. Overall, these findings suggest that achieving and maintaining stable social dominance leads to sex-specific neural plasticity in the MeP that underlies status-dependent changes in stress vulnerability.

Stress in groups: Lessons from non-traditional rodent species and housing models

A major feature of life in groups is that individuals experience social stressors of varying intensity and type. Social stress can have profound effects on health, social behavior, and ongoing relationships. Relationships can also buffer the experience of exogenous stressors. Social stress has most commonly been investigated in dyadic contexts in mice and rats that produce intense stress. Here we review findings from studies of diverse rodents and non-traditional group housing paradigms, focusing on laboratory studies of mice and rats housed in visible burrow systems, prairie and meadow voles, and mole-rats. We argue that the use of methods informed by the natural ecology of rodent species provides novel insights into the relationship between social stress, behavior and physiology. In particular, we describe how this ethologically inspired approach reveals how individuals vary in their experience of and response to social stress, and how ecological and social contexts impact the effects of stress. Social stress induces adaptive changes, as well as long-term disruptive effects on behavior and physiology.

Sex and dose-dependent responses of urinary and faecal glucocorticoid metabolite concentrations following an ACTH challenge in eastern rock sengis (Elephantulus myurus)

Non-invasive methods for measuring glucocorticoids and their metabolites are frequently used in ecological, behavioural and physiological studies of mammals. Using faeces, urine and other matrices for such a measurement has considerable advantages in comparison to more traditional methods, but also requires thorough validation of the methods used. Eastern rock sengis (Elephantulus myurus) are fascinating African mammals and the non-invasive monitoring of the adrenocortical activity opens up new opportunities to study their biology. We were able to validate two assays for measuring urinary (uGCM) and faecal glucocorticoid metabolite (fGCM) concentrations in this species using a dose-dependent challenge with adrenocorticotropic hormone (ACTH). A higher concentration of ACTH elicited higher uGCM and fGCM concentrations in both males and females. Interestingly, uGCM and fGCM concentrations and the responses to ACTH were higher in females than in males and small changes in faecal glucocorticoid metabolites could not be reliably detected in males. In contrast to ACTH, a saline injection did not result in an increase in uGCM or fGCM concentrations. The study also provided insight into when responses to a stressor are likely to be detected in the urine and faeces of sengis and opens up new opportunities to study the stress physiology of this and other sengi species. It further emphasises the importance of thoroughly validating non-invasive methods for measuring hormones in both sexes of a species and for incorporating dose-dependent approaches.

The cross talk of adrenal and Leydig cell steroids in Leydig cells

Glucocorticoid is secreted by adrenal cortex, which binds to intracellular glucocorticoid and mineralocorticoid receptors to regulate steroidogenesis-related gene expression and testosterone production in Leydig cells. Glucocorticoid receptor activity shows inhibitory action on Leydig cell steroidogenesis, while mineralocorticoid receptor activity shows the stimulatory action. Leydig cells contain two important glucocorticoid-metabolizing enzymes, 11β-hydroxysteroid dehydrogenase type 1 and type 2, regulating the intracellular levels of glucocorticoids by a pre-receptor mechanism. 11β-Hydroxysteroid dehydrogenase type 1 is a bidirectional enzyme, and its direction is regulated by intracellular NADP⁺/NADPH redox potential. Leydig cells contain many steroidogenic enzymes, possibly regulating NADP⁺/NADPH redox potential by coupling with 11β-hydroxysteroid dehydrogenase type 1. Here, we review the 11β-hydroxysteroid dehydrogenase regulation and possible consequences in Leydig cell biology and pathology.

Diethylstilbestrol inhibits human and rat 11β-hydroxysteroid dehydrogenase 2

Glucocorticoid hormone might cause intrauterine growth restriction. The glucocorticoid-metabolizing enzyme 11β-hydroxysteroid dehydrogenase 2 (HSD11B2) in the placenta eliminates excess levels of glucocorticoids during pregnancy. The aim of the current study was to define the effects of diethylstilbestrol (DES) on HSD11B2 activity in the mammalian placentas and identify its mode of action. Rat and human placental microsomal HSD11B2 were incubated with different concentrations of DES, and IC50 values were determined. The mode of action was analyzed by incubation of DES together with substrates, glucocorticoid and NAD+. DES suppressed rat and human HSD11B2 with IC50 values of 5.33 and 12.62 μM, respectively. DES was a competitive inhibitor of rat and human HSD11B2 when steroid substrates were added, while it was an uncompetitive inhibitor when cofactor NAD+ was exposed. Oral administration of DES (0.5 mg/kg) to the rat delayed the cortisol metabolism in adult female Sprague-Dawley rats, as indicated by the increases in cortisol's elimination half-life, maximum concentration and area under the curve. In conclusion, DES is a potent HSD11B2 inhibitor, possibly contributing to the intrauterine growth restriction.

Social dominance differentially alters gene expression in the medial prefrontal cortex without affecting adult hippocampal neurogenesis or stress and anxiety-like behavior

Social hierarchies are crucial for a group's survival and can influence the way an individual behaves and relates to a given social context. The study of social rank has been classically based on ethological and observational paradigms, but it recently has taken advantage of the use of other approaches, such as the tube test that measures territorial dominance without the display of in situ aggression and is executable in group-living animals. However, little is known about how previous basal individual differences affect the development of dominance hierarchy measured in the tube test. We have analyzed in male mice body weight, locomotion, anxiety, and serum corticosterone both before and after the tube test, as well as adult hippocampal neurogenesis and transcriptome in the prefrontal cortex after the hierarchy had been established. We found differential gene expression between dominants and subordinates but no association between the other parameters and social status, neither pre- nor posttest. Our findings reveal that social rank in mice is stable along time and is not related to basal differences in stress, mood, or physical features. Lastly, real-time quantitative PCR analysis confirmed differential expression of vomeronasal and olfactory receptors in the cerebral cortex between dominant and subordinate individuals, suggesting that differential brain gene expression in the medial prefrontal cortex could potentially be used as a biomarker of social dominance.-Pallé, A., Zorzo, C., Luskey, V. E., McGreevy, K. R., Fernández, S., Trejo, J. L. Social dominance differentially alters gene expression in the medial prefrontal cortex without affecting adult hippocampal neurogenesis or stress and anxiety-like behavior.

Neuropharmacology of the mesolimbic system and associated circuits on social hierarchies

Most socially living species are organized hierarchically, primarily based on individual differences in social dominance. Dominant individuals typically gain privileged access to important resources, such as food, mating partners and territories, whereas submissive conspecifics are often devoid of such benefits. The benefits associated with a high social status provide a strong incentive to become dominant. Importantly, motivational- and reward-related processes are regulated, to a large extent, by the mesolimbic system. Consequently, several studies point to a key role for the mesolimbic system in social hierarchy formation. This review summarizes the growing body of literature that implicates the mesolimbic system, and associated neural circuits, on social hierarchies. In particular, we discuss the neurochemical and pharmacological studies that have highlighted the contributions of the mesolimbic system and associated circuits including dopamine signaling through the D1 or D2 receptors, GABAergic neurotransmission, the androgen receptor system, and mitochondria and bioenergetics. Given that low social status has been linked to the emergence of anxiety- and depressive-like disorders, a greater understanding of the neurochemistry underlying social dominance could be of tremendous benefit for the development of pharmacological treatments to dysfunctions in social behaviors. This article is part of the Special Issue entitled 'The neuropharmacology of social behavior: from bench to bedside'.

Non-invasive assessment of glucocorticoid and androgen metabolite levels in cooperatively breeding Damaraland mole-rats (Fukomys damarensis)

Dominant females of cooperative breeding species often use aggression to suppress reproduction of subordinate females, resulting in subordinates experiencing stress-related increases in glucocorticoid levels, which may cause reproductive down-regulation. This would suggest a general pattern with higher glucocorticoid levels in subordinate compared to dominant individuals; however, the opposite was found in a number of cooperatively breeding species. Furthermore, breeding females of the cooperatively breeding Damaraland mole-rats (Fukomys damarensis) exhibit very high androgen concentrations during the wet season, presumably to support their breeding monopoly. Hormone analysis in Damaraland mole-rats have typically been measured using plasma and urine, but faecal analysis offers additional advantages especially for field studies on this species. The present study examines the suitability of Damaraland mole-rat faecal samples for determining glucocorticoid metabolite (fGCM) and androgen metabolite (fAM) concentrations using enzyme immunoassays. Using these assays, we further evaluated the effects of breeding status on fGCM and fAM concentrations in wild-caught and captive Damaraland mole-rats. Wild-caught breeding and non-breeding males and females exhibited no differences in fAM concentrations. Immunoreactive fGCM concentrations were only high in male breeders and comparatively low in non-breeders and breeding females. Concentrations of fAMs and fGCMs were similar in captive males and females, but fAM concentrations were elevated in captive compared to wild-caught individuals, which may be related to a higher reproductive activity due to removal from the breeding female. The relatively uniform fAM and fGCM concentrations found in wild-caught mole-rats may be explained by a stable colony structure during the dry season during which this study was conducted. Limited dispersal opportunities result in lower aggression and stress levels within a colony and as a result lower fAM and fGCM concentrations.

Sex and Trait Anxiety Differences in Psychological Stress are Modified by Environment

Evidence-based research has revealed how physiological and emotional responses to acute stress are adaptive. However, under conditions of unpredictable or protracted stress, health and drug vulnerability can be compromised. In this study, we examined anxiety-like behavioral responses of 4th generation adolescent male and female Long Evans rats selectively bred for high (HAn) and low (LAn) anxiety-like behavior when housed in an isolated environment (IE) versus a social environment (SE). After 35 days in IE or SE, animals were tested in the elevated plus maze (EPM), injected with amphetamine (AMPH: 0.5 mg/kg, IP) in the locomotor activity (LMA) chamber, measured for basal and post air puff-stressor core body temperature and blood pressure. Following select rearing, SE reduced the anxiogenic response in HAn rats with females displaying the lowest anxiety-like behavior in the EPM. During habituation in the LMA, IE rats remained active, while post-AMPH injection HAn females were hyperactive, followed closely by LAn females. Our findings from the post-stressor physiological measurements indicate that temperature differences due to environment are observed only in the SE females. We also observed group differences for diastolic (DBP) and systolic (SBP) blood pressure. HAn IE males experienced higher DBP and SBP but LAn IE females only experienced higher SBP. Not only do our findings corroborate earlier work on HAn/LAn lines but the findings obtained from this research offer new insights about the role of environment and the role of sex in (1) modulation of anxiety-like behavior, (2) AMPH sensitivity, and (3) basal and stress-induced physiological changes.

Sex Differences in Hippocampal Memory and Kynurenic Acid Formation Following Acute Sleep Deprivation in Rats

Inadequate sleep is a prevalent problem within our society that can result in cognitive dysfunction. Elevations in kynurenic acid (KYNA), a metabolite of the kynurenine pathway (KP) of tryptophan degradation known to impact cognition, in the brain may constitute a molecular link between sleep loss and cognitive impairment. To test this hypothesis, we investigated the impact of 6 hours of sleep deprivation on memory and KP metabolism (brain and plasma) in male and female rats. Sleep-deprived males were impaired in a contextual memory paradigm, and both sexes were impaired in a recognition memory paradigm. After sleep deprivation, hippocampal KYNA levels increased significantly only in males. The response in hippocampal KYNA levels to sleep loss was suppressed in gonadectomized males, delineating a role of circulating gonadal hormones. Circulating corticosterone, which has previously been linked to KP metabolism, correlated negatively with hippocampal KYNA in sleep-deprived females, however the relationship was not significant in male animals. Taken together, our study introduces striking sex differences in brain KYNA formation and circulating corticosterone in response to sleep deprivation. Relating these findings to sex differences in cognitive outcomes after sleep deprivation may further advance the development of novel therapeutic agents to overcome sleep loss-induced cognitive dysfunction.

Advances in understanding neural mechanisms of social dominance

Dominance hierarchy profoundly impacts social animals' survival, physical and mental health and reproductive success. As the measurements of dominance hierarchy in rodents become established, it is now possible to understand the neural mechanism mediating the intrinsic and extrinsic factors determining social hierarchy. This review summarizes the latest advances in assay development for measuring dominance hierarchy in laboratory mice. It also reviews our current understandings on how activity and plasticity of specific neural circuits shape the dominance trait and mediate the 'winner effect'.

Therapeutic Effects of Anthocyanins and Environmental Enrichment in R6/1 Huntington's Disease Mice

BACKGROUND

Huntington's disease (HD) is a progressive neurodegenerative disease with no effective treatment or cure. Environmental enrichment has been used to slow processes leading to ageing and neurodegenerative diseases including HD. Phenolic phytochemicals including anthocyanins have also been shown to improve brain function in ageing and neurodegenerative diseases.

OBJECTIVE

This study examined the effects of anthocyanin dietary supplementation and environmental enrichment on behavioural phenotypes and brain cholesterol metabolic alterations in the R6/1 mouse model of HD.

METHODS

R6/1 HD mice and their wild-type littermate controls were randomised into the different experimental conditions, involving either environmentally enriched versus standard housing conditions, or anthocyanin versus control diet. Motor dysfunction was assessed from 6 to 26 weeks using the RotaRod and the hind-paw clasping tests. Gas chromatography - tandem mass spectrometry was used to quantify a broad range of sterols in the striatum and cortex of R6/1 HD mice.

RESULTS

Anthocyanin dietary supplementation delayed the onset of motor dysfunction in female HD mice. Environmental enrichment improved motor function and the hind paw clasping phenotype in male HD mice only. These mice also had lower levels of cholesterol oxidation products in the cortex compared to standard-housed mice.

CONCLUSION

Both anthocyanin supplementation and environmental enrichment are able to improve the motor dysfunction phenotype of R6/1 mice, however the effectiveness of these interventions was different between the two sexes. The interventions examined did not alter brain cholesterol metabolic deficits that have been reported previously in this mouse model of HD.

A closer look at the subordinate population within the visible burrow system

The visible burrow system (VBS) utilizes the natural social behavior of rodents to model chronic social stress. Classically, when male and female rats are housed together in the VBS a dominance hierarchy rapidly forms with one dominant (DOM) and three subordinate (SUB) males. SUB animals show signs of chronic social stress, including loss of body weight and elevated basal corticosterone. This study furthered examined differences among the SUB population. Quantitative observations across numerous VBS colonies within the Sakai Lab suggest that there is variability in the effects of stress on the SUB population, specifically that some animals may experience more severe effects of chronic social stress than others. To further examine this observation, SUB animals were classified as OMEGA if they received a disproportionate amount of their colonies' wounds. OMEGA animals received more wounds to their body compared to SUB (P<0.0001) and lost significantly more weight throughout the stress period compared to all other VBS-housed animals (group×time interaction P<0.0001). Following VBS housing it was determined the OMGEA also lost lean body mass (P<0.01 vs. controls and DOM), are hyporesponsive to an acute restraint challenge (P<0.01 vs all other groups) and show depressive-like behavior during a forced swim test. Furthermore, expression of neuropeptide Y within the amygdala, known for anxiolytic properties following chronic stress, was elevated among OMEGA (group×region interaction P<0.001). Together these observations suggest that an additional phenotype exists among the SUB animals within a VBS colony and represents the variability of the effects of chronic social stress.

Early life adversity during the infant sensitive period for attachment: Programming of behavioral neurobiology of threat processing and social behavior

Animals, including humans, require a highly coordinated and flexible system of social behavior and threat evaluation. However, trauma can disrupt this system, with the amygdala implicated as a mediator of these impairments in behavior. Recent evidence has further highlighted the context of infant trauma as a critical variable in determining its immediate and enduring consequences, with trauma experienced from an attachment figure, such as occurs in cases of caregiver-child maltreatment, as particularly detrimental. This review focuses on the unique role of caregiver presence during early-life trauma in programming deficits in social behavior and threat processing. Using data primarily from rodent models, we describe the interaction between trauma and attachment during a sensitive period in early life, which highlights the role of the caregiver's presence in engagement of attachment brain circuitry and suppressing threat processing by the amygdala. These data suggest that trauma experienced directly from an abusive caregiver and trauma experienced in the presence of caregiver cues produce similar neurobehavioral deficits, which are unique from those resulting from trauma alone. We go on to integrate this information into social experience throughout the lifespan, including consequences for complex scenarios, such as dominance hierarchy formation and maintenance.

The visible burrow system: A view from across the hall

The visible burrow system (VBS) is an ethologically relevant social stress model that creates a distinct dominance hierarchy in rats. Randall Sakai's laboratory performed an impressive series of studies documenting the very different impact of VBS exposure on the brain and behavior of dominants (DOM) and subordinates (SUBs). Hierarchy formation causes pronounced changes in metabolism in SUBs relative to both DOMs and unstressed controls, resulting in marked weight loss and metabolic imbalance. Stress testing revealed multiple phenotypes in the VBS, including DOMs, stress-responsive SUBs and stress-non-responsive SUBs. Stress-responsive SUBs have adrenal hypertrophy and elevated baseline corticosterone, consistent with prolonged HPA axis activation; however, peak acute stress responses are not sensitized. In contrast, stress non-responsive individuals do not mount a response to an acute stress, suggesting HPA axis hypofunction. In brain, SUBs exhibit a pattern of gene regulation consistent with impaired stress inhibition (e.g., hippocampal adrenocorticosteroid receptor down-regulation and dendritic retraction) and drive of stress pathways (e.g., increased locus coeruleus tyrosine hydroxylase expression). The non-responsive phenotype is distinguished by down-regulation of paraventricular nucleus corticotropin releasing hormone expression and enhanced neuropeptide Y expression in amygdala. The brain 'signature' created by VBS hierarchy formation differed substantially from that of another well-studied chronic stress model (chronic variable stress). Thus, the impact of VBS is mediated by neurocircuit mechanisms at least in part distinct that of other chronic stress modalities, and suggests that the nature of the stressor may be an essential consideration in development of treatment strategies for stress-related diseases.

Viral-mediated Zif268 expression in the prefrontal cortex protects against gonadectomy-induced working memory, long-term memory, and social interaction deficits in male rats

In humans, some males experience reductions in testosterone levels, as a natural consequence of aging or in the clinical condition termed hypogonadism, which are associated with impaired cognitive performance and mood disorder(s). Some of these behavioral deficits can be reversed by testosterone treatment. Our previous work in rats reported that sex differences in the expression of the transcription factor Zif268, a downstream target of testosterone, within the medial prefrontal cortex (mPFC) mediates sex differences in social interaction. In the present study, we aimed to examine the effects of gonadectomy (GNX) in male rats on mPFC Zif268 expression, mood and cognitive behaviors. We also examined whether reinstitution of Zif268 in GNX rats will correct some of the behavioral deficits observed following GNX. Our results show that GNX induced a downregulation of Zif268 protein in the mPFC, which was concomitant with impaired memory in the y-maze and spontaneous object recognition test, reduced social interaction time, and depression-like behaviors in the forced swim test. Reinstitution of mPFC Zif268, using a novel adeno-associated-viral (AAV) construct, abrogated GNX-induced working memory and long-term memory impairments, and reductions in social interaction time, but not GNX-induced depression-like behaviors. These findings suggest that mPFC Zif268 exerts beneficial effects on memory and social interaction, and could be a potential target for novel treatments for behavioral impairments observed in hypogonadal and aged men with declining levels of gonadal hormones.

Effects of social experience on pair bonding in a monogamous fish (Amatitlania nigrofasciata)

For species in which individuals spend at least some time in groups, dominance relationships and various social cues are often important for mate assessment and choice. For pair bonding species, social experiences may affect reproductive decisions in both sexes. We tested whether prior experience in a mixed-sex group and having a higher dominance status coincides with faster pair formation or spawning in a monogamous fish. Individuals having prior experience in mixed-sex groups paired with a novel fish more frequently than fish from same-sex groups. Fish in mixed-sex groups performed more bites and lateral displays. Although spawning occurred infrequently across pairs, dominant fish from mixed-sex groups spawned more than dominant fish from same-sex groups. Otherwise, there were no clear behavioural relationships between treatment group and subsequent pair formation or spawning, nor were behaviours of the paired fishes related to their prior treatment group. We do not know how mixed-sex social experience may have affected the physiology of those individuals, although our results support a reproductive priming effect.

The brain on stress: Insight from studies using the Visible Burrow System

The discovery of adrenal steroid receptors outside of the hypothalamus in the hippocampus and other forebrain regions catalyzed research on the effects of stress upon cognitive function, emotions and self-regulatory behaviors as well as the molecular, cellular and neuroanatomical mechanisms underlying acute and chronic stress effects on the brain. Indeed, this work has shown that the brain is a plastic and vulnerable organ in the face of acute and chronic stress. The insight that Bob and Caroline Blanchard had in developing and interpreting findings using the Visible Burrow System model made an enormous contribution to the current view that the human brain is very sensitive to the social environment and to agonistic interactions between individuals. Their collaboration with Sakai and McEwen at The Rockefeller University extended application of the Visible Burrow System model to demonstrate that it also was a unique and highly relevant neuroethological model with which to study stress and adaptation to stressors. Those studies focused on the brain and systemic organ responses to stress and, in turn, described that the brain is also very responsive to changes in systemic physiology.

In tribute to Bob Blanchard: Divergent behavioral phenotypes of 16p11.2 deletion mice reared in same-genotype versus mixed-genotype cages

Mouse models offer indispensable heuristic tools for studying genetic and environmental causes of neuropsychiatric disorders, including autism. Development of useful animal models of complex human behaviors depends not only on extensive knowledge of the human disease, but also on a deep understanding of animal behavior and ethology. Robert and Caroline Blanchard pioneered a number of elegant social paradigms in rodents. Their early work led to systematic delineations of rodent naturalist defensive behaviors,which were proven to be highly useful models of human psychiatric disorders, including fear and anxiety. Their work using the Visible Burrow System to study social stress in rats represented an unprecedented approach to study biological mechanisms of depression. In recent years, their extensive knowledge of mouse behavior and ethology enabled them to quickly become leading figures in the field of behavioral genetics of autism. To commemorate Robert Blanchard's influences on animal models of human psychiatric disorders, here we describe a study conceptualized and led by Mu Yang who was trained as a graduate student in the Blanchard laboratory in the early 2000s. This investigation focuses on social housing in a genetic mouse model of 16p11.2 deletion syndrome. Heterozygous deletions and duplications of a segment containing about 29 genes on human chromosome 16 appear in approximately 0.5–1% of all cases of autism. 16p11.2 deletion syndrome is also associated with intellectual disabilities and speech impairments. Our previous studies showed that a mouse model of 16p11.2 deletion syndrome exhibited deficits in vocalizations and novel object recognition, as compared to wildtype littermate control cagemates. In the spirit of Bob Blanchard's careful attention to the role of social dominance in rodent behaviors, we became interested in the question of whether behavioral outcomes of a mutation differ when mutants are housed in mixed genotype cages, versus housing only mutants together in one group cage, and only wildtype littermates together in another group cage after weaning. 16p11.2 deletion presented a particularly good model organism to investigate this question, because the heterozygotes are smaller than their wildtype littermates, and may therefore become subordinate to their larger cagemates.Wildtype and heterozygotes were housed with cagemates of the same genotype (same-genotype cage) or with cagemates of the opposite genotype (mixed-genotype cage). Current results replicated social vocalization and object recognition deficits that we previously found in heterozygotes living in mixed-genotype cages. In contrast, heterozygotes that lived in same-genotype cages emitted normal numbers of vocalizations during male–female interactions, and displayed normal novel object recognition, indicating that the deletion per se was not sufficient to cause cognitive or social deficits. Social approach, same-sex social interaction, anxiety-related behavior, depression-related behavior, and open field exploration were not different between genotypes, and were not affected by housing in mixed versus in same-genotype cages. These findings suggest that elements of the home cage social environment could interact with genotype to impact aspects of disease phenotypes. Current findings are discussed as potentially reflecting behavioral deficits resulted from social stress, as inspired by a seminal paper by Bob and Caroline Blanchard [1].

Nuance and behavioral cogency: How the Visible Burrow System inspired the Stress-Alternatives Model and conceptualization of the continuum of anxiety

By creating the Visible Burrow System (VBS) Bob Blanchard found a way to study the interaction of genetics, physiology, environment, and adaptive significance in a model with broad validity. The VBS changed the way we think about anxiety and affective disorders by allowing the mechanisms which control them to be observed in a dynamic setting. Critically, Blanchard used the VBS and other models to show how behavioral systems like defense are dependent upon context and behavioral elements unique to the individual. Inspired by the VBS, we developed a Stress Alternatives Model (SAM) to further explore the multifaceted dynamics of the stress response with a dichotomous choice condition. Like the VBS, the SAM is a naturalistic model built upon risk assessment and defensive behavior, but with a choice of response: escape or submission to a large conspecific aggressor. The anxiety of novelty during the first escape must be weighed against fear of the aggressor, and a decision must be made. Both outcomes are adaptively significant, evidenced by a 50/50 split in outcome across several study systems. By manipulating the variables of the SAM, we show that a gradient of anxiety exists that spans the contextual settings of escaping an open field, escaping from aggression, and submitting to aggression. These findings correspond with increasing levels of corticosterone and increasing levels of NPS and BDNF in the central amygdala as the context changes.Whereas some anxiolytics were able to reduce the latency to escape for some animals, only with the potent anxiolytic drug antalarmin (CRF1R-blocker) and the anxiogenic drug yohimbine (α2 antagonist) were we able to reverse the outcome for a substantial proportion of individuals. Our findings promote a novel method for modeling anxiety, offering a distinction between low-and-high levels, and accounting for individual variability. The translational value of the VBS is immeasurable, and it guided us and many other researchers to seek potential clinical solutions through a deeper understanding of regional neurochemistry and gene expression in concert with an ecological behavioral model.

Chronic social subordination stress modulates glutamic acid decarboxylase (GAD) 67 mRNA expression in central stress circuits

Chronic social subordination is a well-known precipitant of numerous psychiatric and physiological health concerns. In this study, we examine the effects of chronic social stress in the visible burrow system (VBS) on the expression of glutamic acid decarboxylase (GAD) 67 and brain-derived neurotropic factor (BDNF) mRNA in forebrain stress circuitry. Male rats in the VBS system form a dominance hierarchy, whereby subordinate males exhibit neuroendocrine and physiological profiles characteristic of chronic exposure to stress. We found that social subordination decreases GAD67 mRNA in the peri-paraventricular nucleus region of the hypothalamus and the interfascicular nucleus of the bed nucleus of the stria terminalis (BNST), and increases in GAD67 mRNA in the hippocampus, medial prefrontal cortex, and dorsal medial hypothalamus. Expression of BDNF mRNA increased in the dorsal region of the BNST, but remained unchanged in all other regions examined. Results from this study indicate that social subordination is associated with several region-specific alterations in GAD67 mRNA expression in central stress circuits, whereas changes in the expression of BDNF mRNA are limited to the BNST.

Social behavior, hormones and adult neurogenesis

A variety of experiences have been shown to affect the production of neurons in the adult hippocampus. These effects may be mediated by experience-driven hormonal changes, which, in turn, interact with factors such as sex, age and life history to alter brain plasticity. Although the effects of physical experience and stress have been extensively characterized, various types of social experience across the lifespan trigger profound neuroendocrine changes in parallel with changes in adult neurogenesis. This review article focuses on the influence of specific social experiences on adult neurogenesis in the dentate gyrus and the potential role of hormones in these effects.

Zearalenone Inhibits Rat and Human 11β-Hydroxysteroid Dehydrogenase Type 2

Zearalenone is a mycotoxin produced by Fusarium spp. 11β-Hydroxysteroid dehydrogenases, isoforms 1 (HSD11B1) and 2 (HSD11B2), have been demonstrated to be the regulators of the local level of active glucocorticoid, which has a broad range of physiological actions. In the present study, the potency of zearalenone was tested for the inhibition of HSD11B1 and HSD11B2 in rat and human tissues. Zearalenone showed potent inhibition of HSD11B2 with the half-maximal inhibitory concentration (IC₅₀) calculated at 49.63 and 32.22 μM for the rat and human, respectively. Results showed that zearalenone competitively inhibited HSD11B2 when a steroid substrate was used. However, it served as an uncompetitive inhibitory factor when the cofactor NAD⁺ was used. In contrast, the potency of zearalenone to inhibit both rat and human HSD11B1 was diminished, with the concentration of 100 μM causing almost no inhibitory effect on the isoform. In conclusion, we observed that zearalenone is a selective inhibitor of HSD11B2, implying that this agent may cause excessive glucocorticoid action in local tissues such as kidney and placentas.

Developmental and environmental influences on physiology and behavior--2014 Alan N. Epstein Research Award

Environmental factors acting during development of an individual may influence future health and disease susceptibility. Stressors, including altered diet, psychosocial stress, and immune challenge, during gestation can have negative consequences on the intrauterine environment and increase disease susceptibility of the developing fetus. The long-term effects on offspring have been observed in humans and include greater susceptibility to psychiatric disease, such as depression and anxiety disorders, and adverse metabolic conditions including obesity, diabetes and cardiovascular disease. Studies in my laboratory use rodent models and incorporate a multilevel approach to determine the behavioral, physiological, and neurobiological correlates of disease development as a consequence of early life stressors. The road I took in developing this research program was a rather circuitous one and navigating that path would not have been possible without the many mentors, colleagues, fellows and students who provided critical support. Although my name appears on the plaque of the Alan N. Epstein Research Award, I share this with all those I had the privilege of working with along that road, as briefly summarized in this article.

Butylated Hydroxyanisole Potently Inhibits Rat and Human 11β-Hydroxysteroid Dehydrogenase Type 2

Butylated hydroxyanisole (BHA) is a widely used antioxidant for food preservation. 11β-hydroxysteroid dehydrogenases, isoforms 1 (HSD11B1) and 2 (HSD11B2) have been demonstrated to be the regulators of the local level of active glucocorticoid, which has a broad range of physiological actions. In this study, the potency of BHA was tested for the inhibition of HSD11B1 and HSD11B2 in rat and human tissues. BHA showed potent inhibition of HSD11B2 with the half maximal inhibitory concentration calculated at 13.99 and 69.25 µmol/l for the rat and human, respectively. Results showed that BHA competitively inhibited HSD11B2 when a steroid substrate was used. However, it served as a mixed inhibition factor when the cofactor NAD+ was used. In contrast, the potency of BHA to inhibit both rat and human HSD11B1 was diminished, with the concentration of 100 μmol/l causing no inhibitory effect on the isoform. In conclusion, we observed that BHA is a selective inhibitor of HSD11B2, implying that this agent may cause excessive glucocorticoid action in local tissues such as kidney and placentas.

Neurobiological mechanisms supporting experience-dependent resistance to social stress

Humans and other animals show a remarkable capacity for resilience following traumatic, stressful events. Resilience is thought to be an active process related to coping with stress, although the cellular and molecular mechanisms that support active coping and stress resistance remain poorly understood. In this review, we focus on the neurobiological mechanisms by which environmental and social experiences promote stress resistance. In male Syrian hamsters, exposure to a brief social defeat stressor leads to increased avoidance of novel opponents, which we call conditioned defeat. Also, hamsters that have achieved dominant social status show reduced conditioned defeat as well as cellular and molecular changes in the neural circuits controlling the conditioned defeat response. We propose that experience-dependent neural plasticity occurs in the prelimbic (PL) cortex, infralimbic (IL) cortex, and ventral medial amygdala (vMeA) during the maintenance of dominance relationships, and that adaptations in these neural circuits support stress resistance in dominant individuals. Overall, behavioral treatments that promote success in competitive interactions may represent valuable interventions for instilling resilience.

Peer pressures: social instability stress in adolescence and social deficits in adulthood in a rodent model

Studies in animal models generate and test hypotheses regarding developmental stage-specific vulnerability that might inform research questions about human development. In both rats and humans, peer relationships are qualitatively different in adolescence than at other stages of development, and social experiences in adolescence are considered important determinants of adult social function. This review describes our adolescent rat social instability stress model and the long-lasting effects social instability has on social behaviour in adulthood as well as the possible neural underpinnings. Effects of other adolescent social stress experiences in rats on social behaviours in adulthood also are reviewed. We discuss the role of hypothalamic-pituitary-adrenal (HPA) function and glucocorticoid release in conferring differential susceptibility to social experiences in adolescents compared to adults. We propose that although differential perception of social experiences rather than immature HPA function may underlie the heightened vulnerability of adolescents to social instability, the changes in the trajectory of brain development and resultant social deficits likely are mediated by the heightened glucocorticoid release in response to repeated social stressors in adolescence compared to in adulthood.

Life events are positively associated with luteinizing hormone in middle age adult men: role of cortisol as a third variable

Previous studies have tested the relationship between chronic stress and sex hormones, but inconsistent results have been found. One possibility is that this association may depend on other biological factors. This study examined the relationship between stressful life events (LE) and sex hormones in men, and whether cortisol is involved in this relationship. From a total number of 2906 men who completed a screening for the early detection of prostate cancer, 139 healthy men (mean ± SD age, 57.8 ± 5.7 years) were included in this study. Participants were assessed with the Holmes and Rahe questionnaire in relation to their experience of LE during the previous 1-5 years. Salivary and serum cortisol was measured at 08:00-09:00 h, as well as luteinizing hormone (LH), total testosterone, epinephrine (E) and norepinephrine (NE). LE weight sum and LE number positively correlated with LH (r = 0.293, p = 0.004; r = 0.220, p = 0.031, respectively). In a multiple regression analysis, LE-sum explained an additional and significant 10.4% of the variance in LH levels, after statistically controlling for the effects of age, waist circumference (WC) and BMI (F(1,90) = 6.61, p < 0.05). Importantly, cortisol interacted with LE in relation to total testosterone. In men with high cortisol values (≥15.4 µg/dl), there was a statistically significant positive relationship between LE number and total testosterone levels (p = 0.05), while LE were unrelated to total testosterone in men with low cortisol. LE correlated with sex hormones, predicting LH values, and in men with high cortisol levels shows a possible moderator effect of cortisol on the relationship between LE and total testosterone.

Hyperleptinemia directly affects testicular maturation at different sexual stages in mice, and suppressor of cytokine signaling 3 is involved in this process

BACKGROUND

Leptin plays an important role in reproductive function, and the mechanism of this phenomenon primarily focuses on the hypothalamic-pituitary-gonadal axis. However, until now, the direct effects of leptin on the testes during development from infancy to adulthood remained unclear. The aim of the present study was to explore the effects and molecular mechanisms that underlie leptin's action in the testes during sexual maturation.

METHODS

We used a monosodium glutamate (MSG)-treated mouse model to assess the effects of endogenous hyperleptinemia on the development of the testes from infancy to adulthood. Then, a variety of reproductive parameters were measured, including the concentration of testosterone, the weight and volume of the testicles, the diameter of the seminiferous tubules, and numbers of spermatogonia, spermatocytes, sperm, Leydig cells and offspring. In addition, we assessed the direct role of leptin and suppressor of cytokine signalling 3 (SOCS3)/phosphorylated signal transducer and activator of transcription 3 (pSTAT3) on the testes in vitro.

RESULTS

Testosterone secretion exhibited a diverse response: a low concentration of leptin induced testosterone secretion, and a high concentration inhibited testosterone secretion both in vivo and in vitro. A variety of reproductive parameters decreased in hyperleptinemic mice, including the weight and volume of the testicles, the diameter of the seminiferous tubules, and the numbers of spermatocytes, sperm, Leydig cells and offspring. The amount of spermatogonia was also elevated. The development of the testes was partially recovered after hyperleptinemia withdrawal. A high concentration of leptin induced SOCS3 expression and inhibited pSTAT3 expression in the testes.

CONCLUSIONS

The results indicated that MSG-induced hyperleptinemia directly affects testicular structure and function and that SOCS3/pSTAT3 played an important role in this process. These results also indicated the importance of monitoring and controlling leptin levels in obese male children. SOCS3 is a potential therapeutic target for leptin-induced dysgenesis.

Environmentally enriched male mink gain more copulations than stereotypic, barren-reared competitors

Wild carnivores in zoos, conservation breeding centres, and farms commonly live in relatively small, unstimulating enclosures. Under these captive conditions, in a range of species including giant pandas, black-footed ferrets, and European mink, male reproductive abilities are often poor. Such problems have long been hypothesized to be caused by these animals' housing conditions. We show for the first time that rearing under welfare-improving (i.e., highly valued and stress-reducing) environmental enrichments enhances male carnivores' copulatory performance: in mate choice competitions, enriched male American mink (Neovison vison) mated more often than non-enriched males. We screened for several potential mediators of this effect. First was physiological stress and its impact on reproductive physiology; second, stress-mediated changes in morphology and variables related to immunocompetence that could influence male attractiveness; and third, behavioural changes likely to affect social competence, particularly autistic-like excessive routine and repetition ('perseveration') as is reflected in the stereotypies common in captive animals. Consistent with physiological stress, excreted steroid metabolites revealed that non-enriched males had higher cortisol levels and lower androgen levels than enriched conspecifics. Their os penises (bacula) also tended to be less developed. Consistent with reduced attractiveness, non-enriched males were lighter, with comparatively small spleens and a trend to greater fluctuating asymmetry. Consistent with impaired social competence, non-enriched males performed more stereotypic behaviour (e.g., pacing) in their home cages. Of all these effects, the only significant predictor of copulation number was stereotypy (a trend suggesting that low bodyweights may also be influential): highly stereotypic males gained the fewest copulations. The neurophysiological changes underlying stereotypy thus handicap males sexually. We hypothesise that such males are abnormally perseverative when interacting with females. Investigating similar problems in other taxa would be worthwhile, since many vertebrates, wild and domestic, live in conditions that cause stereotypic behaviour and/or impair neurological development.

Stress induced obesity: lessons from rodent models of stress

Stress was once defined as the non-specific result of the body to any demand or challenge to homeostasis. A more current view of stress is the behavioral and physiological responses generated in the face of, or in anticipation of, a perceived threat. The stress response involves activation of the sympathetic nervous system and recruitment of the hypothalamic-pituitary-adrenal (HPA) axis. When an organism encounters a stressor (social, physical, etc.), these endogenous stress systems are stimulated in order to generate a fight-or-flight response, and manage the stressful situation. As such, an organism is forced to liberate energy resources in attempt to meet the energetic demands posed by the stressor. A change in the energy homeostatic balance is thus required to exploit an appropriate resource and deliver useable energy to the target muscles and tissues involved in the stress response. Acutely, this change in energy homeostasis and the liberation of energy is considered advantageous, as it is required for the survival of the organism. However, when an organism is subjected to a prolonged stressor, as is the case during chronic stress, a continuous irregularity in energy homeostasis is considered detrimental and may lead to the development of metabolic disturbances such as cardiovascular disease, type II diabetes mellitus and obesity. This concept has been studied extensively using animal models, and the neurobiological underpinnings of stress induced metabolic disorders are beginning to surface. However, different animal models of stress continue to produce divergent metabolic phenotypes wherein some animals become anorexic and lose body mass while others increase food intake and body mass and become vulnerable to the development of metabolic disturbances. It remains unclear exactly what factors associated with stress models can be used to predict the metabolic outcome of the organism. This review will explore a variety of rodent stress models and discuss the elements that influence the metabolic outcome in order to further extend our understanding of stress-induced obesity.

Sustained in vivo blockade of α₁-adrenergic receptors prevented some of stress-triggered effects on steroidogenic machinery in Leydig cells

This study was designed to systematically analyze and evaluate the effects of in vivo blockade of α₁-adrenergic receptors (α₁-ADRs) on the stress-induced disturbance of steroidogenic machinery in Leydig cells. Parameters followed 1) steroidogenic enzymes/proteins, transcription factors, and cAMP/testosterone production; 2) the main hallmarks of stress (epinephrine, glucocorticoids); and 3) transcription profiles of ADRs and oxidases with high affinity to inactivate glucocorticoids. Results showed that sustained blockade of α₁-ADRs prevented stress-induced 1) decrease of the transcripts/proteins for main steroidogenic CYPs (CYP11A1, CYP17A1); 2) decrease of Scarb1 and Hsd3b1 transcripts; 3) decrease of transcript for Nur77, one of the main activator of the steroidogenic expression; and 4) increase of Dax1 and Arr19, the main steroidogenic repressors in Leydig cells. In the same cells, the expression of steroidogenic stimulatory factor Creb1, StAR, and androgen receptor increased. In this signaling scenario, stress-induced stimulation of Adra1a/Adra1b/Adrbk1 and Hsd11b2 (the unidirectional oxidase with high affinity to inactivate glucocorticoids) was not changed. Blockade additionally stimulated stress-increased transcription of the most abundantly expressed ADRs Adra1d/Adrb1/Adrb2 in Leydig cells. In the same cells, stress-decreased testosterone production, the main marker of Leydig cells functionality, was completely prevented, while reduction of cAMP, the main regulator of androgenesis, was partially prevented. Accordingly, the presented data provide a new molecular/transcriptional base for "fight/adaptation" of steroidogenic cells and new molecular insights into the role of α₁-ADRs in stress-impaired Leydig cell steroidogenesis. The results are important in term of wide use of α₁-ADR selective antagonists, alone/in combination, to treat high blood pressure, nightmares associated with posttraumatic stress disorder, and disrupted sexual health.

The microsomal enzyme 17β-hydroxysteroid dehydrogenase 3 faces the cytoplasm and uses NADPH generated by glucose-6-phosphate dehydrogenase

Recent studies proposed a functional coupling between 17β-hydroxysteroid dehydrogenase 3 (17β-HSD3)-dependent testosterone formation and 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1)-mediated interconversion of glucocorticoids through competition for the luminal pyridine nucleotide pool. To test this hypothesis, we used human embryonic kidney-293 cells transfected with 17β-HSD3 and/or 11β-HSD1, in the absence or presence of hexose-6-phosphate dehydrogenase that generates reduced nicotinamide adenine dinucleotide phosphate (NADPH) in the endoplasmic reticulum and determined enzyme activities. As an endogenous cell model, mouse MA-10 Leydig cells were used. 17β-HSD3-dependent reduction of Δ4-androstene-3,17-dione was affected by neither coexpression with 11β-HSD1 nor overexpression or knockdown of hexose-6-phosphate dehydrogenase. In contrast, knockdown of glucose-6-phosphate dehydrogenase decreased 17β-HSD3 activity, indicating dependence on cytoplasmic NADPH. Upon selective permeabilization of the plasma membrane by digitonin, 17β-HSD3 but not 11β-HSD1 was detected by antibodies against C-terminal epitope tags, suggesting a cytoplasmic orientation of 17β-HSD3. The cytoplasmic orientation was confirmed using proteinase K digestion of microsomal preparations and by analysis of glycosylation of wild-type 17β-HSD3 and chimera in which the N-terminal anchor sequences between 17β-HSD3 and 11β-HSD1 were exchanged. In conclusion, the results demonstrate a cytoplasmic orientation of 17β-HSD3 and dependence on glucose-6-phosphate dehydrogenase-generated NADPH, explaining the lack of a direct functional coupling with the luminal 11β-HSD1-mediated glucocorticoid metabolism.

Low testosterone correlates with delayed development in male orangutans

Male orangutans (Pongo spp.) display an unusual characteristic for mammals in that some adult males advance quickly to full secondary sexual development while others can remain in an adolescent-like form for a decade or more past the age of sexual maturity. Remarkably little is understood about how and why differences in developmental timing occur. While fully-developed males are known to produce higher androgen levels than arrested males, the longer-term role of steroid hormones in male life history variation has not been examined. We examined variation in testosterone and cortisol production among 18 fully-developed ("flanged") male orangutans in U.S. captive facilities. Our study revealed that while testosterone levels did not vary significantly according to current age, housing condition, and species origin, males that had undergone precocious development had higher testosterone levels than males that had experienced developmental arrest. While androgen variation had previously been viewed as a state-dependent characteristic of male developmental status, our study reveals that differences in the physiology of early and late developing males are detectable long past the developmental transition and may instead be trait-level characteristics associated with a male's life history strategy. Further studies are needed to determine how early in life differences in testosterone levels emerge and what consequences this variation may have for male behavioral strategies.

Amylin blunts hyperphagia and reduces weight and fat gain during recovery in socially stressed rats

During recovery from social stress in a visible burrow system (VBS), during which a dominance hierarchy is formed among the males, rats display hyperphagia and gain weight preferentially as visceral adipose tissue. By proportionally increasing visceral adiposity, social stress may contribute to the establishment of metabolic disorder. Amylin was administered to rats fed ad libitum during recovery from VBS stress in an attempt to prevent hyperphagia and the resultant gain in body weight and fat mass. Amylin treatment reduced food intake, weight gain, and accumulation of fat mass in male burrow rats, but not in male controls that spent time housed with a single female rather than in the VBS. Amylin did not alter neuropeptide Y (NPY), agouti-related peptide (AgRP), or proopiomelanocortin (POMC) mRNA expression in the arcuate nucleus of the hypothalamus as measured at the end of the recovery period, nor did it affect plasma corticosterone or leptin. Amylin exerted most of its effect on food intake during the first few days of recovery, possibly through antagonism of NPY and/or increasing leptin sensitivity. The potential for chronic social stress to contribute to metabolic disorder is diminished by amylin treatment, though the neuroendocrine mechanisms behind this effect remain elusive.

Social status, glucocorticoids, immune function, and health: can animal studies help us understand human socioeconomic-status-related health disparities?

For humans in developed nations, socioeconomic status (SES)--relative income, education and occupational position in a society--is a strong predictor of morbidity and mortality rates, with increasing SES predicting longer life span (e.g. Marmot et al., 1991). Mechanisms underlying this relationship have been examined, but the relative role of each mechanism still remains unknown. By understanding the relative role of specific mechanisms that underlie dramatic health disparities between high and low social status individuals we can begin to identify effective, targeted methods to alleviate health disparities. In the current paper, we take advantage of a growing number of animal studies that have quantified biological health-related correlates (glucocorticoid production and immune function) of social status and compare these studies to the current literature on human SES and health to determine if and how animal studies can further our understanding of SES-associated human health disparities. Specifically, we compared social-status related glucocorticoid production and immune function in humans and animals. From the review, we show that our present understanding of the relationships between social status and glucocorticoid production/immune function is still growing, but that there are already identifiable parallels (and non-parallels) between humans and animals. We propose timely areas of future study focused on (1) specific aspects of social status that may influence stress-related physiology, (2) mechanisms underlying long-term influences of social status on physiology and health, and (3) intervention studies to alleviate potentially negative physiological correlates of social status.

Maternal care associates with play dominance rank among adult female rats

Variations in maternal care influence important life history traits that determine reproductive fitness. The adult female offspring of mothers that show reduced levels of pup licking/grooming (LG; i.e., low-LG mothers) show increased defensive responses to stress, accelerated pubertal development, and greater sexual receptivity than the female offspring of high-LG mothers. Amongst several species an accelerated pattern of reproductive development is associated with increased dominance-related behaviors and higher social rank. We hypothesize that rats from low-LG dams may thus also secure higher social rank as a means to compete for limited resources with conspecifics. In this study, social interactions were observed in triads of adult female rats aged p90 that received low, mid, and high levels of pup LG over the first week of life. Low- and mid-LG females had the highest pinning scores and high-LG rats the lowest, showing that low- and mid-LG adult females engage in greater play dominance-related behavior. Likewise, low- and mid-LG rats spent significantly more time drinking following 24 hr of water deprivation in a water competition test thus allowing them to secure a limited resource more easily than high-LG rats. Interestingly, pinning by play dominant females was increased when subordinates were sexually receptive (proestrus/estrus), suggestive of a process of reproductive suppression. Some evidence suggests that low-LG and mid-LG rats also show greater fecundity than high-LG rats. Variations in maternal care may thus have a long-term influence on the development of play dominance and possibly social rank in the female rat, which might contribute to reproductive success within a competitive environment.

Social subordination produces distinct stress-related phenotypes in female rhesus monkeys

Social subordination in female macaques is imposed by harassment and the threat of aggression and produces reduced control over one's social and physical environment and a dysregulation of the limbic-hypothalamic-pituitary-adrenal axis resembling that observed in people suffering from psychopathologies. These effects support the contention that this particular animal model is an ethologically relevant paradigm in which to investigate the etiology of stress-induced psychological illness related to women. Here, we sought to expand this model by performing a discriminate analysis (DA) on 33 variables within three domains; behavioral, metabolic/anthropomorphic, and neuroendocrine, collected from socially housed female rhesus monkeys in order to assess whether exposure to social subordination produces a distinct phenotype. A receiver operating characteristic (ROC) curve was also calculated to determine each domain's classification accuracy. DA found significant markers within each domain that differentiated dominant and subordinate females. Subordinate females received more aggression, showed more submissive behavior, and received less of affiliation from others than did dominant females. Metabolic differences included increased leptin, and reduced adiponectin in dominant compared to subordinate females. Dominant females exhibited increased sensitivity to hormonal stimulation with higher serum LH in response to estradiol, cortisol in response to ACTH, and increased glucocorticoid negative feedback. Serum oxytocin, CSF DOPAC and serum PACAP were all significantly higher in dominant females. ROC curve analysis accurately predicted social status in all three domains. Results suggest that socially house rhesus monkeys represent a cogent animal model in which to study the physiology and behavioral consequences of chronic psychosocial stress in humans.

Repeated immobilization stress disturbed steroidogenic machinery and stimulated the expression of cAMP signaling elements and adrenergic receptors in Leydig cells

This study was designed to evaluate the effect of acute (2 h daily) and repeated (2 h daily for 2 or 10 consecutive days) immobilization stress (IMO) on: 1) the steroidogenic machinery homeostasis; 2) cAMP signaling; and the expression of receptors for main markers of 3) adrenergic and 4) glucocorticoid signaling in Leydig cells of adult rats. The results showed that acute IMO inhibited steroidogenic machinery in Leydig cells by downregulation of Scarb1 (scavenger receptor class B), Cyp11a1 (cholesterol side-chain cleavage enzyme), Cyp17a1 (17α-hydroxylase/17,20 lyase), and Hsd17b3 (17β-hydroxysteroid dehydrogenase) expression. In addition to acute IMO effects, repeated IMO increased transcription of Star (steroidogenic acute regulatory protein) and Arr19 (androgen receptor corepressor 19 kDa) in Leydig cells. In the same cells, the transcription of adenylyl cyclases (Adcy7, Adcy9, Adcy10) and cAMP-specific phosphodiesterases (Pde4a, Pde4b, Pde4d, Pde7a, Pde8a) was stimulated, whereas the expression of the genes encoding protein kinase A subunits were unaffected. Ten times repeated IMO increased the levels of all adrenergic receptors and β-adrenergic receptor kinase (Adrbk1) in Leydig cells. The transcription analysis was supported by cAMP/testosterone production. In this signaling scenario, partial recovery of testosterone production in medium/content was detected. The physiological significance of the present results was proven by ex vivo application of epinephrine, which increased cAMP/testosterone production by Leydig cells from control rats in greater fashion than from stressed. IMO did not affect the expression of transcripts for Crhr1/Crhr2 (corticotropin releasing hormone receptors), Acthr (adrenocorticotropin releasing hormone receptor), Gr (glucocorticoid receptor), and Hsd11b1 [hydroxysteroid (11-β) dehydrogenase 1], while all types of IMO stimulated the expression of Hsd11b2, the unidirectional oxidase with high affinity to inactivate glucocorticoids. Thus, presented data provide new molecular/transcriptional base for "fight/adaptation" of Leydig cells and new insights into the role of cAMP, epinephrine, and glucocorticoid signaling in recovery of stress-impaired Leydig cell steroidogenesis.

The imposition of, but not the propensity for, social subordination impairs exploratory behaviors and general cognitive abilities

Imposed social subordination, such as that which accompanies physical defeat or alienation, has been associated with impaired cognitive function in both human and non-human animals. Here we examined whether domain-specific and/or domain-general learning abilities (c.f. general intelligence) are differentially influenced by the imposition of social subordination. Furthermore, we assessed whether the impact of subordination on cognitive abilities was the result of imposed subordination per se, or if it reflected deficits intrinsically expressed in subjects that are predisposed to subordination. Subordinate and dominant behaviors were assessed in two groups of CD-1 male mice. In one group (Imposed Stratification), social stratification was imposed (through persistent physical defeat in a colonized setting) prior to the determination of cognitive abilities, while in the second group (Innate Stratification), an assessment of social stratification was made after cognitive abilities had been quantified. Domain-specific learning abilities were measured as performance on individual learning tasks (odor discrimination, fear conditioning, spatial maze learning, passive avoidance, and egocentric navigation) while domain-general learning abilities were determined by subjects' aggregate performance across the battery of learning tasks. We observed that the imposition of subordination prior to cognitive testing decreased exploratory tendencies, moderately impaired performance on individual learning tasks, and severely impaired general cognitive performance. However, similar impairments were not observed in subjects with a predisposition toward a subordinate phenotype (but which had not experienced physical defeat at the time of cognitive testing). Mere colonization, regardless of outcome (i.e., stratification), was associated with an increase in stress-induced serum corticosterone (CORT) levels, and thus CORT elevations were not themselves adequate to explain the effects of imposed stratification on cognitive abilities. These findings indicate that absent the imposition of subordination, individuals with subordinate tendencies do not express learning impairments. This observation could have important ramifications for individuals in environments where social stratification is prevalent (e.g., schools or workplace settings).