Roles of estrogen receptor-alpha gene expression in reproduction-related behaviors in female mice

The Role of Androgens and Estrogens in Social Interactions and Social Cognition

Gonadal hormones are becoming increasingly recognized for their effects on cognition. Estrogens, in particular, have received attention for their effects on learning and memory that rely upon the functioning of various brain regions. However, the impacts of androgens on cognition are relatively under investigated. Testosterone, as well as estrogens, have been shown to play a role in the modulation of different aspects of social cognition. This review explores the impact of testosterone and other androgens on various facets of social cognition including social recognition, social learning, social approach/avoidance, and aggression. We highlight the relevance of considering not only the actions of the most commonly studied steroids (i.e., testosterone, 17β-estradiol, and dihydrotestosterone), but also that of their metabolites and precursors, which interact with a plethora of different receptors and signalling molecules, ultimately modulating behaviour. We point out that it is also essential to investigate the effects of androgens, their precursors and metabolites in females, as prior studies have mostly focused on males. Overall, a comprehensive analysis of the impact of steroids such as androgens on behaviour is fundamental for a full understanding of the neural mechanisms underlying social cognition, including that of humans.

Expression pattern of sex steroid hormone receptors in the adult male rabbit brain

Progesterone (P4), estradiol (E2), and testosterone (T) are crucial for reproduction and are pivotal in several vertebrate central nervous system (CNS) functions. These hormones act by binding to their corresponding receptors, including those intracellularly located, such as progesterone receptor (PR), estrogen receptor (ER), and androgen receptor, which in this manuscript we named testosterone receptor (TR). The expression pattern of these receptors in the rabbit male brain is unknown. We studied PR, ER, and TR expression at mRNA and protein levels in several intact adult male brain regions by RT-qPCR and Western blot. We found the highest PR mRNA levels in the prefrontal cortex (PC) and the preoptic area (POA). PR protein content (110 kDa) was similar in all the analyzed brain regions. Maximum ERα mRNA levels were found in the mesencephalon (MSC) compared with the scarce levels presented in POA and cerebellum (CER). The two leading ERα bands (54 and 66 kDa) showed comparable content among analyzed brain regions, except in the olfactory bulb (OB). Considerable TR mRNA levels were found in the analyzed brain areas except in CER. TR protein (110 kDa) content was also high in MSC. The CER showed the lowest PR, ERα, and TR mRNA levels, but the corresponding protein contents were similar to those of different areas. These data reflect regional variability in the expression of sex steroid hormone receptors in the adult male rabbit brain. They constitute the basis for defining the distribution pattern of these receptors in the rabbit brain; in addition, they would allow comparisons to be made with reports of the expression of these receptors in female rabbit brains and the search for understanding their role in rabbits.

Hormonal Actions in the Medial Preoptic Area Governing Parental Behavior: Novel Insights From New Tools

The importance of hormones in mediating a behavioral transition in mammals from a virgin or nonparenting state to parental state was established around 50 years ago. Extensive research has since revealed a highly conserved neural circuit that underlies parental behavior both between sexes and between mammalian species. Within this circuit, hormonal action in the medial preoptic area of the hypothalamus (MPOA) has been shown to be key in timing the onset of parental behavior with the birth of offspring. However, the mechanism underlying how hormones act in the MPOA to facilitate this change in behavior has been unclear. Technical advances in neuroscience, including single cell sequencing, novel transgenic approaches, calcium imaging, and optogenetics, have recently been harnessed to reveal new insights into maternal behavior. This review aims to highlight how the use of these tools has shaped our understanding about which aspects of maternal behavior are regulated by specific hormone activity within the MPOA, how hormone-sensitive MPOA neurons integrate within the wider neural circuit that governs maternal behavior, and how maternal hormones drive changes in MPOA neuronal function during different reproductive states. Finally, we review our current understanding of hormonal modulation of MPOA-mediated paternal behavior in males.

Sexually dimorphic control of aggression by androgen signaling in a cichlid

Innate social behaviors like aggression are modulated by sex steroid hormones such as androgens and estrogens. However, we know little about how the same hormone regulates similar behaviors in both sexes. We investigated the role of androgenic signaling in the regulation of aggression in Astatotilapia burtoni, a social fish in which males and females perform similar aggressive behaviors. We used androgen receptor (AR) α knockout (KO) animals for this study since this gene was recently shown to be required for male-typical aggression and mating. Surprisingly, ARα KO females did not show deficits in aggression. We also determined that females lacking the other AR, ARβ, showed normal levels of aggression. Blocking both ARs pharmacologically confirmed that neither AR is necessary for aggression in females. However, ARα KO males showed clear deficits in attacks. Thus, in A. burtoni there appears to be a sexual dimorphism in the role of ARα in the control of aggression.

Reproductive function and behaviors: an update on the role of neural estrogen receptors alpha and beta

Infertility is becoming a major public health problem, with increasing frequency due to medical, environmental and societal causes. The increasingly late age of childbearing, growing exposure to endocrine disruptors and other reprotoxic products, and increasing number of medical reproductive dysfunctions (endometriosis, polycystic ovary syndrome, etc.) are among the most common causes. Fertility relies on fine-tuned control of both neuroendocrine function and reproductive behaviors, those are critically regulated by sex steroid hormones. Testosterone and estradiol exert organizational and activational effects throughout life to establish and activate the neural circuits underlying reproductive function. This regulation is mediated through estrogen receptors (ERs) and androgen receptor (AR). Estradiol acts mainly via nuclear estrogen receptors ERα and ERβ. The aim of this review is to summarize the genetic studies that have been undertaken to comprehend the specific contribution of ERα and ERβ in the neural circuits underlying the regulation of the hypothalamic-pituitary-gonadal axis and the expression of reproductive behaviors, including sexual and parental behavior. Particular emphasis will be placed on the neural role of these receptors and the underlying sex differences.

Influence of sex hormones on the aggressive behavior during peck order establishment and stabilization in meat and egg type chickens

In the poultry industry, broiler and layer strains are genetically selected for different purposes (e.g., high meat-yield and high egg-production). Genetic selection for productivity can have unintended consequences on the behavioral repertoire of the birds, including aggression. Alongside the increasing societal concern regarding the welfare of animal in agriculture, the number of countries that are advocating the prohibition of using battery cages for laying hens has resulted in the transition and adoption of cage-free or free-range systems. Thus, both broiler and layer chickens are housed in large flocks rather than housed individually in cages. Housing birds in groups increases the opportunity for birds to engage in social behaviors, including aggression, that are used to establish social status. Aggressive interactions are associated with the risk of injury and the potential for a subordinate animal to have unmet needs (e.g., access to feed). The aim of this study was to characterize the relationships among aggressive behavior, neurobiology, and hormones during peck order establishment and social hierarchy stabilization of 2 divergently selected strains (meat- and egg-type chicken). Meat-type strains performed more male on male (P < 0.001), male on female (P < 0.0001), and female on female (P < 0.0001) non-reciprocal aggression behavior (NRA) than egg-type strains. Greater serum testosterone and estradiol concentrations in the weeks after the peck order establishment were observed in meat-type birds compared those in egg-type birds for both males and females (all P < 0.05). Greater (P < 0.05) cellular densities of androgen receptors, but not estrogen receptors, were observed in the hypothalamus of meat-type birds compared to egg-type birds. These findings suggest that greater sex hormone concentrations in the meat-type birds may be a consequence of genetic selection for rapid growth resulting in more sex hormones-induced aggressive behavior.

Bibliometric analysis on cannibalism/infanticide and maternal aggression towards pups in laboratory rodents

Animal welfare has evolved during the past decades to improve not only the quality of life of laboratory rodents but also the quality and reproducibility of scientific investigations. Bibliometric analysis has become an important tool to complete the current knowledge with academic databases. Our objective was to investigate whether scientific research on cannibalism/infanticide is connected with maternal aggression towards the offspring in laboratory rodents. To carry out our research, we performed a specific search for published articles on each concept. Results were analyzed in the open-source environment RStudio with the package Bibliometrix. We obtained 253 and 134 articles for the first search (cannibalism/infanticide) and the second search (maternal aggression towards the pups) respectively. We observed that the interest in infanticide/cannibalism started in the 1950s, while researchers started showing interest in maternal aggression towards the pups 30 years later. Our analyses indicated that maternal aggression had better citations in scientific literature. In addition, although our results showed some common features (e.g. oxytocin or medial preoptic area in the brain), we observed a gap between cannibalism/infanticide and maternal aggression towards the pups with only 14 published articles in common for both the searches. Therefore, we recommend researchers to combine both concepts in further investigations in the context of cannibalism for better dissemination and higher impact in laboratory rodents' welfare research.

Hormonal and circuit mechanisms controlling female sexual behavior

Sexual behavior is crucial for reproduction in many animals. In many vertebrates, females exhibit sexual behavior only during a brief period surrounding ovulation. Over the decades, studies have identified the roles of ovarian sex hormones, which peak in levels around the time of ovulation, and the critical brain regions involved in the regulation of female sexual behavior. Modern technical innovations have enabled a deeper understanding of the neural circuit mechanisms controlling this behavior. In this review, I summarize our current knowledge and discuss the neural circuit mechanisms by which female sexual behavior occurs in association with the ovulatory phase of their cycle.

Exploring sex differences: insights into gene expression, neuroanatomy, neurochemistry, cognition, and pathology

Increased knowledge about sex differences is important for development of individualized treatments against many diseases as well as understanding behavioral and pathological differences. This review summarizes sex chromosome effects on gene expression, epigenetics, and hormones in relation to the brain. We explore neuroanatomy, neurochemistry, cognition, and brain pathology aiming to explain the current state of the art. While some domains exhibit strong differences, others reveal subtle differences whose overall significance warrants clarification. We hope that the current review increases awareness and serves as a basis for the planning of future studies that consider both sexes equally regarding similarities and differences.

Neurobiology of Pathogen Avoidance and Mate Choice: Current and Future Directions

Animals are under constant threat of parasitic infection. This has influenced the evolution of social behaviour and has strong implications for sexual selection and mate choice. Animals assess the infection status of conspecifics based on various sensory cues, with odours/chemical signals and the olfactory system playing a particularly important role. The detection of chemical cues and subsequent processing of the infection threat that they pose facilitates the expression of disgust, fear, anxiety, and adaptive avoidance behaviours. In this selective review, drawing primarily from rodent studies, the neurobiological mechanisms underlying the detection and assessment of infection status and their relations to mate choice are briefly considered. Firstly, we offer a brief overview of the aspects of mate choice that are relevant to pathogen avoidance. Then, we specifically focus on the olfactory detection of and responses to conspecific cues of parasitic infection, followed by a brief overview of the neurobiological systems underlying the elicitation of disgust and the expression of avoidance of the pathogen threat. Throughout, we focus on current findings and provide suggestions for future directions and research.

Arginine vasopressin injection rescues delayed oviposition in cyp19a1b-/- mutant female zebrafish

In zebrafish, estrogens produced in the ovaries via Cyp19a1a activity are required for both sexual differentiation of the ovary during early development as well as maintenance of the ovarian state during adulthood. The importance of Cyp19a1b that is highly expressed in the brain for female reproduction is still under study. We previously reported that female cyp19a1b -/- mutant zebrafish have significantly lower brain estradiol levels and impaired spawning behavior characterized by an increased latency to oviposition during dyadic sexual behavior encounters. In the current study, we provide evidence that the delayed oviposition in female cyp19a1b -/- mutants is linked to impaired arginine vasopressin (Avp) signaling. Droplet digital PCR experiments revealed that levels of the estrogen receptors, avp, and oxytocin (oxt) are lower in the hypothalamus of mutant females compared to wildtype fish. We then used acute intraperitoneal injections of Avp and Oxt, along with mixtures of their respective receptor antagonists, to determine that Avp can uniquely rescue the delayed oviposition in female cyp19a1b -/- mutants. Using immunohistochemistry, we demonstrated that Cyp19a1b-expressing radial glial cell (RGC) fibers surround and are in contact with Avp-immunopositive neurons in the preoptic areas of the brain. This could provide the neuroanatomical proximity for RGC-derived estrogens to diffuse to and activate estrogen receptors and regulate avp expression levels. Together these findings identify a positive link between Cyp19a1b and Avp for female zebrafish sexual behavior. They also suggest that the female cyp19a1b -/- mutant behavioral phenotype is likely a consequence of impaired processing of Avp-dependent social cues important for mate identification and assessment.

Steroid hormone-mediated regulation of sexual and aggressive behaviour by non-genomic signalling

Sex and aggression are well studied examples of social behaviours that are common to most animals and are mediated by an evolutionary conserved group of interconnected nuclei in the brain called the social behaviour network. Though glucocorticoids and in particular estrogen regulate these social behaviours, their effects in the brain are generally thought to be mediated by genomic signalling, a slow transcriptional regulation mediated by nuclear hormone receptors. In the last decade or so, there has been renewed interest in understanding the physiological significance of rapid, non-genomic signalling mediated by steroids. Though the identity of the membrane hormone receptors that mediate this signalling is not clearly understood and appears to be different in different cell types, such signalling contributes to physiologically relevant behaviours such as sex and aggression. In this short review, we summarise the evidence for this phenomenon in the rodent, by focusing on estrogen and to some extent, glucocorticoid signalling. The use of these signals, in relation to genomic signalling is manifold and ranges from potentiation of transcription to the possible transduction of environmental signals.

Hormone-mediated neural remodeling orchestrates parenting onset during pregnancy

During pregnancy, physiological adaptations prepare the female body for the challenges of motherhood. Becoming a parent also requires behavioral adaptations. Such adaptations can occur as early as during pregnancy, but how pregnancy hormones remodel parenting circuits to instruct preparatory behavioral changes remains unknown. We found that action of estradiol and progesterone on galanin (Gal)-expressing neurons in the mouse medial preoptic area (MPOA) is critical for pregnancy-induced parental behavior. Whereas estradiol silences MPOAGal neurons and paradoxically increases their excitability, progesterone permanently rewires this circuit node by promoting dendritic spine formation and recruitment of excitatory synaptic inputs. This MPOAGal-specific neural remodeling sparsens population activity in vivo and results in persistently stronger, more selective responses to pup stimuli. Pregnancy hormones thus remodel parenting circuits in anticipation of future behavioral need.

The Sexual Incentive Motivation Model and Its Clinical Applications

Sexual motivation (desire) requires the simultaneous presence of an active central motive state and a stimulus with sexual significance. Once activated, sexual motivation leads to visceral responses and approach behaviors directed toward the emitter of the sexual stimulus. In humans, such behaviors follow cognitive evaluation of the context, including predictions of the approached individual's response. After successful approach and establishment of physical contact, manifest sexual activities may be initiated. Sexual interaction is associated with and followed by a state of positive affect in most animals, whereas aversive consequences may be experienced by humans. The affective reactions may become associated with stimuli present during sexual interaction, and these stimuli may thereby alter their incentive properties. Here we show how the incentive motivation model can be used to explain the origins and possible treatments of sexual dysfunctions, notably disorders of desire. We propose that associations formed between negative outcomes of sexual interaction and the salient stimuli, for example, the partner, underlies hypoactive desire disorder. Highly positive outcomes of sexual interaction enhance the incentive value of the stimuli present, and eventually lead to hyperactive sexual desire. Treatments aim to alter the impact of sexual incentives, mainly by modifying cognitive processes.

Estrogen-responsive neural circuits governing male and female mating behavior in mice

Decades of knockout analyses have highlighted the crucial involvement of estrogen receptors and downstream genes in controlling mating behaviors. More recently, advancements in neural circuit research have unveiled a distributed subcortical network comprising estrogen-receptor or estrogen-synthesis-enzyme-expressing cells that transforms sensory inputs into sex-specific mating actions. This review provides an overview of the latest discoveries on estrogen-responsive neurons in various brain regions and the associated neural circuits that govern different aspects of male and female mating actions in mice. By contextualizing these findings within previous knockout studies of estrogen receptors, we emphasize the emerging field of "circuit genetics", where identifying mating behavior-related neural circuits may allow for a more precise evaluation of gene functions within these circuits. Such investigations will enable a deeper understanding of how hormone fluctuation, acting through estrogen receptors and downstream genes, influences the connectivity and activity of neural circuits, ultimately impacting the manifestation of innate mating actions.

Sex and Brain: The Role of Sex Chromosomes and Hormones in Brain Development and Parkinson's Disease

Sex hormones and genes on the sex chromosomes are not only key factors in the regulation of sexual differentiation and reproduction but they are also deeply involved in brain homeostasis. Their action is crucial for the development of the brain, which presents different characteristics depending on the sex of individuals. The role of these players in the brain is fundamental in the maintenance of brain function during adulthood as well, thus being important also with respect to age-related neurodegenerative diseases. In this review, we explore the role of biological sex in the development of the brain and analyze its impact on the predisposition toward and the progression of neurodegenerative diseases. In particular, we focus on Parkinson's disease, a neurodegenerative disorder that has a higher incidence in the male population. We report how sex hormones and genes encoded by the sex chromosomes could protect from the disease or alternatively predispose toward its development. We finally underline the importance of considering sex when studying brain physiology and pathology in cellular and animal models in order to better understand disease etiology and develop novel tailored therapeutic strategies.

Distribution of estrogen receptors alpha and beta in the brain of male rats with same-sex preference

Two distinct estrogen receptors (ERs) exist, ERα and ERβ. Both receptors participate in the sexual differentiation of the rat brain and likely participate in the regulation of adult sexual orientation (i.e. partner preference). This last idea was investigated herein by examining males treated with the aromatase inhibitor, letrozole, administered prenatally (0.56 μg/kg G10-22). This treatment usually provokes same-sex preference in 1-2 males per litter. Vehicle-treated males (with female preference) and females in spontaneous proestrus (with male preference) were included as controls. ERα and ERβ expression was analyzed by immunohistochemistry in brain areas known to control masculine sexual behavior and partner preference, like the medial preoptic area (MPOA), bed nucleus of the stria terminalis (BNST), medial amygdala (MeA) and ventromedial hypothalamic nucleus (VMH), as well as other brain regions suspected to participate in these processes. In addition, serum levels of estradiol were determined in all male groups. Letrozole-treated male rats that preferred sexually experienced males (LPM) showed over-expressed ERα in the hippocampal cornu Ammonis (CA 1, 3, 4) and dentate gyrus. The LPM group showed up-regulated ERβ expression in the CA2 and reticular thalamic nucleus. The levels of estradiol did not differ between the groups. The higher expression of ERs in these males was different than their expression in females, with male sex-preference. This suggests that males with same-sex preference showed a unique brain, this sui generis steroid receptor expression probably participates in the biological underpinnings of sexual preference.

Hearing Vocalizations during First Social Experience with Pups Increase Bdnf Transcription in Mouse Auditory Cortex

While infant cues are often assumed to innately motivate maternal response, recent research highlights how the neural coding of infant cues is altered through maternal care. Infant vocalizations are important social signals for caregivers, and evidence from mice suggests that experience caring for mouse pups induces inhibitory plasticity in the auditory cortex (AC), though the molecular mediators for such AC plasticity during the initial pup experience are not well delineated. Here, we used the maternal mouse communication model to explore whether transcription in AC of a specific, inhibition-linked, memory-associated gene, brain-derived neurotrophic factor (Bdnf) changes due to the very first pup caring experience hearing vocalizations, while controlling for the systemic influence of the hormone estrogen. Ovariectomized and estradiol or blank-implanted virgin female mice hearing pup calls with pups present had significantly higher AC exon IV Bdnf mRNA compared to females without pups present, suggesting that the social context of vocalizations induces immediate molecular changes at the site of auditory cortical processing. E2 influenced the rate of maternal behavior but did not significantly affect Bdnf mRNA transcription in the AC. To our knowledge, this is the first time Bdnf has been associated with processing social vocalizations in the AC, and our results suggest that it is a potential molecular component responsible for enhancing future recognition of infant cues by contributing to AC plasticity.

Urocortin-3 neurons in the perifornical area are critical mediators of chronic stress on female infant-directed behavior

Infant avoidance and aggression are promoted by activation of the Urocortin-3 expressing neurons of the perifornical area of hypothalamus (PeFA^Ucn3) in male and female mice. PeFA^Ucn3 neurons have been implicated in stress, and stress is known to reduce maternal behavior. We asked how chronic restraint stress (CRS) affects infant-directed behavior in virgin and lactating females and what role PeFA^Ucn3 neurons play in this process. Here we show that infant-directed behavior increases activity in the PeFA^Ucn3 neurons in virgin and lactating females. Chemogenetic inhibition of PeFA^Ucn3 neurons facilitates pup retrieval in virgin females. CRS reduces pup retrieval in virgin females and increases activity of PeFA^Ucn3 neurons, while CRS does not affect maternal behavior in lactating females. Inhibition of PeFA^Ucn3 neurons blocks stress-induced deficits in pup-directed behavior in virgin females. Together, these data illustrate the critical role for PeFA^Ucn3 neuronal activity in mediating the impact of chronic stress on female infant-directed behavior.

Effects of maternal cigarette smoke exposure on the progression of nonalcoholic steatohepatitis in offspring mice

Cigarette smoke (CS) is a dominant carcinogenic agent in a variety of human cancers. CS exposure during pregnancy can adversely affect the fetus. Non-alcoholic fatty liver disease (NAFLD) is considered as a hepatic manifestation of a metabolic disorder, and ranges from simple steatosis to cirrhosis leading to hepatocellular carcinoma. Non-alcoholic steatohepatitis (NASH) is a more severe phase of NAFLD. Recently, there is increasing apprehension about the CS-related chronic liver diseases. Therefore, we examined whether maternal CS exposure could affect the pathogenesis of NASH in offspring. Mainstream CS (MSCS) was exposed to pregnant C57BL/6 mice via nose-only inhalation for 2 h/day, 5 days/week for 2 weeks from day 6 to 17 of gestation at 0, 300, or 600 μg/L. Three-week-old male offspring mice were fed methionine and choline-supplemented (MCS) diet or methionine and choline-deficient including high-fat (MCDHF) diet for 6 weeks to induce NASH. Maternal MSCS exposure increased the severity of NASH by increasing serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, hepatic total cholesterol (TC) and triglyceride (TG) levels, pro-inflammation, fibrosis, and steatosis in offspring mice. Especially, maternal MSCS exposure significantly downregulated the phosphorylation of AMP-activated protein kinase (AMPK) in MCDHF diet-fed offspring mice. Subsequently, the protein levels of sterol regulatory element-binding protein (SREBP)-1c and stearoyl-CoA desaturase-1 (SCD1) were upregulated by maternal MSCS exposure. In conclusion, maternal MSCS exposure exacerbates the progression of NASH by modulating lipogenesis on offspring mice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-022-00153-1.

Effects of chronic tamoxifen treatment in female rat sexual behaviour

The medial preoptic (MPN) and the ventromedial hypothalamic nuclei (VMN) modulate the estrogen receptor (ER)-dependent female sexual behavior, a response that is inhibited by tamoxifen (TAM), a modulator of the steroid receptor activation. With the objective to assess TAM action in the brain areas involved in the modulation sexual cues, an animal model on long-term TAM therapy to intact female rats, was used to mimic the 5-year prophylactic TAM therapy offered to women at higher risk of breast cancer. After three months treatment, female sexual behavior with a stud male rat was evaluated. Upon sacrifice, the brains were removed and the MPN and the ventrolateral division of the VMN were screened for the effects of TAM in the expression of ERα, ERβ and progesterone receptor. Results show that TAM inhibited the receptive component of the female sexual behavior. Even though TAM decreased estrogen and progesterone levels to values similar to the ones of estrous and diestrus rats, the biochemical data failed to demonstrate such possible causation for the behavioral response. In fact, TAM administration induced a constant low level of ovarian hormones that changed the pattern of ER and PR expression as well as receptor co-expression in the brain areas regulating the behavioral response, dissimilar to the ones seen in the cycle phases with the same low hormone levels. Nevertheless, present data suggests that by affecting ER- and/or PR-dependent mechanisms, TAM may modulate the hypothalamus, a region known to participate in several social behaviors.

Hypomorphism of a Novel Long ERα Isoform Causes Severe Reproductive Dysfunctions in Female Mice

Estrogen receptor alpha (ERα)-mediated estrogen signaling plays a pivotal role in both reproductive and nonreproductive functions. Transcriptional regulation of the ERα gene is highly complex, with multiple transcript variants being differentially produced across the tissues. However, tissue-specific variation and physiological specificity of the ERα variants are not yet fully understood. In an attempt to generate a Cre-dependently restorable ERα-null mouse for functional genetic studies, we unexpectedly produced ERα hypomorphic mice with biased downregulation of a previously unappreciated long ERα isoform that is enriched in the female reproductive organs (uterus and ovaries) and the pituitary but minimally expressed in the brain. Female homozygous mutant mice were capable of pregnancy but displayed irregular estrus cycle and rarely kept newborn pups alive. No significant morphological and pathological changes in reproductive system or disruption of body weight homeostasis were seen in female homozygous mutant mice. Collectively, our results define a tissue-specific enriched long ERα isoform and its preferential role in female reproductive function rather than body weight homeostasis.

Differential Gene Expression Correlates with Behavioural Polymorphism during Collective Behaviour in Cockroaches

Simple Summary

It is currently well accepted that animals differ from one another in their behaviour and tendency to perform actions, a property we refer to as animal personality. In group-living animals, variation in animal personality can be important to determine group survival, as it determines how individuals interact with each other and with their environment. However, we have little knowledge of the proximal mechanisms underlying personality, particularly in group-living organisms. Here, we investigate the relationship between gene expression and two behavioural types (bold and shy) in a gregarious species: the American cockroach. Our results show that bold individuals have upregulated genes with functions associated with sensory activity (phototaxis and odour detection) and aggressive/dominant behaviour, and suggest that social context can modulate gene expression related to bold/shy characteristics. This work could help identify genes important in the earliest stages of group living and social life, and provides a first step toward establishing cockroaches as a focal group for the study of the evolution of sociality.

Abstract

Consistent inter-individual variation in the propensity to perform different tasks (animal personality) can contribute significantly to the success of group-living organisms. The distribution of different personalities in a group influences collective actions and therefore how these organisms interact with their environment. However, we have little understanding of the proximate mechanisms underlying animal personality in animal groups, and research on this theme has often been biased towards organisms with advanced social systems. The goal of this study is to investigate the mechanistic basis for personality variation during collective behaviour in a species with rudimentary societies: the American cockroach. We thus use an approach which combines experimental classification of individuals into behavioural phenotypes (‘bold’ and ‘shy’ individuals) with comparative gene expression. Our analyses reveal differences in gene expression between behavioural phenotypes and suggest that social context may modulate gene expression related to bold/shy characteristics. We also discuss how cockroaches could be a valuable model for the study of genetic mechanisms underlying the early steps in the evolution of social behaviour and social complexity. This study provides a first step towards a better understanding of the molecular mechanisms associated with differences in boldness and behavioural plasticity in these organisms.

Aromatase Inhibition Eliminates Sexual Receptivity Without Enhancing Weight Gain in Ovariectomized Marmoset Monkeys

Context

Ovarian estradiol supports female sexual behavior and metabolic function. While ovariectomy (OVX) in rodents abolishes sexual behavior and enables obesity, OVX in nonhuman primates decreases, but does not abolish, sexual behavior, and inconsistently alters weight gain.

Objective

We hypothesize that extra-ovarian estradiol provides key support for both functions, and to test this idea, we employed aromatase inhibition to eliminate extra-ovarian estradiol biosynthesis and diet-induced obesity to enhance weight gain.

Methods

Thirteen adult female marmosets were OVX and received (1) estradiol-containing capsules and daily oral treatments of vehicle (E2; n = 5); empty capsules and daily oral treatments of either (2) vehicle (VEH, 1 mL/kg, n = 4), or (3) letrozole (LET, 1 mg/kg, n = 4).

Results

After 7 months, we observed robust sexual receptivity in E2, intermediate frequencies in VEH, and virtually none in LET females (P = .04). By contrast, few rejections of male mounts were observed in E2, intermediate frequencies in VEH, and high frequencies in LET females (P = .04). Receptive head turns were consistently observed in E2, but not in VEH and LET females. LET females, alone, exhibited robust aggressive rejection of males. VEH and LET females demonstrated increased % body weight gain (P = .01). Relative estradiol levels in peripheral serum were E2 >>> VEH > LET, while those in hypothalamus ranked E2 = VEH > LET, confirming inhibition of local hypothalamic estradiol synthesis by letrozole.

Conclusion

Our findings provide the first evidence for extra-ovarian estradiol contributing to female sexual behavior in a nonhuman primate, and prompt speculation that extra-ovarian estradiol, and in particular neuroestrogens, may similarly regulate sexual motivation in other primates, including humans.

Estrogenic Action in Stress-Induced Neuroendocrine Regulation of Energy Homeostasis

Estrogens are among important contributing factors to many sex differences in neuroendocrine regulation of energy homeostasis induced by stress. Research in this field is warranted since chronic stress-related psychiatric and metabolic disturbances continue to be top health concerns, and sex differences are witnessed in these aspects. For example, chronic stress disrupts energy homeostasis, leading to negative consequences in the regulation of emotion and metabolism. Females are known to be more vulnerable to the psychological consequences of stress, such as depression and anxiety, whereas males are more vulnerable to the metabolic consequences of stress. Sex differences that exist in the susceptibility to various stress-induced disorders have led researchers to hypothesize that gonadal hormones are regulatory factors that should be considered in stress studies. Further, estrogens are heavily recognized for their protective effects on metabolic dysregulation, such as anti-obesogenic and glucose-sensing effects. Perturbations to energy homeostasis using laboratory rodents, such as physiological stress or over-/under- feeding dietary regimen prevalent in today’s society, offer hints to the underlying mechanisms of estrogenic actions. Metabolic effects of estrogens primarily work through estrogen receptor α (ERα), which is differentially expressed between the sexes in hypothalamic nuclei regulating energy metabolism and in extrahypothalamic limbic regions that are not typically associated with energy homeostasis. In this review, we discuss estrogenic actions implicated in stress-induced sex-distinct metabolic disorders.

Anti-anger Effects of Herbal Medicine: A Mini-Review of Rat Studies

OBJECTIVE

To analyze the available data on the anti-anger effects of herbal medicines (HMs) as well as their underlying mechanisms in rat models.

METHODS

From 6 electronic databases [PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), Wanfang, Oriental Medicine Advanced Searching Integrated System (OASIS), and Research Information Sharing Service (RISS)], relevant animal experiments were searched by using "anger," "rats," and "animal" as search keywords. The last search was conducted on November 22, 2019, and all experiments involving rat models of anger and treatment using HMs published until the date of the search were considered.

RESULTS

A total of 24 studies with 16 kinds of HMs were included. Most studies have used the "tail irritating method" and "social isolation and resident intruder" method to establish anger models. According to the included studies, the therapeutic mechanisms of HMs for anger regulation and important herbs by their frequency and/or preclinical evidence mainly incladed regulation of hemorheology (Bupleuri Radix, Paeoniae Radix Alba, and Glycyrrhizae Radix), regulation of sex hormones (Bupleuri Radix, Cyperi Rhizoma, and Paeoniae Radix Alba), regulation of neurotransmitters (Cyperi Rhizoma), regulation of anger-related genes (Bupleuri Radix, Glycyrrhizae Radix, and Paeoniae Radix Alba), and other effects. Overall, Liver (Gan) qi-smoothing herbs including Bupleuri Radix and Cyperi Rhizoma were the most frequently used.

CONCLUSIONS

This review found the frequent methods to establish an anger model, and major mechanisms of anti-anger effects of HMs. Interestingly, some Liver qi-smoothing herbs have been frequently used to investigate the anti-anger effects of HM. These findings provide insight into the role and relevance of HMs in the field of anger management.

Application of Transgenic Zebrafish Models for Studying the Effects of Estrogenic Endocrine Disrupting Chemicals on Embryonic Brain Development

Endocrine disrupting chemicals (EDCs) are environmental pollutants that mimic hormones and/or disrupt their function. Estrogenic EDCs (eEDCs) interfere with endogenous estrogen signalling pathway(s) and laboratory animal and human epidemiological studies have provided evidence for a causal link between exposure to them during embryonic/early life and neurological impairments. However, our understanding of the molecular and cellular mechanism(s) underlying eEDCs exposure effects on brain development, tissue architecture and function and behaviour are limited. Transgenic (TG) zebrafish models offer new approach methodologies (NAMs) to help identify the modes of action (MoAs) of EDCs and their associated impacts on tissue development and function. Estrogen biosensor TG zebrafish models have been applied to study eEDC interactions and resulting transcriptional activation (via a fluorescent reporter expression) across the entire body of the developing zebrafish embryo, including in real time. These estrogen biosensor TG zebrafish models are starting to deepen our understanding of the spatiotemporal actions of eEDCs and their resulting impacts on neurological development, brain function and behaviour. In this review, we first investigate the links between early life exposure to eEDCs and neurodevelopmental alterations in model organisms (rodents and zebrafish) and humans. We then present examples of the application of estrogen biosensor and other TG zebrafish models for elucidating the mechanism(s) underlying neurodevelopmental toxicities of eEDCs. In particular we illustrate the utility of combining estrogen biosensor zebrafish models with other TG zebrafish models for understanding the effects of eEDCs on the brain, spanning cellular processes, brain circuitry, neurophysiology and behaviour. Finally, we discuss the future prospects of TG zebrafish models as experimental models for studying more complex scenarios for exposure to contaminant mixtures on neurological development and function.

Neuroendocrine regulation of female aggression

Classically the neurobiology of aggression has been studied exclusively in males. Thus, females have been considered mildly aggressive except during lactation. Interestingly, recent studies in rodents and humans have revealed that non-lactating females can show exacerbated and pathological aggression similarly to males. This review provides an overview of recent findings on the neuroendocrine mechanisms regulating aggressive behavior in females. In particular, the focus will be on novel rodent models of exaggerated aggression established in non-lactating females. Among the neuromodulatory systems influencing female aggression, special attention has been given to sex-steroids and sex-steroid-sensitive neuronal populations (i.e., the core nuclei of the neural pathway of aggression) as well as to the neuropeptides oxytocin and vasopressin which are major players in the regulation of social behaviors.

Functions of habenula in reproduction and socio-reproductive behaviours

Habenula is an evolutionarily conserved structure in the brain of vertebrates. Recent reports have drawn attention to the habenula as a processing centre for emotional decision-making and its role in psychiatric disorders. Emotional decision-making process is also known to be closely associated with reproductive conditions. The habenula receives innervations from reproductive centres within the brain and signals from key reproductive neuroendocrine regulators such as gonadal sex steroids, gonadotropin-releasing hormone (GnRH), and kisspeptin. In this review, based on morphological, biochemical, physiological, and pharmacological evidence we discuss an emerging role of the habenula in reproduction. Further, we discuss the modulatory role of reproductive endocrine factors in the habenula and their association with socio-reproductive behaviours such as mating, anxiety and aggression.

Estrogens regulate early embryonic development of the olfactory sensory system via estrogen-responsive glia

Estrogens are well-known to regulate development of sexual dimorphism of the brain; however, their role in embryonic brain development prior to sex-differentiation is unclear. Using estrogen biosensor zebrafish models, we found that estrogen activity in the embryonic brain occurs from early neurogenesis specifically in a type of glia in the olfactory bulb (OB), which we name estrogen-responsive olfactory bulb (EROB) cells. In response to estrogen, EROB cells overlay the outermost layer of the OB and interact tightly with olfactory sensory neurons at the olfactory glomeruli. Inhibiting estrogen activity using an estrogen receptor antagonist, ICI182,780 (ICI), and/or EROB cell ablation impedes olfactory glomerular development, including the topological organisation of olfactory glomeruli and inhibitory synaptogenesis in the OB. Furthermore, activation of estrogen signalling inhibits both intrinsic and olfaction-dependent neuronal activity in the OB, whereas ICI or EROB cell ablation results in the opposite effect on neuronal excitability. Altering the estrogen signalling disrupts olfaction-mediated behaviour in later larval stage. We propose that estrogens act on glia to regulate development of OB circuits, thereby modulating the local excitability in the OB and olfaction-mediated behaviour.

Parental Behavior in Rodents

Members of the order Rodentia are among the best-studied mammals for understanding the patterns, outcomes, and biological determinants of maternal and paternal caregiving. This research has provided a wealth of information but has historically focused on just a few rodents, mostly members of the two Myomorpha families that easily breed and can be studied within a laboratory setting (including laboratory rats, mice, hamsters, voles, gerbils). It is unclear how well this small collection of animals represents the over 2000 species of extant rodents. This chapter provides an overview of the hormonal and neurobiological systems involved in parental care in rodents, with a purposeful eye on providing information known or could be gleaned about parenting in various less-traditional members of Rodentia. We conclude from this analysis that the few commonly studied rodents are not necessarily even representative of the highly diverse members of Myomorpha, let alone other rodent suborders, and that additional laboratory and field studies of members of this order more broadly would surely provide invaluable information toward revealing a more representative picture of the rich diversity in rodent parenting.

Immunofluorescent Verification of Silencing Estrogen Receptor α with siRNA in the Intact Rodent Brain

The ability to silence the expression of gene products in a chemically, spatially, and temporally specific manner in the brains of animals has enabled key breakthroughs in the field of behavioral neuroscience. Using this technique, estrogen receptor alpha (ERα) has been specifically implicated in a multitude of behaviors in mice, including sexual, aggressive, locomotor, and maternal behaviors, in a variety of brain regions, including the medial preoptic area, ventromedial hypothalamus, and amygdala. In this chapter, we describe the techniques involved in the generation of the small hairpin RNAs (shRNAs) specifically designed to silence ERα, the construction of the adeno-associated viral (AAV) vector for delivery of the shRNA, the procedures to confirm the silencing of ERα (in vitro and in vivo) and in vivo delivery of the shRNAs to the brains of animals.

Membrane-initiated actions of sex steroids and reproductive behavior: A historical account

It was assumed for a long time that sex steroids are activating reproductive behaviors by the same mechanisms that produce their morphological and physiological effects in the periphery. However during the last few decades an increasing number of examples were identified where behavioral effects of steroids were just too fast to be mediated via changes in DNA transcription. This progressively forced behavioral neuroendocrinologists to recognize that part of the effects of steroids on behavior are mediated by membrane-initiated events. In this review we present a selection of these early data that changed the conceptual landscape and we provide a summary the different types of membrane-associated receptors (estrogens, androgens and progestagens receptors) that are playing the most important role in the control of reproductive behaviors. Then we finally describe in more detail three separate behavioral systems in which membrane-initiated events have clearly been established to contribute to behavior control.

Effect of combined exposure to silica nanoparticles and cadmium chloride on female zebrafish ovaries

Silica nanoparticles (SiNPs) and cadmium chloride (CdCl2) are two important environmental pollutants. In previous research, found that SiNPs in zebrafish larvae can amplify the cardiovascular damage caused by cadmium. Whether SiNPs in the ovaries can amplify the adverse effects of cadmium on the zebrafish ovaries is worth studying problem. In this study, sexually mature female zebrafish were used as model organisms and exposed to 1 μmol/L CdCl2 and/or 25 μg/mL SiNPs for 30 days. The results showed that the structure and function of ovaries in the sole and combined exposure groups changed significantly, resulting in reduced ovarian quality, decreased number of mature oocytes, and the development of malformed offspring. A deep-sequencing analysis showed that organisms' lipid metabolism and transportation, estrogen metabolism, and response to the maturation, meiosis, and vitellogenin synthesis of oocytes were significantly affected by single exposure or combined exposure. These findings provide further insights into the harm of cooperation of CdCl2 and/or SiNPs to the aquatic ecosystems.

The potential role of stress and sex steroids in heritable effects of sevoflurane†

Most surgical procedures require general anesthesia, which is a reversible deep sedation state lacking all perception. The induction of this state is possible because of complex molecular and neuronal network actions of general anesthetics (GAs) and other pharmacological agents. Laboratory and clinical studies indicate that the effects of GAs may not be completely reversible upon anesthesia withdrawal. The long-term neurocognitive effects of GAs, especially when administered at the extremes of ages, are an increasingly recognized health concern and the subject of extensive laboratory and clinical research. Initial studies in rodents suggest that the adverse effects of GAs, whose actions involve enhancement of GABA type A receptor activity (GABAergic GAs), can also extend to future unexposed offspring. Importantly, experimental findings show that GABAergic GAs may induce heritable effects when administered from the early postnatal period to at least young adulthood, covering nearly all age groups that may have children after exposure to anesthesia. More studies are needed to understand when and how the clinical use of GAs in a large and growing population of patients can result in lower resilience to diseases in the even larger population of their unexposed offspring. This minireview is focused on the authors' published results and data in the literature supporting the notion that GABAergic GAs, in particular sevoflurane, may upregulate systemic levels of stress and sex steroids and alter expressions of genes that are essential for the functioning of these steroid systems. The authors hypothesize that stress and sex steroids are involved in the mediation of sex-specific heritable effects of sevoflurane.

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.

Calcitonin receptor signaling in the medial preoptic area enables risk-taking maternal care

Maternal mammals exhibit heightened motivation to care for offspring, but the underlying neuromolecular mechanisms have yet to be clarified. Here, we report that the calcitonin receptor (Calcr) and its ligand amylin are expressed in distinct neuronal populations in the medial preoptic area (MPOA) and are upregulated in mothers. Calcr+ MPOA neurons activated by parental care project to somatomotor and monoaminergic brainstem nuclei. Retrograde monosynaptic tracing reveals that significant modification of afferents to Calcr+ neurons occurs in mothers. Knockdown of either Calcr or amylin gene expression hampers risk-taking maternal care, and specific silencing of Calcr+ MPOA neurons inhibits nurturing behaviors, while pharmacogenetic activation prevents infanticide in virgin males. These data indicate that Calcr+ MPOA neurons are required for both maternal and allomaternal nurturing behaviors and that upregulation of amylin-Calcr signaling in the MPOA at least partially mediates risk-taking maternal care, possibly via modified connectomics of Calcr+ neurons postpartum.

Endocrine disrupting chemicals (EDCs) and sex steroid receptors

Sex-steroid receptors (SSRs) are essential mediators of estrogen, progestin, and androgen signaling that are critical in vast aspects of human development and multi-organ homeostasis. Dysregulation of SSR function has been implicated in numerous pathologies including cancers, obesity, Type II diabetes mellitus, neuroendocrine disorders, cardiovascular disease, hyperlipidemia, male and female infertility, and other reproductive disorders. Endocrine disrupting chemicals (EDCs) modulate SSR function in a wide variety of cell and tissues. There exists strong experimental, clinical, and epidemiological evidence that engagement of EDCs with SSRs may disrupt endogenous hormone signaling leading to physiological abnormalities that may manifest in disease. In this chapter, we discuss the molecular mechanisms by which EDCs interact with estrogen, progestin, and androgen receptors and alter SSR functions in target cells. In addition, the pathological consequences of disruption of SSR action in reproductive and other organs by EDCs is described with an emphasis on underlying mechanisms of receptors dysfunction.

In Vitro and Vivo Identification, Metabolism and Action of Xenoestrogens: An Overview

Xenoestrogens (XEs) are substances that imitate endogenous estrogens to affect the physiologic functions of humans or other animals. As endocrine disruptors, they can be either synthetic or natural chemical compounds derived from diet, pesticides, cosmetics, plastics, plants, industrial byproducts, metals, and medications. By mimicking the chemical structure that is naturally occurring estrogen compounds, synthetic XEs, such as polychlorinated biphenyls (PCBs), bisphenol A (BPA), and diethylstilbestrol (DES), are considered the focus of a group of exogenous chemical. On the other hand, nature phytoestrogens in soybeans can also serve as XEs to exert estrogenic activities. In contrast, some XEs are not similar to estrogens in structure and can affect the physiologic functions in ways other than ER-ERE ligand routes. Studies have confirmed that even the weakly active compounds could interfere with the hormonal balance with persistency or high concentrations of XEs, thus possibly being associated with the occurrence of the reproductive tract or neuroendocrine disorders and congenital malformations. However, XEs are most likely to exert tissue-specific and non-genomic actions when estrogen concentrations are relatively low. Current research has reported that there is not only one factor affected by XEs, but opposite directions are also found on several occasions, or even different components stem from the identical endocrine pathway; thus, it is more challenging and unpredictable of the physical health. This review provides a summary of the identification, detection, metabolism, and action of XEs. However, many details of the underlying mechanisms remain unknown and warrant further investigation.

Hormonal and biochemical changes in female Proechimys guyannensis, an animal model of resistance to pilocarpine-induced status epilepticus

The Amazon rodent Proechimys guyannensis is widely studied for hosting various pathogens, though rarely getting sick. Previous studies on male Proechimys have revealed an endogenous resistance to epilepsy. Here, we assess in female Proechimys, whether sex hormones and biochemical aspects can interfere with the induction of status epilepticus (SE). The lithium-pilocarpine ramp-up protocol was used to induce SE, and blood sera were collected at 30 and 90 min after SE, alongside brains, for biochemical, western blot and immunohistochemical analyses. Results from non-ovariectomised (NOVX) Proechimys were compared to ovariectomised (OVX) animals. Data from female Wistars were used as a positive control of SE inductions. SE latency was similar in NOVX, OVX, and female Wistars groups. However, the pilocarpine dose required to induce SE in Proechimys was higher (25- to 50-folds more). Despite a higher dose, Proechimys did not show strong SE like Wistars; they only reached stage 2 of the Racine scale. These data suggest that female Proechimys are resistant to SE induction. Glucose and progesterone levels increased at 30 min and returned to normal at 90 min after SE. A relevant fact because in humans and rodents, SE leads to hypoglycaemia after 30 min of SE and does not return to normal levels in a short time, a typical adverse effect of SE. In OVX animals, a decrease in GABAergic receptors within 90 min of SE may suggest that ovariectomy produces changes in the hippocampus, including a certain vulnerability to seizures. We speculate that progesterone and glucose increases form part of the compensatory mechanisms that provide resistance in Proechimys against SE induction.

Inside the supergene of the bird with four sexes

The white-throated sparrow (Zonotrichia albicollis) offers unique opportunities to understand the adaptive value of supergenes, particularly their role in alternative phenotypes. In this species, alternative plumage morphs segregate with a nonrecombining segment of chromosome 2, which has been called a 'supergene'. The species mates disassortatively with respect to the supergene; that is, each breeding pair consists of one individual with it and one without it. This species has therefore been called the "bird with four sexes". The supergene segregates with a behavioral phenotype; birds with it are more aggressive and less parental than birds without it. Here, we review our efforts to identify the genes inside the supergene that are responsible for the behavioral polymorphism. The gene ESR1, which encodes estrogen receptor α, differs between the morphs and predicts both territorial and parental behavior. Variation in the regulatory regions of ESR1 causes an imbalance in expression of the two alleles, and the degree to which this imbalance favors the supergene allele predicts territorial singing. In heterozygotes, knockdown of ESR1 causes a phenotypic switch, from more aggressive to less aggressive. We recently showed that another gene important for social behavior, vasoactive intestinal peptide (VIP), is differentially expressed between the morphs and predicts territorial singing. We hypothesize that ESR1 and VIP contribute to behavior in a coordinated way and could represent co-adapted alleles. Because the supergene contains more than 1000 individual genes, this species provides rich possibilities for discovering alleles that work together to mediate life-history trade-offs and maximize the fitness of alternative complex phenotypes.

Estrogen Receptor Beta (ERβ): A Ligand Activated Tumor Suppressor

Estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) belong to a superfamily of nuclear receptors called steroid hormone receptors, which, upon binding ligand, dimerize and translocate to the nucleus where they activate or repress the transcription of a large number of genes, thus modulating critical physiologic processes. ERβ has multiple isoforms that show differing association with prognosis. Expression levels of the full length ERβ1 isoform are often lower in aggressive cancers as compared to normal tissue. High ERβ1 expression is associated with improved overall survival in women with breast cancer. The promise of ERβ activation, as a potential targeted therapy, is based on concurrent activation of multiple tumor suppressor pathways with few side effects compared to chemotherapy. Thus, ERβ is a nuclear receptor with broad-spectrum tumor suppressor activity, which could serve as a potential treatment target in a variety of human cancers including breast cancer. Further development of highly selective agonists that lack ERα agonist activity, will be necessary to fully harness the potential of ERβ.

Brain Aromatase and the Regulation of Sexual Activity in Male Mice

The biologically active estrogen estradiol has important roles in adult brain physiology and sexual behavior. A single gene, Cyp19a1, encodes aromatase, the enzyme that catalyzes the conversion of testosterone to estradiol in the testis and brain of male mice. Estradiol formation was shown to regulate sexual activity in various species, but the relative contributions to sexual behavior of estrogen that arises in the brain versus from the gonads remained unclear. To determine the role of brain aromatase in regulating male sexual activity, we generated a brain-specific aromatase knockout (bArKO) mouse. A newly generated whole-body total aromatase knockout mouse of the same genetic background served as a positive control. Here we demonstrate that local aromatase expression and estrogen production in the brain is partially required for male sexual behavior and sex hormone homeostasis. Male bArKO mice exhibited decreased sexual activity in the presence of strikingly elevated circulating testosterone. In castrated adult bArKO mice, administration of testosterone only partially restored sexual behavior; full sexual behavior, however, was achieved only when both estradiol and testosterone were administered together. Thus, aromatase in the brain is, in part, necessary for testosterone-dependent male sexual activity. We also found that brain aromatase is required for negative feedback regulation of circulating testosterone of testicular origin. Our findings suggest testosterone activates male sexual behavior in part via conversion to estradiol in the brain. These studies provide foundational evidence that sexual behavior may be modified through inhibition or enhancement of brain aromatase enzyme activity and/or utilization of selective estrogen receptor modulators.

Neonatal exposure to genistein affects reproductive physiology and behavior in female and male Long-Evans rats

The present study was designed to examine the effects of neonatal genistein exposure on measures of reproductive physiology and behavior. Approximately 24 h after birth, female and male Long-Evans rat pups were injected daily with genistein (150 µg, subcutaneous; n = 29) or olive oil (n = 23) between postnatal days 1 and 5. After weaning, we examined all subjects daily until they reached puberty (i.e. vaginal opening in female rats and preputial separation in male rats). For all female subjects, we also examined vaginal cytology. After monitoring estrous cyclicity, the female subjects were given the opportunity to interact with a gonadally intact male or a sexually receptive female rat on the day of behavioral estrus to assess sexual motivation (i.e. partner-preference test with and without physical contact), which has never been evaluated before. For all male subjects, we assessed the development of copulatory behavior and sexual motivation (partner-preference test without physical contact). Consistent with previous findings, we found that neonatal exposure to genistein did not affect puberty onset in female or male rats. However, female rats exposed to genistein displayed significantly more irregular estrous cycles than controls. Neonatal genistein exposure also altered the development of male copulatory behavior, as indicated by an increase in mount frequency and intromission frequency and shorter interintromission intervals. We extended previous findings confirming that neither female nor male sexual motivation was affected by neonatal genistein. The results of the present study have important implications for the development of reproductive physiology and behavior in human neonates exposed to genistein in soy-based baby formula.

Detection and Characterization of Estrogen Receptor Beta Expression in the Brain with Newly Developed Transgenic Mice

Two types of nuclear estrogen receptors, ERα and ERβ, have been shown to be differentially involved in the regulation of various types of behaviors. Due to a lack of tools for identifying ERβ expression, detailed anatomical distribution and neurochemical characteristics of ERβ expressing cells and cellular co-expression with ERα remain unclear. We have generated transgenic mice ERβ-RFP^tg, in which RFP was inserted downstream of ERβ BAC promotor. We verified RFP signals as ERβ by confirming: (1) high ERβ mRNA levels in RFP-expressing cells collected by fluorescence-activated cell sorting; and (2) co-localization of ERβ mRNA and RFP proteins in the paraventricular nucleus (PVN). Strong ERβ-RFP signals were found in the PVN, medial preoptic area (MPOA), bed nucleus of the stria terminalis, medial amygdala (MeA), and dorsal raphe nucleus (DRN). In the MPOA and MeA, three types of cell populations were identified; those expressing both ERα and ERβ, and those expressing exclusively either ERα or ERβ. The majority of PVN and DRN cells expressed only ERβ-RFP. Further, ERβ-RFP positive cells co-expressed oxytocin in the PVN, and tryptophan hydroxylase 2 and progesterone receptors in the DRN. In the MeA, some ERβ-RFP positive cells co-expressed oxytocin receptors. These findings collectively suggest that ERβ-RFP^tg mice can be a powerful tool for future studies on ERβ function in the estrogenic regulation of social behaviors.

The interactions of diet-induced obesity and organophosphate flame retardant exposure on energy homeostasis in adult male and female mice

Previously, sex-dependent alterations in energy homeostasis were reported in adult mice fed a standard chow attributed to exposure to a mixture of organophosphate flame retardants (OPFRs) via estrogen receptors (ERα). In this study, adult male and female mice (C57BL/6J; Taconic) were treated with the same mixture of OPFRs (1 mg/kg each of tricresyl phosphate (TCP), triphenyl phosphate (TPP), and tris(1-3-dichloro-2propyl)phosphate (TDCPP)) for 7 weeks on a low-fat diet (LFD, 10% kcal fat) or a high fat (HFD, 45% kcal fat) in a diet-induced obesity model. Consistent with our previous observations, OPFRs altered weight gain in males, differentially with diet, while females remained unaffected. OPFR treatment also revealed sex-dependent perturbations in metabolic activity. During the night (approximately 0100-0400 hr), males exhibited elevated activity and oxygen consumption, while in females these parameters were decreased, irrespective of diet. OPFR disrupted feeding behavior and abolished diurnal water intake patterns in females while increasing nighttime fluid consumption in males. Despite no marked effect of OPFRs on glucose or insulin tolerance, OPFR treatment altered circulating insulin and leptin in females and ghrelin in males. Data indicate that adult OPFR exposure might influence, and perhaps exacerbate, the effects of diet-induced obesity in adult mice by altering activity, ingestive behavior, and metabolism.

Construction of reporter gene assays using CWP and PDR mutant yeasts for enhanced detection of various sex steroids

Background

Sex steroid hormone receptors are classified into three classes of receptors: estrogen receptors (ER) α and β, androgen receptor (AR), and progesterone receptor (PR). They belong to the nuclear receptor superfamily and activate their downstream genes in a ligand-dependent manner. Since sex steroid hormones are involved in a wide variety of physiological processes and cancer development, synthetic chemical substances that exhibit sex steroid hormone activities have been applied as pharmaceuticals and consumed in large amounts worldwide. They are potentially hazardous contaminants as endocrine disruptors in the environment because they may induce inappropriate gene expression mediated by sex steroid hormone receptors in vivo.

Results

To develop simple reporter gene assays with enhanced sensitivity for the detection of sex steroid hormones, we newly established mutant yeast strains lacking the CWP and PDR genes encoding cell wall mannoproteins and plasma membrane drug efflux pumps, respectively, and expressing human ERα, ERβ, AR, and PR. Reporter gene assays with mutant yeast strains responded to endogenous and synthetic ligands more strongly than those with wild-type strains. Sex steroid hormone activities in some pharmaceutical oral tablets and human urine were also detectable in these yeast assays.

Conclusions

Yeast reporter gene assay systems for all six steroid hormone receptors, including previously established glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) assay yeasts, are now available. Environmental endocrine disrupters with steroid hormone activity will be qualitatively detectable by simple and easy procedures. The yeast-based reporter gene assay will be valuable as a primary screening tool to detect and evaluate steroid hormone activities in various test samples. Our assay system will strongly support the detection of agonists, antagonists, and inverse agonists of steroid hormone receptors in the field of novel drug discovery and assessments of environmental pollutants.

Amygdalohippocampal Area Neurons That Project to the Preoptic Area Mediate Infant-Directed Attack in Male Mice

Male animals may show alternative behaviors toward infants: attack or parenting. These behaviors are triggered by pup stimuli under the influence of the internal state, including the hormonal environment and/or social experiences. Converging data suggest that the medial preoptic area (MPOA) contributes to the behavioral selection toward the pup. However, the neural mechanisms underlying how integrated stimuli affect the MPOA-dependent behavioral selection remain unclear. Here we focus on the amygdalohippocampal area (AHi) that projects to MPOA and expresses oxytocin receptor, a hormone receptor mediating social behavior toward pups. We describe the activation of MPOA-projection AHi neurons in male mice by social contact with pups. Input mapping using the TRIO method reveals that MPOA-projection AHi neurons receive prominent inputs from several regions, including the thalamus, hypothalamus, and olfactory cortex. Electrophysiological and histologic analysis demonstrates that oxytocin modulates inhibitory synaptic responses on MPOA-projection AHi neurons. In addition, AHi forms the excitatory monosynapse to MPOA, and pharmacological activation of MPOA-projection AHi neurons enhances only aggressive behavior, but not parental behavior. Interestingly, this promoted behavior was related to social experience in male mice. Collectively, our results identified a presynaptic partner of MPOA that can integrate sensory input and hormonal state, and trigger pup-directed aggression.SIGNIFICANCE STATEMENT The medial preoptic area (MPOA) plays critical roles in parental behavior, such as motor control, motivation, and social interaction. The MPOA projects to multiple brain regions, and these projections contribute to several neural controls in parental behavior. In contrast, how inputs to MPOA are regulated by social and environmental information is poorly understood. In this study, we focus on the amygdalohippocampal area (AHi) that connects to MPOA and expresses oxytocin receptor. We demonstrate the disruption of the expression of parental behavior triggered by the activation of MPOA-projection AHi neurons. This behavior may be regulated not only by oxytocin but also by neural input from several regions.

Estrogen Receptors and Ubiquitin Proteasome System: Mutual Regulation

This review provides information on the structure of estrogen receptors (ERs), their localization and functions in mammalian cells. Additionally, the structure of proteasomes and mechanisms of protein ubiquitination and cleavage are described. According to the modern concept, the ubiquitin proteasome system (UPS) is involved in the regulation of the activity of ERs in several ways. First, UPS performs the ubiquitination of ERs with a change in their functional activity. Second, UPS degrades ERs and their transcriptional regulators. Third, UPS affects the expression of ER genes. In addition, the opportunity of the regulation of proteasome functioning by ERs—in particular, the expression of immune proteasomes—is discussed. Understanding the complex mechanisms underlying the regulation of ERs and proteasomes has great prospects for the development of new therapeutic agents that can make a significant contribution to the treatment of diseases associated with the impaired function of these biomolecules.