Oestrogen receptor alpha localisation in the prefrontal cortex of three mammalian species

Serum testosterone levels are related to cognitive function in men with schizophrenia

BACKGROUND

Sex steroids such as oestrogen and testosterone are potent neurodevelopmental hormones that also play a role in neuromodulation and neuroprotection of the mature brain. Sex steroid hormones may also be involved in the pathophysiology of schizophrenia as reduced circulating sex steroid levels and changes in brain sex steroid receptors are found in people with schizophrenia compared to controls. In men with schizophrenia, recent studies have documented an inverse correlation between serum testosterone and negative symptoms. Our study sought to confirm whether men with schizophrenia had lower levels of testosterone relative to controls and to determine whether lower testosterone levels were related to higher symptom severity and impaired cognition.

METHOD

Circulating serum hormone levels (testosterone, oestrogen, and prolactin), cognitive function and symptoms were assessed in 29 chronically ill men with schizophrenia or schizoaffective disorder. Twenty healthy men were recruited as a comparison group. A series of regression analyses were performed to determine the extent to which circulating sex steroid hormone levels predict cognition and symptoms in men with schizophrenia.

RESULTS

We did not find a significant difference in serum testosterone levels between groups. However, circulating testosterone levels significantly predicted performance on verbal memory, processing speed, and working memory in men with schizophrenia. With the exception of an effect of oestrogen on verbal memory, circulating sex steroid levels did not predict cognitive function in healthy men. Testosterone levels were not related to positive or negative symptom severity, but testosterone influenced excitement/hostility levels in our schizophrenia sample.

CONCLUSIONS

The results suggest that circulating sex steroids may modulate cognitive deficits associated with schizophrenia.

Sex differences and estrous cycle in female rats interact with the effects of fluoxetine treatment on fear extinction

A common treatment for anxiety disorders is chronic administration of selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine. Recent data suggest that SSRIs modulate fear responses after conditioned fear extinction and that gonadal hormones influence fear extinction. In this study we investigated the influence of sex and the estrous cycle on the effects of acute (experiment 1) and chronic (experiment 2) fluoxetine treatment on fear extinction. In experiment 1, rats received tone-footshock pairings during day 1. On day 2, rats received either fluoxetine (10mg/kg in 0.5mL) or vehicle prior to extinction learning. On day 3, extinction memory was assessed during extinction recall. In experiment 2, rats were exposed to a similar behavioral protocol, except that fluoxetine and vehicle were administered for 14 consecutives days after conditioning (days 2-15). Extinction learning and extinction recall occurred on days 15 and 16, respectively. Acute administration of fluoxetine increased fear responses equally in males and females during extinction learning and extinction recall. Chronic administration of fluoxetine reduced fear responses during extinction learning and extinction recall in female but not in male rats and this effect seems to be modulated by the estrous cycle. The SSRI-induced reduction of freezing during extinction learning and recall suggest a general anxiolytic effect of the drug treatment rather than a specific effect on extinction learning per se. Our data show evidence of sex-specific anxiolytic effects of 14-day treatment of fluoxetine while the acute anxiogenic effect of SSRI seems independent of sex effects.

Abnormalities of dorsolateral prefrontal function in women with premenstrual dysphoric disorder: a multimodal neuroimaging study

OBJECTIVE

To investigate the neural substrate of premenstrual dysphoric disorder (PMDD), the authors used [15O]H2O positron emission tomography (PET) regional cerebral blood flow (rCBF) and blood-oxygen-level-dependent (BOLD) functional MRI (fMRI) signal measurements during working memory in conjunction with a 6-month hormone manipulation protocol.

METHOD

PET and fMRI scans were obtained from women with prospectively confirmed PMDD and asymptomatic comparison subjects while they completed the n-back task during three hormone conditions: ovarian suppression induced by the gonadotropin-releasing hormone agonist leuprolide acetate, leuprolide plus estradiol, and leuprolide plus progesterone. Fifteen patients and 15 matched comparison subjects underwent PET imaging. Fourteen patients and 14 comparison subjects underwent fMRI. For each hormone condition, rCBF was measured with [15O]H2O PET, and BOLD signal was measured with fMRI, both during an n-back working memory paradigm. Global Assessment of Functioning Scale (GAF) scores and clinical characteristics were obtained for each patient before hormone manipulation, and symptoms were measured before and during the protocol.

RESULTS

In both the PET and fMRI studies, a main effect of diagnosis was observed, with PMDD patients showing greater prefrontal activation than comparison subjects. In the patient group, the degree to which dorsolateral prefrontal cortex activation was abnormally increased correlated with several dimensions of disease: disability as indicated by GAF scores, age at symptom onset, duration of PMDD, and differences in pre- and postmenses PMDD symptoms.

CONCLUSIONS

Abnormal working memory activation in PMDD, specifically in the dorsolateral prefrontal cortex, is related to PMDD severity, symptoms, age at onset, and disease burden. These results support the clinical relevance of the findings and the proposal that dorsolateral prefrontal cortex dysfunction represents a substrate of risk for PMDD. The concordance of the fMRI and PET data attests to the neurobiological validity of the results.

17β-Estradiol and genistein acute treatments improve some cerebral cortex homeostasis aspects deteriorated by aging in female rats

Aging is associated with decreased insulin sensitivity and impaired cerebral glucose homeostasis. These changes increase neural sensitivity to metabolic damage contributing to cognitive decline, being the decrease in plasma estrogen following menopause one of the main factors involved in aged females. Phytoestrogens as genistein are structurally similar to 17β-estradiol, bind to estrogen receptors, and can evoke both estrogenic and anti-estrogenic effects. Estrogens and phytoestrogens have neuroprotective potential, but the physiological mechanisms are not fully understood. Young and aged female Wistar rats were ovariectomized and treated acutely with 17β-estradiol (1.4μg/kg body weight), genistein (10 or 40 mg/kg body weight), or vehicle. Cortical expression of glucose transporter-3 (GLUT-3) and -4 (GLUT-4), cytochrome c oxidase (CO), estrogen receptor-α (ERα) and -β (ERβ) was measured by Western blotting. There was an age-related decline in GLUT-4, CO and ERβ levels. Both drugs, estradiol and genistein, were able to reverse GLUT-3 downregulation in the cortex following late ovariectomy. However, genistein was the only treatment able to restore completely GLUT-4 levels in aged rats. In contrast, estradiol was more potent than genistein at increasing CO, a marker of cerebral oxidative metabolism. As regards ER levels, estradiol increased the ERα67 quantity diminished by late ovariectomy, while genistein did the same with the other ERα isoform, ERα46, highlighting drug-specific differences in expression changes for both isoforms. On the other hand, no treatment-related differences were found regarding ERβ levels. Therefore, genistein like estradiol could be suitable treatments against cortical metabolic dysfunction caused by aging. These treatments may hold promise as neuroprotective strategies against diabetes and age-related neurodegenerative diseases.

Blockade of estrogen by hormonal contraceptives impairs fear extinction in female rats and women

BACKGROUND

Fear extinction is a laboratory model of fear inhibition and is the basis of exposure therapy for anxiety disorders. Emerging evidence from naturally cycling female rodents and women indicates that estrogens are necessary to the consolidation of fear extinction. Hormonal contraceptives (HCs) inhibit estrogen production; yet, their effects on fear extinction are unknown.

METHODS

We used a cross-species translational approach to investigate the impact of HCs and estradiol supplementation on fear extinction in healthy women (n=76) and female rats (n = 140).

RESULTS

Women using HCs exhibited significantly poorer extinction recall compared with naturally cycling women. The extinction impairment was also apparent in HC-treated female rats and was associated with reduced serum estradiol levels. The impairment could be rescued in HC-treated rats either by terminating HC treatment after fear learning or by systemic injection of estrogen-receptor agonists before fear extinction, all of which restored serum estradiol levels. Finally, a single administration of estradiol to naturally cycling women significantly enhanced their ability to recall extinction memories.

CONCLUSIONS

Together, these findings suggest that HCs may impact women's ability to inhibit fear but that this impairment is not permanent and could potentially be alleviated with estrogen treatment.

Cognitive dysfunction with aging and the role of inflammation

As the average lifespan continues to climb because of advances in medical care, there is a greater need to understand the factors that contribute to quality of life in the elderly. The capacity to live independently is highly significant in this regard, but is compromised by cognitive dysfunction. Aging is associated with decreases in cognitive function, including impairments in episodic memory and executive functioning. The prefrontal cortex appears to be particularly vulnerable to the effects of advancing age. Although the mechanism of age-related cognitive decline is not yet known, age-related inflammatory changes are likely to play a role. New insights from preclinical and clinical research may give rise to novel therapeutics which may have efficacy in slowing or preventing cognitive decline with advancing age.

Interaction of sex steroid hormones and brain-derived neurotrophic factor-tyrosine kinase B signalling: relevance to schizophrenia and depression

Sex steroid hormones and neurotrophic factors are involved in pruning and shaping the developing brain and have been implicated in the pathogenesis of neurodevelopmental disorders. Sex steroid hormones are also involved in the regulation of brain-derived neurotrophic factor expression. A review of the literature is provided on the relationship between brain-derived neurotrophic factor and sex steroid hormones, as well as the mechanisms behind this interaction, in the context of how this relationship may be involved in the development of neurodevelopmental psychiatric illnesses, such as schizophrenia and depression.

Language lateralization and cognitive control across the menstrual cycle assessed with a dichotic-listening paradigm

Lateralization has been shown to vary across the menstrual cycle, however, the underlying mechanisms are not fully understood, and results are inconsistent. Additionally, it has been suggested that estradiol enhances cognitive control. By modulating attention in a consonant-vowel dichotic listening test, the current study aims to investigate the effects of cycle-related changes on language lateralization (non-forced condition), as well as the effects of estradiol-modulated cognitive control (forced left condition) on the ear advantage. Fifteen women and fifteen men tested three times on the dichotic listening test, women once in menstrual, follicular, and luteal phase (verified by hormone assays). Whereas the results from the non-forced and forced-right condition remained stable, results from the forced left condition changed across the cycle, where women in the follicular phase compared to both menstrual and luteal phases showed a stronger left ear advantage, i.e. better cognitive control performance. The increase in performance from menstrual to follicular phase correlated negatively with increase in estradiol levels, indicating a shift from a stimulus-driven right ear advantage (indicating a left hemispheric asymmetry for language) when estradiol levels were low toward a cognitively controlled left ear advantage when estradiol levels were high. This finding strongly suggests an active role of estradiol on cognitive control. The study further suggests that the degree of cognitive control demands of a given task is important to consider when investigating lateralization across the menstrual cycle.

Estrogens and memory in physiological and neuropathological conditions

Ovarian hormones can influence brain regions crucial to higher cognitive functions, such as learning and memory, acting at structural, cellular and functional levels, and modulating neurotransmitter systems. Among the main effects of estrogens, the protective role that they may play against the deterioration of cognitive functions occurring with normal aging is of essential importance. In fact, during the last century, there has been a 30 years increase in female life expectancy, from 50 to 83 years; however, the mean age of spontaneous menopause remains stable, 50-51 years, with variability related to race and ethnicity. Therefore, women are now spending a greater fraction of their lives in a hypoestrogenic state. Although many cognitive functions seem to be unaffected by normal aging, age-related impairments are particularly evident in tasks involving working memory (WM), whose deficits are a recognized feature of Alzheimer's disease (AD). Many studies conducted over the past two decades showed that the female gonadal hormone estradiol can influence performance of learning and memory tasks, both in animal and humans. There is a great deal of evidence, mostly from animal models, that estrogens can facilitate or enhance performance on WM tasks; therefore, it is very important to clarify their role on this type of memory. To this aim, in this review we briefly describe the most relevant neurobiological bases of estrogens, that can explain their effects on cognitive functioning, and then we summarize the results of works conducted in our laboratory, both on animals and humans, utilizing the menstrual/estrous cycle as a useful noninvasive model. Finally, we review the possible role of estrogens in neuropathological conditions, such as AD and schizophrenia.

Firing patterns of maternal rat prelimbic neurons during spontaneous contact with pups

Extracellular single unit activity was recorded from medial prefrontal cortex (mPFC) of postpartum dams over the course of 3 days while they engaged in spontaneous pup-directed behaviors and non-specific exploratory behavior. Out of 109 units identified over the course of the experiment, 15 units were observed to be pup-responsive and 15 increased their discharge rates non-specifically while not attending to pups. An association between neuronal activity and typical maternal behaviors (e.g., retrieval, pup-grooming, nursing) was not observed. Instead, brief bouts of snout contact with pups were accompanied by phasic increases and decreases in spike rates. The observed pup contact responsive cells might play a role in processing of sensory feedback from pups or the transmission of modulatory output to other subcortical maternal brain areas.

Gender-specific reduction of estrogen-sensitive small RNA, miR-30b, in subjects with schizophrenia

Estrogen signaling pathways affect cortical function and metabolism, are thought to play a role in the pathophysiology of schizophrenia, and exert neuroprotective effects in female subjects at risk. However, the molecular signatures of estrogen signaling in normal and diseased cerebral cortex remain largely unexplored. Expression of the estrogen-sensitive small RNA, microRNA-30b (miR-30b), was studied in 30 controls and 30 matched samples from subjects diagnosed with schizophrenia from prefrontal cortex (PFC), as well as in 23 samples from parietal cortex (12 controls and 11 schizophrenia cases). The majority of case and control samples were genotyped for an estrogen receptor α (Esr1) sequence variant (rs2234693) previously associated with genetic risk, and a subset of them were subjected to further analysis to determine expression of mature and precursor forms of miR-30b (pre/pri-miR-30b). Gender-dimorphic expression was also explored in mouse frontal cortex and hippocampus. A significant interaction between gender and diagnosis was discovered for changes in mature miR-30b levels, so that miR-30b expression was significantly reduced in the cerebral cortex of female but not male subjects with schizophrenia. In addition, disease-related changes in miR-30b expression in a subset of female subjects were further modulated by Esr1 genotype. Changes after antipsychotic drug exposure remained insignificant. These preliminary findings point to the possibility that disease-related changes in the expression of small noncoding RNAs such as miR-30b in schizophrenia could be influenced by gender and potentially regulated by estrogen signaling.

Sex differences, gonadal hormones and the fear extinction network: implications for anxiety disorders

Convergent data from rodents and human studies have led to the development of models describing the neural mechanisms of fear extinction. Key components of the now well-characterized fear extinction network include the amygdala, hippocampus, and medial prefrontal cortical regions. These models are fueling novel hypotheses that are currently being tested with much refined experimental tools to examine the interactions within this network. Lagging far behind, however, is the examination of sex differences in this network and how sex hormones influence the functional activity and reactivity of these brain regions in the context of fear inhibition. Indeed, there is a large body of literature suggesting that sex hormones, such as estrogen, do modulate neural plasticity within the fear extinction network, especially in the hippocampus.After a brief overview of the fear extinction network, we summarize what is currently known about sex differences in fear extinction and the influence of gonadal hormones on the fear extinction network. We then go on to propose possible mechanisms by which sex hormones, such as estrogen, may influence neural plasticity within the fear extinction network. We end with a discussion of how knowledge to be gained from developing this line of research may have significant ramifications towards the etiology, epidemiology and treatment of anxiety disorders.

Sex-specific, rapid neuroestrogen fluctuations and neurophysiological actions in the songbird auditory forebrain

Recent evidence shows that brain-derived steroids such as estrogens ("neuroestrogens") are controlled in a manner very similar to traditional neurotransmitters. The advent of in vivo microdialysis for steroids in songbirds has provided new information about the spatial and temporal dynamics of neuroestrogen changes in a region of the auditory cortex, the caudomedial nidopallium (NCM). Here, experiments using in vivo microdialysis demonstrate that neuroestradiol (E(2)) fluctuations occur within the auditory NCM during presentation of naturalistic auditory and visual stimuli in males but only to the presentation of auditory stimuli in females. These changes are acute (within 30 min) and appear to be specific to the NCM, because similar treatments elicit no changes in E(2) in a nearby mesopallial region or in circulating plasma. Further experiments coupling in vivo steroid microdialysis with extracellular recordings in NCM show that neuroestrogens rapidly boost auditory responses to song stimuli in females, similar to recent observations in males. We also find that the rapid actions of estradiol on auditory responses are fully mimicked by the cell membrane-impermeable estrogen biotinylestradiol, consistent with acute estrogen actions at the neuronal membrane. Thus we conclude that local and acute E(2) flux is regulated by convergent multimodal sensory input, and that this regulation appears to be sex-specific. Second, rapid changes in local E(2) levels in NCM have consequences for the modulation of auditory processing in females and males. Finally, the rapid actions of neuroestrogens on NCM auditory processing appear to be mediated by a nonclassical, membrane-bound estrogen receptor.

Estrogen receptors localization in the spinal trigeminal nucleus: an immunohistochemical study in humans

There is increasing evidence for estrogenic modulation of neurotransmission within the trigeminal pain pathway. It is also likely that the effects of estrogens may be influenced by the presence and localization of estrogen receptors (ERs) in a given brain area. To date, human data on the localization of ERs in the spinal trigeminal nucleus (STN), a key brain region in craniofacial nociception, are lacking. To ascertain whether ERs are expressed in the human STN, we performed immunohistochemical analysis on medulla oblongata samples taken from eight adult subjects (three men and five women; age range, 23-71 years) who had died from causes unrelated to neurologic or endocrine diseases. Paraffin-embedded sections at the level of the subnucleus caudalis and interpolaris were incubated with anti-estrogen receptor alpha (ERα) and anti-estrogen receptor beta (ERβ) antibodies. ERα immunoreactivity was detected in the nucleus and cytoplasm of neuronal and glial cells in the STN and in the nerve fibers within the spinal trigeminal tract in all eight subjects; ERβ immunoreactivity was observed in the cytoplasm of neuronal cells in five subjects. This study is the first to provide evidence in humans that ER immunoreactivity is detectable on neuronal and glial cells of the STN. The two ER subtypes exhibited different expression patterns, with higher expression levels of ERα than ERβ. The presence of ER-containing cells in the STN suggests that estrogens may directly affect trigeminal neuron excitability in humans.

Dynamic molecular and anatomical changes in the glucocorticoid receptor in human cortical development

The glucocorticoid receptor (GR) has a critical role in determining the brain's capacity to respond to stress, and has been implicated in the pathogenesis of psychiatric illness. We hypothesized that key changes in cortical GR occur during adolescence and young adulthood, at a time when individuals are at increased risk of developing schizophrenia, bipolar disorder and major depression. We investigated the mRNA and protein expression of GR in the dorsolateral prefrontal cortex across seven developmental time points from infancy to adulthood. GR mRNA expression, determined by microarray and quantitative real-time PCR, was lowest in neonates and peaked around young adulthood. Western blotting revealed two dynamic patterns of GRα protein expression across the lifespan, with N-terminal variants displaying differing unique patterns of abundance. GRα-A and a 67-kDa GRα isoform mirrored mRNA trends and peaked in toddlers and late in adolescence, whereas a 40-kDa isoform, very likely a GRα-D variant, peaked in neonates and decreased across the lifespan. GRα protein was localized to pyramidal neurons throughout life and most strikingly in young adulthood, but to white matter astrocytes only in neonates and infants (<130 days). These results suggest that the neonatal and late adolescent periods represent critical windows of stress pathway development, and highlight the importance of white matter astrocytes and pyramidal neurons, respectively, at these stages of cortical development. Evidence of dynamic patterns of GR isoform expression and cellular localization across development strengthens the hypothesis that windows of vulnerability to stress exist across human cortical development.

Estrogen shapes dopamine-dependent cognitive processes: implications for women's health

The prefrontal cortex (PFC) is exquisitely sensitive to its neurochemical environment. Minor fluctuations in cortical dopamine (DA) can profoundly alter working memory, a PFC-dependent cognitive function that supports an array of essential human behaviors. Dopamine's action in the PFC follows an inverted U-shaped curve, where an optimal DA level results in maximal function and insufficient or excessive DA impairs PFC function. In animals, 17β-estradiol (the major estrogen in most mammals, referred to henceforth as estradiol) has been shown to enhance DA activity, yet no human study has adequately addressed whether estradiol's impact on cognition occurs by way of modulating specific neurochemical systems. Here we examined the effects of endogenous fluctuations in estradiol on working memory in healthy young women as a function of baseline PFC DA [indexed by catechol-O-methyltransferase (COMT) Val(158)Met genotype and, at a finer scale, COMT enzyme activity]. The results demonstrate that estradiol status impacts working memory function and, crucially, the direction of the effect depends on indices of baseline DA. Moreover, consistent with a DA cortical efficiency hypothesis, functional MRI revealed that inferred optimal DA was associated with reduced PFC activity sustained across task blocks and selectively enhanced PFC activity on trials with the greatest demand for cognitive control. The magnitude of PFC activity during high control trials was predictive of an individual's performance. These findings show that although estrogen, considered in isolation, may have unpredictable effects on cognitive performance, its influence is clarified when considered within a larger neuromodulatory framework. Given the clinical prevalence of dopaminergic drugs, understanding the relationship between estrogen and DA is essential for advancing women's health.

Estradiol synthesis and action at the synapse: evidence for "synaptocrine" signaling

Classically, the modulation of brain function and behavior by steroid hormones was linked exclusively to secretion by peripheral endocrine glands. Subsequently, steroid actions within the brain were shown dependent upon either synthesis and secretion by peripheral organs or by production within the CNS itself using peripheral sources of precursors. Discovery of the estrogen-synthetic enzyme aromatase in brain further bolstered the latter view and served as a catalyst for expanding concepts of neurosteroidogenesis. In parallel research, several steroids, including estradiol, were found to have rapid effects on neuronal excitability, partially explained by novel actions at neuronal membranes. Recent findings from multiple levels of analysis and labs necessitate an updated view on how steroids are delivered to neural circuits. There is now considerable evidence for expression of the aromatase enzyme within synaptic boutons in the vertebrate CNS. Furthermore, additional work now directly couples rapid regulation of neuroestrogen synthesis with neurophysiological and behavioral outcomes. In this review we summarize evidence for targeted and acute synaptic estrogen synthesis and perisynaptic estrogen actions in the CNS of songbirds. We evaluate these findings in the context of criteria associated with classic neuromodulatory signaling. We term this novel form of signaling "synaptocrine," and discuss its implications.

Inactivation or inhibition of neuronal activity in the medial prefrontal cortex largely reduces pup retrieval and grouping in maternal rats

Previous research suggests that the maternal medial prefrontal cortex (mPFC) may play a role in maternal care and that cocaine sensitization before pregnancy can affect neuronal activity within this region. The present work was carried out to test whether the mPFC does actually play a role in the expression of maternal behaviors in the rats and to understand what specific behaviors this cortical area may modulate. In the first experiment, tetrodotoxin (TTX) was used to chemically inactivate the mPFC during tests for maternal behavior latencies. Lactating rats were tested on postpartum days 7-9. The results of this first experiment indicate that there is a large effect of TTX-induced inactivation on retrieval behavior latencies. TTX nearly abolished the expression of maternal retrieval of pups without significantly impairing locomotor activity. In the second experiment, GABA-mediated inhibition was used to test maternal behavior latencies and durations of maternal and other behaviors in postpartum dams. In agreement with experiment 1, it was observed that dams capable of retrieving are rendered incapable by inhibition in the mPFC. GABA-mediated inhibition in the mPFC largely reduced retrieval without altering other indices of maternal care and non-specific behavior such as ambulation time, self-grooming, and inactivity. Moreover, in both experiments, dams were able to establish contact with pups within seconds. The overall results indicate that the mPFC may play an active role in modulating maternal care, particularly retrieval behavior. External factors that affect the function of the frontal cortical site may result in significant impairments in maternal goal-directed behavior as reported in our earlier work.

Sex differences in the adolescent brain

Adolescence is a time of increased divergence between males and females in physical characteristics, behavior, and risk for psychopathology. Here we will review data regarding sex differences in brain structure and function during this period of the lifespan. The most consistent sex difference in brain morphometry is the 9-12% larger brain size that has been reported in males. Individual brain regions that have most consistently been reported as different in males and females include the basal ganglia, hippocampus, and amygdala. Diffusion tensor imaging and magnetization transfer imaging studies have also shown sex differences in white matter development during adolescence. Functional imaging studies have shown different patterns of activation without differences in performance, suggesting male and female brains may use slightly different strategies for achieving similar cognitive abilities. Longitudinal studies have shown sex differences in the trajectory of brain development, with females reaching peak values of brain volumes earlier than males. Although compelling, these sex differences are present as group averages and should not be taken as indicative of relative capacities of males or females.

Vertebrate sex steroid receptors: evolution, ligands, and neurodistribution

This review focuses on our current understanding of vertebrate sex steroid receptors, with an emphasis on their evolutionary relationships. These relationships are discussed based on nucleotide and amino acid sequence data, which provide clues to the process by which structure-function relations have originated, evolved, and been maintained over time. The importance of the distribution of sex steroid receptors in the vertebrate brain is discussed using the example of androgen receptor sites and their relatively conserved localizations in the vertebrate brain.

Gonadectomy negatively impacts social behavior of adolescent male primates

Social behavior changes dramatically during primate adolescence. However, the extent to which testosterone and other gonadal hormones are necessary for adolescent social behavioral development is unknown. In this study, we determined that gonadectomy significantly impairs social dominance in naturalistic settings and changes reactions to social stimuli in experimental settings. Rhesus macaques were castrated (n= 6) or sham operated (n=6) at age 2.4 years, group-housed for 2 years, and ethograms were collected weekly. During adolescence the gonadally intact monkeys displayed a decrease in subordinate behaviors and an increase in dominant behaviors, which ultimately related to a rise in social status and rank in the dominance hierarchy. We measured monkey's reactions to emotional faces (fear, threat, neutral) of conspecifics of three ages (adult, peer, infant). Intact monkeys were faster to retrieve a treat in front of a threatening or infant face, while castrated monkeys did not show a differential response to different emotional faces or ages. No group difference in reaction to an innate fear-eliciting object (snake) was found. Approach and proximity responses to familiar vs unfamiliar conspecifics were tested, and intact monkeys spent more time proximal to a novel conspecific as compared to castrates who tended to spend more time with a familiar conspecific. No group differences in time spent with novel or familiar objects were found. Thus, gonadectomy resulted in the emergence of significantly different responses to social stimuli, but not non-social stimuli. Our work suggests that intact gonads, which are needed to produce adolescent increases in circulating testosterone, impact social behavior during adolescences in primates.

Transcriptional interaction of an estrogen receptor splice variant and ErbB4 suggests convergence in gene susceptibility pathways in schizophrenia

Mounting evidence from clinical and basic research suggests that estrogen signaling may be altered in the brains of people with schizophrenia. Previously, we found that DNA sequence variation in the estrogen receptor (ER) alpha gene, lower ERalpha mRNA levels, and/or blunted ERalpha signaling is associated with schizophrenia. In this study, we asked whether the naturally occurring truncated ERalpha isoform, Delta7, which acts as a dominant negative, can attenuate gene expression induced by the wild-type (WT) receptor in an estrogen-dependent manner in neuronal (SHSY5Y) and non-neuronal (CHOK1 and HeLa) cells. In addition, we determined the extent to which ERalpha interacts with NRG1-ErbB4, a leading schizophrenia susceptibility pathway. Reductions in the transcriptionally active form of ErbB4 comprising the intracytoplasmic domain (ErbB4-ICD) have been found in schizophrenia, and we hypothesized that ERalpha and ErbB4 may converge to control gene expression. In the present study, we show that truncated Delta7-ERalpha attenuates WT-ERalpha-driven gene expression across a wide range of estrogen concentrations in cells that express functional ERalpha at base line or upon co-transfection of full-length ERalpha. Furthermore, we find that ErbB4-ICD can potentiate the transcriptional activity of WT-ERalpha at EREs in two cell lines and that this potentiation effect is abolished by the presence of Delta7-ERalpha. Immunofluorescence microscopy revealed nuclear co-localization of WT-ERalpha, Delta7-ERalpha, and ErbB4-ICD, whereas immunoprecipitation assays showed direct interaction. Our findings demonstrate convergence between ERalpha and ErbB4-ICD in the transcriptional control of ERalpha-target gene expression and suggest that this may represent a convergent pathway that may be disrupted in schizophrenia.