Sex differences in the brain: a whole body perspective

Exploring the material basis and molecular targets of Changma Xifeng tablet in treating Tourette syndrome: an integrative approach of network pharmacology and miRNA analysis

This study was to investigate the mechanism of Changma Xifeng tablet, a traditional Chinese medicine in the treatment of Tourette syndrome. Network pharmacology was utilized to pinpoint blood-entering constituents of Changma Xifeng and explore their potential targets. Additionally, differential microRNA expression analysis was conducted to predict Tourette syndrome-associated targets, complemented by molecular docking and dynamics simulations to support the interactions of the active compounds with these targets. The study identified 98 common targets between Changma Xifeng and Tourette syndrome, which may be involved in the treatment process. A protein-protein interaction network and a drug-active ingredient-disease target network highlighted the formulation's multi-component, multi-target therapeutic approach. Eight pivotal targets-AR, GRM5, MET, RORA, HTR2A, CNR1, PDE4B, and TOP1-were identified at the intersection of microRNA and drug targets. Molecular docking revealed 12 complexes with favorable binding energies below - 7 kcal/mol, specifically: AR with Alfacalcidol, TOP1 with Albiflorin, GRM5 with Arachidic Acid, GRM5 with Palmitic Acid, AR with Arachidic Acid, AR with 2-Hydroxyoctadecanoic Acid, RORA with Pinellic Acid, RORA with Palmitic Acid, AR with Acoronene, AR with Epiacoronene, AR with 4,4'-Methylenediphenol, and HTR2A with Calycosin. Our molecular docking and molecular dynamics simulations suggest potential stable interactions between the formulation's active components and target proteins. These computational methods provide a preliminary theoretical framework that will guide our future experimental work. The study provides a scientific rationale for the use of traditional Chinese medicine in Tourette syndrome management and offers new insights for drug development.

Vocal Fold Injury Produces Similar Biomechanical Outcomes in Male and Female Rabbits

OBJECTIVE

Sex differences in response to trauma and physiologic stressors have been identified in numerous organ systems but have not yet been defined in the larynx. The objective of this study was to develop an endoscopic vocal fold injury model in rabbits and to compare structural and functional outcomes between male and female subjects.

STUDY DESIGN

Basic science study.

METHODS

Two male and two female rabbits underwent unilateral endoscopic cordectomy. Animals were intubated with a size 3-0 neonatal endotracheal tube, and laryngoscopy was performed with a 4 mm Hopkins rod telescope. While visualizing, a 2 mm cupped forceps grasped and resected the mid-membranous portion of the right true vocal fold. Larynges were then harvested after 8weeks. Excised larynx phonation with high-speed videography and kymography was used to assess vibrational quality. Tissue elastic (Young's) modulus was measured by indentation.

RESULTS

Injured larynges phonated with fundamental frequencies between 237-415 Hz. In both males and females, the scarred vocal fold exhibited an increased Young's modulus compared to the contralateral nonoperated vocal fold. There were no notable differences in glottal closure pattern or vocal fold oscillation symmetry between sexes.

CONCLUSION

We have demonstrated a model for vocal fold scarring in rabbits. Vibrational and structural outcomes were similar between the examined male and female larynges.

Do Sex and Gender Have Separate Identities?

The largely binary nature of biological sex and its conflation with the socially constructed concept of gender has created much strife in the last few years. The notion of gender identity and its differences and similarities with sex have fostered much scientific and legal confusion and disagreement. Settling the debate can have significant repercussions for science, medicine, legislation, and people's lives. The present review addresses this debate though different levels of analysis (i.e., genetic, anatomical, physiological, behavioral, and sociocultural), and their implications and interactions. We propose a rationale where both perspectives coexist, where diversity is the default, establishing a delimitation to the conflation between sex and gender, while acknowledging their interaction. Whereas sex in humans and other mammals is a biological reality that is largely binary and based on genes, chromosomes, anatomy, and physiology, gender is a sociocultural construct that is often, but not always, concordant with a person' sex, and can span a multitude of expressions.

Sex differences in visuospatial cognition- a female advantage in jigsaw puzzle solving

Mentally visualizing objects, understanding relationships between two- or three- dimensional objects, and manipulating objects in space are some examples of visuospatial abilities. Numerous studies have shown that male participants outperform female participants in visuospatial tasks, particularly in mental rotation. One exception is solving jigsaw puzzles. Performance by seven- to eight-year-old girls was found to be superior to that of boys of the same age (Kocijan et al. 2017). No study, however, has confirmed this finding in an adult population, where sex differences are often detectable. Seventy-nine young adult participants were given four different jigsaw puzzles and the Shepard and Metzler mental rotation test (MRT) with two main goals: First, to investigate possible sex differences in jigsaw puzzle solving, and second, to explore a potential relationship between mental rotation and jigsaw puzzle solving. We hypothesized that female participants would outperform males in the jigsaw puzzles but males would outperform females in the MRT. The findings confirmed this hypothesis. Notably, the male performance in jigsaw puzzle solving was attributed to their sex and mediated by their higher MRT scores. These results yielded two key insights. First, they indicate a dissociation between these two visuospatial abilities, jigsaw puzzle solving and mental rotation; and second, female and male participants capitalize on their distinct cognitive strengths when solving visuospatial tasks.

Does acute aerobic exercise enhance selective attention, working memory, and problem-solving abilities in Alzheimer's patients? A sex-based comparative study

Introduction

The present study aimed to evaluate the effect of acute aerobic exercise on certain cognitive functions known to be affected by Alzheimer's disease (AD), with a particular emphasis on sex differences.

Methods

A total of 53 patients, with a mean age of 70.54 ± 0.88 years and moderate AD, voluntarily participated in the study. Participants were randomly assigned to two groups: the experimental group (EG), which participated in a 20-min moderate-intensity cycling session (60% of the individual maximum target heart rate recorded at the end of the 6-min walk test); and the control group (CG), which participated in a 20-min reading activity. Cognitive abilities were assessed before and after the physical exercise or reading session using the Stroop test for selective attention, the forward and backward digit span test for working memory, and the Tower of Hanoi task for problem-solving abilities.

Results

At baseline, both groups had comparable cognitive performance (p > 0.05 in all tests). Regardless of sex, aerobic acute exercise improved attention in the Stroop test (p < 0.001), enhanced memory performance in both forward (p < 0.001) and backward (p < 0.001) conditions, and reduced the time required to solve the problem in the Tower of Hanoi task (p < 0.001). No significant differences were observed in the number of movements. In contrast, the CG did not significantly improve after the reading session for any of the cognitive tasks (p > 0.05). Consequently, the EG recorded greater performance improvements than the CG in most cognitive tasks tested (p < 0.0001) after the intervention session.

Discussion

These findings demonstrate that, irrespective to sex, a single aerobic exercise session on an ergocycle can improve cognitive function in patients with moderate AD. The results suggest that acute aerobic exercise enhances cognitive function similarly in both female and male patients, indicating promising directions for inclusive therapeutic strategies.

Beyond the binary: Characterizing the relationships between sex and neuropeptide receptor binding density measures in the rat brain

Sex differences exist in numerous parameters of the brain. Yet, sex-related factors are part of a large set of variables that interact to affect many aspects of brain structure and function. This raises questions regarding how to interpret findings of sex differences at the level of single brain measures and the brain as a whole. In the present study, we reanalyzed two datasets consisting of measures of oxytocin, vasopressin V1a, and mu opioid receptor binding densities in multiple brain regions in rats. At the level of single brain measures, we found that sex differences were rarely dimorphic and were largely persistent across estrous stage and parental status but not across age or context. At the level of aggregates of brain measures showing sex differences, we tested whether individual brains are 'mosaics' of female-typical and male-typical measures or are internally consistent, having either only female-typical or only male-typical measures. We found mosaicism for measures showing overlap between females and males. Mosaicism was higher a) with a larger number of measures, b) with smaller effect sizes of the sex difference in these measures, and c) in rats with more diverse life experiences. Together, these results highlight the limitations of the binary framework for interpreting sex effects on the brain and suggest two complementary pathways to studying the contribution of sex to brain function: (1) focusing on measures showing dimorphic and persistent sex differences and (2) exploring the relations between specific brain mosaics and specific endpoints.

Hormone profiles of the African pygmy mouse Mus minutoides, a species with XY female sex reversal

In mammals, most sex differences in phenotype are controlled by gonadal hormones, but recent work on transgenic mice has shown that sex chromosomes can have a direct influence on sex-specific behaviors. In this study, we take advantage of the naturally occurring sex reversal in a mouse species, Mus minutoides, to investigate for the first time the relationship between sex chromosomes, hormones, and behaviors in a wild species. In this model, a feminizing variant of the X chromosome, named X*, produces three types of females with different sex chromosome complements (XX, XX*, and X*Y), associated with alternative behavioral phenotypes, while all males are XY. We thus compared the levels of three major circulating steroid hormones (testosterone, corticosterone, and estradiol) in the four sex genotypes to disentangle the influence of sex chromosomes and sex hormones on behavior. First, we did not find any difference in testosterone levels in the three female genotypes, although X*Y females are notoriously more aggressive. Second, in agreement with their lower anxiety-related behaviors, X*Y females and XY males display lower baseline corticosterone concentration than XX and XX* females. Instead of a direct hormonal influence, this result rather suggests that sex chromosomes may have an impact on the baseline corticosterone level, which in turn may influence behaviors. Third, estradiol concentrations do not explain the enhanced reproductive performance and maternal care behavior of the X*Y females compared to the XX and XX* females. Overall, this study highlights that most of the behaviors varying along with sex chromosome complement of this species are more likely driven by genetic factors rather than steroid hormone concentrations.

Comprehensive review on sexual dimorphism to improve scalp acupuncture in nervous system disease

BACKGROUND

With the development of modern medicine, the Traditional Chinese Medicine (TCM) combined with western medicine began to be produced and applied. Scalp acupuncture (SA) as a Chinese medicine based on neurological theory, has a great advantage compared with TCM in the treatment of nervous system diseases.

METHOD

In this paper, we analyze the physiological and pathological manifestations of sexual dimorphism (SD) to illustrate the necessity of SD treatment. In addition, we review the factors that can affect SD and analyze in physiological structure, function, and pathological neurons. Diseases (pathological basis, pathological manifestations, and incidence) and factors leading to gender differences, which to analyze the possibility of gender differences in SA.

RESULT

Furthermore, we creatively a new insight of SD-SA and provide the complete SD treatment cases on the basis of the existing SA in different kinds of diseases including stroke, migraine, attention deficit hyperactivity disorder (ADHD), and depression.

CONCLUSION

In summary, we believe that it is feasible to improve the clinical effectiveness of SA, which is able to promote the development of SA, and then provides an actionable evidence for the promotion of precision medicine in the future.

HIV/AIDS-related knowledge and attitudes towards HIV rapid testing among Chinese college students: Findings from a cross-sectional survey

Data of the awareness level of college students in China about Human Immunodeficiency Virus/Acquired Immune Deficiency Syndrome (HIV/AIDS) knowledge are limited. Also, the attitudes towards HIV rapid testing remain unknown among this population. Therefore, this study aimed to evaluate the awareness of HIV/AIDS knowledge and attitudes towards HIV rapid testing among Chinese college students. An online cross-sectional survey was performed in 2020. A total of 1,474 participants were finally included. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to examine associated factors for the cognitive levels and attitudes by multivariable logistic regression. Spearman rank correlation was used to examine the relationship between HIV/AIDS-related knowledge and attitudes. About 91% of participants had a high cognitive level on HIV/AIDS-related knowledge and 84.7% held a positive attitude towards the HIV rapid testing. Postgraduates (OR = 1.75, 95% CI: 1.16-2.66) and females (OR = 1.69, 95% CI: 1.13-2.52) were more knowledgeable. Females' attitudes towards the HIV rapid testing were more positive (OR = 1.91, 95% CI: 1.40-2.62). Moreover, the knowledge was positively correlated with attitudes towards the rapid testing (Spearman r = 0.14, p < 0.001). In conclusion, the Chinese college students had a high cognitive level on HIV/AIDS knowledge and positive attitudes towards HIV rapid testing. A high cognitive level of knowledge paralleled with positive attitudes. Special strategies such as tailored education via HIV/AIDS curriculum and awareness campaigns are needed for undergraduates and male students to minimize the gaps regarding HIV/AIDS-related knowledge and attitudes.

Sex-differences in proteasome-dependent K48-polyubiquitin signaling in the amygdala are developmentally regulated in rats

BACKGROUND

Sex differences have been observed in several brain regions for the molecular mechanisms involved in baseline (resting) and memory-related processes. The ubiquitin proteasome system (UPS) is a major protein degradation pathway in cells. Sex differences have been observed in lysine-48 (K48)-polyubiquitination, the canonical degradation mark of the UPS, both at baseline and during fear memory formation within the amygdala. Here, we investigated when, how, and why these baseline sex differences arise and whether both sexes require the K48-polyubiquitin mark for memory formation in the amygdala.

METHODS

We used a combination of molecular, biochemical and proteomic approaches to examine global and protein-specific K48-polyubiquitination and DNA methylation levels at a major ubiquitin coding gene (Uba52) at baseline in the amygdala of male and female rats before and after puberty to determine if sex differences were developmentally regulated. We then used behavioral and genetic approaches to test the necessity of K48-polyubiquitination in the amygdala for fear memory formation.

RESULTS

We observed developmentally regulated baseline differences in Uba52 methylation and total K48-polyubiquitination, with sexual maturity altering levels specifically in female rats. K48-polyubiquitination at specific proteins changed across development in both male and female rats, but sex differences were present regardless of age. Lastly, we found that genetic inhibition of K48-polyubiquitination in the amygdala of female, but not male, rats impaired fear memory formation.

CONCLUSIONS

These results suggest that K48-polyubiquitination differentially targets proteins in the amygdala in a sex-specific manner regardless of age. However, sexual maturity is important in the developmental regulation of K48-polyubiquitination levels in female rats. Consistent with these data, K48-polyubiquitin signaling in the amygdala is selectively required to form fear memories in female rats. Together, these data indicate that sex-differences in baseline K48-polyubiquitination within the amygdala are developmentally regulated, which could have important implications for better understanding sex-differences in molecular mechanisms involved in processes relevant to anxiety-related disorders such as post-traumatic stress disorder (PTSD).

Androgen action on myogenesis throughout the lifespan; comparison with neurogenesis

Androgens' pleiotropic actions in promoting sex differences present not only a challenge to providing a comprehensive account of their function, but also an opportunity to gain insights by comparing androgenic actions across organ systems. Although often overlooked by neuroscientists, skeletal muscle is another androgen-responsive organ system which shares with the nervous system properties of electrochemical excitability, behavioral relevance, and remarkable capacity for adaptive plasticity. Here we review androgenic regulation of mitogenic plasticity in skeletal muscle with the goal of identifying areas of interest to those researching androgenic mechanisms mediating sexual differentiation of neurogenesis. We use an organizational-activational framework to relate broad areas of similarity and difference between androgen effects on mitogenesis in muscle and brain throughout the lifespan, from early organogenesis, through pubertal organization, adult activation, and aging. The focus of the review is androgenic regulation of muscle-specific stem cells (satellite cells), which share with neural stem cells essential functions in development, plasticity, and repair, albeit with distinct, muscle-specific features. Also considered are areas of paracrine and endocrine interaction between androgen action on muscle and nervous system, including mediation of neural plasticity of innervating and distal neural populations by muscle-produced trophic factors.

A neural substrate of sex-dependent modulation of motivation

While there is emerging evidence of sex differences in decision-making behavior, the neural substrates that underlie such differences remain largely unknown. Here we demonstrate that in mice performing a value-based decision-making task, while choices are similar between the sexes, motivation to engage in the task is modulated by action value more strongly in females than in males. Inhibition of activity in anterior cingulate cortex (ACC) neurons that project to the dorsomedial striatum (DMS) preferentially disrupts this relationship between value and motivation in females, without affecting choice in either sex. In line with these effects, in females compared to males, ACC-DMS neurons have stronger representations of negative outcomes and more neurons are active when the value of the chosen option is low. By contrast, the representation of each choice is similar between the sexes. Thus, we identify a neural substrate that contributes to sex-specific modulation of motivation by value.

Sex matters: The impact of oxytocin on healthy conditions and psychiatric disorders

Oxytocin (OT) is involved in the regulation of physiological processes and emotional states, with increasing evidence for its beneficial actions being mediated by the autonomic and immune systems. Growing evidence suggests that OT plays a role in the pathophysiology of different psychiatric disorders. Given the limited information in humans the aim of this study was to retrospectively explore plasma OT levels in psychiatric patients, particularly focusing on sex-related differences, as compared with healthy controls. The patients studied here were divided into three groups diagnosed with obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD) or major depressive disorder (MDD). Plasma OT levels were significantly different between healthy men and women, with the latter showing higher values, while none of the three psychiatric groups showed sex-related differences in the parameters measured here. The intergroup analyses showed that the OT levels were significantly higher in OCD, lower in PTSD and even more reduced in MDD patients than in healthy subjects. These differences were also confirmed when gender was considered, with the exception of PTSD men, in whom OT levels were similar to those of healthy men. The present results indicated that OT levels were higher amongst healthy women than men, while a sex difference was less apparent or reversed in psychiatric patients. Reductions in sex differences in psychopathologies may be related to differential vulnerabilities in processes associated with basic adaptive and social functions.

Experimental setting and protocol impact human colour preference assessment under multiple white light sources

Psychophysical experiment is the most straightforward and reliable way to investigate the impact of lighting on visual colour perception. In this study, a series of experiments were conducted in order to investigate the impact of experimental setting and protocol on the obtained conclusions in visual tests regarding human preference on object colour in applied lighting research. Four light sources of 5,500 K, with Duv values of -0.01, 0, 0.015, and 0.02, were used to illuminate different kinds of objects including blue jeans, fruit and vegetables, bread, artware, fresh pork, and skin tones. The use of those experimental light sources and objects was to provide control study for our former research by deliberately changing certain experimental setup and protocol and testify the robustness of our former conclusions. The results show that some of our former findings, like the dominant impact of lighting on colour preference, the visual cognition process of light booth experiments as well as the correlation between the whiteness of lighting and colour preference, were found to be valid in typical light booth experiment. The impact of experimental object turned out to be much stronger under the newly designed protocol and the significance of sex difference on colour preference judgment was found to vary with experimental setup. These new findings highlight the influence of experimental setting and protocol on the validity of research findings, which we believe, could provide deeper understanding for the psychophysical results of current colour preference studies.

Sex differences in the human brain: a roadmap for more careful analysis and interpretation of a biological reality

The presence, magnitude, and significance of sex differences in the human brain are hotly debated topics in the scientific community and popular media. This debate is largely fueled by studies containing strong, opposing conclusions: either little to no evidence exists for sex differences in human neuroanatomy, or there are small-to-moderate differences in the size of certain brain regions that are highly reproducible across cohorts (even after controlling for sex differences in average brain size). Our Commentary uses the specific comparison between two recent large-scale studies that adopt these opposing views-namely the review by Eliot and colleagues (2021) and the direct analysis of ~ 40k brains by Williams and colleagues (2021)-in an effort to clarify this controversy and provide a framework for conducting this research. First, we review observations that motivate research on sex differences in human neuroanatomy, including potential causes (evolutionary, genetic, and environmental) and effects (epidemiological and clinical evidence for sex-biased brain disorders). We also summarize methodological and empirical support for using structural MRI to investigate such patterns. Next, we outline how researchers focused on sex differences can better specify their study design (e.g., how sex was defined, if and how brain size was adjusted for) and results (by e.g., distinguishing sexual dimorphisms from sex differences). We then compare the different approaches available for studying sex differences across a large number of individuals: direct analysis, meta-analysis, and review. We stress that reviews do not account for methodological differences across studies, and that this variation explains many of the apparent inconsistencies reported throughout recent reviews (including the work by Eliot and colleagues). For instance, we show that amygdala volume is consistently reported as male-biased in studies with sufficient sample sizes and appropriate methods for brain size correction. In fact, comparing the results from multiple large direct analyses highlights small, highly reproducible sex differences in the volume of many brain regions (controlling for brain size). Finally, we describe best practices for the presentation and interpretation of these findings. Care in interpretation is important for all domains of science, but especially so for research on sex differences in the human brain, given the existence of broad societal gender-biases and a history of biological data being used justify sexist ideas. As such, we urge researchers to discuss their results from simultaneously scientific and anti-sexist viewpoints.

Teaching About Sex and Gender in Neuroscience: More Than Meets the "XY"

Offering courses on the neuroscience of sex and gender can help support an inclusive curriculum in neuroscience. At the same time, developing and teaching such courses can be daunting to even the most enthusiastic educators, given the subject's complexities, nuances, and the difficult conversations that it invites. The authors of this article have all developed and taught such courses from different perspectives. Our aim is to provide educators with an overview of important conceptual topics as well as a comprehensive, but non-exhaustive, guide to resources for teaching about sex/gender in neuroscience based on our collective experience teaching courses on the topic. After defining vital terminology and briefly reviewing the biology of sex and sex determination, we describe some common topics within the field and contrast our current nuanced understandings from outdated misconceptions in the field. We review how (mis)representation of the neuroscience of sex/gender serves as a case study for how scientific results are communicated and disseminated. We consider how contextualization of sex/gender neuroscience research within a broader historical and societal framework can give students a wider perspective on the enterprise of science. Finally, we conclude with a brief discussion on how to choose learning goals for your course and implementation notes.

Aerobic exercise improves episodic memory in late adulthood: a systematic review and meta-analysis

Background

Aerobic exercise remains one of the most promising approaches for enhancing cognitive function in late adulthood, yet its potential positive effects on episodic memory remain poorly understood and a matter of intense debate. Prior meta-analyses have reported minimal improvements in episodic memory following aerobic exercise but have been limited by restrictive inclusion criteria and infrequent examination of exercise parameters.

Methods

We conducted a meta-analysis of randomized controlled trials to determine if aerobic exercise influences episodic memory in late adulthood (M = 70.82 years) and examine possible moderators. Thirty-six studies met inclusion criteria, representing data from 2750 participants.

Results

Here we show that aerobic exercise interventions are effective at improving episodic memory (Hedges'g = 0.28; p = 0.002). Subgroup analyses revealed a moderating effect of age (p = 0.027), with a significant effect for studies with a mean age between 55-68 but not 69-85. Mixed-effects analyses demonstrated a positive effect on episodic memory among studies with a high percentage of females (65-100%), participants with normal cognition, studies reporting intensity, studies with a no-contact or nonaerobic physical activity control group, and studies prescribing >3900 total minutes of activity (range 540-8190 min).

Conclusions

Aerobic exercise positively influences episodic memory among adults ≥55 years without dementia, with larger effects observed among various sample and intervention characteristics-the clearest moderator being age. These results could have far-reaching clinical and public health relevance, highlighting aerobic exercise as an accessible, non-pharmaceutical intervention to improve episodic memory in late adulthood.

Human studies of mitochondrial biology demonstrate an overall lack of binary sex differences: A multivariate meta-analysis

Mitochondria are maternally inherited organelles that play critical tissue-specific roles, including hormone synthesis and energy production, that influence human development, health, and aging. However, whether mitochondria from women and men exhibit consistent biological differences remains unclear, representing a major gap in knowledge. This meta-analysis systematically examined four domains and six subdomains of mitochondrial biology (total 39 measures), including mitochondrial content, respiratory capacity, reactive oxygen species (ROS) production, morphometry, and mitochondrial DNA copy number. Standardized effect sizes (Hedge's g) of sex differences were computed for each measure using data in 2258 participants (51.5% women) from 50 studies. Only two measures demonstrated aggregate binary sex differences: higher mitochondrial content in women's WAT and isolated leukocyte subpopulations (g = 0.20, χ² p = .01), and higher ROS production in men's skeletal muscle (g = 0.49, χ² p < .0001). Sex differences showed weak to no correlation with age or BMI. Studies with small sample sizes tended to overestimate effect sizes (r = -.17, p < .001), and sex differences varied by tissue examined. Our findings point to a wide variability of findings in the literature concerning possible binary sex differences in mitochondrial biology. Studies specifically designed to capture sex- and gender-related differences in mitochondrial biology are needed, including detailed considerations of physical activity and sex hormones.

Translating the Transcriptome: Sex Differences in the Mechanisms of Depression and Stress, Revisited

The past decade has produced a plethora of studies examining sex differences in the transcriptional profiles of stress and mood disorders. As we move forward from accepting the existence of extensive molecular sex differences in the brain to exploring the purpose of these sex differences, our approach must become more systemic and less reductionist. Earlier studies have examined specific brain regions and/or cell types. To use this knowledge to develop the next generation of personalized medicine, we need to comprehend how transcriptional changes across the brain and/or the body relate to each other. We provide an overview of the relationships between baseline and depression/stress-related transcriptional sex differences and explore contributions of preclinically identified mechanisms and their impacts on behavior.

Pharmacokinetic and tissue distribution study of ZCY-15, a novel compound against Alzheimer's disease, in rats by liquid chromatography-tandem mass spectrometry

ZCY-15, N-(3,5-dimethyladamatan-1-yl)-N-(3-methylphenyl) urea, is a candidate compound synthesized from the memantine structure and has been shown to be remarkably effective in treating Alzheimer's disease. To elucidate the pharmacokinetics and tissue distribution of ZCY-15 in rats after oral and intravenous administration, a rapid and selective LC-MS/MS method was established for the determination of ZCY-15 in rat plasma and tissues. According to the dissolution characteristics, the plasma samples were prepared by acetonitrile protein precipitation and carbamazepine was selected as the internal standard (IS). After separation by gradient elution using Aqela Venusil ASB C₈ (2.1 × 50 mm, 3 µm), the pretreated samples were analyzed in MRM mode in positive ESI mode. The effective detection limit of this method was 1.95-1000 ng·mL^-1. Tissue samples were collected from the heart, liver, spleen, lung, kidney, fat, muscle, brain, hippocampus, testicles or ovaries, large intestine, small intestine and stomach. The proposed method demonstrated fine precision and accuracy for analyzing ZCY-15 in selected tissues within the concentration range of standard liquid chromatography-tandem mass spectrometry. The whole analysis time was 3.6 min per sample. After oral administration, the blood and tissue concentrations of ZCY-15 in female rats were significantly higher than those in male rats. The clearance rate of ZCY-15 in female rats was lower than that in male rats. The results confirmed that there were gender differences. It has been shown that ZCY-15 could pass through the blood-brain barrier and was highly concentrated in the hippocampus. We established the first bioanalytical method to quantify ZCY-15 in rodent bio-samples for ongoing pharmacokinetic and tissue distribution studies, and the results were expected to lay foundation for the subsequent studies.

Sex and brain region-specific regulation of serotonin transporter activity in synaptosomes in guanine nucleotide-binding protein G(q) alpha knockout mice

The regulation of the serotonin transporter (SERT) by guanine nucleotide-binding protein alpha (Gα) q was investigated using Gαq knockout mice. In the absence of Gαq, SERT-mediated uptake of 5-hydroxytryptamine (5HT) was enhanced in midbrain and frontal cortex synaptosomes, but only in female mice. The mechanisms underlying this sexual dimorphism were investigated using quantitative western blot analysis revealing brain region-specific differences. In the frontal cortex, SERT protein expression was decreased in male knockout mice, seemingly explaining the sex-dependent variation in SERT activity. The differential expression of Gαi1 in female mice contributes to the sex differences in the midbrain. In fact, Gαi1 levels inversely correlate with 5HT uptake rates across both sexes and genotypes. Likely due to differential SERT regulation as well as sex differences in the expression of tryptophan hydroxylase 2, Gαq knockout mice also displayed sex- and genotype-dependent alterations in total 5HT tissue levels as determined by high-performance liquid chromatography. Gαq inhibitors, YM-254890 and BIM-46187, differentially affected SERT activity in both, synaptosomes and cultured cells. YM-254890 treatment mimicked the effect of Gαq knockout in the frontal cortex. BIM-46187, which promotes the nucleotide-free form of Gα proteins, substantially inhibited 5HT uptake, prompting us to hypothesise that Gαq interacts with SERT similarly as with G-protein-coupled receptors and inhibits SERT activity by modulating transport-associated conformational changes. Taken together, our findings reveal a novel mechanism of SERT regulation and impact our understanding of sex differences in diseases associated with dysregulation of serotonin transmission, such as depression and anxiety.

Examining the relationships among adolescent health behaviours, prefrontal function, and academic achievement using fNIRS

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Prior studies document effects of lifestyle behaviors on the brain and academics.

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Among adolescents we found that activity and eating both predict task performance.

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Activity also predicts functional activation in the right lateral dlPFC, but not grades.

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Substance use predicted worse grades but not brain-related mediators.

Several adolescent health behaviours have been hypothesized to improve academic performance via their beneficial impact on cognitive control and functional aspects of the prefrontal cortex (PFC). The primary objective of this study is to examine the association between lifestyle behaviours and academic performance in a sample of adolescents, and to examine the extent to which activity within the PFC and behavioural indices of inhibition may mediate this relationship. Sixty-seven adolescents underwent two study sessions five days apart. Sleep and physical activity were measured using wrist-mounted accelerometry; eating habits, substance use and academic achievement were measured by self-report. Prefrontal function was quantified by Multi-Source Interference Task (MSIT) performance, and task-related activity via functional near-infrared spectroscopy (fNIRS). Higher levels of physical activity predicted higher MSIT accuracy scores (β = .321, ρ = 0.019) as well as greater activation within the right dlPFC (b = .008, SE = .004, ρ = .0322). Frequency of fast-food consumption and substance use were negatively associated with MSIT accuracy scores (β = −0.307, ρ = .023) and Math grades (b = −3.702, SE = 1.563, ρ = .022), respectively. Overall, the results of this study highlight the importance of lifestyle behaviours as predictors of prefrontal function and academic achievement in youth.

Stability analysis of clustering of Norris' visual analogue scale: Applying the consensus clustering approach

ABSTRACT

Visual analogue scales are widely used to measure subjective responses. Norris' 16 visual analogue scales (N_VAS) measure subjective feelings of alertness and mood. Up to now, different scientists have clustered items of N_VAS into different ways and Bond and Lader's way has been the most frequently used in clinical research. However, there are concerns about the stability of this clustering over different subject samples and different drug classes. The aim of this study was to test whether Bond and Lader's clustering was stable in terms of subject samples and drug effects. Alternative clustering of N_VAS was tested.Data from studies with 3 types of drugs: cannabinoid receptor agonist (delta-9-tetrahydrocannabinol [THC]), muscarinic antagonist (scopolamine), and benzodiazepines (midazolam and lorazepam), collected between 2005 and 2012, were used for this analysis. Exploratory factor analysis (EFA) was used to test the clustering algorithm of Bond and Lader. Consensus clustering was performed to test the stability of clustering results over samples and over different drug types. Stability analysis was performed using a three-cluster assumption, and then on other alternative assumptions.Heat maps of the consensus matrix (CM) and density plots showed instability of the three-cluster hypothesis and suggested instability over the 3 drug classes. Two- and four-cluster hypothesis were also tested. Heat maps of the CM and density plots suggested that the two-cluster assumption was superior.In summary, the two-cluster assumption leads to a provably stable outcome over samples and the 3 drug types based on the data used.

Social isolation alters behavior, the gut-immune-brain axis, and neurochemical circuits in male and female prairie voles

The absence of social support, or social isolation, can be stressful, leading to a suite of physical and psychological health issues. Growing evidence suggests that disruption of the gut-immune-brain axis plays a crucial role in the negative outcomes seen from social isolation stress. However, the mechanisms remain largely unknown. The socially monogamous prairie vole (Microtus ochrogaster) has been validated as a useful model for studying negative effects of social isolation on the brain and behaviors, yet how the gut microbiome and central immune system are altered in isolated prairie voles are still unknown. Here, we utilized this social rodent to examine how social isolation stress alters the gut-immune-brain axis and relevant behaviors. Adult male and female prairie voles (n = 48 per sex) experienced social isolation or were cohoused with a same-sex cagemate (control) for six weeks. Thereafter, their social and anxiety-like behaviors, neuronal circuit activation, neurochemical expression, and microgliosis in key brain regions, as well as gut microbiome alterations from the isolation treatment were examined. Social isolation increased anxiety-like behaviors and impaired social affiliation. Isolation also resulted in sex- and brain region-specific alterations in neuronal activation, neurochemical expression, and microgliosis. Further, social isolation resulted in alterations to the gut microbiome that were correlated with key brain and behavioral measures. Our data suggest that social isolation alters the gut-immune-brain axis in a sex-dependent manner and that gut microbes, central glial cells, and neurochemical systems may play a critical, integrative role in mediating negative outcomes from social isolation.

Sex-Related Differential Whole-Brain Input Atlas of Locus Coeruleus Noradrenaline Neurons

As the most important organ in our bodies, the brain plays a critical role in deciding sex-related differential features; however, the underlying neural circuitry basis remains unclear. Here, we used a cell-type-specific rabies virus-mediated monosynaptic tracing system to generate a sex differences-related whole-brain input atlas of locus coeruleus noradrenaline (LC-NE) neurons. We developed custom pipelines for brain-wide comparisons of input sources in both sexes with the registration of the whole-brain data set to the Allen Mouse Brain Reference Atlas. Among 257 distinct anatomical regions, we demonstrated the differential proportions of inputs to LC-NE neurons in male and female mice at different levels. Locus coeruleus noradrenaline neurons of two sexes showed general similarity in the input patterns, but with differentiated input proportions quantitatively from major brain regions and diverse sub-regions. For instance, inputs to male LC-NE neurons were found mainly in the cerebrum, interbrain, and cerebellum, whereas inputs to female LC-NE neurons were found in the midbrain and hindbrain. We further found that specific subsets of nuclei nested within sub-regions contributed to overall sex-related differences in the input circuitry. Furthermore, among the totaled 123 anatomical regions with proportion of inputs >0.1%, we also identified 11 sub-regions with significant statistical differences of total inputs between male and female mice, and seven of them also showed such differences in ipsilateral hemispheres. Our study not only provides a structural basis to facilitate our understanding of sex differences at a circuitry level but also provides clues for future sexually differentiated functional studies related to LC-NE neurons.

Is Oxytocin "Nature's Medicine"?

Oxytocin is a pleiotropic, peptide hormone with broad implications for general health, adaptation, development, reproduction, and social behavior. Endogenous oxytocin and stimulation of the oxytocin receptor support patterns of growth, resilience, and healing. Oxytocin can function as a stress-coping molecule, an anti-inflammatory, and an antioxidant, with protective effects especially in the face of adversity or trauma. Oxytocin influences the autonomic nervous system and the immune system. These properties of oxytocin may help explain the benefits of positive social experiences and have drawn attention to this molecule as a possible therapeutic in a host of disorders. However, as detailed here, the unique chemical properties of oxytocin, including active disulfide bonds, and its capacity to shift chemical forms and bind to other molecules make this molecule difficult to work with and to measure. The effects of oxytocin also are context-dependent, sexually dimorphic, and altered by experience. In part, this is because many of the actions of oxytocin rely on its capacity to interact with the more ancient peptide molecule, vasopressin, and the vasopressin receptors. In addition, oxytocin receptor(s) are epigenetically tuned by experience, especially in early life. Stimulation of G-protein-coupled receptors triggers subcellular cascades allowing these neuropeptides to have multiple functions. The adaptive properties of oxytocin make this ancient molecule of special importance to human evolution as well as modern medicine and health; these same characteristics also present challenges to the use of oxytocin-like molecules as drugs that are only now being recognized. SIGNIFICANCE STATEMENT: Oxytocin is an ancient molecule with a major role in mammalian behavior and health. Although oxytocin has the capacity to act as a "natural medicine" protecting against stress and illness, the unique characteristics of the oxytocin molecule and its receptors and its relationship to a related hormone, vasopressin, have created challenges for its use as a therapeutic drug.

Multi-aspect testing and ranking inference to quantify dimorphism in the cytoarchitecture of cerebellum of male, female and intersex individuals: a model applied to bovine brains

The dimorphism among male, female and freemartin intersex bovines, focusing on the vermal lobules VIII and IX, was analyzed using a novel data analytics approach to quantify morphometric differences in the cytoarchitecture of digitalized sections of the cerebellum. This methodology consists of multivariate and multi-aspect testing for cytoarchitecture-ranking, based on neuronal cell complexity among populations defined by factors, such as sex, age or pathology. In this context, we computed a set of shape descriptors of the neural cell morphology, categorized them into three domains named size, regularity and density, respectively. The output and results of our methodology are multivariate in nature, allowing an in-depth analysis of the cytoarchitectonic organization and morphology of cells. Interestingly, the Purkinje neurons and the underlying granule cells revealed the same morphological pattern: female possessed larger, denser and more irregular neurons than males. In the Freemartin, Purkinje neurons showed an intermediate setting between males and females, while the granule cells were the largest, most regular and dense. This methodology could be a powerful instrument to carry out morphometric analysis providing robust bases for objective tissue screening, especially in the field of neurodegenerative pathologies.

Insulin and β-adrenergic receptors mediate lipolytic and anti-lipolytic signalling that is not altered by type 2 diabetes in human adipocytes

Control of fatty acid storage and release in adipose tissue is fundamental in energy homeostasis and the development of obesity and type 2 diabetes. We here take the whole signalling network into account to identify how insulin and β-adrenergic stimulation in concert controls lipolysis in mature subcutaneous adipocytes obtained from non-diabetic and, in parallel, type 2 diabetic women. We report that, and show how, the anti-lipolytic effect of insulin can be fully explained by protein kinase B (PKB/Akt)-dependent activation of the phosphodiesterase PDE3B. Through the same PKB-dependent pathway β-adrenergic receptor signalling, via cAMP and PI3Kα, is anti-lipolytic and inhibits its own stimulation of lipolysis by 50%. Through this pathway both insulin and β-adrenergic signalling control phosphorylation of FOXO1. The dose–response of lipolysis is bell-shaped, such that insulin is anti-lipolytic at low concentrations, but at higher concentrations of insulin lipolysis was increasingly restored due to inhibition of PDE3B. The control of lipolysis was not altered in adipocytes from diabetic individuals. However, the release of fatty acids was increased by 50% in diabetes due to reduced reesterification of lipolytically liberated fatty acids. In conclusion, our results reveal mechanisms of control by insulin and β-adrenergic stimulation — in human adipocytes — that define a network of checks and balances ensuring robust control to secure uninterrupted supply of fatty acids without reaching concentrations that put cellular integrity at risk. Moreover, our results define how selective insulin resistance leave lipolytic control by insulin unaltered in diabetes, while the fatty acid release is substantially increased.

Sex bias and omission in neuroscience research is influenced by research model and journal, but not reported NIH funding

Neuroscience research has historically demonstrated sex bias that favors male over female research subjects, as well as sex omission, which is the lack of reporting sex. Here we analyzed the status of sex bias and omission in neuroscience research published across six different journals in 2017. Regarding sex omission, 16% of articles did not report sex. Regarding sex bias, 52% of neuroscience articles reported using both males and females, albeit only 15% of articles using both males and females reported assessing sex as an experimental variable. Overrepresentation of the sole use of males compared to females persisted (26% versus 5%, respectively). Sex bias and omission differed across research models, but not by reported NIH funding status. Sex omission differed across journals. These findings represent the latest information regarding the complex status of sex in neuroscience research and illustrate the continued need for thoughtful and informed action to enhance scientific discovery.

Potential frameworks to support evaluation of mechanistic data for developmental neurotoxicity outcomes: A symposium report

A key challenge in systematically incorporating mechanistic data into human health assessments is that, compared to studies of apical health endpoints, these data are both more abundant (mechanistic studies routinely outnumber other studies by several orders of magnitude) and more heterogeneous (e.g. different species, test system, tissue, cell type, exposure paradigm, or specific assays performed). A structured decision-making process for organizing, integrating, and weighing mechanistic DNT data for use in human health risk assessments will improve the consistency and efficiency of such evaluations. At the Developmental Neurotoxicology Society (DNTS) 2016 annual meeting, a symposium was held to address the application of existing organizing principles and frameworks for evaluation of mechanistic data relevant to interpreting neurotoxicology data. Speakers identified considerations with potential to advance the use of mechanistic DNT data in risk assessment, including considering the context of each exposure, since epigenetics, tissue type, sex, stress, nutrition and other factors can modify toxicity responses in organisms. It was also suggested that, because behavior is a manifestation of complex nervous system function, the presence and absence of behavioral change itself could be used to organize the interpretation of multiple complex simultaneous mechanistic changes. Several challenges were identified with frameworks and their implementation, and ongoing research to develop these approaches represents an early step toward full evaluation of mechanistic DNT data for assessments.

Sexual Dimorphism in Drug Metabolism and Pharmacokinetics

Background:

Sex and gender-based differences are observed well beyond the sex organs and affect several physiological and biochemical processes involved in the metabolism of drug molecules. It is essential to understand not only the sex and gender-based differences in the metabolism of the drug but also the molecular mechanisms involved in the regulation of drug metabolism for avoiding sex-related adverse effects of drugs in the human.

Method:

The articles on the sex and gender-based differences in the metabolism of drug molecules were retrieved from the Pub Med database. The articles were classified into the metabolism of the drug molecule, gene expression regulation of drug-metabolizing enzymes, the effect of sex hormones on the metabolism of drug, expression of drugmetabolizing enzymes, etc.

Result:

Several drug molecules are known, which are metabolized differently in males and females. These differences in metabolism may be due to the genomic and non-genomic action of sex hormones. Several other drug molecules still require further evaluation at the molecular level regarding the sex and gender-based differences in their metabolism. Attention is also required at the effect of signaling cascades associated with the metabolism of drug molecules.

Conclusion:

Sex and gender-based differences in the metabolism of drugs exist at various levels and it may be due to the genomic and non-genomic action of sex hormones. Detailed understanding of the effect of sex and related condition on the metabolism of drug molecules will help clinicians to determine the effective therapeutic doses of drugs dependingon the condition of patient and disease.

Domain-specific contributions of biological sex and sex hormones to what, where and when components of episodic-like memory in adult rats

Episodic memory involves the integration and recall of discrete events that include information about what happened, where it happened and when it occurred. Episodic memory function is critical to daily life, and its dysfunction is both a first identifiable indicator and an enduring core feature of cognitive decline in ageing and in neuropsychiatric disorders including Alzheimer's disease and schizophrenia. Available evidence from human studies suggests that biological sex and sex hormones modulate episodic memory function in health and disease. However, knowledge of how this occurs is constrained by the limited availability and underutilization of validated animal models in investigating hormone impacts on episodic-like memory function. Here, adult female, adult male and gonadally manipulated adult male rats were tested on the what-where-when episodic-like memory task to determine whether rats model human sex differences in episodic memory and how the hormonal milieu impacts episodic-like memory processes in this species. These studies revealed salient ways in which rats model human sex differences in episodic memory, including a male advantage in spatial episodic memory performance. They also identified domain-specific roles for oestrogens and androgens in modulating what, where and when discriminations in male rats that were unlike those engaged in corresponding novel object recognition and novel object location tasks. These studies thus identify rats and the what-where-when task as suitable for investigating the neuroendocrine bases of episodic-like memory, and provide new information about the unique contributions that sex and sex hormones make to this complex mnemonic process.

Microglia cytoarchitecture in the brain of adenosine A2A receptor knockout mice: Brain region and sex specificities

Microglia cells exert a critical role in brain development, mainly supported by their immune functions, which predicts an impact on the genesis of psychiatric disorders. In fact, microglia stress during gestation is, for instance, associated with chronic anxiety and cognitive deficits accompanied by long-lasting, region- and sex-specific changes in microglia morphology. We recently reported that the pattern of microglia morphologic plasticity, which is sex-determined, impacts on anxious-like behaviour and cognition. We also reported that the pharmacologic blockade of adenosine A_2A receptors (A_{2 A} R) is able to reshape microglia morphology, in a sex-specific manner and with behavioural sequelae. In order to better understand the role of A_{2 A} R in the sex differentiation of microglia, we now compared their morphology in wild-type and A_{2 A} R knockout male and female C57BL/6 mice in two cardinal brain regions implicated in anxiety-like behaviour and cognition, the prefrontal cortex (PFC) and the dorsal hippocampus (dHIP). We report interregional differences between PFC and dHIP in a sex-specific manner: while males presented more complex microglia in the dHIP, microglia from females had a more complex morphology in the PFC. Surprisingly, the genetic deletion of A_{2 A} R did not alter these sex differences, but promoted the exclusive remodelling (increase in complexity) in PFC microglia from females. These findings further support the existence of a heterogeneous microglial network, distinct between sexes and brain regions, and help characterizing the role of A_{2 A} R in the sex- and brain region-specific morphologic differentiation of microglia.

Sex differences in fear extinction

Despite the exponential increase in fear research during the last years, few studies have included female subjects in their design. The need to include females arises from the knowledge gap of mechanistic processes underlying the behavioral and neural differences observed in fear extinction. Moreover, the exact contribution of sex and hormones in relation to learning and behavior is still largely unknown. Insights from this field could be beneficial as fear-related disorders are twice as prevalent in women compared to men. Here, we review an up-to-date summary of animal and human studies in adulthood that report sex differences in fear extinction from a structural and functional approach. Furthermore, we describe how these factors could contribute to the observed sex differences in fear extinction during normal and pathological conditions.

The role of sex in the genomics of human complex traits

Nearly all human complex traits and disease phenotypes exhibit some degree of sex differences, including differences in prevalence, age of onset, severity or disease progression. Until recently, the underlying genetic mechanisms of such sex differences have been largely unexplored. Advances in genomic technologies and analytical approaches are now enabling a deeper investigation into the effect of sex on human health traits. In this Review, we discuss recent insights into the genetic models and mechanisms that lead to sex differences in complex traits. This knowledge is critical for developing deeper insight into the fundamental biology of sex differences and disease processes, thus facilitating precision medicine.

Both neural and global androgen receptor overexpression affect sexual dimorphism in the mouse brain

Testosterone is the main endocrine mechanism mediating sexual differentiation of the mammalian brain, although testosterone signalling is complex and important mechanistic questions remain. Notably, the extent to which testosterone acts via androgen receptors (AR) in this process remains unknown and it is also not clear where testosterone acts in the body to produce sexual dimorphisms in neuroanatomy. To address these questions, we used a transgenic mouse model of Cre/loxP-driven AR overexpression in which AR was induced selectively in neural tissue (Nestin-cre) or in all tissues (CMV-cre). We then studied sexually dimorphic features of several well-characterised sexual dimorphisms: calbindin-immunoreactive neurones in the medial preoptic area (CALB-SDN), tyrosine hydroxylase neurones in the anteroventral periventricular nucleus, and vasopressin-immunoreactive neurones originating in the bed nucleus of the stria terminalis and their projections in the lateral septum. We additionally evaluated oestrogen receptor α immunoreactivity in these nuclei. Briefly, we found that global but not neural overexpression of AR resulted in masculinisation of CALB-SDN nucleus volume, cell number and cell size in transgenic females. Furthermore, neural AR overexpression resulted in increased oestrogen receptor α staining in females compared to males in the medial preoptic area. AR overexpression did not affect other measures. Overall, the results of the present study provide support for the hypothesis that androgenic mechanisms external to the nervous system can affect sexual differentiation of the brain.

Gender Opportunities in Psychosocial Oncology

So much has happened since the original publication of this chapter. In some ways, the progress made in appreciating the full spectrum of sexual and gender expression has been uneven and in some nations, there has been serious regression and resulting repression. But overall, especially in the industrialized countries, there is much greater awareness of sex and gender and its importance in health and well being. In this updated chapter, we put sex and gender into a historical context that is relevant to psycho-oncology and that openly accepts that society overall, is highly conflicted when it comes to how women and men get the best out of each other, never mind how to best integrate lesbian, gay, bisexual, and transgender (LGBT) communities. With the advent of more tailored treatments and strategic medicine, sex becomes much more important as a variable and this has led to greater scientific requirements to create protocols that integrate sex into all aspects of health from prevention, diagnosis, treatment, survivorship, and death. But we still have a very far way to go. There is a serious dearth of data on sex and gender in science overall and in cancer medicine specifically. Avoidance of discussions of sex and gender in medicine reflects the larger lingering societal discomfort with any discussion that links potential sex and gender differences with superiority. The data shows that there is more intrasexual than intersexual variation in men and women. When speaking about sex and gender the literature reflects that, on average, there are many differences, and although they are small, that when taken together, the impact may be quite robust. Sex and gender differences are relevant to how individuals, couples, and families experience and cope with serious illness; however these important and obvious variables are seldom taken into account when counseling seriously ill patients and their families. Cancer is a complex disease that brings into sharp relief the potential alignments and misalignments in the sexes. In this chapter we have attempted to communicate the imperative for and importance of understanding people under stress within the context of sex and gender. Gender-specific medicine is a very young movement for scientific study but one that has great potential to maximize adaptation and mutual respect at a time when men and women are redefining themselves and adapting to new social realities and challenges.

Individual differences in the biological basis of androphilia in mice and men

For nearly 60 years since the seminal paper from W.C Young and colleagues (Phoenix et al., 1959), the principles of sexual differentiation of the brain and behavior have maintained that female-typical sexual behaviors (e.g., lordosis) and sexual preferences (e.g., attraction to males) are the result of low androgen levels during development, whereas higher androgen levels promote male-typical sexual behaviors (e.g., mounting and thrusting) and preferences (e.g., attraction to females). However, recent reports suggest that the relationship between androgens and male-typical behaviors is not always linear - when androgen signaling is increased in male rodents, via exogenous androgen exposure or androgen receptor overexpression, males continue to exhibit male-typical sexual behaviors, but their sexual preferences are altered such that their interest in same-sex partners is increased. Analogous to this rodent literature, recent findings indicate that high level androgen exposure may contribute to the sexual orientation of a subset of gay men who prefer insertive anal sex and report more male-typical gender traits, whereas gay men who prefer receptive anal sex, and who on average report more gender nonconformity, present with biomarkers suggestive of low androgen exposure. Together, the evidence indicates that for both mice and men there is an inverted-U curvilinear relationship between androgens and sexual preferences, such that low and high androgen exposure increases androphilic sexual attraction, whereas relative mid-range androgen exposure leads to gynephilic attraction. Future directions for studying how individual differences in biological development mediate sexual behavior and sexual preferences in both mice and humans are discussed.

Sex differences and the neurobiology of affective disorders

Observations of the disproportionate incidence of depression in women compared with men have long preceded the recent explosion of interest in sex differences. Nonetheless, the source and implications of this epidemiologic sex difference remain unclear, as does the practical significance of the multitude of sex differences that have been reported in brain structure and function. In this article, we attempt to provide a framework for thinking about how sex and reproductive hormones (particularly estradiol as an example) might contribute to affective illness. After briefly reviewing some observed sex differences in depression, we discuss how sex might alter brain function through hormonal effects (both organizational (programmed) and activational (acute)), sex chromosome effects, and the interaction of sex with the environment. We next review sex differences in the brain at the structural, cellular, and network levels. We then focus on how sex and reproductive hormones regulate systems implicated in the pathophysiology of depression, including neuroplasticity, genetic and neural networks, the stress axis, and immune function. Finally, we suggest several models that might explain a sex-dependent differential regulation of affect and susceptibility to affective illness. As a disclaimer, the studies cited in this review are not intended to be comprehensive but rather serve as examples of the multitude of levels at which sex and reproductive hormones regulate brain structure and function. As such and despite our current ignorance regarding both the ontogeny of affective illness and the impact of sex on that ontogeny, sex differences may provide a lens through which we may better view the mechanisms underlying affective regulation and dysfunction.

Sex differences in neural mechanisms mediating reward and addiction

There is increasing evidence in humans and laboratory animals for biologically based sex differences in every phase of drug addiction: acute reinforcing effects, transition from occasional to compulsive use, withdrawal-associated negative affective states, craving, and relapse. There is also evidence that many qualitative aspects of the addiction phases do not differ significantly between males and females, but one sex may be more likely to exhibit a trait than the other, resulting in population differences. The conceptual framework of this review is to focus on hormonal, chromosomal, and epigenetic organizational and contingent, sex-dependent mechanisms of four neural systems that are known-primarily in males-to be key players in addiction: dopamine, mu-opioid receptors (MOR), kappa opioid receptors (KOR), and brain-derived neurotrophic factor (BDNF). We highlight data demonstrating sex differences in development, expression, and function of these neural systems as they relate-directly or indirectly-to processes of reward and addictive behavior, with a focus on psychostimulants and opioids. We identify gaps in knowledge about how these neural systems interact with sex to influence addictive behavior, emphasizing throughout that the impact of sex can be highly nuanced and male/female data should be reported regardless of the outcome.

Sex differences in psychiatric disorders: what we can learn from sex chromosome aneuploidies

The study of sexual dimorphism in psychiatric and neurodevelopmental disorders is challenging due to the complex interplay of diverse biological, psychological, and social factors. Males are more susceptible to neurodevelopmental disorders including intellectual disability, autism spectrum disorder, and attention-deficit activity disorder. Conversely, after puberty, females are more prone to major depressive disorder and anxiety disorders compared to males. One major biological factor contributing to sex differences is the sex chromosomes. First, the X and Y chromosomes have unique and specific genetic effects as well as downstream gonadal effects. Second, males have one X chromosome and one Y chromosome, while females have two X chromosomes. Thus, sex chromosome constitution also differs between the sexes. Due to this complexity, determining genetic and downstream biological influences on sexual dimorphism in humans is challenging. Sex chromosome aneuploidies, such as Turner syndrome (X0) and Klinefelter syndrome (XXY), are common genetic conditions in humans. The study of individuals with sex chromosome aneuploidies provides a promising framework for studying sexual dimorphism in neurodevelopmental and psychiatric disorders. Here we will review and contrast four syndromes caused by variation in the number of sex chromosomes: Turner syndrome, Klinefelter syndrome, XYY syndrome, and XXX syndrome. Overall we describe an increased rate of attention-deficit hyperactivity disorder and autism spectrum disorder, along with the increased rates of major depressive disorder and anxiety disorders in one or more of these conditions. In addition to contributing unique insights about sexual dimorphism in neuropsychiatric disorders, awareness of the increased risk of neurodevelopmental and psychiatric disorders in sex chromosome aneuploidies can inform appropriate management of these common genetic disorders.

Sex Differences in the Pharmacokinetics of Low-dose Ketamine in Plasma and Brain of Male and Female Rats

Recent work from our group and others has revealed a higher sensitivity of female rodents to the antidepressant-like effects of the N-methyl d-aspartate receptor antagonist ketamine strongly influenced by circulating estrogen and progesterone levels. However, in the absence of any preclinical studies of pharmacokinetic sex differences using low-dose ketamine in rats, it is unclear whether the effects of sex and hormonal milieu on ketamine's behavioral actions are influenced by differences in ketamine metabolism between male and female rats. Therefore, this work examined whether sex and hormonal status affect ketamine metabolism and distribution in male and female rats using a low antidepressant-like dose selectively effective in females. Intact male rats and female rats in either diestrus (low estrogen, progesterone) or proestrus (high estrogen, progesterone) were administered low-dose ketamine, and their plasma and brains were collected to analyze levels of ketamine and its metabolites norketamine (NK) and dehydronorketamine. Females exhibited greater concentrations of ketamine and NK over the first 30 min following treatment in both brain and plasma, largely accounted for by slower clearance rates and longer half-lives. Interestingly, despite the impact of ovarian hormones on behavioral sensitivity to ketamine, no appreciable differences in pharmacokinetic parameters existed between proestrus and diestrus female rats. This work is the first to demonstrate sex differences in ketamine pharmacokinetics in rats, and suggests that while sex differences in metabolism may influence the amount of ketamine and NK reaching target areas in the brain, the impact of circulating hormone levels here is negligible.

Transcriptomic Analysis Reveals Sex-Dependent Expression Patterns in the Basolateral Amygdala of Dominant and Subordinate Animals After Acute Social Conflict

The basolateral amygdala (BLA) is a critical nucleus mediating behavioral responses after exposure to acute social conflict. Male and female Syrian hamsters both readily establish a stable dominant-subordinate relationship among same-sex conspecifics, and the goal of the current study was to determine potential underlying genetic mechanisms in the BLA facilitating the establishment of social hierarchy. We sequenced the BLA transcriptomes of dominant, subordinate, and socially neutral males and females, and using de novo assembly techniques and gene network analyses, we compared these transcriptomes across social status within each sex. Our results revealed 499 transcripts that were differentially expressed in the BLA across both males and females and 138 distinct gene networks. Surprisingly, we found that there was virtually no overlap in the transcript changes or in gene network patterns in males and females of the same social status. These results suggest that, although males and females reliably engage in similar social behaviors to establish social dominance, the molecular mechanisms in the BLA by which these statuses are obtained and maintained are distinct.

Sex Differences in Early Embryogenesis: Inter-Chromosomal Regulation Sets the Stage for Sex-Biased Gene Networks: The dialogue between the sex chromosomes and autosomes imposes sexual identity soon after fertilization

Sex-specific transcriptional and epigenomic profiles are detectable in the embryo very soon after fertilization. I propose that in male (XY) and female (XX) pre-implantation embryos sex chromosomes establish sexually dimorphic interactions with the autosomes, before overt differences become apparent and long before gonadogenesis. Lineage determination restricts expression biases between the sexes, but the epigenetic differences are less constrained and can be perpetuated, accounting for dimorphisms that arise later in life. In this way, sexual identity is registered in the epigenome very early in development. As development progresses, sex-specific regulatory modules are harbored within shared transcriptional networks that delineate common traits. In reviewing this field, I propose that analyzing the mechanisms for sexual dimorphisms at the molecular and biochemical level and incorporating developmental and environmental factors will lead to a greater understanding of sex differences in health and disease. Also see the video abstract here: https://youtu.be/9BPlbrHtkHQ.

Sex-Linked Behavior: Evolution, Stability, and Variability

Common understanding of human sex-linked behaviors is that proximal mechanisms of genetic and hormonal sex, ultimately shaped by the differential reproductive challenges of ancestral males and females, act on the brain to transfer sex-linked predispositions across generations. Here, we extend the debate on the role of nature and nurture in the development of traits in the lifetime of an individual, to their role in the cross-generation transfer of traits. Advances in evolutionary theory that posit the environment as a source of trans-generational stability, and new understanding of sex effects on the brain, suggest that the cross-generation stability of sex-linked patterns of behavior are sometimes better explained in terms of inherited socioenvironmental conditions, with biological sex fostering intrageneration variability.

Non-neural androgen receptors affect sexual differentiation of brain and behaviour

Although gonadal testosterone is the principal endocrine factor that promotes masculine traits in mammals, the development of a male phenotype requires local production of both androgenic and oestrogenic signals within target tissues. Much of our knowledge concerning androgenic components of testosterone signalling in sexual differentiation comes from studies of androgen receptor (Ar) loss of function mutants. Here, we review these studies of loss of Ar function and of AR overexpression either globally or selectively in the nervous system of mice. Global and neural mutations affect socio-sexual behaviour and the neuroanatomy of these mice in a sexually differentiated manner. Some masculine traits are affected by both global and neural mutation, indicative of neural mediation, whereas other masculine traits are affected only by global mutation, indicative of an obligatory non-neural androgen target. These results support a model in which multiple sites of androgen action coordinate to produce masculine phenotypes. Furthermore, AR overexpression does not always have a phenotype opposite to that of loss of Ar function mutants, indicative of a nonlinear relationship between androgen dose and masculine phenotype in some cases. Potential mechanisms of Ar gene function in non-neural targets in producing masculine phenotypes are discussed.

Sexual Differentiation and Sex Differences in Neural Development

Sex determination occurs at the moment of conception, as a result of XX or XY chromosome pairing. From that point, the body undergoes the process of sexual differentiation, inducing the development of physical characteristics that are easily distinguishable between the sexes and are often reflected in one's physical appearance and gender identity. Although less apparent, the brain also undergoes sexual differentiation. Sex differences in the brain are organized during a critical period of neural development and have an instrumental role in determining the physiology and behavior of an individual throughout the lifespan. Understanding the extent of sex differences in neurodevelopment also influences our understanding of the potential risk for a number of neurodevelopmental, neurological, and mental health disorders that exhibit strong sex biases. Advances made in our understanding of sexually dimorphic brain nuclei, sex differences in neural cell communication, and sex differences in the communication between the brain and peripheral organs are all research fields that have provided valuable information related to the physiological and behavioral outcomes of sex differences in brain development. More recently, investigations into the impact of epigenetic mechanisms on sexual differentiation of the brain have indicated that changes in gene expression, via epigenetic modifications, also contribute to sexual differentiation of the developing brain. Still, there are a number of important questions and ideas that have arisen from our current understanding of sex differences in neurodevelopmental processes that necessitate more time and attention in this field.

Sex Differences in Medium Spiny Neuron Excitability and Glutamatergic Synaptic Input: Heterogeneity Across Striatal Regions and Evidence for Estradiol-Dependent Sexual Differentiation

Steroid sex hormones and biological sex influence how the brain regulates motivated behavior, reward, and sensorimotor function in both normal and pathological contexts. Investigations into the underlying neural mechanisms have targeted the striatal brain regions, including the caudate-putamen, nucleus accumbens core (AcbC), and shell. These brain regions are of particular interest to neuroendocrinologists given that they express membrane-associated but not nuclear estrogen receptors, and also the well-established role of the sex steroid hormone 17β-estradiol (estradiol) in modulating striatal dopamine systems. Indeed, output neurons of the striatum, the medium spiny neurons (MSNs), exhibit estradiol sensitivity and sex differences in electrophysiological properties. Here, we review sex differences in rat MSN glutamatergic synaptic input and intrinsic excitability across striatal regions, including evidence for estradiol-mediated sexual differentiation in the nucleus AcbC. In prepubertal animals, female MSNs in the caudate-putamen exhibit a greater intrinsic excitability relative to male MSNs, but no sex differences are detected in excitatory synaptic input. Alternatively, female MSNs in the nucleus AcbC exhibit increased excitatory synaptic input relative to male MSNs, but no sex differences in intrinsic excitability were detected. Increased excitatory synaptic input onto female MSNs in the nucleus AcbC is abolished after masculinizing estradiol or testosterone exposure during the neonatal critical period. No sex differences are detected in MSNs in prepubertal nucleus accumbens shell. Thus, despite possessing the same neuron type, striatal regions exhibit heterogeneity in sex differences in MSN electrophysiological properties, which likely contribute to the sex differences observed in striatal function.