Polymorphisms in the dopamine D4 receptor gene (DRD4) contribute to individual differences in human sexual behavior: desire, arousal and sexual function

Alpha Synuclein Toxicity and Non-Motor Parkinson's

Parkinson's disease (PD) is a common multisystem neurodegenerative disorder affecting 1% of the population over the age of 60 years. The main neuropathological features of PD are the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the presence of alpha synuclein (αSyn)-rich Lewy bodies both manifesting with classical motor signs. αSyn has emerged as a key protein in PD pathology as it can spread through synaptic networks to reach several anatomical regions of the body contributing to the appearance of non-motor symptoms (NMS) considered prevalent among individuals prior to PD diagnosis and persisting throughout the patient's life. NMS mainly includes loss of taste and smell, constipation, psychiatric disorders, dementia, impaired rapid eye movement (REM) sleep, urogenital dysfunction, and cardiovascular impairment. This review summarizes the more recent findings on the impact of αSyn deposits on several prodromal NMS and emphasizes the importance of early detection of αSyn toxic species in biofluids and peripheral biopsies as prospective biomarkers in PD.

Improving the synthetic H2 production catalyst design strategy with the neurotransmitter dopamine

The strategic incorporation of the neurotransmitter dopamine around a cobaloxime core resulted in excellent electrocatalytic (rate 8400 s^-1) and photocatalytic H₂ production under neutral aqueous conditions. The influence of the synthetic outer coordination sphere features continues even with a phenylene-diimino-dioxime motif-coordinated cobalt core.

The functions and effects of CUL3-E3 ligases mediated non-degradative ubiquitination

Ubiquitination of substrates usually have two fates: one is degraded by 26S proteasome, and the other is non-degradative ubiquitination modification which is associated with cell cycle regulation, chromosome inactivation, protein transportation, tumorigenesis, achondroplasia, and neurological diseases. Cullin3 (CUL3), a scaffold protein, binding with the Bric-a-Brac-Tramtrack-Broad-complex (BTB) domain of substrates recognition adaptor and RING-finger protein 1 (RBX1) form ubiquitin ligases (E3). Based on the current researches, this review has summarized the functions and effects of CUL3-E3 ligases mediated non-degradative ubiquitination.

Dopamine Increases the Intrinsic Excitability of Parvalbumin-Expressing Fast-Spiking Cells in the Piriform Cortex

The piriform cortex (PCx) is essential for the adaptive processing of olfactory information. Neuromodulatory systems, including those utilizing serotonin, acetylcholine, noradrenaline, and dopamine, innervate and regulate neuronal activity in the PCx. Previous research has demonstrated the importance of acetylcholine, noradrenaline and serotonin in odor learning and memory. In contrast, the role of dopamine in the PCx remains under-explored. Here we examined how dopamine modulates the intrinsic electrical properties of identified classes of neurons in the PCx. We found that dopamine had no consistent effect on the intrinsic electrical properties of two types of glutamatergic neurons (semilunar and superficial pyramidal cells) or three types of GABAergic interneurons (horizontal, neurogliaform and somatastatin-expressing regular-spiking cells). However, dopamine had a striking effect on the intrinsic excitability of the parvalbumin-expressing fast-spiking (FS) class of GABAergic interneuron. Dopamine depolarized the resting potential, increased the input resistance and increased the firing frequency of FS cells. Co-application of dopamine with the D1-class dopamine receptor antagonist SCH 23390 blocked the effects of dopamine modulation on FS cells. Conversely, co-application of dopamine with the D2-class antagonist RS-(±)-sulpiride had no effect on dopamine modulation of these cells. Our results indicate that dopamine binds to D1-class dopamine receptors to increase the intrinsic excitability of FS cells. These findings suggest that dopamine has a highly targeted effect in the PCx and reveal how dopamine may modulate the balance between excitation and inhibition, with consequences for odor processing. In addition, our findings provide clues for understanding why neurodegenerative disorders that modify the dopamine system, such as Parkinson's disease, have a deleterious effect on the sense of smell, and may suggest novel diagnostics for the early detection of such disorders.

Bipolar disorder: An evolutionary psychoneuroimmunological approach

Bipolar disorder is a mental health disorder characterized by extreme shifts in mood, high suicide rate, sleep problems, and dysfunction of psychological traits like self-esteem (feeling inferior when depressed and superior when manic). Bipolar disorder is rare among populations that have not adopted contemporary Western lifestyles, which supports the hypothesis that bipolar disorder results from a mismatch between Homo sapiens's evolutionary and current environments. Recent studies have connected bipolar disorder with low-grade inflammation, the malfunctioning of the internal clock, and the resulting sleep disturbances. Stress is often a triggering factor for mania and sleep problems, but stress also causes low-grade inflammation. Since inflammation desynchronizes the internal clock, chronic stress and inflammation are the primary biological mechanisms behind bipolar disorder. Chronic stress and inflammation are driven by contemporary Western lifestyles, including stressful social environments, unhealthy dietary patterns, limited physical activity, and obesity. The treatment of bipolar disorder should focus on reducing stress, stress sensitivity, and inflammation by lifestyle changes rather than just temporarily alleviating symptoms with psychopharmacological interventions.

Introducing sexual dysfunction in mental care

Introduction: People with any psychiatric disorder tend to have difficulties in responding sexually. However,sexual dysfunction (SD) is usually under-recognized, even the tightly hormonal and neuronal common connexions through the brain-sex axis. Multiple sources of resistance to SD assessment and intervention persist. Areas covered: The present review aims to underline the feasibility to introduce SD evaluation in patients with any psychiatric disorders, evaluating the potential mutual benefits of their management. Expert opinion: Women and men living with mental disorders frequently display sexual difficulties; however, some of them consider sexuality as a relevant parameter of their quality of life. In fact, SD as a side effect is a frequent reason for stopping the intake of medication. What is more, a holistic approach integrating sexual function could foster a better understanding of mental pathologies due to a common origin of pathogenesis. This could improve care quality, in keeping with the global tendency toward the development of personalized medicine. Consistently, the integration of SD assessment is highly recommended in mental health, all the more so when a psychotropic drug is prescribed. An expected consequence would be a reconstruction of the healthcare professional's consideration for the sexuality of people experiencing mental disorders.

Using Anthropological Principles to Transform the Teaching of Human "Difference" and Genetic Variation in College Classrooms

Exposure to information about genetics is at an all-time high, while a full understanding of the biocultural complexity of human difference is low. This paper demonstrates the value of an "anthropological approach" to enhance genetics education in biology, anthropology, and other related disciplines, when teaching about human differences such as race/ethnicity, sex/gender, and disability. As part of this approach, we challenge educators across social and natural sciences to critically examine and dismantle the tacit cultural assumptions that shape our understanding of genetics and inform the way we perceive (and teach about) human differences. It calls on educators from both social and natural science disciplines to "de-silo" their classrooms and uses examples from our biological anthropology and sociocultural anthropology classrooms, to demonstrate how educators can better contextualize the "genetics" of human difference in their own teaching. Numerous opportunities to transform our teaching exist, and we are doing a disservice to our students by not taking these critical steps.

Gene Polymorphisms Affecting Erectile Dysfunction

INTRODUCTION

Erectile dysfunction (ED) is usually developed from psychological, neurological, hormonal, and vascular pathologies or a combination of these factors. However, the possible genetic polymorphisms that might underlie this disorder were not thoroughly investigated.

OBJECTIVES

This review article aimed to assess the possible involvement of gene polymorphisms in men with ED.

METHODS

A systematic review was conducted until January 2020 based on a search of all relevant articles in many electronic sites such as PubMed, Medline Medical Subject Headings, Science Direct, Scopus, Cochrane Library, EMBASE, CINAHL, and Egyptian Knowledge Bank databases with no language restriction. Keywords used to assess the outcome and estimates for relevant associations were sexual health, genes, erectile dysfunction, polymorphisms, and cavernous tissues.

RESULTS

Many genetic studies were carried out to inspect the contribution of different encoded genotypes and ED. Overall, 50 studies were reviewed and were classified as per the type of gene polymorphisms. These studies have investigated 10,174 men with ED compared with 6,891 healthy men as controls. 35 studies were case-controlled, 13 cross-sectional cohort studies, one retrospective study, and one genome-wide association study. So far, the most relevant gene polymorphisms linked with men with ED included endothelial nitric oxide synthase (eNOS), angiotensin-converting enzyme (ACE), androgen receptor (AR) CAG repeat, G-protein β3 (GNB3) subunit, methylenetetrahydrofolate reductase (MTHFR), vascular endothelial growth factor (VEGF), TGFB1, proprotein convertase subtilisin/kexin type 9 (PCSK9), ARG1, DRD2, DRD4, DDAH, and HNF4A genes. Both PROGINS and IGFBP-3 polymorphisms were investigated in only one study each but with irrelevant significance.

CONCLUSIONS

Although several genetic studies exposed the association between different genotypes and men with ED with varied outcomes, such a relationship should not be overlooked. Therefore, more studies should be encouraged to elucidate the exact role, if any, for such association. Mostafa T, Taymour M. Gene Polymorphisms Affecting Erectile Dysfunction. Sex Med 2020;8:561-572.

Dopamine: Functions, Signaling, and Association with Neurological Diseases

The dopaminergic system plays important roles in neuromodulation, such as motor control, motivation, reward, cognitive function, maternal, and reproductive behaviors. Dopamine is a neurotransmitter, synthesized in both central nervous system and the periphery, that exerts its actions upon binding to G protein-coupled receptors. Dopamine receptors are widely expressed in the body and function in both the peripheral and the central nervous systems. Dopaminergic signaling pathways are crucial to the maintenance of physiological processes and an unbalanced activity may lead to dysfunctions that are related to neurodegenerative diseases. Unveiling the neurobiology and the molecular mechanisms that underlie these illnesses may contribute to the development of new therapies that could promote a better quality of life for patients worldwide. In this review, we summarize the aspects of dopamine as a catecholaminergic neurotransmitter and discuss dopamine signaling pathways elicited through dopamine receptor activation in normal brain function. Furthermore, we describe the potential involvement of these signaling pathways in evoking the onset and progression of some diseases in the nervous system, such as Parkinson's, Schizophrenia, Huntington's, Attention Deficit and Hyperactivity Disorder, and Addiction. A brief description of new dopaminergic drugs recently approved and under development treatments for these ailments is also provided.

Evolution of sex-specific pace-of-life syndromes: genetic architecture and physiological mechanisms

Sex differences in life history, physiology, and behavior are nearly ubiquitous across taxa, owing to sex-specific selection that arises from different reproductive strategies of the sexes. The pace-of-life syndrome (POLS) hypothesis predicts that most variation in such traits among individuals, populations, and species falls along a slow-fast pace-of-life continuum. As a result of their different reproductive roles and environment, the sexes also commonly differ in pace-of-life, with important consequences for the evolution of POLS. Here, we outline mechanisms for how males and females can evolve differences in POLS traits and in how such traits can covary differently despite constraints resulting from a shared genome. We review the current knowledge of the genetic basis of POLS traits and suggest candidate genes and pathways for future studies. Pleiotropic effects may govern many of the genetic correlations, but little is still known about the mechanisms involved in trade-offs between current and future reproduction and their integration with behavioral variation. We highlight the importance of metabolic and hormonal pathways in mediating sex differences in POLS traits; however, there is still a shortage of studies that test for sex specificity in molecular effects and their evolutionary causes. Considering whether and how sexual dimorphism evolves in POLS traits provides a more holistic framework to understand how behavioral variation is integrated with life histories and physiology, and we call for studies that focus on examining the sex-specific genetic architecture of this integration.

The effect of 8-OH-DPAT and dapoxetine on gene expression in the brain of male rats during ejaculation

The 5-HT_1A receptor agonist 8-hydroxy-2-[di-n-propylamino] tetralin (8-OH-DPAT) promotes ejaculation of male rats, whereas dapoxetine delays this process. However, the gene expression profile of the brain at ejaculation following administrationof these two compounds has not been fully elucidated. In the present study, a transcriptomic BodyMap was generated by conducting mRNA-Seq on brain samples of male Sprague–Dawley rats. The study included four groups: pre-copulatory control (CK) group, ejaculation (EJ) group, 0.5 mg/kg 8-OH-DPAT-ejaculation group (DPAT), and 60 mg/kg dapoxetine-ejaculation (DAP) group. The resulting analysis generated an average of approximately 47 million sequence reads. Significant differences in the gene expression profiles of the aforementioned groups were observed in the EJ (257 genes), DPAT (349 genes) and the DAP (207 genes) compared with the control rats. The results indicate that the expression of Drd1 and Slc6a3 was significantly different after treatment with 8-OH-DPAT, whereas the expression of Drd4 was significantly different after treatment with dapoxetine. Other genes, such as Wnt9b, Cdkn1a and Fosb, exhibited significant differences in expression after the two treatments and are related to bladder cancer, renal cell carcinoma and sexual addiction. The present study reveals the basic pattern of gene expression that was activated at ejaculation in the presence of 8-OH-DPAT or dapoxetine, providing preliminary gene expression information during rat ejaculation.

Impact of estrogen receptor α gene and oxytocin receptor gene polymorphisms on female sexuality

Over the past decades, research attention has increasingly been paid to the neurobiological component of sexual behavior. The aim of the present study was to investigate the correlation of estrogen receptor α (ERA) gene polymorphism (rs2234693-PvuII) (T→C substitution) and oxytocin receptor gene polymorphism (rs53576) (G→A substitution) with sexuality parameters of young, healthy women. One hundred thirty-three Greek heterosexual women, students in higher education institutions, 20-25 years of age, sexually active, with normal menstrual cycles (28-35 days), were recruited in the study. Exclusion criteria were chronic and/or major psychiatric diseases, use of oral contraceptive pills (OCs), polycystic ovary syndrome (PCOS), thyroid diseases as well as drugs that are implicated in hypothalamus-pituitary-gonadal axis. T allele (wildtype) of rs2234693 (PvuII) polymorphism of ERA gene was correlated with increased levels of arousal and lubrication, whereas A allele (polymorphic) of rs53576 (OXTR) polymorphism was correlated with increased arousal levels. The simultaneous presence of both T allele of rs2234693 (PvuII) and A allele of rs53576 (OXTR) polymorphisms (T + A group) was correlated with increased arousal, orgasm levels as well as female sexual function index full score. To our knowledge, this is the first study to investigate the interaction between ERA and OXTR with regard to sexual function in women. Female sexuality is a complex behavioral trait that encompasses both biological and psychological components. It seems that variability in female sexual response stems from genetic variability that characterizes endocrine, neurotransmitter and central nervous system influences.

Paraphilic Sexual Offenders Do Not Differ From Control Subjects With Respect to Dopamine- and Serotonin-Related Genetic Polymorphisms

INTRODUCTION

Rape and pedophilic child molestation are the most commonly convicted sexual offenses in Poland. Recent studies have suggested a possible genetic contribution toward pathologic sexual interests and behaviors.

AIM

To analyze and compare functional polymorphisms of genes associated with the activity of the serotonin and dopamine systems in a group of paraphilic sexual offenders and control subjects.

METHODS

The study sample (n = 97) consisted of two groups: paraphilic sexual offenders (65 pedophilic child molesters and 32 rapists) and controls (n = 76). Genetic polymorphisms previously associated with behavioral control, addictive behaviors, and sexual functions were chosen for analyses. Specifically, functional polymorphisms in dopamine receptors genes (DRD1, DRD2, DRD4), catechol-O-methyltransferase gene (COMT), dopamine transporter gene (DAT), serotonin transporter gene (SLC6A4), serotonin type 2A receptor gene (5HTR2A), tryptophan hydroxylase 2 gene (TPH2), monoamine oxidase A gene (MAOA), and brain-derived neurotrophic factor gene (BDNF) were analyzed.

MAIN OUTCOME MEASURES

An association between a history of sexual offense and the distribution of genotypes and alleles in the analyzed polymorphisms.

RESULTS

Our results found no association between a history of sexual offense and the distribution of genotypes or alleles in the analyzed polymorphisms.

CONCLUSION

Although these results are limited by the small sample and are exploratory, they highlight a novel approach to sample selection in a population that is difficult to access and study. Future research should include larger samples and other relevant polymorphisms to advance this field of study.

Self-Reported Sexual Behavioral Interests and Polymorphisms in the Dopamine Receptor D4 (DRD4) Exon III VNTR in Heterosexual Young Adults

Polymorphisms in the dopamine D4 receptor (DRD4) have previously been shown to associate with a variety of human behavioral phenotypes, including ADHD pathology, alcohol and tobacco craving, financial risk-taking in males, and broader personality traits such as novelty seeking. Recent research has linked the presence of a 7-repeat (7R) allele in a 48-bp variable number of tandem repeats (VNTR) along exon III of DRD4 to age at first sexual intercourse, sexual desire, arousal and function, and infidelity and promiscuity. We hypothesized that carriers of longer DRD4 alleles may report interest in a wider variety of sexual behaviors and experiences than noncarriers. Participants completed a 37-item questionnaire measuring sexual interests as well as Cloninger's Temperament and Character Inventory, and were genotyped for the 48-bp VNTR on exon III of DRD4. Based on our final genotyped sample of female (n = 139) and male (n = 115) participants, we found that 7R carriers reported interest in a wider variety of sexual behaviors (r = 0.16) within a young adult heterosexual sample of European descent. To our knowledge, this is the first reported association between DRD4 exon III VNTR genotype and interest in a variety of sexual behaviors. We discuss these findings within the context of DRD4 research and broader trends in human evolutionary history.

PPL2ab neurons restore sexual responses in aged Drosophila males through dopamine

Male sexual desire typically declines with ageing. However, our understanding of the neurobiological basis for this phenomenon is limited by our knowledge of the brain circuitry and neuronal pathways controlling male sexual desire. A number of studies across species suggest that dopamine (DA) affects sexual desire. Here we use genetic tools and behavioural assays to identify a novel subset of DA neurons that regulate age-associated male courtship activity in Drosophila. We find that increasing DA levels in a subset of cells in the PPL2ab neuronal cluster is necessary and sufficient for increased sustained courtship in both young and aged male flies. Our results indicate that preventing the age-related decline in DA levels in PPL2ab neurons alleviates diminished courtship behaviours in male Drosophila. These results may provide the foundation for deciphering the circuitry involved in sexual motivation in the male Drosophila brain.

We currently lack a detailed understanding of the neurobiological basis for the decline of male sexual desire with age. Here the authors demonstrate that restoring impaired dopaminergic signalling in a specific cluster of neurons in the Drosophila brain increases sexual behaviour in ageing male flies.

Increased brain activity to unpleasant stimuli in individuals with the 7R allele of the DRD4 gene

The aim of the study was to examine functional brain activity in response to unpleasant images in individuals with the 7-repeat (7R) allele compared to individuals with the 4-repeat (4R) allele of the dopamine receptor D4 (DRD4) gene (VNTR in exon 3). Based on the response ready hypothesis, individuals with the DRD4-4R/7R genotype were expected to show greater functional brain activity in response to unpleasant compared to neutral stimuli in specific regions of the frontal, temporal, parietal and limbic lobes, which form the networks involved in attentional, emotional, and preparatory responses. Functional Magnetic Resonance Imaging activity was studied in 26 young adults (13 with the DRD4-4R/7R genotype and 13 with the DRD4-4R/4R genotype). Participants were asked to look at and subjectively rate unpleasant and neutral images. Results showed increased brain activity in response to unpleasant images compared to neutral images in the right temporal lobe in participants with the DRD4-4R/7R genotype versus participants with the DRD4-4R/4R genotype. The increase in right temporal lobe activity in individuals with DRD4-4R/7R suggests greater involvement in processing negative emotional stimuli. Intriguingly, no differences were found between the two genotypes in the subjective ratings of the images. The findings corroborate the response ready hypothesis, which suggests that individuals with the 7R allele are more responsive to negative emotional stimuli compared to individuals with the 4R allele of the DRD4 gene.

Dopamine receptor gene d4 polymorphisms and early sexual onset: gender and environmental moderation in a sample of african-american youth

PURPOSE

Early sexual onset and its consequences disproportionately affect African-American youth, particularly male youth. The dopamine receptor D4 gene (DRD4) has been linked to sexual activity and other forms of appetitive behavior, particularly for male youth and in combination with environmental factors (gene × environment [G × E] effects). The differential susceptibility perspective suggests that DRD4 may exert this effect by amplifying the effects of both positive and negative environments. We hypothesized that DRD4 status would amplify the influence of both positive and negative neighborhood environments on early sexual onset among male, but not female, African-Americans.

METHODS

Hypotheses were tested with self-report, biospecimen, and census data from five prospective studies of male and female African-American youth in rural Georgia communities, N = 1,677. Early sexual onset was defined as intercourse before age 14.

RESULTS

No significant G × E findings emerged for female youth. Male youth with a DRD4 long allele were more likely than those with two DRD4 short alleles to report early sexual onset in negative community environments and not to report early onset in positive community environments.

CONCLUSIONS

Dopaminergic regulation of adolescent sexual behaviors may operate differently by gender. DRD4 operated as an environmental amplification rather than a vulnerability factor.

Therapygenetics in mindfulness-based cognitive therapy: do genes have an impact on therapy-induced change in real-life positive affective experiences?

Positive affect (PA) has an important role in resilience against depression and has been shown to increase with mindfulness-based cognitive therapy (MBCT). To elucidate the underlying mechanisms of change in PA as well as develop insights that may benefit personalized medicine, the current study examined the contribution of genetic variation to individual differences in change in PA in response to MBCT. Individuals (n=126) with residual depressive symptoms were randomized to either an MBCT group or treatment as usual. PA was assessed using experience sampling methodology (ESM). Single-nucleotide polymorphisms (SNPs) in genes known to be involved in reward functioning were selected. SNPs in the genes for brain-derived neurotrophic factor (BDNF), the muscarinic acetylcholine receptor M2 (CHRM2), the dopamine receptor D4 (DRD4) and the μ1 opioid receptor (OPRM1) significantly moderated the impact of treatment condition over time on PA. Genetic variation in the genes for CHRM2 and OPRM1 specifically had an impact on the level of PA following MBCT. The current study shows that variation in response to MBCT may be contingent on genetic factors associated with the regulation of PA. These findings contribute to our understanding of the processes moderating response to treatment and prediction of treatment outcome.

Factors associated with sexual arousal, sexual sensation seeking and sexual satisfaction among female African American adolescents

BACKGROUND

Sexuality-related constructs, such as sexual arousal, sexual sensation seeking (SSS) and sexual satisfaction, have been related to sexual behaviours that place one at risk of adverse consequences, such as sexually transmissible infections, HIV and unintended pregnancy. The biopsychosocial model posits an array of factors, ranging from social environmental factors to biological and psychological predispositions, that may be associated with these sexuality constructs in adolescents.

METHODS

Female African Americans aged 14-20 years were recruited from reproductive health clinics for an HIV intervention. Baseline survey and follow-up DNA data (n=304) were used to assess biological, psychological and social environmental associations with the sexuality constructs of arousal, SSS and sexual satisfaction.

RESULTS

Multivariate linear regression analysis revealed that a higher depressive symptom rating was associated with higher arousability, whereas short serotonin transporter gene allele(s) status was associated with lower arousability. Impulsivity and perceived peer norms supportive of unsafe sexual behaviours were associated with increased SSS, whereas short serotonin transporter gene allele(s) status was associated with lower SSS. Higher social support was associated with higher levels of sexual satisfaction, whereas short serotonin transporter gene allele(s) status was associated with lower satisfaction. The sexuality constructs were also significantly related to the number of sex partners, the frequency of vaginal sex and the number of unprotected vaginal sex acts in the past 6 months.

CONCLUSIONS

The findings emphasise the importance of understanding biopsychosocial factors, including the role of serotonin as an indicator of natural variations in sexual inclination and behaviours, that influence sexuality constructs, which, in turn, are associated with sexual behaviours, to allow further refinement of sexual health clinical services and programs and promote the development of healthy sexuality.

Genetic influences on adolescent sexual behavior: Why genes matter for environmentally oriented researchers

There are dramatic individual differences among adolescents in how and when they become sexually active adults, and early sexual activity is frequently cited as a cause of concern for scientists, policymakers, and the general public. Understanding the causes and developmental impact of adolescent sexual activity can be furthered by considering genes as a source of individual differences. Quantitative behavioral genetics (i.e., twin and family studies) and candidate gene association studies now provide clear evidence for the genetic underpinnings of individual differences in adolescent sexual behavior and related phenotypes. Genetic influences on sexual behavior may operate through a variety of direct and indirect mechanisms, including pubertal development, testosterone levels, and dopaminergic systems. Genetic differences may be systematically associated with exposure to environments that are commonly treated as causes of sexual behavior (gene-environment correlation). Possible gene-environment correlations pose a serious challenge for interpreting the results of much behavioral research. Multivariate, genetically informed research on adolescent sexual behavior compares twins and family members as a form of quasi experiment: How do twins who differ in their sexual experiences differ in their later development? The small but growing body of genetically informed research has already challenged dominant assumptions regarding the etiology and sequelae of adolescent sexual behavior, with some studies indicating possible positive effects of teenage sexuality. Studies of Gene × Environment interaction may further elucidate the mechanisms by which genes and environments combine to shape the development of sexual behavior and its psychosocial consequences. Overall, the existence of heritable variation in adolescent sexual behavior has profound implications for environmentally oriented theory and research.

Brain region-specific transcriptomic markers of serotonin-1A receptor agonist action mediating sexual rejection and aggression in female marmoset monkeys

INTRODUCTION

In a marmoset model of hypoactive female sexual function, we have shown that repeated administration of the serotonin (5-HT)-1A agonist R-(+)-8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) inhibits sexual receptivity in female marmoset monkeys and increases aggression toward the male pairmate.

AIM

The aims of this study are to investigate gene expression changes induced by 8-OH-DPAT in laser-microdissected brain areas that regulate female sexual function and to identify genes, functional gene classes, and pathways associated with 8-OH-DPAT-mediated inhibition of female sexual receptivity.

METHODS

Gene expression was measured in the medial prefrontal cortex (mPFC), medial preoptic area (mPOA), cornu ammonis-1 (CA1) area of the hippocampus (CA1), and dorsal raphé nucleus (DRN) of four 8-OH-DPAT-treated (0.1 mg/kg; daily administration for 16 weeks) and four vehicle-treated female marmosets using a marmoset-specific microarray (European Marmoset Microarray [EUMAMA]) and validated by real-time quantitative polymerase chain reaction (RTqPCR). Enriched functional gene classes were determined. In a parallel candidate gene approach, the expression of serotonergic candidate genes, i.e., the 5-HT1A, 5-HT2A, and 5-HT7 receptors and the 5-HT transporter (5-HTT), was measured by RTqPCR.

MAIN OUTCOME MEASURES

The main outcome is the differential expression of genes between 8-OH-DPAT- and vehicle-treated marmosets.

RESULTS

8-OH-DPAT affected the gene classes important to neural development (mPFC, mPOA, and DRN), neurotransmission (mPOA), energy production (mPFC and mPOA), learning and memory (CA1), and intracellular signal transduction (DRN). Oxytocin (OXT) in the mPOA and 5-HTT in the DRN were strongly increased by 8-OH-DPAT. 5-HT1A tended to increase in the mPFC, while 5-HT7 was decreased in the CA1.

CONCLUSIONS

Brain region-specific alterations of gene expression regulating neural circuitries, energy demands, and learning processes are associated with 8-OH-DPAT-induced decrease in female sexual receptivity and increase in pairmate aggression. The role of OXT in the serotonergic regulation of female sexual behavior and partner interactions warrants attention in future studies.

Synthesis of novel analogs of cabergoline: improving cardiovascular safety by removing 5-HT2B receptor agonism

The dopamine agonist cabergoline has been used to treat prolactinomas, Parkinson's disease, Cushing's disease and sexual dysfunction. However, its clinical use was severely curtailed when it was found that patients taking cabergoline had an increased risk of developing cardiac-valve regurgitation. This potentially life-threatening condition has been associated with drugs, such as cabergoline, that are 5-HT_2B receptor agonists. We prepared analogs of cabergoline and have identified several that have limited or no agonism at the 5-HT_2B receptor.

Polymorphic variants of neurotransmitter receptor genes may affect sexual function in aging males: data from the HALS study

BACKGROUND/AIMS

Human behavior is influenced by a number of brain neurotransmitters. Central dopamine, serotonin and melanocortin systems have special importance for male sexual function. We searched for associations between male aging symptoms and polymorphic sites of serotonin (5-HTR1B), melanocortin (MC4R) and dopamine (DRD2, DRD4) receptors.

METHODS

In a population-based sample, genotyping of 5-HTR1B (polymorphism: G861C), MC4R (polymorphisms: C-2745T, Val103Ile), DRD2 (polymorphism: C313T) and DRD4 (polymorphism: 48-bp VNTR) was performed in 387 healthy men. The Aging Males' Symptoms (AMS) scale was used to evaluate specific ailments of aging men. We analyzed answers to questions from the AMS scale. Five points of the questionnaire addressed sexual symptoms of the aging male: feeling of passing one's peak, decrease in beard growth, decrease in ability/frequency to perform sexually, decrease in the number of morning erections, and decrease in sexual desire/libido (lacking pleasure in sex, lacking desire for sexual intercourse). Relations between reported symptoms and variants of the polymorphic sites of the studied genes were assessed.

RESULTS

After adjusting for confounding factors (education, arterial hypertension, physical activity, weight, waist circumference) an association between the sexual dimension of AMS and genetic variants of 5-HTR1B G861C (p = 0.04) was observed.

CONCLUSIONS

Variability of neurotransmitter receptor genes may be associated with sexual symptoms of aging in men.

Bringing sex research into the 21st century: genetic and epigenetic approaches on female sexual function

Behavioral genetic evidence offers a useful way to disentangle some of the multifactorial etiological pathways toward the now clearly multidimensional construct of female sexual dysfunction (FSD) and has already shown its potential in providing a better understanding of the heterogeneous factors underlying FSD. Understanding the genetic basis and therefore physiologic key mechanisms of sexual function and dysfunction has the potential for improved treatments (i.e., the development of new medication) and ultimately prevention. However, genetic epidemiologic research into FSD is scarce and highlights the need for more in-depth exploration using larger samples and more accurate phenotypes. Knowledge gained from genetic studies also highlights the importance of environmental factors and gene-environment interactions in disease development and maintenance. Exploration of DNA epigenetic patterns that regulate gene expression profiles could therefore provide the missing link between epigenomic state and FSD, and as such may offer a new biological framework for the multifactorial pathoetiology underlying FSD.

Sex, drugs, and rock 'n' roll: hypothesizing common mesolimbic activation as a function of reward gene polymorphisms

The nucleus accumbens, a site within the ventral striatum, plays a prominent role in mediating the reinforcing effects of drugs of abuse, food, sex, and other addictions. Indeed, it is generally believed that this structure mandates motivated behaviors such as eating, drinking, and sexual activity, which are elicited by natural rewards and other strong incentive stimuli. This article focuses on sex addiction, but we hypothesize that there is a common underlying mechanism of action for the powerful effects that all addictions have on human motivation. That is, biological drives may have common molecular genetic antecedents, which if impaired, lead to aberrant behaviors. Based on abundant scientific support, we further hypothesize that dopaminergic genes, and possibly other candidate neurotransmitter-related gene polymorphisms, affect both hedonic and anhedonic behavioral outcomes. Genotyping studies already have linked gene polymorphic associations with alcohol and drug addictions and obesity, and we anticipate that future genotyping studies of sex addicts will provide evidence for polymorphic associations with specific clustering of sexual typologies based on clinical instrument assessments. We recommend that scientists and clinicians embark on research coupling the use of neuroimaging tools with dopaminergic agonistic agents to target specific gene polymorphisms systematically for normalizing hyper- or hypo-sexual behaviors.

Dopamine modulates reward system activity during subconscious processing of sexual stimuli

Dopaminergic medication influences conscious processing of rewarding stimuli, and is associated with impulsive-compulsive behaviors, such as hypersexuality. Previous studies have shown that subconscious subliminal presentation of sexual stimuli activates brain areas known to be part of the 'reward system'. In this study, it was hypothesized that dopamine modulates activation in key areas of the reward system, such as the nucleus accumbens, during subconscious processing of sexual stimuli. Young healthy males (n=53) were randomly assigned to two experimental groups or a control group, and were administered a dopamine antagonist (haloperidol), a dopamine agonist (levodopa), or placebo. Brain activation was assessed during a backward-masking task with subliminally presented sexual stimuli. Results showed that levodopa significantly enhanced the activation in the nucleus accumbens and dorsal anterior cingulate when subliminal sexual stimuli were shown, whereas haloperidol decreased activations in those areas. Dopamine thus enhances activations in regions thought to regulate 'wanting' in response to potentially rewarding sexual stimuli that are not consciously perceived. This running start of the reward system might explain the pull of rewards in individuals with compulsive reward-seeking behaviors such as hypersexuality and patients who receive dopaminergic medication.

A genome-wide association study of female sexual dysfunction

BACKGROUND

Female sexual dysfunction (FSD) is an important but controversial problem with serious negative impact on women's quality of life. Data from twin studies have shown a genetic contribution to the development and maintenance of FSD.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a genome-wide association study (GWAS) on 2.5 million single-nucleotide polymorphisms (SNPs) in 1,104 female twins (25-81 years of age) in a population-based register and phenotypic data on lifelong sexual functioning. Although none reached conventional genome-wide level of significance (10 × -8), we found strongly suggestive associations with the phenotypic dimension of arousal (rs13202860, P = 1.2 × 10(-7); rs1876525, P = 1.2 × 10(-7); and rs13209281 P = 8.3 × 10(-7)) on chromosome 6, around 500 kb upstream of the locus HTR1E (5-hydroxytryptamine receptor 1E) locus, related to the serotonin brain pathways. We could not replicate previously reported candidate SNPs associated with FSD in the DRD4, 5HT2A and IL-1B loci.

CONCLUSIONS/SIGNIFICANCE

We report the first GWAS of FSD symptoms in humans. This has pointed to several "risk alleles" and the implication of the serotonin and GABA pathways. Ultimately, understanding key mechanisms via this research may lead to new FSD treatments and inform clinical practice and developments in psychiatric nosology.

Evaluation of 18F-labeled benzodioxine piperazine-based dopamine D4 receptor ligands: lipophilicity as a determinate of nonspecific binding

Derivatization of the putative neuroleptic 1-(2,3-dihydrobenzo[1,4]dioxin-6-yl)-4-(4-fluorobenzyl)piperazine (3a) led to a series of new dopamine receptor D4 ligands displaying high affinity (Ki=1.1-15 nM) and D2/D4 subtype selectivities of about 800-6700. These ligands were labeled with the short-lived positron emitter fluorine-18 and analyzed for their potential application for imaging studies by positron emission tomography (PET). In vitro autoradiography was used to determine their nonspecific binding behavior as a result of their structural and thus physicochemical properties. The biodistribution, in vivo stability, and brain uptake of the most promising D4 radioligand candidate were determined. This proved to be 1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-4-((6-fluoropyridin-3-yl)methyl)piperazine ([18F]3d), which revealed an excellent binding pattern with a high selectivity and limited nonspecific binding in vitro. This analogue also exhibited a high stability and an extremely high brain uptake in vivo with specific binding in hippocampus, cortex, colliculus, and cerebellum as determined by ex vivo autoradiography. Thus, [18F]3d appears as a suitable D4 radioligand for in vivo imaging, encouraging continued evaluation by PET studies.

Bladder, bowel, and sexual dysfunction in Parkinson's disease

Bladder dysfunction (urinary urgency/frequency), bowel dysfunction (constipation), and sexual dysfunction (erectile dysfunction) (also called “pelvic organ” dysfunctions) are common nonmotor disorders in Parkinson's disease (PD). In contrast to motor disorders, pelvic organ autonomic dysfunctions are often nonresponsive to levodopa treatment. The brain pathology causing the bladder dysfunction (appearance of overactivity) involves an altered dopamine-basal ganglia circuit, which normally suppresses the micturition reflex. By contrast, peripheral myenteric pathology causing slowed colonic transit (loss of rectal contractions) and central pathology causing weak strain and paradoxical anal sphincter contraction on defecation (PSD, also called as anismus) are responsible for the bowel dysfunction. In addition, hypothalamic dysfunction is mostly responsible for the sexual dysfunction (decrease in libido and erection) in PD, via altered dopamine-oxytocin pathways, which normally promote libido and erection. The pathophysiology of the pelvic organ dysfunction in PD differs from that in multiple system atrophy; therefore, it might aid in differential diagnosis. Anticholinergic agents are used to treat bladder dysfunction in PD, although these drugs should be used with caution particularly in elderly patients who have cognitive decline. Dietary fibers, laxatives, and “prokinetic” drugs such as serotonergic agonists are used to treat bowel dysfunction in PD. Phosphodiesterase inhibitors are used to treat sexual dysfunction in PD. These treatments might be beneficial in maximizing the patients' quality of life.

Is love passion an addictive disorder?

AIMS

Inquiry regarding the relationship between passionate love and addiction has long been a topic of intense debate. Recent advances in neurobiology now allow for an examination between these two states.

METHODS

After describing the clinical distinctions between "love passion," "love addiction," and "sex addiction," we compare clinical, neuropsychological, neurobiological, and neuroimaging data on love, passion, pathological gambling (PG) and substance dependence.

RESULTS

There are no recognized definitions or diagnostic criteria for "love addiction," but its phenomenology has some similarities to substance dependence: euphoria and unrestrained desire in the presence of the love object or associated stimuli (drug intoxication); negative mood, anhedonia, and sleep disturbance when separated from the love object (drug withdrawal); focussed attention on and intrusive thoughts about the love object; and maladaptive or problematic patterns of behavior (love relation) leading to clinically significant impairment or distress, with pursuit despite knowledge of adverse consequences. Limited animal and human studies suggest that brain regions (e.g., insula, anterior cingulated [ACC], orbitofrontal [OFC]) and neurotransmitters (dopamine) that mediate substance dependence may also be involved with love addiction (as for PG). Ocytocin (OT), which is implicated in social attachment and mating behavior, may also be involved in substance dependence. There are no data on the epidemiology, genetics, co-morbidity, or treatment of love addiction.

CONCLUSION

There are currently insufficient data to place some cases of "love passion" within a clinical disorder, such as "love addiction," in an official diagnostic nomenclature or to firmly classify it as a behavioral addiction or disorder of impulse control. Further clinical and scientific studies are needed to improve our understanding and treatment of this condition. For these studies, we propose new criteria for evaluating addiction to love.

Associations between dopamine D4 receptor gene variation with both infidelity and sexual promiscuity

BACKGROUND

Human sexual behavior is highly variable both within and between populations. While sex-related characteristics and sexual behavior are central to evolutionary theory (sexual selection), little is known about the genetic bases of individual variation in sexual behavior. The variable number tandem repeats (VNTR) polymorphism in exon III of the human dopamine D4 receptor gene (DRD4) has been correlated with an array of behavioral phenotypes and may be predicatively responsible for variation in motivating some sexual behaviors, particularly promiscuity and infidelity.

METHODOLOGY/PRINCIPAL FINDINGS

We administered an anonymous survey on personal history of sexual behavior and intimate relationships to 181 young adults. We also collected buccal wash samples and genotyped the DRD4 VNTR. Here we show that individuals with at least one 7-repeat allele (7R+) report a greater categorical rate of promiscuous sexual behavior (i.e., having ever had a "one-night stand") and report a more than 50% increase in instances of sexual infidelity.

CONCLUSIONS/SIGNIFICANCE

DRD4 VNTR genotype varies considerably within and among populations and has been subject to relatively recent, local selective pressures. Individual differences in sexual behavior are likely partially mediated by individual genetic variation in genes coding for motivation and reward in the brain. Conceptualizing these findings in terms of r/K selection theory suggests a mechanism for selective pressure for and against the 7R+ genotype that may explain the considerable global allelic variation for this polymorphism.

Dopamine D4 receptor gene associated with fairness preference in ultimatum game

In experimental economics, the preference for reciprocal fairness has been observed in the controlled and incentivized laboratory setting of the ultimatum game, in which two individuals decide on how to divide a sum of money, with one proposing the share while the second deciding whether to accept. Should the proposal be accepted, the amount is divided accordingly. Otherwise, both would receive no money. A recent twin study has shown that fairness preference inferred from responder behavior is heritable, yet its neurogenetic basis remains unknown. The D4 receptor (DRD4) exon3 is a well-characterized functional polymorphism, which is known to be associated with attention deficit hyperactivity disorder and personality traits including novelty seeking and self-report altruism. Applying a neurogenetic approach, we find that DRD4 is significantly associated with fairness preference. Additionally, the interaction among this gene, season of birth, and gender is highly significant. This is the first result to link preference for reciprocal fairness to a specific gene and suggests that gene × environment interactions contribute to economic decision making.