Modulation of intracellular cyclic AMP levels by different human dopamine D4 receptor variants

Differential Susceptibility: The Genetic Moderation of Peer Pressure on Alcohol Use

Although peer pressure can influence adolescents' alcohol use, individual susceptibility to these pressures varies across individuals. The dopamine receptor D4 gene (DRD4) is a potential candidate gene that may influence adolescents' susceptibility to their peer environment due to the role dopamine plays in reward sensation during social interaction. We hypothesized that DRD4 genotype status would moderate the impact of 7th-grade antisocial peer pressure on 12th-grade lifetime alcohol use (n = 414; 58.7% female; 92.8% White). The results revealed significant main effects for antisocial peer pressure, but no main effects for DRD4 genotype on lifetime alcohol use. Adolescent DRD4 genotype moderated the association between peer pressure and lifetime alcohol use. For individuals who carried at least one copy of the DRD4 7-repeat allele (7+), antisocial peer pressure was associated with increased lifetime alcohol use. These findings indicate that genetic sensitivity to peer pressure confers increased alcohol use in late adolescence.

The Molecular Neurobiology of Twelve Steps Program & Fellowship: Connecting the Dots for Recovery

There are some who suggest that alcoholism and drug abuse are not diseases at all and that they are not consequences of a brain disorder as espoused recently by the American Society of Addiction Medicine (ASAM). Some would argue that addicts can quit on their own and moderate their alcohol and drug intake. When they present to a treatment program or enter the 12 Step Program & Fellowship, many addicts finally achieve complete abstinence. However, when controlled drinking fails, there may be successful alternatives that fit particular groups of individuals. In this expert opinion, we attempt to identify personal differences in recovery, by clarifying the molecular neurobiological basis of each step of the 12 Step Program. We explore the impact that the molecular neurobiological basis of the 12 steps can have on Reward Deficiency Syndrome (RDS) despite addiction risk gene polymorphisms. This exploration has already been accomplished in part by Blum and others in a 2013 Springer Neuroscience Brief. The purpose of this expert opinion is to briefly, outline the molecular neurobiological and genetic links, especially as they relate to the role of epigenetic changes that are possible in individuals who regularly attend AA meetings. It begs the question as to whether "12 steps programs and fellowship" does induce neuroplasticity and continued dopamine D2 receptor proliferation despite carrying hypodopaminergic type polymorphisms such as DRD2 A1 allele. "Like-minded" doctors of ASAM are cognizant that patients in treatment without the "psycho-social-spiritual trio," may not be obtaining the important benefits afforded by adopting 12-step doctrines. Are we better off with coupling medical assisted treatment (MAT) that favors combining dopamine agonist modalities (DAM) as possible histone-deacetylase activators with the 12 steps followed by a program that embraces either one or the other? While there are many unanswered questions, at least we have reached a time when "science meets recovery," and in doing so, can further redeem joy in recovery.

DRD4 and SLC6A3 gene polymorphisms are associated with food intake and nutritional status in children in early stages of development

Variants of dopamine system genes such as the DRD4 and the SLC6A3 genes may be involved in food intake regulation because the dopaminergic system influences food reward. We investigated an association of polymorphisms in the DRD4 (exon 3 VNTR) and SLC6A3 (3'UTR VNTR, rs2550948, rs2652511 and rs1048953) genes with food intake and nutritional status in children. This prospective cohort study recruited 359 children at birth. Dietary data and nutritional status were collected at 1 year, 3-4 years, and 7-8 years of age. The polymorphisms were analyzed using polymerase chain reaction based techniques. Food intake and nutritional status were compared among the different SNP genotypes. In the first year of life, DRD4.7R- children showed higher BMI Z-scores (P=.019) than the DRD4.7R+ cohort. At 3-4 years old, DRD4.7R- and SLC6A3.10R/10R children showed a higher intake of palatable foods (P=.024) and a higher waist circumference (P=.017). The rs1048953 SLC6A3 polymorphism was associated with average daily energy intake (P=.003) at 3-4 years and with a waist-to-height ratio of children at 7-8 years (P=.041). Carriers of high dopamine activity alleles of the VNTRs studied in DRD4 and SLC6A3 genes and carriers of T/T genotype of the variant rs1048953 SLC6A3 can present an increased risk for obesity related to overeating because high dopamine activity can increase the perceived incentive value of food reward.

Parent and youth dopamine D4 receptor genotypes moderate multilevel contextual effects on rural African American youth's risk behavior

The present investigation extends research on Gene × Environment interactions and youth risk behavior by linking multilevel contextual factors, such as community disadvantage and protective parenting practices, to both parental and youth dopamine D4 receptor (DRD4) genotypes. We expected community disadvantage to influence youth risk behavior via a series of indirect effects involving protective parenting and youth's planful future orientation when both parents' and youth's DRD4 status was considered. Genetic moderation processes also were tested to determine whether they conformed to a diathesis-stress or a differential susceptibility model. Hypotheses were investigated with data from 361 rural African American youth and their parents assessed 3 times when youth were ages 16 to 19. Community disadvantage interacted with parental DRD4 status to predict low levels of protective parenting. Protective parenting, in turn, interacted with youth DRD4 status to forecast increases in youth's planful future orientations, a proximal influence on changes in risk behavior. The Parental DRD4 × Community Disadvantage interaction, but not youth DRD4 × Protective Parenting, conformed to a differential susceptibility model. Indirect effect analyses revealed a significant indirect path linking community disadvantage to youth risk behavior through a series of multilevel Gene × Environment interaction processes.

A review of pharmacogenetic studies of substance-related disorders

BACKGROUND

Substance-related disorders (SRDs) are a major cause of morbidity and mortality worldwide. Family, twin, and adoption studies have demonstrated the substantial heritability of SRDs. To determine the impact of genetic variation on risk for SRD and the response to treatment, researchers have conducted a number of secondary data analyses and quasi-experimental studies that target one or more candidate gene variants.

METHODS

This review examines studies in which candidate polymorphisms were examined as mediator variables to identify pharmacogenetic effects on subjective responses to drug administration or cues or outcomes of medication trials for SRDs. Efforts to use a meta-analytic approach to quantify these effects are premature because the number of available studies using similar methods and outcomes is limited, so the present review is qualitative.

RESULTS

Findings from these studies provide preliminary evidence of clinically relevant pharmacogenetic effects. However, independent replication of these findings has been sparse.

CONCLUSIONS

Although this growing body of literature has produced conflicting results, improved statistical controls may help to clarify the findings. Additionally, the use of empirically derived sub-phenotypes (i.e., which serve to differentiate distinct groups of affected individuals) may also help to identify genetic mediators of pharmacologic response in relation to SRDs. The identification of genetic mediators can inform clinical care both by identifying risk factors for SRDs and predicting adverse events and therapeutic outcomes associated with specific pharmacotherapies.

Dopamine D4 receptor polymorphism and sex interact to predict children's affective knowledge

Affective knowledge, the ability to understand others' emotional states, is considered to be a fundamental part in efficient social interaction. Affective knowledge can be seen as related to cognitive empathy, and in the framework of theory of mind (ToM) as affective ToM. Previous studies found that cognitive empathy and ToM are heritable, yet little is known regarding the specific genes involved in individual variability in affective knowledge. Investigating the genetic basis of affective knowledge is important for understanding brain mechanisms underlying socio-cognitive abilities. The 7-repeat (7R) allele within the third exon of the dopamine D4 receptor gene (DRD4-III) has been a focus of interest, due to accumulated knowledge regarding its relevance to individual differences in social behavior. A recent study suggests that an interaction between the DRD4-III polymorphism and sex is associated with cognitive empathy among adults. We aimed to examine the same association in two childhood age groups. Children (N = 280, age 3.5 years, N = 283, age 5 years) participated as part of the Longitudinal Israel Study of Twins. Affective knowledge was assessed through children's responses to an illustrated story describing different emotional situations, told in a laboratory setting. The findings suggest a significant interaction between sex and the DRD4-III polymorphism, replicated in both age groups. Boy carriers of the 7R allele had higher affective knowledge scores than girls, whereas in the absence of the 7R there was no significant sex effect on affective knowledge. The results support the importance of DRD4-III polymorphism and sex differences to social development. Possible explanations for differences from adult findings are discussed, as are pathways for future studies.

Associations Between a Dopamine D4 Receptor Gene, Alcohol Use, and Sexual Behaviors among Female Adolescent African Americans

Adolescent African-American females are disproportionately impacted by HIV, thus there is a clear need to understand factors associated with increased HIV-risk behaviors among this vulnerable population. We sought to explore the association between a dopamine D4 receptor gene (DRD4), a genetic marker associated with natural variations in rewarding behaviors, and self-reported alcohol-use and sexual risk-behaviors, while controlling for other known correlates of risk-taking such as impulsivity, sensation seeking, and peer norms among a group of high-risk African American female adolescents to evaluate whether this biological factor enhances our understanding of patterns of risk in this vulnerable group.

Polymorphism in variable number of tandem repeats of dopamine d4 gene is a genetic risk factor in attention deficit hyperactive egyptian children: pilot study

INTRODUCTION

The variable number of tandem repeats (VNTR) of the dopamine receptor D4 (DRD4) gene among humans may elucidate individual differences in susceptibility to neuropsychiatric diseases. Dopamine dysfunction may be involved with Attention Deficit Hyperactivity Disorder (ADHD) symptoms. In this study, we report the association between the phenotype of ADHD, a condition characterized by inattentiveness, hyperactivity, and impulsiveness, and a 48-base pair VNTR in exon 3 of the DRD4 polymorphism.

SUBJECTS AND METHODS

We used a case control approach conducted on 29 ADHD and 31 ethnically matched control Egyptian children (ages 6-12 years). Cases were assessed by a psychiatric semi-structured interview and the Conners' Parent Rating Scale. VNTR polymorphisms of the DRD4 gene were done by touchdown PCR program using exon 3-specific primers followed by agarose gel electrophoresis.

RESULTS

We observed a significant association between the existence of D4.4 allele of DRD4 and ADHD (P, 0.002); 6.9% of cases showed a single D4.4 and 10.3% showed a double D4.4 as compared to controls in whom D4.4 has never been detected.

CONCLUSION

Children with smaller number of repeat alleles (two to four repeats) of the DRD4 gene have higher possibility to develop ADHD in Egyptian children.

Childhood Sexual Abuse and Impulsive Personality Traits: Mixed Evidence for Moderation by DRD4 Genotype

This project examines associations between childhood sexual abuse (CSA) and two dimensions of impulsivity (sensation seeking and premeditation), and tests whether CSA-personality associations are moderated by the DRD4 exon III VNTR polymorphism. Sample 1 is from a longitudinal study of university students measured at 10 waves over ages 18-24 years (n = 500). Sample 2 is from a national sample of young adult sibling pairs, ages 18-24, from the National Longitudinal Study of Adolescent Health (n = 2,559). In both samples, CSA was associated with elevated sensation seeking. In Sample 1, the association between CSA and sensation seeking was moderated by DRD4 genotype; this gene × environment interaction effect, however, was not replicated in Sample 2. Results suggest new avenues for research on CSA in the area of normal-range personality variation.

Interparental Relationship Sensitivity Leads to Adolescent Internalizing Problems: Different Genotypes, Different Pathways

Several studies have established that child interparental conflict evaluations link parent relationship functioning and adolescent adjustment. Using differential susceptibility theory and its vantage sensitivity complement as their framework, the authors examined differences between adolescents who vary in the DRD4 7 repeat genotype (i.e. 7+ vs. 7-) in how both interparental conflict and positivity affect adolescents' evaluations of interparental conflict (i.e., threat appraisals) and how these evaluations affect internalizing problems. Results from longitudinal multiple-group path models using PROSPER data (N = 452) supported the hypothesis that threat appraisals for 7+ adolescents would be more affected by perceptions of interparental positivity compared to 7- adolescents; however, threat appraisals for 7+ adolescents were also less affected by interparental conflict. Among 7- adolescents, interparental conflict perceptions were associated with higher threat appraisals, and no association was found for perceptions of positivity. For adolescents of both genotypes, higher threat was associated with greater internalizing problems.

An association between a dopamine transporter gene (SLC6A3) haplotype and ADHD symptom measures in nonclinical adults

Previous genetic studies have postulated that attention deficit hyperactivity disorder (ADHD) should be regarded as the extreme end of a set of behavioural traits that can be continuously measured in the general population. The current study adopted a quantitative trait approach to examine the relationship between dopamine gene variants and self-reported ADHD symptoms in 517 nonclinical adults. Although genetic associations with variants of both the dopamine transporter (DAT1; SLC6A3) and D4 receptor (DRD4) genes have been reliably reported in children, results in adults are less consistent. We probed two potentially functional variable number of tandem repeat (VNTR) polymorphisms in the 3'UTR and intron 8 of DAT1, the 10-repeat and 6-repeat alleles of which respectively form a haplotype (10/6 DAT1 haplotype) that is associated with childhood ADHD. We also genotyped the exon 3 VNTR of DRD4, the 7-repeat allele of which is also an established risk factor for childhood ADHD. Permutation analysis showed an influence of the 10/6 DAT1 haplotype on both CAARS-G and CAARS-H (DSM-IV ADHD Symptoms Total and ADHD Index respectively), such that ADHD symptom scores increased with each additional copy of the 10/6 DAT1 haplotype. This result survived corrections for multiple comparisons both at the level of genotype and phenotype. A nominal association with CAARS-G was also found for the 7-repeat allele of the DRD4 VNTR however this did not survive multiple comparison correction. Our results provide further support for the influence of variation in the 10/6 DAT1 haplotype and individual differences in ADHD symptoms in adults.

Developmental differences in early adolescent aggression: a gene × environment × intervention analysis

Aggression-related problems such as assault and homicide among adolescents and young adults exact considerable social and economic costs. Although progress has been made, additional research is needed to help combat this persistent problem. Several lines of research indicate that parental hostility is an especially potent predictor of adolescent aggression, although most longitudinal research has focused on clarifying the direction of effects. In this study, we used longitudinal data from the PROSPER project (N = 580; 54.8% female), a primarily rural Caucasian preventative intervention sample, to examine developmental change in early- to mid-adolescent aggressive behavior problems (age 11-16 years). In addition, we examined maternal hostility as a predictor of developmental change in aggression and the PROSPER preventative intervention, designed to reduce substance use and aggression, as a potential influence on this association. Lastly, several studies indicate that variation in the DRD4 7-repeat gene moderates both parenting and intervention influences on externalizing behavior. Accordingly, we examined the potential moderating role of DRD4. As hypothesized, there was a significant maternal hostility by intervention interaction indicating that the intervention reduced the negative impact of maternal hostility on adolescent change in aggressive behavior problems. DRD4 7-repeat status (7+ vs. 7-) further conditioned this association whereby control group 7+ adolescents with hostile mothers showed increasing aggressive behavior problems. In contrast, aggression decreased for 7+ adolescents with similarly hostile mothers in the intervention. Implications for prevention are discussed as well as current perspectives in candidate gene-by-environment interaction research.

Cognitive and neural correlates of the 5-repeat allele of the dopamine D4 receptor gene in a population lacking the 7-repeat allele

The 5-repeat allele of a common length polymorphism in the gene that encodes the dopamine D4 receptor (DRD4) is robustly associated with the risk of attention deficit hyperactivity disorder (ADHD) and substantially exists in Asian populations, which have a lower ADHD prevalence. In this study, we investigated the effect of this allele on microstructural properties of the brain and on its functional activity during externally directed attention-demanding tasks and creative performance in the 765 Asian subjects. For this purpose, we employed diffusion tensor imaging, N-back functional magnetic resonance imaging paradigms, and a test to measure creativity by divergent thinking. The 5-repeat allele was significantly associated with increased originality in the creative performance, increased mean diffusivity (the measure of how the tissue includes water molecules instead of neural and vessel components) in the widespread gray and white matter areas of extensive areas, particularly those where DRD4 is expressed, and reduced task-induced deactivation in the areas that are deactivated during the tasks in the course of both the attention-demanding working memory task and simple sensorimotor task. The observed neural characteristics of 5-repeat allele carriers may lead to an increased risk of ADHD and behavioral deficits. Furthermore, the increased originality of creative thinking observed in the 5-repeat allele carriers may support the notion of the side of adaptivity of the widespread risk allele of psychiatric diseases.

The conditioning of intervention effects on early adolescent alcohol use by maternal involvement and dopamine receptor D4 (DRD4) and serotonin transporter linked polymorphic region (5-HTTLPR) genetic variants

Data drawn from the in-home subsample of the PROSPER intervention dissemination trial were used to investigate the moderation of intervention effects on underage alcohol use by maternal involvement and candidate genes. The primary gene examined was dopamine receptor D4 (DRD4). Variation in this gene and maternal involvement were hypothesized to moderate the influence of intervention status on alcohol use. The PROSPER data used were drawn from 28 communities randomly assigned to intervention or comparison conditions. Participating youth were assessed in five in-home interviews from sixth to ninth grades. A main effect of sixth-grade pretest maternal involvement on ninth-grade alcohol use was found. Neither intervention status nor DRD4 variation was unconditionally linked to ninth-grade drinking. However, moderation analyses revealed a significant three-way interaction among DRD4 status, maternal involvement, and intervention condition. Follow-up analyses revealed that prevention reduced drinking risk, but only for youth with at least one DRD4 seven-repeat allele who reported average or greater pretest levels of maternal involvement. To determine if this conditional pattern was limited to the DRD4 gene, we repeated analyses using the serotonin transporter linked polymorphic region site near the serotonin transporter gene. The results for this supplemental analysis revealed a significant three-way interaction similar but not identical to that found for DRD4.

Intra-Individual Response Variability Assessed by Ex-Gaussian Analysis may be a New Endophenotype for Attention-Deficit/Hyperactivity Disorder

Intra-individual variability of response times (RTisv) is considered as potential endophenotype for attentional deficit/hyperactivity disorder (ADHD). Traditional methods for estimating RTisv lose information regarding response times (RTs) distribution along the task, with eventual effects on statistical power. Ex-Gaussian analysis captures the dynamic nature of RTisv, estimating normal and exponential components for RT distribution, with specific phenomenological correlates. Here, we applied ex-Gaussian analysis to explore whether intra-individual variability of RTs agrees with criteria proposed by Gottesman and Gould for endophenotypes. Specifically, we evaluated if normal and/or exponential components of RTs may (a) present the stair-like distribution expected for endophenotypes (ADHD > siblings > typically developing children (TD) without familiar history of ADHD) and (b) represent a phenotypic correlate for previously described genetic risk variants. This is a pilot study including 55 subjects (20 ADHD-discordant sibling-pairs and 15 TD children), all aged between 8 and 13 years. Participants resolved a visual Go/Nogo with 10% Nogo probability. Ex-Gaussian distributions were fitted to individual RT data and compared among the three samples. In order to test whether intra-individual variability may represent a correlate for previously described genetic risk variants, VNTRs at DRD4 and SLC6A3 were identified in all sibling-pairs following standard protocols. Groups were compared adjusting independent general linear models for the exponential and normal components from the ex-Gaussian analysis. Identified trends were confirmed by the non-parametric Jonckheere-Terpstra test. Stair-like distributions were observed for μ (p = 0.036) and σ (p = 0.009). An additional "DRD4-genotype" × "clinical status" interaction was present for τ (p = 0.014) reflecting a possible severity factor. Thus, normal and exponential RTisv components are suitable as ADHD endophenotypes.

Neurogenetic and Neuroimaging Evidence for a Conceptual Model of Dopaminergic Contributions to Obesity

As the incidence of obesity continues to rise, clinicians and researchers alike are seeking explanations for why some people become obese while others do not. While caloric intake and physical activity most certainly play a role, some individuals continue to gain weight despite careful attention to these factors. Increasing evidence suggests that genetics may play a role, with one potential explanation being genetic variability in genes within the neurotransmitter dopamine pathway. This variability can lead to a disordered experience with the rewarding properties of food. This review of literature examines the extant knowledge about the relationship between obesity and the dopaminergic reward pathways in the brain, with particularly strong evidence provided from neuroimaging and neurogenetic data. Pubmed, Google Scholar, and Cumulative Index to Nursing and Allied Health Literature searches were conducted with the search terms dopamine, obesity, weight gain, food addiction, brain regions relevant to the mesocortical and mesolimbic (reward) pathways, and relevant dopaminergic genes and receptors. These terms returned over 200 articles. Other than a few sentinel articles, articles were published between 1993 and 2013. These data suggest a conceptual model for obesity that emphasizes dopaminergic genetic contributions as well as more traditional risk factors for obesity, such as demographics (age, race, and gender), physical activity, diet, and medications. A greater understanding of variables contributing to weight gain and obesity is imperative for effective clinical treatment.

Symptoms of attention-deficit/hyperactivity disorder in Down syndrome: effects of the dopamine receptor D4 gene

This study examined individual differences in ADHD symptoms and executive function (EF) in children with Down syndrome (DS) in relation to the dopamine receptor D4 (DRD4) gene, a gene often linked to ADHD in people without DS. Participants included 68 individuals with DS (7-21 years), assessed through laboratory tasks, caregiver reports, and experimenter ratings. Saliva samples were collected from the DS group and 66 children without DS to compare DRD4 allele distribution, showing no difference between the groups. When the sample with DS was stratified for ethnicity (n  =  32), the DRD4 7-repeat allele significantly related to parent and experimenter ratings, but not to laboratory assessments. These results suggest that nontrisomy genetic factors may contribute to individual differences in ADHD symptoms in persons with DS.

Relation of the multilocus genetic composite reflecting high dopamine signaling capacity to future increases in BMI

Because food intake exerts its rewarding effect by increasing dopamine (DA) signaling in reward circuitry, it theoretically follows that individuals with a greater number of genotypes putatively associated with high DA signaling capacity are at increased risk for overeating and subsequent weight gain. We tested the association between the multilocus genetic composite risk score, defined by the total number of genotypes putatively associated with greater DA signaling capacity (i.e. TaqIA A2 allele, DRD2-141C Ins/Del and Del/Del genotypes, DRD4-S allele, DAT1-S allele, and COMT Val/Val genotype), and future increases in Body Mass Index (BMI) in three prospective studies. Participants in Study 1 (N = 30; M age = 15.2; M baseline BMI = 26.9), Study 2 (N = 34; M age = 20.9; M baseline BMI = 28.2), and Study 3 (N = 162; M age = 15.3, M baseline BMI = 20.8) provided saliva samples from which epithelial cells were collected, permitting DNA extraction. The multilocus genetic composite risk score was associated with future increases in BMI in all three studies (Study 1, r = 0.37; Study 2, r = 0.22; Study 3, r = 0.14) and the overall sample (r = 0.19). DRD4-S was associated with increases in BMI in Study 1 (r = 0.42), Study 2 (r = 0.27), and in the overall sample (r = 0.17). DAT1-S was associated with increases in BMI in Study 3 (r = 0.17) and in the overall sample (r = 0.12). There were no associations between the other genotypes (TaqIA, COMT, and DRD2-141C) and change in BMI over 2-year follow-up. Data suggest that individuals with a genetic propensity for greater DA signaling capacity are at risk for future weight gain and that combining alleles that theoretically have a similar function may provide a more reliable method of modeling genetic risk associated with future weight gain than individual genotypes.

Dopamine receptor D4 (DRD4) gene modulates the influence of informational masking on speech recognition

Listeners vary substantially in their ability to recognize speech in noisy environments. Here we examined the role of genetic variation on individual differences in speech recognition in various noise backgrounds. Background noise typically varies in the levels of energetic masking (EM) and informational masking (IM) imposed on target speech. Relative to EM, release from IM is hypothesized to place greater demand on executive function to selectively attend to target speech while ignoring competing noises. Recent evidence suggests that the long allele variant in exon III of the DRD4 gene, primarily expressed in the prefrontal cortex, may be associated with enhanced selective attention to goal-relevant high-priority information even in the face of interference. We investigated the extent to which this polymorphism is associated with speech recognition in IM and EM conditions. In an unscreened adult sample (Experiment 1) and a larger screened replication sample (Experiment 2), we demonstrate that individuals with the DRD4 long variant show better recognition performance in noise conditions involving significant IM, but not in EM conditions. In Experiment 2, we also obtained neuropsychological measures to assess the underlying mechanisms. Mediation analysis revealed that this listening condition-specific advantage was mediated by enhanced executive attention/working memory capacity in individuals with the long allele variant. These findings suggest that DRD4 may contribute specifically to individual differences in speech recognition ability in noise conditions that place demands on executive function.

DRD4 and susceptibility to peer influence on alcohol use from adolescence to adulthood

BACKGROUND

The long allele of DRD4 is associated with greater susceptibility to peer influences on alcohol use in young adulthood, but it is unclear whether this increased susceptibility extends to other developmental periods. This study examined the interactive effects of DRD4 polymorphism and friends' alcohol use from adolescence to adulthood.

METHODS

Participants (N = 340; 59% female; 98% White) reported on their own and their friends' alcohol use at four time points between mean ages 17 and 33. Autoregressive cross-lagged models evaluated reciprocal relationships between friends' alcohol use and participants' own alcohol use and frequency of heavy drinking over time. Multigroup modeling tested differences in model paths and covariances across high vs. low risk DRD4 polymorphisms.

RESULTS

Alcohol use at age 33 was predicted by previous friends' alcohol use and correlated with current friends' alcohol use only for carriers of the DRD4 long allele. Regardless of DRD4 genotype, friends' alcohol use at age 17 predicted greater alcohol use and more frequent heavy drinking at age 23. Alcohol use and/or heavy drinking predicted greater friends' alcohol use at later time points for both genotype groups across adolescence and adulthood.

CONCLUSIONS

The long allele of DRD4 is associated with increased susceptibility to peer influences on alcohol use in young adulthood, but not earlier in development. Adults with the long allele of DRD4 may benefit from interventions educating them about this risk and equipping them with strategies to reduce affiliations with and influence of drinking friends.

Are infants differentially sensitive to parenting? Early maternal care, DRD4 genotype and externalizing behavior during adolescence

Insensitive and unresponsive caregiving during infancy has been linked to externalizing behavior problems during childhood and adolescence. The 7-repeat (7r) allele of the dopamine D4 receptor (DRD4) gene has meta-analytically been associated with a heightened susceptibility to adverse as well as supportive environments. In the present study, we examined long-term effects of early maternal care, DRD4 genotype and the interaction thereof on externalizing and internalizing psychopathology during adolescence. As part of an ongoing epidemiological cohort study, early maternal care was assessed at child's age 3 months during a nursing and playing situation. In a sample of 296 offspring, externalizing and internalizing symptoms were assessed using a psychiatric interview conducted at age 15 years. Parents additionally filled out a questionnaire on their children's psychopathic behaviors. Results indicated that adolescents with the DRD4 7r allele who experienced less responsive and stimulating early maternal care exhibited more symptoms of ADHD and CD/ODD as well as higher levels of psychopathic behavior. In accordance with the hypothesis of differential susceptibility, 7r allele carriers showed fewer ADHD symptoms and lower levels of psychopathic behavior when exposed to especially beneficial early caregiving. In contrast, individuals without the DRD4 7r allele proved to be insensitive to the effects of early maternal care. This study replicates earlier findings with regard to an interaction between DRD4 genotype and early caregiving on externalizing behavior problems in preschoolers. It is the first one to imply continuity of this effect until adolescence.

Differential susceptibility in a developmental perspective: DRD4 and maternal sensitivity predicting externalizing behavior

This study is the first to investigate the longitudinal effects of gene-environment interplay between DRD4 genotype and maternal sensitivity on child externalizing behavior. Multiple measures of maternal sensitivity (14, 36, and 48 months) and externalizing behavior (18 months, 36 months, and 5 years) were assessed in a large cohort study (N = 548). Early maternal insensitivity (14 months) was associated with early externalizing behavior (18 months) in a for better and for worse manner, but only in children with at least one DRD4 7-repeat, consistent with a differential susceptibility model. Later insensitivity (48 months) predicted externalizing behavior at age 5 independent of DRD4 genotype. A structural equation model including all measures across time supported the differential susceptibility model: The overall effect of early maternal sensitivity on later externalizing behavior was significant only for children with a DRD4 7-repeat allele. The results highlight the importance of studying gene-environment interactions across development.

Ondansetron and sertraline may interact with 5-HTTLPR and DRD4 polymorphisms to reduce drinking in non-treatment seeking alcohol-dependent women: exploratory findings

The purpose of this exploratory study was to examine the interaction of 5-HTTLPR and DRD4 exon III polymorphisms with gender in non-treatment seeking alcohol-dependent (AD) individuals while alternately taking ondansetron and sertraline. Evidence suggests that alcohol dependence may be influenced by a genetic interaction that may be gender-specific with temporal changes making pharmacological treatment with serotonergic drugs complex. The main trial was a within-subject double-blind placebo-controlled human laboratory study with 77 non-treatment-seeking AD individuals randomized (55 completed, 49 complete data) to receive 200 mg/day of sertraline or 0.5 mg/day of ondansetron for 3 weeks followed by an alcohol self-administration experiment (ASAE), then placebo for 3 weeks followed by a second ASAE, then receive the alternate drug, in a counterbalanced order, for 3 weeks followed by a third ASAE. Results for men were not significant. Women with the LL 5-HTTLPR genotype receiving ondansetron and SS/SL 5-HTTLPR genotype receiving sertraline (matched), drank significantly fewer drinks per drinking day (DDD) during the 7 days prior to the first and third ASAEs than women receiving the mismatched medication (i.e., sertraline to LL and ondansetron to SS/SL). In a 3-way interaction, 5-HTTLPR alleles by DRD4 alleles by medications, women with the LL genotype who received ondansetron and had DRD4≥7 exon III repeats drank significantly fewer DDD as did SS/SL women who received sertraline but conversely had DRD4<7 repeats in the 7-day period leading up to the first and third ASAEs. Consistent with these data was a significant reduction of milliliters consumed ad libitum during these same ASAEs. These exploratory findings add possible support to gender and genetic differences among AD individuals in response to serotonergic pharmacotherapies. Future trials should be powerful enough to take into account that endophenotypes and a targeting of serotonergic interactions may be essential to successfully treat alcohol dependence.

Neural correlates of inhibitory control and functional genetic variation in the dopamine D4 receptor gene

BACKGROUND

The dopamine D4 receptor gene (DRD4) has been implicated in psychiatric disorders in which deficits of self-regulation are a prominent feature (e.g., attention-deficit hyperactivity disorder and substance use disorders) and in dopamine D4 receptor insensitivity within prefrontal regions of the brain. Our hypothesis was that carriers of 7-repeats in the Variable Number of Tandem Repeats (VNTR) of DRD4 (7R+) would recruit prefrontal brain regions involved in successful inhibitory control to a lesser degree than non-carriers (7R-) and demonstrate less inhibitory control as confirmed by observation of locally reduced blood oxygenation level dependent (BOLD) % signal change and lower accuracy while performing "No-Go" trials of a Go/No-Go task.

METHODS

Participants (age=18, n=62, 33 females) were recruited from the general population of the St. Louis, Missouri region. Participants provided a blood or saliva sample for genotyping, completed drug and alcohol-related questionnaires and IQ testing, and performed a Go/No-Go task inside of a 3T fMRI scanner.

RESULTS

Go/No-Go task performance did not significantly differ between 7R+ and 7R- groups. Contrast of brain activity during correct "No-Go" trials with a non-target letter baseline revealed significant BOLD activation in a network of brain regions previously implicated in inhibitory control including bilateral dorsolateral prefrontal, inferior frontal, middle frontal, medial prefrontal, subcortical, parietal/temporal, and occipital/cerebellar brain regions. Mean BOLD % signal change during "No-Go" trials was significantly modulated by DRD4 genotype, with 7R+ showing a lower hemodynamic response than 7R- in right anterior prefrontal cortex/inferior frontal gyrus, left premotor cortex, and right occipital/cerebellar areas. Follow-up analyses suggested that 7-repeat status accounted for approximately 5-6% of the variance in the BOLD response during "No-Go" trials.

DISCUSSION

The DRD4 7-repeat allele may alter dopaminergic function in brain regions involved in inhibitory control. When individuals must inhibit a prepotent motor response, presence of this allele may account for 5-6% of the variance in BOLD signal in brain regions critically associated with inhibitory control, but its influence may be associated with a greater effect on brain than on behavior in 18-year-olds from the general population.

Genetics of preparation and response control in ADHD: the role of DRD4 and DAT1

BACKGROUND

Difficulties with performance and brain activity related to attentional orienting (Cue-P3), cognitive or response preparation (Cue-CNV) and inhibitory response control (Nogo-P3) during tasks tapping executive functions are familial in ADHD and may represent endophenotypes. The aim of this study was to clarify the impact of dopamine receptor D4 (DRD4) and dopamine transporter (DAT1) gene polymorphisms on these processes in ADHD and control children.

METHODS

Behavioural and electrophysiological parameters from cued continuous performance tests with low and high attentional load were assessed in boys with ADHD combined type (N = 94) and controls without family history of ADHD (N = 31). Both groups were split for the presence of at least one DRD4 7-repeat allele and the DAT1 10-6 haplotype.

RESULTS

Children with ADHD showed diminished performance and lower Cue-P3, CNV and Nogo-P3 amplitudes. Children with DRD4 7R showed similar performance problems and lower Cue-P3 and CNV, but Nogo-P3 was not reduced. Children with the DAT1 10-6 haplotype had no difficulties with performance or Cue-P3 and CNV, but contrary to expectations increased Nogo-P3. There were no Genotype by ADHD interactions.

CONCLUSIONS

This study detected specific effects of DRD4 7R on performance and brain activity related to attentional orienting and response preparation, while DAT1 10-6 was associated with elevated brain activity related to inhibitory response control, which potentially compensates increased impulsivity. As these genotype effects were additive to the impact of ADHD, the current results indicate that DRD4 and DAT1 polymorphisms are functionally relevant risk factors for ADHD and presumably other disorders sharing these endophenotypes.

Interaction between prenatal stress and dopamine D4 receptor genotype in predicting aggression and cortisol levels in young adults

RATIONALE

Considerable evidence suggests that genetic factors combine with environmental influences to impact on the development of aggressive behavior. A genetic variant that has repeatedly been reported to render individuals more sensitive to the presence of adverse experiences, including stress exposure during fetal life, is the seven-repeat allele of the dopamine D4 receptor (DRD4) gene.

OBJECTIVES

The present investigation concentrated on the interplay of prenatal maternal stress and DRD4 genotype in predicting self-reported aggression in young adults. As disruption of the hypothalamic-pituitary-adrenal system has been discussed as a pathophysiological pathway to aggression, cortisol stress reactivity was additionally examined.

METHODS

As part of an epidemiological cohort study, prenatal maternal stress was assessed by maternal interview 3 months after childbirth. Between the ages of 19 and 23 years, 298 offspring (140 males, 158 females) completed the Young Adult Self-Report to measure aggressive behavior and were genotyped for the DRD4 gene. At 19 years, 219 participants additionally underwent the Trier Social Stress Test to determine cortisol reactivity.

RESULTS

Extending earlier findings with respect to childhood antisocial behavior, the results revealed that, under conditions of higher prenatal maternal stress, carriers of the DRD4 seven-repeat allele displayed more aggression in adulthood (p = 0.032). Moreover, the same conditions which seemed to promote aggression were found to predict attenuated cortisol secretion (p = 0.028).

CONCLUSIONS

This is the first study to indicate a long-term impact of prenatal stress exposure on the cortisol stress response depending on DRD4 genotype.

ADHD, altered dopamine neurotransmission, and disrupted reinforcement processes: implications for smoking and nicotine dependence

Attention deficit hyperactivity disorder (ADHD) is a common and impairing disorder affecting millions of children, adolescents, and adults. Individuals with ADHD smoke cigarettes at rates significantly higher than their non-diagnosed peers and the disorder also confers risk for a number of related adverse smoking outcomes including earlier age of initiation, faster progression to regular use, heavier smoking/greater dependence, and more difficulty quitting. Progress in our understanding of dopamine neurotransmission and basic behavioral reinforcement processes in ADHD may help increase our understanding of the ADHD-smoking comorbidity. This review will examine how these areas have been studied and how further work may aid in the development of better prevention and treatment for smoking in those with ADHD.

Association between urine phthalate levels and poor attentional performance in children with attention-deficit hyperactivity disorder with evidence of dopamine gene-phthalate interaction

Although there is some evidence supporting the existence of an association between prenatal maternal or postnatal child's urine phthalate metabolite concentrations and poor attentional performances, the interaction between urine phthalate metabolite levels and genetic variation for neuropsychological deficit of attention-deficit hyperactivity disorder (ADHD) has not been examined. The aim of this study was to determine whether phthalate metabolites in urine are associated with poor neuropsychological performance in children with ADHD, and whether such association is affected by genotype-phthalate interaction. A cross-sectional examination of urine phthalate metabolite concentrations and the continuous performance test (CPT) were performed in 179 Korean children with ADHD recruited from department of psychiatry of university hospital. Correlations between urine phthalate metabolite concentrations and the CPT scores were investigated, and the interaction of phthalate metabolite levels with the selected polymorphisms at major candidate genes for ADHD, namely dopamine receptor D4 (DRD4), dopamine transporter, α-2A-adrenergic receptor, and norepinephrine transporter genes. For the subjects with the DRD4 4/4 genotype, there were significant associations of the urine phthalate metabolite concentrations with the number of omission errors, the number of commission errors, and the response time variability scores on the CPT. However, for the subjects without the DRD4 4/4 genotype, no significant associations were found. The results of this study suggest a possible association between phthalate metabolite concentrations and poor attentional performances of ADHD as well as a genetic influence on this association. Further prospective and epigenetic studies are needed to investigate causality and pathophysiological mechanisms.

Response inhibition and interference control in obsessive-compulsive spectrum disorders

Over the past 20 years, motor response inhibition and interference control have received considerable scientific effort and attention, due to their important role in behavior and the development of neuropsychiatric disorders. Results of neuroimaging studies indicate that motor response inhibition and interference control are dependent on cortical–striatal–thalamic–cortical (CSTC) circuits. Structural and functional abnormalities within the CSTC circuits have been reported for many neuropsychiatric disorders, including obsessive–compulsive disorder (OCD) and related disorders, such as attention-deficit hyperactivity disorder, Tourette’s syndrome, and trichotillomania. These disorders also share impairments in motor response inhibition and interference control, which may underlie some of their behavioral and cognitive symptoms. Results of task-related neuroimaging studies on inhibitory functions in these disorders show that impaired task performance is related to altered recruitment of the CSTC circuits. Previous research has shown that inhibitory performance is dependent upon dopamine, noradrenaline, and serotonin signaling, neurotransmitters that have been implicated in the pathophysiology of these disorders. In this narrative review, we discuss the common and disorder-specific pathophysiological mechanisms of inhibition-related dysfunction in OCD and related disorders.

ADHD pharmacogenetics across the life cycle: New findings and perspectives

Attention-deficit/hyperactivity disorder (ADHD) is a complex and heterogeneous disorder, affecting individuals across the life cycle. Although its etiology is not yet completely understood, genetics plays a substantial role. Pharmacological treatment is considered effective and safe for children and adults, but there is considerable inter-individual variability among patients regarding response to medication, required doses, and adverse events. We present here a systematic review of the literature on ADHD pharmacogenetics to provide a critical discussion of the existent findings, new approaches, limitations, and recommendations for future research. Our main findings are: first, the number of studies continues to grow, making ADHD one of the mental health areas with more pharmacogenetic studies. Second, there has been a focus shift on ADHD pharmacogenetic studies in the last years. There is an increasing number of studies assessing gene-gene and gene-environment interactions, using genome-wide association approaches, neuroimaging, and assessing pharmacokinetic properties. Third and most importantly, the heterogeneity in methodological strategies employed by different studies remains impressive. The question whether pharmacogenetics studies of ADHD will improve clinical management by shifting from trial-and-error approach to a pharmacological regimen that takes into account the individual variability remains unanswered. © 2014 Wiley Periodicals, Inc.

Functionally selective dopamine D₂, D₃ receptor partial agonists

Dopamine D2 receptor-promoted activation of Gα(o) over Gα(i) may increase synaptic plasticity and thereby might improve negative symptoms of schizophrenia. Heterocyclic dopamine surrogates comprising a pyrazolo[1,5-a]pyridine moiety were synthesized and investigated for their binding properties when low- to subnanomolar K(i) values were determined for D(2L), D(2S), and D3 receptors. Measurement of [(35)S]GTPγS incorporation at D(2S) coexpressed with G-protein subunits indicated significant bias for promotion of Gα(o1) over Gα(i2) coupling for several test compounds. Functionally selective D(2S) activation was most striking for the carbaldoxime 8b (Gα(o1), pEC50 = 8.87, E(max) = 65%; Gα(i2), pEC50 = 6.63, E(max) = 27%). In contrast, the investigated 1,4-disubstituted aromatic piperazines (1,4-DAPs) behaved as antagonists for β-arrestin-2 recruitment, implying significant ligand bias for G-protein activation over β-arrestin-2 recruitment at D(2S) receptors. Ligand efficacy and selectivity between D(2S) and D3 activation were strongly influenced by regiochemistry and the nature of functional groups attached to the pyrazolo[1,5-a]pyridine moiety.

Potential contribution of dopaminergic gene variants in ADHD core traits and co-morbidity: a study on eastern Indian probands

Association of dopaminergic genes, mainly receptors and transporters, with Attention Deficit Hyperactivity Disorder (ADHD) has been investigated throughout the world due to the importance of dopamine (DA) in various physiological functions including attention, cognition and motor activity, traits. However, till date, etiology of ADHD remains unknown. We explored association of functional variants in the DA receptor 2 (rs1799732 and rs6278), receptor 4 (exon 3 VNTR and rs914655), and transporter (rs28363170 and rs3836790) with hyperactivity, cognitive deficit, and co-morbid disorders in eastern Indian probands. Diagnostic and Statistical Manual for Mental Disorders-IV was followed for recruitment of nuclear families with ADHD probands (N = 160) and ethnically matched controls (N = 160). Cognitive deficit and hyperactive traits were measured using Conner's parents/teachers rating scale. Peripheral blood was collected after obtaining informed written consent and used for genomic DNA isolation. Genetic polymorphisms were analyzed by PCR-based methods followed by population- as well as family-based statistical analyses. Association between genotypes and cognitive/hyperactivity traits and co-morbidities was analyzed by the Multifactor dimensionality reduction (MDR) software. Case-control analysis showed statistically significant difference for rs6278 and rs28363170 (P = 0.004 and 1.332e-007 respectively) while family-based analysis exhibited preferential paternal transmission of rs28363170 '9R' allele (P = 0.04). MDR analyses revealed independent effects of rs1799732, rs6278, rs914655, and rs3836790 in ADHD. Significant independent effects of different sites on cognitive/hyperactivity traits and co-morbid disorders were also noticed. It can be summarized from the present investigation that these gene variants may influence cognitive/hyperactive traits, thereby affecting the disease etiology and associated co-morbid features.

The Dopamine D4 Receptor Gene (DRD4) Moderates Cultural Difference in Independent Versus Interdependent Social Orientation

Prior research suggests that cultural groups vary on an overarching dimension of independent versus interdependent social orientation, with European Americans being more independent, or less interdependent, than Asians. Drawing on recent evidence suggesting that the dopamine D4 receptor gene ( DRD4) plays a role in modulating cultural learning, we predicted that carriers of DRD4 polymorphisms linked to increased dopamine signaling (7- or 2-repeat alleles) would show higher levels of culturally dominant social orientations, compared with noncarriers. European Americans and Asian-born Asians (total N = 398) reported their social orientation on multiple scales. They were also genotyped for DRD4. As in earlier work, European Americans were more independent, and Asian-born Asians more interdependent. This cultural difference was significantly more pronounced for carriers of the 7- or 2-repeat alleles than for noncarriers. Indeed, no cultural difference was apparent among the noncarriers. Implications for potential coevolution of genes and culture are discussed.

Pharmacological approaches to reducing craving in patients with alcohol use disorders

Research on the concept of craving may lead to better understanding of the biobehavioural circuitries that contribute to the complexity of alcohol use disorders (AUDs). The experiences described as craving or desire to drink are often associated with physical responses such as increased salivation and heart rate, and alteration of stress hormones, as well as psychological responses such as anxiety and depression. Greater craving has been associated with an increased probability of alcohol relapse. Reversal of craving, which is understood as a symptom of protracted abstinence, offers the possibility of preventing relapses and treating alcoholism. Various medications have been studied to establish whether they are able to reduce craving; however, the results obtained from clinical studies have been inconsistent. Here, we review the interdisciplinary models developed to evaluate craving, then the different approaches used to assess and measure craving and, finally, the medications utilized and tested to lessen craving in patients suffering from AUDs.

Effects of nicotine deprivation and replacement on BOLD-fMRI response to smoking cues as a function of DRD4 VNTR genotype

INTRODUCTION

Reactivity to smoking cues is an important factor in the motivation to smoke and has been associated with the dopamine receptor 4 variable number tandem repeat (DRD4 exon III VNTR) polymorphism. However, little is known about the associated neural mechanisms.

METHODS

Non-treatment-seeking Caucasian smokers completed overnight abstinence and viewed smoking and neutral cues during 2 separate functional magnetic resonance imaging scans while wearing either a nicotine or placebo patch (order randomized) and were genotyped for the DRD4 VNTR. We conducted mixed-effects repeated-measures analyses of variance (within-subject factor: nicotine or placebo patch; between-subject factor: DRD4 long [L: ≥ 1 copy of ≥ 7 repeats] or short [S: 2 copies ≤ 6 repeats] genotype) of 6 a priori regions of interest.

RESULTS

Relative to neutral cues, smoking cues elicited greater activity in bilateral ventral striatum and left amygdala during nicotine replacement and deactivation in these regions during nicotine deprivation. A patch × DRD4 interaction was observed in the left amygdala, an area associated with appetitive reinforcement and relapse risk, such that S allele carriers demonstrated greater activation on active patch than on placebo patch.

CONCLUSIONS

Brain systems associated with reward salience may become primed and overreactive at nicotine replacement doses intended for the first step of smoking cessation and may become inhibited during nicotine withdrawal in DRD4 S but not in DRD4 L carriers. These findings are consistent with the role of these regions in drug reinforcement and suggest a differential influence of nicotine replacement on amygdala activation in the association of incentive salience with smoking stimuli across DRD4 genotypes.

Gene Effects and G × E Interactions in the Differential Prediction of Three Aspects of Impulsiveness

Several polymorphisms relevant to dopamine and serotonin have been identified as potential contributors to individual differences in impulsivity versus self-control. Because impulsivity is a multifaceted construct, a need remains to examine more closely how various genes relate to different aspects of impulsivity. We examined four dopamine-related polymorphisms and the serotonin transporter as predictors of three aspects of impulsivity, two bearing on impulsive reactions to emotions and one on difficulty in completing intended actions. Early adversity was also examined as a potentiator of genetic effects. Undergraduates completed measures of impulsivity and early adversity and were genotyped. COMT, BDNF, DRD4, and 5HTTLPR (the latter two in interaction with early adversity) made independent contributions to prediction of Pervasive Influence of Feelings. BDNF made a contribution to Lack of Follow-Through. ANKK1 and 5HTTLPR (both in interaction with early adversity) made independent contributions to Feelings Trigger Action. Thus, five polymorphisms contributed to predicting impulsivity, but different polymorphisms related to different aspects.

The dopaminergic reward system and leisure time exercise behavior: a candidate allele study

PURPOSE

Twin studies provide evidence that genetic influences contribute strongly to individual differences in exercise behavior. We hypothesize that part of this heritability is explained by genetic variation in the dopaminergic reward system. Eight single nucleotide polymorphisms (SNPs in DRD1: rs265981, DRD2: rs6275, rs1800497, DRD3: rs6280, DRD4: rs1800955, DBH: rs1611115, rs2519152, and in COMT: rs4680) and three variable number of tandem repeats (VNTRs in DRD4, upstream of DRD5, and in DAT1) were investigated for an association with regular leisure time exercise behavior.

MATERIALS AND METHODS

Data on exercise activities and at least one SNP/VNTR were available for 8,768 individuals aged 7 to 50 years old that were part of the Netherlands Twin Register. Exercise behavior was quantified as weekly metabolic equivalents of task (MET) spent on exercise activities. Mixed models were fitted in SPSS with genetic relatedness as a random effect.

RESULTS

None of the genetic variants were associated with exercise behavior (P>.02), despite sufficient power to detect small effects.

DISCUSSION AND CONCLUSIONS

We did not confirm that allelic variants involved in dopaminergic function play a role in creating individual differences in exercise behavior. A plea is made for large genome-wide association studies to unravel the genetic pathways that affect this health-enhancing behavior.

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.

The role of attachment styles in regulating the effects of dopamine on the behavior of salespersons

Two classic strategic orientations have been found to pervade the behavior of modern salespersons: a sales orientation (SO) where salespersons use deception or guile to get customers to buy even if they do not need a product, and a customer orientation (CO) where salespersons first attempt to discover the customer's needs and adjust their product and selling approach to meet those needs. Study 1 replicates recent research and finds that the Taq A1 variant of the DRD2 gene is not related to either sales or CO, whereas the 7-repeat variant of the DRD4 gene is related to CO but not SO. Study 2 investigates gene × phenotype explanations of orientation of salespersons, drawing upon recent research in molecular genetics and biological/psychological attachment theory. The findings show that attachment style regulates the effects of DRD2 on CO, such that greater avoidant attachment styles lead to higher CO for persons with the A2/A2 variant but neither the A1/A2 nor A1/A1 variants. Likewise, attachment style regulates the effects of DRD4 on CO, such that greater avoidant attachment styles lead to higher CO for persons with the 7-repeat variant but not other variants. No effects were found on a SO, and secure and anxious attachment styles did not function as moderators.

Functional characterization of rare variants in human dopamine receptor D4 gene by genotype-phenotype correlations

Next generation sequencing technologies have facilitated a notable shift from common disease common variant hypothesis to common disease rare variant, as also witnessed in recent literature on schizophrenia. Dopamine receptor D4 (DRD4), a G-protein-coupled receptor is associated with psychiatric disorders and has high affinity for atypical antipsychotic clozapine. We investigated the functional role of rare genetic variants in DRD4 which may have implications for translational medicine. CHO-K1 cells independently expressing four rare non-synonymous variants of DRD4 namely R237L, A281P, S284G located in the third cytosolic loop and V194G, located in the fifth transmembrane domain were generated. Their genotype-phenotype correlations were evaluated using [³H]spiperone binding, G-protein activation and molecular dynamics-simulation studies. A281P and S284G were functionally similar to wildtype (WT). With R237L, potency of dopamine and quinpirole reduced ∼sixfold and threefold respectively compared to WT; [³H]spiperone binding studies showed a reduction in total number of binding sites (∼40%) but not binding affinity, in silico docking studies revealed that binding of both dopamine and spiperone to R237L was structurally similar to WT. Of note, V194G variant failed to inhibit forskolin-stimulated adenylate cyclase activity and phosphorylate extracellular signal-regulated kinase; showed significant reduction in binding affinity (K(d)=2.16 nM) and total number of binding sites (∼66%) compared to WT in [³H]spiperone binding studies; and ligand docking studies showed that binding of dopamine and spiperone is superficial due to probable structural alteration. Transmembrane variant V194G in DRD4.4 results in functional alteration warranting continuing functional analysis of rare variants.

Integrating genetics and social science: genetic risk scores

The sequencing of the human genome and the advent of low-cost genome-wide assays that generate millions of observations of individual genomes in a matter of hours constitute a disruptive innovation for social science. Many public use social science datasets have or will soon add genome-wide genetic data. With these new data come technical challenges, but also new possibilities. Among these, the lowest-hanging fruit and the most potentially disruptive to existing research programs is the ability to measure previously invisible contours of health and disease risk within populations. In this article, we outline why now is the time for social scientists to bring genetics into their research programs. We discuss how to select genetic variants to study. We explain how the polygenic architecture of complex traits and the low penetrance of individual genetic loci pose challenges to research integrating genetics and social science. We introduce genetic risk scores as a method of addressing these challenges and provide guidance on how genetic risk scores can be constructed. We conclude by outlining research questions that are ripe for social science inquiry.

Pharmacogenetics of addiction therapy

Drug addiction is a serious relapsing disease that has high costs to society and to the individual addicts. Treatment of these addictions is still in its nascency, with only a few examples of successful therapies. Therapeutic response depends upon genetic, biological, social, and environmental components. A role for genetic makeup in the response to treatment has been shown for several addiction pharmacotherapies. For several addiction pharmacotherapies, response to treatment varies based on individual genetic makeup. In this chapter, we discuss the role of genetics in pharmacotherapies, specifically for cocaine, alcohol, and opioid dependences. The elucidation of the role of genetics should aid in the development of new treatments and increase the efficacy of existing treatments.

A longitudinal analysis of the effects of a DRD4 polymorphism on marijuana use

The current study used a variable- and person-centered approach to examine whether a DRD4 polymorphism explained within-individual differences in frequency of marijuana use from adolescence into emerging adulthood. Data were analyzed from 1897 respondents from the genetic subsample of the National Longitudinal Study of Adolescent Health (Add Health) at waves I (ages 13-17), II (ages 14-18), and III (ages 21-25). Latent class growth model results revealed that marijuana use was characterized by four trajectories (non-users/experimenters, increasers, desisters, and chronic users), and that the DRD4 polymorphism differentiated increasers from non-users/experimenters. Overall, the results suggested that the DRD4 polymorphism may be relevant to differences in the developmental trajectories of marijuana use.

Association analyses for dopamine receptor gene polymorphisms and weight status in a longitudinal analysis in obese children before and after lifestyle intervention

Background

Dopamine receptors are involved in midbrain reward circuit activation. Polymorphisms in two dopamine receptor genes, DRD2 and DRD4, have been associated with altered perception of food reward and weight gain. The objective of this study was to determine whether the same risk alleles were associated with overweight/obesity and with lower reduction of overweight after a 1-year lifestyle intervention.

Methods

In a longitudinal study the association of polymorphisms in DRD2 (rs18000497, risk allele: T, formerly A1 allele at the TaqI A1 polymorphism) and DRD4 (variable number of tandem repeats (VNTR); 48 bp repeat in exon III; risk alleles: 7 repeats or longer: 7R+) was tested on weight loss success following a 1-year lifestyle childhood obesity intervention (OBELDICKS). An additional exploratory cross-sectional case-control study was performed to compare the same DRD polymorphisms in these overweight/obese children and adolescents versus lean adult controls. Subjects were 423 obese and 28 overweight children participating in lifestyle intervention (203 males), age median 12.0 (interquartile range 10.0–13.7) years, body mass index - standard deviation score (BMI-SDS) 2.4 ± 0.5; 583 lean adults (232 males); age median 25.3 (interquartile range 22.5–26.8) years, BMI 19.1 ± 1.9 kg/m². BMI, BMI-SDS and skinfold thickness measures were assessed at baseline and after 1 year; genotyping was performed for DRD2 risk variant rs1800497 and DRD4 exon III VNTR.

Results

The DRD2 genotype had a nominal effect on success in the weight loss intervention. The weakest BMI-SDS reduction was in children homozygous for two rs1800497 T-alleles (n = 11) compared to the combined group with zero (n = 308) or one (n = 132) rs1800497 T-allele (-0.08 ± 0.36 vs. -0.28 ± 0.34; p < 0.05). There was no association between the DRD4 VNTR alleles and genotypes and success in the weight loss intervention. No associations of the risk alleles of the DRD2 and DRD4 polymorphisms and obesity were observed in the cross-sectional part of the study.

Conclusions

We did not find association between polymorphisms in DRD2 and DRD4 genes and weight status. However, obese carriers of two DRD2 rs1800497 T-alleles may be at risk for weak responses to lifestyle interventions aimed at weight reduction.

Trial registration

Obesity intervention program “Obeldicks” is registered at clinicaltrials.gov (NCT00435734).