Local competition sparks concerns for fairness in the ultimatum game

Humans reject uneven divisions of resources, even at personal cost. This is observed in countless experiments using the ultimatum game, where a proposer offers to divide a resource with a responder who either accepts the division or rejects it (whereupon both earn zero). Researchers debate why humans evolved a psychology that is so averse to inequity within partnerships. We suggest that the scale of competition is crucial: under local competition with few competitors, individuals reject low offers, because they cannot afford to be disadvantaged relative to competitors. If one competes against the broader population (i.e. global competition), then it pays to accept low offers to increase one''s absolute pay-off. We support this intuition with an illustrative game-theoretical model. We also conducted ultimatum games where participants received prizes based on pay-offs relative to immediate partners (local competition) versus a larger group (global competition). Participants demanded higher offers under local competition, suggesting that local competition increases people''s demands for fairness and aversion to inequality.     

Dopamine D1 receptor gene polymorphism is associated with myocardial infarction

Dopamine D1 receptor (DRD1) gene is associated with the pathogenesis of myocardial infarction (MI) in aspects of plaque rupture, platelet aggregation, and neutrophil-mediated injury of cardiac myocytes. Thus, the study was designed to explore whether the A-48G polymorphism of the DRD1 gene was associated with MI. The genotype of the DRD1A-48G polymorphism was determined by polymerase chain reaction in the 602 Han Chinese participants, 255 MI patients and 347 controls without MI. A significant association was found between the A-48G polymorphism of DRD1 and MI (genotype model: χ(2)=13.2, unadjusted p=0.001; χ(2)=13.9, adjusted p=0.0002; dominant model: adjusted OR 2.05, 95%CI 1.40-3.00, p=0.0002; recessive model: adjusted OR 2.34, 95%CI 1.01-5.39, p=0.047). The G allele was a risk-increased allele for MI (unadjusted OR 1.83, 95%CI 1.34-2.50, p=0.0001; adjusted OR 1.94, 95%CI 1.40-2.68, p=0.00007). Thus, the study demonstrated the significant association between A-48G polymorphism of the DRD1 gene and MI.     

Dopamine D4 receptor oligomerization--contribution to receptor biogenesis

Dopamine D(4) receptors (D(4) Rs) are G protein-coupled receptors that play a role in attention and cognition. In the present study, we investigated the dimerization properties of this receptor. Western blot analysis of the human D(4.2)R, D(4.4)R and D(4.7)R revealed the presence of higher molecular weight immunoreactive bands, which might indicate the formation of receptor dimers and multimers. Homo- and heterodimerization of the receptors was confirmed by co-immunoprecipitation and bioluminescence resonance energy transfer studies. Although dimerization of a large number of G protein-coupled receptors has been described, the functional importance often remains to be elucidated. Folding efficiency is rate-limiting for D(4)R biogenesis and quality control in the endoplasmic reticulum plays an important role for D(4)R maturation. Co-immunoprecipitation and immunofluorescence microscopy studies using wild-type and a nonfunctional D(4.4)R folding mutant show that oligomerization occurs in the endoplasmic reticulum and that this plays a role in the biogenesis and cell surface targeting of the D(4)R. The different polymorphic repeat variants of the D(4)R display differential sensitivity to the chaperone effect. In the present study, we show that this is also reflected by bioluminescence resonance energy transfer saturation assays, suggesting that the polymorphic repeat variants have different relative affinities to form homo- and heterodimers. In summary, we conclude that D(4)Rs form oligomers with different affinities and that dimerization plays a role in receptor biogenesis.     

Suffering makes you egoist: acute pain increases acceptance rates and reduces fairness during a bilateral ultimatum game

Social preferences like interpersonal altruism, fairness, reciprocity and inequity aversion are inherently linked to departures from pure self-interest. During economic interactions, for example, defectors may be punished even if this implies a cost for the punishers. This violation of canonical assumptions in economics indicates that socially oriented decisions may predominate over self-centred stances. Here we explore whether the personal experience of pain changes the balance between self-gain and socially based choices. We used laser stimulation to induce pain or a warm sensation in subjects playing a modified version of the Ultimatum Game (UG) both in the role of responder and proposer. After each shot, responders evaluated the fairness of the offer. Moreover, responders and proposers rated the intensity and unpleasantness of the sensation evoked by the laser stimulation. Results show that suffering proposers decrease fair offers and suffering responders increase their acceptance rate irrespective of economic offer. Crucially, the intensity of painful stimulation has a predictive role on Moderately Unfair offers' acceptance rates. Thus the personal experience of pain may favour the emergence of a self-centered perspective aimed at maximizing self-gain. The results suggest that bodily states play a fundamental role in higher-order interpersonal negotiations and interactions.     

Dopamine D4 receptor and serotonin transporter gene effects on the longitudinal development of infant temperament

Existing studies of the effect on infant temperament of the 48 base pair variable number of tandem repeats polymorphism in exon 3 of the dopamine D4 receptor gene, DRD4 VNTR, and the serotonin transporter-linked polymorphic region, 5-HTTLPR, have provided contradictory results, and age seems to be an important factor. The present study investigated the effect of these two polymorphisms on the stability of infant temperament between 4 and 9 months of age. Furthermore, the effect of a recently discovered single nucleotide polymorphism which modulates the 5-HTTLPR (rs25531) was investigated in relation to infant temperament. The study sample consisted of 90 infants, who were assessed by parental report at the two ages under consideration using the Revised Infant Behavior Questionnaire. It was found that infants carrying the 7-repeat allele of the DRD4 VNTR had higher levels of Negative Affect. Furthermore, there was an interaction between DRD4 VNTR and 5-HTTLPR genotype such that infants with the DRD4 VNTR 7-repeat allele and the highest expressing 5-HTTLPR genotype (L(A) L(A) ) had the highest level of Negative Affect. These effects were largely driven by scores on the Falling Reactivity scale. Genetic effects were stable across age. The results emphasize the need for developmental studies of genetic effects on temperament.     

酒精依赖综合征患者DRD2、DRD4和DAT基因多态性的研究

目的:探讨云南地区人群中DRD2(TaqIA、-141C)、DRD4和DAT基因多态性与酒精依赖的相关性.方法:采用聚合酶链式反应-限制性片断长度多态性(PCR-RFLP)分析技术以及聚合酶链式反应-可变数目串联重复序列多态性(PCR-VNTR)分析技术检测酒依赖组(80例)和对照组(70例)在3个候选基因中的基因型和等位基因频率.结果:上述三个基因多态性的基因型和等位基因频率在酒依赖组和对照组中差异均无统计学意义(P>0.05),对DRD2基因中的TaqIA和-141C进行单倍型分析时发现,Del/Al是一种保护单倍型,能抑制酒依赖综合征的发生.结论:在云南地区人群中,携带有Del/Al单倍型基因的人不易形成酒依赖.     

Dopamine D2 and D4 receptor heteromerization and its allosteric receptor-receptor interactions

Dopamine D₂ and D₄ receptors partially codistribute in the dorsal striatum and appear to play a fundamental role in complex behaviors and motor function. The discovery of D₂R–D_4.xR (D_4.2R, D_4.4R or D_4.7R) heteromers has been made in cellular models using co-immunoprecipitation, in situ Proximity Ligation Assays and BRET¹ techniques with the D₂R and D_4.7R receptors being the least effective in forming heteromers. Allosteric receptor–receptor interactions in D₂R–D_4.2R and D₂R–D_4.4 R heteromers were observed using the MAPK assays indicating the existence of an enhancing allosteric receptor–receptor interaction in the corresponding heteromers between the two orthosteric binding sites. The bioinformatic predictions suggest the existence of a basic set of common triplets (ALQ and LRA) in the two participating receptors that may contribute to the receptor–receptor interaction interfaces.     

Vitamin D receptor gene polymorphism is associated with chronic periodontitis

Chronic periodontitis (CP) is caused by enhanced resorption of the alveolar bone supporting the teeth and is associated with intraoral inflammation after infection with certain bacteria. The VDR gene polymorphism was reported recently to be deeply related to the occurrence of tuberculosis and infection of chronic hepatitis B virus. This may be interpreted to indicate a close relationship between VDR gene polymorphism and the immunological action, because vitamin D activates monocytes, stimulates cell-mediated immunity, and suppresses lymphocyte proliferation. The purpose of the present study was to clarify whether polymorphisms in VDR gene exons are associated with the incidence of CP. A case-controlled study was performed on a group of 168 unrelated Japanese subjects whose ages ranged from 35 to 65 years. The Taq I polymorphism in the VDR gene was found to be associated significantly with CP (X2=4.48, P=0.034). We performed multiple logistic regression analyses on the TT genotype, which was found to be associated with CP, and on well-recognized risk factors, smoking and diabetes. The odds ratio (OR) for the genotype (TT/Tt) was 2.73 (95% CI 1.11-6.68, P=0.028), being larger than the unadjusted value. This indicates that the VDR gene polymorphism (TT genotype) is a risk factor for CP, independently of smoking and diabetes.     

Fluctuating asymmetry and behavior in the ultimatum game in Jamaica

The ultimatum game measures cooperative tendencies in humans under experimental conditions. One individual can split money between oneself and another, while the other has the option of accepting or rejecting the offer, with each player receiving the accepted split or nothing if the split is rejected. We studied the association of players' degree of symmetry [fluctuating asymmetry (FA)] with behavior in the ultimatum game. Symmetrical males were expected to be less cooperative and, thus, make lower offers (while being more likely to reject unfair offers). In a population of young adult Jamaicans, who are well-characterized for bodily symmetry, we found that symmetrical males made significantly lower offers than asymmetrical ones (p<.001), but found no effect on rejection rates (perhaps due to a very small sample size). No significant association of symmetry and game playing was found in women, but women with a higher body mass index made less generous offers (p<.05).     

Dopamine D1 receptor interaction with arrestin3 in neostriatal neurons

Dopamine D1 receptor interactions with arrestins have been characterized using heterologously expressed D1 receptor and arrestins. The purpose of this study was to investigate the interaction of the endogenous D1 receptor with endogenous arrestin2 and 3 in neostriatal neurons. Endogenous arrestin2 and 3 in striatal homogenates bound to the C-terminus of the D1 receptor in a glutathione-S-transferase (GST) pulldown assay, with arrestin3 binding more strongly. The D1 C-terminus and, to a lesser extent, the third cytoplasmic loop also bound purified arrestin2 and 3. In neostriatal neurons, 2, 5, and 20 min agonist treatment increased the colocalization of the D1 receptor and arrestin3 immunoreactivity without altering the colocalization of the D1 receptor and arrestin2. Further, agonist treatment for 5 and 20 min caused translocation of arrestin3, but not arrestin2, to the membrane. The binding of arrestin3, but not arrestin2, to the D1 receptor was increased as assessed by coimmunoprecipitation after agonist treatment for 5 and 20 min. Agonist treatment of neurons induced D1 receptor internalization (35-45%) that was maximal within 2-5 min, a time-course similar to that of the increase in colocalization of the D1 receptor with arrestin3. These data indicate that the D1 receptor preferentially interacts with arrestin3 in neostriatal neurons.     

The 7R polymorphism in the dopamine receptor D4 gene (DRD4) is associated with financial risk taking in men

Individuals exhibit substantial heterogeneity in financial risk aversion. Recent work on twins demonstrated that some variation is influenced by individual heritable differences. Despite this, there has been no study investigating possible genetic loci associated with financial risk taking in healthy individuals. Here, we examined whether there is an association between financial risk preferences, elicited experimentally in a game with real monetary payoffs, and the presence of the 7-repeat allele (7R+) in the dopamine receptor D₄ gene as well as the presence of the A1 allele (A1+) in the dopamine receptor D₂ gene in 94 young men. Although we found no association between the A1 allele and risk preferences, we did find that 7R+ men are significantly more risk loving than 7R? men. This polymorphism accounts for roughly 20% of the heritable variation in financial risk taking. We suggest that selection for the 7R allele may be for a behavioral phenotype associated with risk taking. This is consistent with previous evolutionary explanations suggesting that selection for this allele was for behaviors associated with migration and male competition, both of which entail an element of risk.     

Dopamine D3 receptor signaling alleviates mouse rheumatoid arthritis by promoting Toll-like receptor 4 degradation in mast cells

Dopamine receptors are involved in several immunological diseases. We previously found that dopamine D3 receptor (D3R) on mast cells showed a high correlation with disease activity in patients with rheumatoid arthritis, but the mechanism remains largely elusive. In this study, a murine collagen-induced arthritis (CIA) model was employed in both DBA/1 mice and D3R knockout mice. Here, we revealed that D3R-deficient mice developed more severe arthritis than wild-type mice. D3R suppressed mast cell activation in vivo and in vitro via a Toll-like receptor 4 (TLR4)-dependent pathway. Importantly, D3R promoted LC3 conversion to accelerate ubiquitin-labeled TLR4 degradation. Mechanistically, D3R inhibited mTOR and AKT phosphorylation while enhancing AMPK phosphorylation in activated mast cells, which was followed by autophagy-dependent protein degradation of TLR4. In total, we found that D3R on mast cells alleviated inflammation in mouse rheumatoid arthritis through the mTOR/AKT/AMPK-LC3-ubiquitin-TLR4 signaling axis. These findings identify a protective function of D3R against excessive inflammation in mast cells, expanding significant insight into the pathogenesis of rheumatoid arthritis and providing a possible target for future treatment.Subject terms: Immunological disorders, Rheumatic diseases     

Dopamine receptor antagonism disrupts social preference in zebrafish: a strain comparison study

Zebrafish form shoals in nature and in the laboratory. The sight of conspecifics has been found reinforcing in zebrafish learning tasks. However, the mechanisms of shoaling, and those of its reinforcing properties, are not known. The dopaminergic system has been implicated in reward among other functions and it is also engaged by drugs of abuse as shown in a variety of vertebrates including zebrafish. The ontogenetic changes in dopamine levels and, to a lesser degree, in serotonin levels, have been found to accompany the maturation of shoaling in zebrafish. Thus, we hypothesized that the dopaminergic system may contribute to shoaling in zebrafish. To test this we employed a D1-receptor antagonist and quantified behavioral responses of our subjects using a social preference (shoaling) paradigm. We found significant reduction of social preference induced by the D1-R antagonist, SCH23390, in the AB strain of zebrafish, an alteration that was not accompanied by changes in motor function or vision. We also detected D1-R antagonist-induced changes in the level of dopamine, DOPAC, serotonin and 5HIAA, respectively, in the brain of AB zebrafish as quantified by HPLC with electrochemical detection. We found the antagonist-induced behavioral changes to be absent and the levels of these neurochemicals to be lower in another zebrafish population, SF, demonstrating naturally occurring genetic variability in these traits. We conclude that this variability may be utilized to unravel the mechanisms of social behavior in zebrafish, a line of research that may be extended to other vertebrates including our own species.     

Dopamine D4 receptor activation restores CA1 LTP in hippocampal slices from aged mice

Normal aging is characterized with a decline in hippocampal memory functions that is associated with changes in long‐term potentiation (LTP) of the CA3‐to‐CA1 synapse. Age‐related deficit of the dopaminergic system may contribute to impairment of CA1 LTP. Here we assessed how the modulation of CA1 LTP by dopamine is affected by aging and how it is dependent on the Ca²⁺ source. In slices from adult mice, the initial slope of the field potential showed strong LTP, but in slices from aged mice LTP was impaired. Dopamine did not affect LTP in adult slices, but enhanced LTP in aged slices. The dopamine D1/D5 receptor (D1R/D5R) agonist SKF‐81297 did not affect LTP in adult but caused a relative small increase in LTP in aged slices; however, although there was no difference in dopamine D4 receptor (D4R) expression, the D4R agonist PD168077 increased LTP in aged slices to a magnitude similar to that in adult slices. The N‐Methyl‐D‐aspartate receptor antagonist D‐AP5 reduced LTP in adult slices, but not in aged slices. However, in the presence of D‐AP5, PD168077 completely blocked LTP in aged slices. The voltage‐dependent calcium channel (VDCC) blocker nifedipine reduced LTP in adult slices, but surprisingly enhanced LTP in aged slices. Furthermore, in the presence of nifedipine, PD168077 caused a strong enhancement of LTP in aged slices to a magnitude exceeding LTP in adult slices. Our results indicate that the full rescue of impaired LTP in aging by the selective D4R activation and that a large potentiation role on LTP by co‐application of D4R agonist and VDCC blocker may provide novel strategies for the intervention of cognitive decline of aging and age‐related diseases.     

Dopamine receptor genes are associated with age at first sexual intercourse

The dopaminergic system in the brain seems to play an important role in the regulation of sexual behaviour. The relationship between genes for the D1, D2 and D4 dopamine receptors and age at first sexual intercourse (AFSI) was examined in a sample of 414 non-Hispanic, European-American men and women. A significant association was observed between a DRD2 allele and AFSI and an even stronger association when the DRD2 allele was interacted with a DRD1 allele. A constrained regression model was constructed predicting AFSI using sex and a group of nine psychosocial variables as predictors. Adding the DRD2 and the DRD2-by-DRD1 predictors to this model increased the explained variance by 23 and 55%, respectively. Although these findings suggest a stronger association among males than among females, further research will be necessary to clarify this question, as well as to establish whether the observed association holds in other racial/ethnic groups.