OBJECTIVEAttention deficit hyperactivity disorder (ADHD) is one of the most common behavior disorders in childhood and adolescent. The etiology of ADHD is unknown. The aim of this study was to investigate the relationship between each of the 14 polymorphisms in the five candidate genes and ADHD, and between the combination of some polymorphisms in those genes and ADHD, in attempting to examine whether combinations of genotypes would confer a significant susceptibility to ADHD.

METHODSOne hundred and thirty-nine children with ADHD and one hundred and nineteen normal children were enrolled. Eight single nucleotide polymorphisms (SNP) of three candidate genes were examined with PCR and RFLP techniques. 48 bp VNTR in DRD4 gene was examined with PCR, nondenaturing polyacrylamide gel electrophoresis and silver staining. Five microsatellites (MS) of three candidate genes were examined with genotyping. The relationship between the combinations of 12 polymorphisms and ADHD was examined with logistic regression analysis.

RESULTS1.The frequency of 1065T/1065T genotype and the 1065T allele were significantly higher in ADHD children than that in normal controls (P<0.05). The frequency of -48G/-48G genotype of the A-48G polymorphism of DRD1 gene was significantly lower in ADHD children than that in normal controls (P<0.05). 2. A specific combination of three polymorphisms in the two genes showing an association with ADHD gave a prediction level of 77.5%.

CONCLUSIONSThe T1065G polymorphism in the SNAP-25 may be associated with ADHD. The 1065T/1065T genotype and the 1065T allele may be a risk factor for ADHD. The A-48G polymorphism of DRDI may be associated with ADHD. The -48G/-48G genotype may be a protective factor for ADHD. The specific combination of three sites of SNP in SNAP-25 gene and DRDI gene is found and shows an association with ADHD in 12 polymorphisms of the five candidate genes on glutamatergic/dopaminergic pathway.

Adolescent ; Attention Deficit Disorder with Hyperactivity ; genetics ; Child ; Female ; Humans ; Logistic Models ; Male ; Minisatellite Repeats ; Polymorphism, Single Nucleotide ; Receptors, Dopamine D3 ; genetics ; Receptors, Dopamine D4 ; genetics ; Receptors, Dopamine D5 ; genetics ; Receptors, N-Methyl-D-Aspartate ; genetics ; Synaptosomal-Associated Protein 25 ; genetics

Repeated psychostimulants induce electroencephalographic (EEG) changes, which reflect adaptation of the neural substrate related to dopaminergic pathways. To study the role of dopamine receptors in EEG changes, we examined the effect of apomorphine, the dopamine D1 receptor antagonist, SCH-23390, and the D2 receptor antagonist, haloperidol, on EEG in rats. For single and repeated apomorphine treatment groups, the rats received saline or apomorphine for 4 days followed by a 3-day withdrawal period and then apomorphine (2.5 mg/kg, i.p.) challenge after pretreatment with saline, SCH-23390, or haloperidol on the day of the experiment. EEGs from the frontal and parietal cortices were recorded. On the frontal cortex, apomorphine decreased the power of all the frequency bands in the single treatment group, and increased the theta (4.5~8 Hz) and alpha (8~13 Hz) powers in the repeated treatment group. Changes in both groups were reversed to the control values by SCH-23390. On the parietal cortex, single apomorphine treatment decreased the power of some frequency bands, which were reversed by haloperidol but not by SCH-23390. Repeated apomorphine treatment did not produce significant changes in the power profile. These results show that adaptation of dopamine pathways by repeated apomorphine treatment could be identified with EEG changes such as increases in theta and alpha power of the frontal cortex, and this adaptation may occur through changes in the D1 receptor and/or the D2 receptor.
Animals ; Apomorphine ; Benzazepines ; Dopamine ; Electroencephalography ; Haloperidol ; Rats ; Receptors, Dopamine ; Receptors, Dopamine D1 ; Receptors, Dopamine D2

The results regarding an association between the polymorphism sites in the dopamine D1 receptor gene and schizophrenia compelled us to study the distribution of the polymorphism in Korean schizophrenia and controls. Eighty-eight schizophrenic patients and normal controls were examined by case-control study for distribution of the polymorphism of the dopamine D1 receptor gene in Korean popualtion to minimize the effect of racial differencies in gene frequencies. The frequencies of the B1 and B2 in schizophrenic patients were 0.11 and 9.89, respectively. And 0.10 and 0.90 in normal control. There was no significant differences in the frequencies in the allele B1 and 2 between schizophrenic patients and normal controls. The author present here the evidence of a lack of alleic association between the polymorphism of the dopamine D1 receptor gene and Korean schizophrenic. The assumption that the dopamine D1 receptor gene has genetic role in the development of schizophrenia was not supported by this case-control study.
Alleles* ; Case-Control Studies ; Dopamine* ; Gene Frequency ; Humans ; Receptors, Dopamine D1 ; Receptors, Dopamine D2 ; Schizophrenia*

Desensitization and acute tolerance are terms used to describe the attenuation of receptor responsiveness by prolonged or intermittent exposure to an agonist. Unlike desensitization of G protein-coupled receptors (GPCRs), which is commonly explained by steric hindrance caused by the β-arrestins that are translocated to the activated receptors, molecular mechanisms involved in the acute tolerance of GPCRs remain unclear. Our studies with several GPCRs and related mutants showed that the acute tolerance of GPCRs could occur independently of agonist-induced β-arrestin translocation. A series of co-immunoprecipitation experiments revealed a correlation between receptor tolerance and interactions among receptors, β-arrestin2, and Gβγ. Gβγ displayed a stable interaction with receptors and β-arrestin2 in cells expressing GPCRs that were prone to undergo tolerance compared to the GPCRs that were resistant to acute tolerance. Strengthening the interaction between Gβγ and β-arrestin rendered the GPCRs to acquire the tendency of acute tolerance. Overall, stable interaction between the receptor and Gβγ complex is required for the formation of a complex with β-arrestin, and determines the potential of a particular GPCR to undergo acute tolerance. Rather than turning off the signal, β-arrestins seem to contribute on continuous signaling when they are in the context of complex with receptor and Gβγ.
Immunoprecipitation ; Receptors, Dopamine D3

BACKGROUND: Recent research demonstrates a strong association between smoking-related behaviors and genetic variation. We investigated the clinical features and genetic effects of dopamine receptors and a serotonin transporter on smoking cessation in Koreans. METHODS: Smokers (n=51) wanting to quit smoking were included as the study population. They were genotyped for polymorphisms in dopamine D2 receptor (DRD2) (TaqI and -141C), dopamine D4 receptor (DRD4), and a serotonin transporter (5-HTT). We defined abstinence as stopping smoking at six months after enrollment. RESULTS: Eighteen patients (35.3%) stopped smoking at six months. The abstinence group had a higher rate of alcohol use whereas the non-abstinence group had more coughing. However, there were no significant differences in average smoking rate, starting age of smoking, gender, nicotine dependence, and forced expiratory volume in one second between the two groups. As for the genes in the dopamine pathway, the polymorphisms of DRD2 TaqI (A1 allele) and DRD2 -141C (Ins C allele) were not genotypically different between the two groups (P=0.245 and 0.409, respectively). The genetic variation in the DRD4 variable number of tandem repeats (VNTR) also showed a similar distribution in the two groups. Regarding the polymorphisms of 5-HTT, there was no difference in the long allele between the two groups (P=0.852). CONCLUSIONS: This study suggests that the genetic variations of DRD2 TaqI, DRD2 -141C, DRD4 VNTR, and 5-HTT might have little influence on smoking cessation in Korean smokers.
Alleles ; Cough ; DNA ; Dopamine ; Forced Expiratory Volume ; Genetic Variation ; Humans ; Minisatellite Repeats ; Polymorphism, Genetic ; Receptors, Dopamine ; Receptors, Dopamine D2 ; Receptors, Dopamine D4 ; Serotonin Plasma Membrane Transport Proteins ; Smoke ; Smoking ; Smoking Cessation ; Tobacco Use Disorder

G protein-coupled receptors (GPCRs) are membrane receptors whose agonist-induced dynamic conformational changes trigger heterotrimeric G protein activation, followed by GRK-mediated phosphorylation and arrestin-mediated desensitization. Cytosolic regions of GPCRs have been studied extensively because they are direct contact sites with G proteins, GRKs, and arrestins. Among various cytosolic regions, the role of helix 8 is least understood, although a few studies have suggested that it is involved in G protein activation, receptor localization, and/or internalization. In the present study, we investigated the role of helix 8 in dopamine receptor signaling focusing on dopamine D1 receptor (D1R) and dopamine D2 receptor (D2R). D1R couples exclusively to Gs, whereas D2R couples exclusively to Gi. Bioinformatic analysis implied that the sequences of helix 8 may affect GPCR-G protein coupling selectivity; therefore, we evaluated if swapping helix 8 between D1R and D2R changed G protein selectivity. Our results suggest that helix 8 is not involved in D1R-Gs or D2R-Gi coupling selectivity. Instead, we observed that D1R with D2R helix 8 or D1R with an increased number of hydrophobic residues in helix 8 relative to wild-type showed diminished β-arrestin-mediated desensitization, resulting in increased Gs signaling.
Arrestin ; Arrestins ; Computational Biology ; Cytosol ; Dopamine ; Family Characteristics ; GTP-Binding Proteins ; Membranes ; Phosphorylation ; Receptors, Dopamine D1 ; Receptors, Dopamine D2 ; Receptors, Dopamine

We investigated the possible association between genetic polymorphisms in the dopamine receptor and serotonin transporter genes and the responses of schizophrenic patients treated with either risperidone or perospirone. The subjects comprised 27 patients with schizophrenia who were clinically evaluated both before and after treatment. The genotyping of the polymorphisms of the dopamine D2 receptor gene (DRD2) (rs1801028 and rs6277), the dopamine D4 receptor gene (DRD4) (120-bp tandem repeats and rs1800955), and serotonin transporter gene (5HTT)(variable number of tandem repeats; VNTR) were performed using the real-time polymerase chain reaction and sequencing. In DRD2 and 5HTT-VNTR, there were no significant correlations between clinical response and polymorphism in the case of risperidone, and for perospirone treatment it was impossible to analyze the clinical evaluation due to the absence of genotype information. On the other hand, in DRD4 there were significant correlations in the two-factor interaction effect on the Positive and Negative Syndrome Scale (PANSS) between the two drugs [120-bp tandem repeat, p=0.003; rs1800955, p=0.043]. Although the small sample represents a serious limitation, these results suggest that variants in DRD4 are a predictor of whether treatment will be more effective with risperidone or with perospirone in individual patients.
Genotype ; Hand ; Humans ; Isoindoles ; Polymorphism, Genetic ; Real-Time Polymerase Chain Reaction ; Receptors, Dopamine ; Receptors, Dopamine D2 ; Receptors, Dopamine D4 ; Risperidone ; Schizophrenia ; Serotonin Plasma Membrane Transport Proteins ; Tandem Repeat Sequences ; Thiazoles

Alterations in nitric oxide (NO) release in response to psychostimulants in the striatum cause a plastic change contributing to the development and expression of addiction. In this study, regulation of NO efflux evoked by acute cocaine in the dorsal striatum was investigated using real-time detection of NO in vivo. We found that acute systemic injection of cocaine (20 mg/kg) increased NO efflux, which was reduced by the intrastriatal infusion of the dopamine D1 receptor antagonist, SCH23390 (7.5 nmol), and the dopamine D2 receptor agonist, quinpirole (5 nmol). Increased levels of NO efflux by acute cocaine were also reduced by the intrastriatal infusion of the N-methyl-D-aspartate (NMDA) receptor antagonists, MK801 (2 nmol) and AP5 (2 nmol). These findings suggest that interactions of dopamine D1 receptors and NMDA receptors after acute exposure to cocaine participate in the upregulation of NO efflux in the dorsal striatum.
Benzazepines ; Cocaine ; Dizocilpine Maleate ; Dopamine ; Glutamic Acid ; N-Methylaspartate ; Nitric Oxide ; Plastics ; Quinpirole ; Receptors, Dopamine D1 ; Receptors, Dopamine D2 ; Receptors, N-Methyl-D-Aspartate ; Up-Regulation

OBJECTIVE: Dopamine plays a key role in the proliferation regulation of the smooth muscle cells. The purpose of this study was to observe the degree of expression of dopamine D1 and D2 receptors and dopamine transporter (DAT) and to evaluate the influence of methylation about control of expression of DAT in uterine leiomyoma and normal myometrial tissue. METHODS: In 20 patients who underwent hysterectomy due to uterine leiomyoma, normal myometrial and leiomyoma specimens were obtained. The expression of dopamine D1 and D2 receptors and DAT was demonstrated by using RT-PCR and immunohistochemistry in each normal myometrium and leiomyoma. Analysis of the DNA methylation status of DAT was conducted using HpaII digestion and the methylation-sensitive PCR. RESULTS: The mRNA level of dopamine D1 receptor was relatively higher in normal myometrium than D2 receptor and it was also unchanged in leiomyomas. However, the mRNA levels of dopamine D2 receptor and DAT in leiomyomas were much higher than normal myometrium. Consistent with elevated mRNA levels, high levels of dopamine receptors protein expression were detected by immunohistochemistry in leiomyomas. The degree of methylation at CpG sites of the area intron 1 of DAT (genomic position, +377 - +888) was decreased in leiomyomas. CONCLUSION: These results suggest that overexpressed dopamine D2 receptor and DAT would be associated with proliferation of human uterine leiomyomas and the methylation status of the CpG island of DAT determines its expression.
Animals ; CpG Islands ; Digestion ; DNA Methylation ; Dopamine Plasma Membrane Transport Proteins* ; Dopamine* ; Female ; Humans ; Hysterectomy ; Immunohistochemistry ; Introns ; Leiomyoma* ; Methylation ; Mice ; Myocytes, Smooth Muscle ; Myometrium ; Polymerase Chain Reaction ; Receptors, Dopamine D1 ; Receptors, Dopamine D2 ; Receptors, Dopamine* ; RNA, Messenger

PURPOSE: In an attempt to predict the interpersonal differences of therapeutic response to antipsychotic drugs on pharmaco-genetic bases, this study was designed to investigate the relationship between the therapeutic response to antipsychotic drugs and Taq I A dopamine D2 receptor polymorphism in schizophrenic patients. METHODS: The subjects were 158 patients diagnosed with schizophrenia(DSM-IV). The therapeutic response to antipsychotic drugs was evaluated using the Treatment Response Scale(TRS) retrospectively. Patients were divided into two groups, dopamine receptor antagonist responders, and serotonin-dopamine antagonist responders. The patients' Taq I A dopamine D2 receptor polymorphism was determined by polymerase chain reaction(PCR) and restriction fragment length polymorphism(RFLP). RESULTS: The dopamine receptor antagonist responders had the A1 allele in significantly higher incidences (chi2(1)=4.875, p=0.027, two-tailed). No significant difference was found among the serotonin-dopamine antagonist responders between those with or without the A1 allele. CONCLUSIONS: The patients with the A1 allele responded better to dopamine receptor antagonists than those with no A1 allele. Based on these results, it is suggested that the pharmacological effect of dopamine receptor antagonists can be predicted depending on the presence of the A1 allele in schizophrenic patients.
Alleles ; Antipsychotic Agents* ; Dopamine Antagonists ; Dopamine* ; Humans ; Incidence ; Receptors, Dopamine ; Receptors, Dopamine D2* ; Retrospective Studies ; Schizophrenia