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Results for “Receptors, Dopamine D4”

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At least 19 recordsLinked to original sources

PubMed2003

Association analysis for dopamine D3 receptor, dopamine D4 receptor and dopamine transporter genetic polymorphisms and P300 event-related potentials for normal young females.

OBJECTIVE: It has been demonstrated that the P300 components, a positive event-related potential, are heritable and are influenced by dopaminergic activity. We tested the genetic effects of the dopaminergic system in P300 components by association study. METHODS: In a sample population consisting of 120 normal young Han-Chinese females, we explored the association between the P300 components, and, the genetic polymorphisms including the dopamine D3 receptor (serine-to-glycine polymorphism in exon I), the dopamine D4 receptor (variable number tandem repeat polymorphism in exon III), and the dopamine transporter (variable number tandem repeat polymorphism in promoter region). RESULTS: No associations were demonstrated between the polymorphisms of these three genes and the P300 components. CONCLUSIONS: Our negative findings suggest that these genetic polymorphisms do not play a major role in the modulation of P300 event-related potentials.

Adult↗

PubMed1995

Full-length cDNA cloning and distribution of human dopamine D4 receptor.

Dopamine D4 receptor is the focus of interest in terms of pharmacological profile and possible relation to the disease. Using poly A+RNA from human retina as a template, we succeeded in cloning of full-length cDNA of the human dopamine D4 receptor by improved reverse transcription-polymerase chain reaction (RT-PCR). From the RT-PCR products, two polymorphic variants which had two and four tandem repeats in the putative third cytoplasmic loop were obtained. Transient expression of the full-length cDNA in COS-1 cells produced [3H]spiperone binding sites with a high affinity. These results confirmed the existence of the D4 receptor mRNA containing a different number of polymorphic tandem repeats in native human tissues. The RT-PCR method demonstrated the restricted distribution of the D4 mRNA in human tissues and brain regions. The mRNA was detected at the highest level in the retina, followed by the brain, placenta, and kidney. Among brain regions, relatively low levels for mRNA of the human D4 receptor were observed in the nigrostriatal pathway compared with the mesolimbic system. The distribution of the mRNA in human brain suggests that the D4 receptor plays a different role in the central nervous system compared with the D2 receptor.

Base Sequence↗

PubMed1994

Analysis of the D4 dopamine receptor gene variant in an Italian schizophrenia kindred.

BACKGROUND: Among the different dopamine receptors, the D4 dopamine receptor is of particular interest in schizophrenia because of its high affinity for the atypical neuroleptic clozapine. Recently, the gene for the D4 dopamine receptor has been cloned and a new and intriguing polymorphism has been described. Different versions of the receptor have varying affinity for clozapine, and thus variant froms of D4 with differing pharmacologic activity exist in the human population. Our hypothesis was that these variants play a role in susceptibility to psychotic illness. Thus, our objective was to test the D4 dopamine receptor genes for linkage to schizophrenia. METHODS: Our genetic linkage study was carried out in a large Italian kindred segregating schizophrenia. Diagnoses were made by using a structured clinical interview and a consensus diagnosis was established. For the computer analysis, 80 members of the family were constructed into a linked set of relatives with 15 of these individuals affected by schizophrenia. The functional variants of the D4 dopamine receptor gene were identified by a combination of Southern blot techniques and the polymerase chain reaction. The gene for tyrosine hydroxylase (TH) was also tested for linkage to schizophrenia in this family. Linkage analyses were done with both a single-locus and a two-locus model. RESULTS: Our results revealed significantly negative lod scores in the region of the D4 dopamine receptor gene and the TH gene. The application of different models of transmission for schizophrenia had an effect on the magnitude of the lod scores, but did not modify the direction of the results. CONCLUSIONS: Our results provide significant evidence for exclusion for linkage between schizophrenia and the dopamine D4 receptor gene and the TH gene under the models specified. Furthermore, we tabulated the distribution of D4 dopamine gene variants in the diseased vs healthy individuals in the family and the results showed that no specific form of the receptor gene is significantly associated with the presence of schizophrenia in the family. Our study does not exclude the possibility that regulatory elements of the D4 dopamine gene located elsewhere in the genome may be involved in the etiology of schizophrenia.

Blotting, Southern↗

PubMed1994

Characterization of the functional activity of dopamine ligands at human recombinant dopamine D4 receptors.

The human D4 dopamine receptor has been expressed in Sf9 insect cells where it appears to couple to endogenous G proteins. Increased guanine nucleotide exchange to G proteins is a reflection of receptor activation and can be followed using a [35S]GTP gamma S binding assay. By measuring D4 receptor stimulation of [35S]-GTP gamma S binding we have been able to characterize several dopaminergic compounds for their functional activity at this receptor. In Sf9 cells expressing the D4 receptor, dopamine, quinpirole, and dp-2-aminodihydroxy-1,2,3,4-tetrahydronaphthalene were all full agonists, whereas (-)-apomorphine appeared to be a partial agonist. No increase in [35S]GTP gamma S binding was observed for noninfected cells or cells infected with an unrelated sequence. The quinpirole-stimulated [35S]GTP gamma S binding could be inhibited by the antagonists clozapine, eticlopride, and haloperidol, and a Schild analysis of these data showed that all three compounds were acting as competitive antagonists of D4 receptors. The rank order of affinities derived from the Schild analysis correlated with that obtained from [3H]spiperone competition binding assays. In conclusion, we have shown that, using this assay system, it is possible to investigate functionally the pharmacology of a recombinant G protein-coupled receptor in the absence of any information regarding the eventual second messenger pathways involved.

Animals↗

PubMed2002

Dysfunctional light-evoked regulation of cAMP in photoreceptors and abnormal retinal adaptation in mice lacking dopamine D4 receptors.

Dopamine is a retinal neuromodulator that has been implicated in many aspects of retinal physiology. Photoreceptor cells express dopamine D4 receptors that regulate cAMP metabolism. To assess the effects of dopamine on photoreceptor physiology, we examined the morphology, electrophysiology, and regulation of cAMP metabolism in mice with targeted disruption of the dopamine D4 receptor gene. Photoreceptor morphology and outer segment disc shedding after light onset were normal in D4 knock-out (D4KO) mice. Quinpirole, a dopamine D2/D3/D4 receptor agonist, decreased cAMP synthesis in retinas of wild-type (WT) mice but not in retinas of D4KO mice. In WT retinas, the photoreceptors of which were functionally isolated by incubation in the presence of exogenous glutamate, light also suppressed cAMP synthesis. Despite the similar inhibition of cAMP synthesis, the effect of light is directly on the photoreceptors and independent of dopamine modulation, because it was unaffected by application of the D4 receptor antagonist l-745,870. Nevertheless, compared with WT retinas, basal cAMP formation was reduced in the photoreceptors of D4KO retinas, and light had no additional inhibitory effect. The results suggest that dopamine, via D4 receptors, normally modulates the cascade that couples light responses to adenylyl cyclase activity in photoreceptor cells, and the absence of this modulation results in dysfunction of the cascade. Dark-adapted electroretinogram (ERG) responses were normal in D4KO mice. However, ERG b-wave responses were greatly suppressed during both light adaptation and early stages of dark adaptation. Thus, the absence of D4 receptors affects adaptation, altering transmission of light responses from photoreceptors to inner retinal neurons. These findings indicate that dopamine D4 receptors normally play a major role in regulating photoreceptor cAMP metabolism and adaptive retinal responses to changing environmental illumination.

Adaptation, Ocular↗

PubMed1999

Short- and long-term heterologous sensitization of adenylate cyclase by D4 dopamine receptors.

The D4 dopamine receptor, a member of the D2-like dopamine receptor family, may be important in the etiology and treatment of schizophrenia. The present study was designed to examine the effects of dopamine agonist exposure on adenylate cyclase activity in HEK293 cells stably expressing recombinant-D4 receptors. Two hour pretreatment with dopamine receptor agonists resulted in heterologous sensitization of forskolin-stimulated cyclic AMP accumulation in intact cells expressing the D4.2, D4.4, or D4.7 dopamine receptor variant. The potency and efficacy of dopamine for sensitization of cyclic AMP accumulation was comparable at all D4 receptor variants. D4 dopamine receptor-mediated sensitization was blocked by the D4 antagonist, clozapine, and prevented by overnight pretreatment with pertussis toxin, implying a role for Gi/Go proteins in heterologous sensitization. Further, long-term (18 h) agonist exposure resulted in a greater degree of sensitization of forskolin-stimulated cyclic AMP accumulation in both intact cells and membrane preparations of cells expressing the D4 receptor, compared to 2 h agonist exposure, without altering the density of the receptors. In addition, long-term agonist exposure decreased the abundance of Gialpha without altering the abundance of Gsalpha, whereas short-term agonist treatment had no effect on the immunoreactivity of either G protein. In summary, long-term agonist-induced sensitization of adenylate cyclase by the D4 receptor may involve mechanisms that do not contribute to short-term sensitization.

Adenylyl Cyclases↗

PubMed1994

Pharmacology of a human dopamine D4 receptor expressed in HEK293 cells.

Dopamine receptors play an important role in neurotransmission within the central nervous system, as evidenced by their affinity to and apparent site of action of a variety of psychotropic agents. The cloning of dopamine receptor subtypes makes possible the discovery of subtype-selective agonist and antagonist compounds useful for the study of receptor physiology and for the development of more effective treatments for disturbances stemming from aberrant dopamine neurotransmission. We describe in this report the receptor pharmacology of a human D4-dopamine receptor expressed in HEK293 cells from a synthetic gene. The affinities of monoaminergic antagonists in competition with [3H]spiperone-labeled sites in these cells matched very closely their rank order potency measured by other investigators for D4 receptors expressed in COS-7 cells. Further, the sites expressed in the HEK293-D4-24 line met six specific pharmacological criteria by which the D4 subtype has been distinguished from other D2-like dopamine receptors. The site expressed in this cell investigators for D4 receptors expressed in COS-7 cells. Further, the sites expressed in the HEK293-D4-24 line met six specific pharmacological criteria by which the D4 subtype has been distinguished from other D2-like dopamine receptors. The site expressed in this cell line thus bears the earmarks of a human D4-dopamine receptor. Competition of several agonists best fit a two-site binding model. This result, along with the measured 10-fold GTP-shift for dopamine, strongly suggests functional coupling of this receptor to endogenous G-proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2005

PD-168077, a selective dopamine D4 receptor agonist, induces penile erection when injected into the paraventricular nucleus of male rats.

The effect of PD-168077 (N-methyl-4-(2-cyanophenyl)piperazynil-3-methylbenzamide maleate), a selective D4 dopamine receptor agonist, injected into the paraventricular nucleus of the hypothalamus on penile erection was studied in male rats. PD-168077 (1-200 ng) induced penile erection in a dose-dependent manner. The minimal effective dose was 50 ng, while the maximal response was found with 200 ng of the compound, which increased penile erection episodes from 0.3+/-0.03 to 1.7+/-0.21. The proerectile effect of PD-168077 was reduced almost completely by L-745,870 (3-(4-[chlorophenyl]piperazin-1-yl)-methyl-1H-pyrrolo[2,3-B]pyridine trihydrochloride), a selective D4 dopamine receptor antagonist, (1 microg) given into the paraventricular nucleus before the D4 dopamine agonist, and by other nonselective dopamine receptor antagonists, such as haloperidol (1 microg) and clozapine (1 microg), which block all dopamine receptor subtypes. The pro-erectile effect of PD-168077 was also reduced by the NO synthase inhibitor NG-nitro-L-arginine methylester (25 microg), but not by the oxytocin receptor antagonist d(CH2)5Tyr(Me)2-Orn8-vasotocin (1 microg), when given into the paraventricular nucleus. In spite of its inability to prevent the pro-erectile effect of PD-168077 when given in the paraventricular nucleus, d(CH2)5Tyr(Me)2-Orn8-vasotocin (1 microg) reduced almost completely PD-168077-induced penile erection when given into the lateral ventricles. The present results show that D4 dopamine receptors present in the paraventricular nucleus may influence penile erection by modulating the activity of paraventricular oxytocinergic neurons mediating erectile function.

Animals↗

PubMed1996

The naphtosultam derivative RP 62203 (fananserin) has high affinity for the dopamine D4 receptor.

The dopamine D4 receptor is a potential target for novel antipsychotic drugs. Most available compounds with affinity for the dopamine D4 receptor also bind to dopamine D2 receptors. This report describe the affinity of the 5-HT2A receptor antagonist RP 62203 (fananserin) for the human dopamine D4 receptor. Fananserin displaces [3H]spiperone binding to recombinant human dopamine D4 receptors with a Ki of 2.93 nM. This compares with an affinity (Ki) of 0.37 nM for the rat 5-HT2A receptor and of 726 mM for the rat dopamine D2 receptor. [3H]Fananserin can be used to label the recombinant dopamine D4 receptor expressed in Chinese hamster ovary cells with a KD of 0.725 nM. Fananserin is, thus, the first compound to be reported that distinguishes between dopamine D4 and D2 receptors.

Animals↗

PubMed2006

Influence of the antipsychotic drug pipamperone on the expression of the dopamine D4 receptor.

The dopamine D4 receptor is a G protein-coupled receptor that binds with high affinity various antipsychotics. The receptor may be involved in attention/cognition, and in genetic studies a polymorphic repeat sequence in its coding sequence has been associated with attention deficit/hyperactivity disorder. We developed an inducible episomal expression system based on the reverse tetracycline transactivator and Epstein-Barr viral sequences. In HEK293rtTA cells expressing the dopamine D4 receptor from this episomal expression vector, addition of doxycycline in combination with sodium butyrate and trichostatin A induces high levels of receptor expression, resulting in 1970 +/- 20 fmol/mg membrane protein. Addition of the dopamine D4 receptor and serotonin 5-HT2A receptor antagonist pipamperone to these cells further increased the expression of the dopamine receptor, reaching 3800 +/- 60 fmol/mg membrane protein. This up-regulation was not restricted to the dopamine D4 receptor but was also found for the serotonin 5-HT2A receptor. We further provide evidence that the increase in receptor expression is not due to increased mRNA synthesis. As pipamperone could rescue the expression of a folding mutant of the dopamine D4 receptor (M345), we propose that pipamperone acts as a pharmacological chaperone for correct receptor folding thereby resulting in an increased dopamine D4 receptor expression. This study describes a strong and inducible expression system for proteins, difficult to express in other heterologous expression systems. This study also demonstrates that pipamperone, an antipsychotic, acts as a pharmacological chaperone and by doing so, increases the expression level of the dopamine D4 receptor. The fact that ligands can also act as pharmacological chaperones is a fairly new additional element in the regulation of receptor expression levels with potential great impact in drug treatment.

Animals↗

PubMed1998

SH3 binding domains in the dopamine D4 receptor.

The dopamine D4 receptor is a G protein-coupled receptor (GPCR) that belongs to the dopamine D2-like receptor family. Functionally, the D2-like receptors are characterized by their ability to inhibit adenylyl cyclase. The dopamine D4 receptor as well as many other catecholaminergic receptors contain several putative SH3 binding domains. Most of these sites in the D4 receptor are located in a polymorphic repeat sequence and flanking sequences in the third intracellular loop. Here we demonstrate that this region of the D4 receptor can interact with a large variety of SH3 domains of different origin. The strongest interactions were seen with the SH2-SH3 adapter proteins Grb2 and Nck. The repeat sequence itself is not essential in this interaction. The data presented indicate that the different SH3 domains in the adapter proteins interact in a cooperative fashion with two distinct sites immediately upstream and downstream from the repeat sequence. Removal of all the putative SH3 binding domains in the third intracellular loop of the dopamine D4 receptor resulted in a receptor that could still bind spiperone and dopamine. Dopamine could not modulate the coupling of these mutant receptors to adenylyl cyclase and MAPK, although dopamine modulated receptor-G protein interaction appeared normal. The receptor deletion mutants show strong constitutive internalization that may account for the deficiency in functional activation of second messengers. The data indicates that the D4 receptor contains SH3 binding sites and that these sites fall within a region involved in the control of receptor internalization.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Dopamine D4 receptor gene polymorphism and personality traits in healthy volunteers.

An association between long alleles of a variable number tandem repeat (VNTR) polymorphism in the dopamine receptor D4 gene and the extraversion related personality traits Excitement and Novelty Seeking has been reported in healthy subjects. In an attempt to replicate the previous findings, 256 healthy Caucasian volunteers were analysed for a potential relationship between the dopamine receptor D4 exon III VNTR polymorphism and Extraversion as assessed by the Revised Neo Personality Inventory (NEO PI-R). The present study did not yield evidence for an association between Extraversion and the dopamine receptor D4 polymorphism.

Adult↗

PubMed1996

Identification and pharmacological characterization of [125I]L-750,667, a novel radioligand for the dopamine D4 receptor.

We identified a novel azaindole derivative, L-750,667, that has high affinity (Ki = 0.51 nM) and >2000-fold selectivity for D4 dopamine receptors compared with its activity at D2 and D3 dopamine receptors. L-750,667 had little affinity for rat D1/D5 dopamine receptors, sigma binding sites, or 5-hydroxytryptamine1A or 5-hydroxytryptamine2 receptors. In functional studies, L-750,667 exhibited high affinity antagonist activity at D4 receptors, reversing dopamine (1 microM)-induced inhibition of cAMP accumulation in human embryonic kidney (HEK) cells expressing the human D4 receptor (hD4 HEK) with an EC50 value of 80 nM. The radioiodinated form of L-750,667 bound specifically to the human dopamine D4 receptor expressed in HEK cells and saturation analysis revealed a single high affinity binding site for [125I]L-750,667 (Kd = 0.16 +/- 0.06 nM). The maximum number of binding sites (Bmax) estimated using [125I]L-750,667 in hD4 HEK cells was 251 +/- 71 fmol/mg, which correlated well with the Bmax value determined using [3H]spiperone (227 +/- 83 fmol/mg) in the same membrane preparations. The pharmacological profile of [125I]L-750,667 binding to hD4 HEK cells was evaluated using known dopamine receptor agonists and antagonists. The rank order of potencies for dopamine receptor agonists was dopamine > quinpirole > 6,7-aminodihydroxytetralin > 5,6-aminodihydroxytetralin. Dopamine receptor antagonists also showed high affinity, with a rank order of haloperidol > chlorpromazine > domperidone > (+)-butaclamol > (-)-sulpiride = (+)-sulpiride > (+)-SCH23390 > (-)-butaclamol. [125I]L-750,667, bound to D4 receptors in a stereoselective manner with (+)-butaclamol showing higher activity than its respective enantiomer (-)-butaclamol. These results show that [125I]L-750,667 is a novel, highly selective radioligand for dopamine D4 receptors and may be used to investigate the dopamine D4 receptor population in the central nervous system.

Animals↗

PubMed1998

Selective dopamine D4 receptor antagonists reverse apomorphine-induced blockade of prepulse inhibition.

Recent evidence suggests that the dopamine D4 receptor may play a role in schizophrenia, and that the atypical properties of the antipsychotic clozapine may be attributable in part to its antagonistic actions at this receptor. In the present study, clozapine and three other compounds having D4 dopamine receptor antagonist properties were examined for their effectiveness in reducing losses in prepulse inhibition (PPI) induced in rats by the dopamine receptor agonist apomorphine. Previously, activity in the PPI model has been shown to correlate highly with the antipsychotic potency of a number of neuroleptics. As previously reported, clozapine (1-5.6 mg/kg) significantly reduced apomorphine-induced PPI deficits. The three D4-selective compounds, CP-293,019 (5.6-17.8 mg/kg), U-101,387 (3-30 mg/kg) and L-745,870 (1-10 mg/kg), also significantly blocked the losses in PPI produced by apomorphine. Taken together, these results suggest that dopamine receptor antagonists with selectivity for the D4 dopamine receptor subtype may be effective in the treatment of schizophrenia, while being less likely to produce dyskinesias associated with D2 receptor antagonists.

Animals↗

PubMed1997

Cloning and characterization of the 5'-flanking region of the human dopamine D4 receptor gene.

Dopamine D4 receptor (DRD4) has received attention in terms of pathogenesis of schizophrenia and association with human personalities. We isolated the human DRD4 gene containing the 5'-flanking region and determined its sequence. Analysis of the DRD4 transcripts by 5'-RACE (5'-rapid amplification of cDNA ends) revealed a region of the transcription initiation located between -501 and -436 relative to the first nucleotide of the initiation codon. There is a CpG island spanning from -900 to +500 but no TATA or CAAT boxes in the 5'-flanking region. Functional analysis of the 5'-flanking region of the DRD4 gene by a transient expression method revealed the presence of a negative modulator between -770 and -679. The region between -591 and -123 gave the highest transcriptional activity in IMR32 (neuroblastoma) and Y-79 (retinoblastoma) cells but not in HeLa cells, suggesting that this housekeeping gene-like promoter regulates the cell-type specific gene expression.

Base Sequence↗

PubMed2001

5'-untranslated region of the dopamine D4 receptor gene and attention-deficit hyperactivity disorder.

Recently the molecular genetic basis of attention-deficit hyperactivity disorder (ADHD) has been the focus of a number of studies with the majority of these investigating the role of dopamine system genes. A great deal of attention has been focused on the possible involvement of the dopamine D4 receptor gene (DRD4) following a report of an association of ADHD with the allele containing seven copies of the 48-bp repeat in the third exon. In this paper we extended the search for the molecular explanation for the observed association by testing three polymorphisms in the region 5' to the dopamine receptor D4 gene transcription start site for linkage to ADHD. We specifically targeted polymorphisms in the region 5' to the start site of transcription as DNA variants in this region could alter the transcription level of the gene and hence the phenotype. We did not observe significant evidence for biased transmission of any of the alleles at these three polymorphisms to ADHD probands using the transmission disequilibrium test. We conclude that these three polymorphisms are not related to the ADHD phenotype.

5' Untranslated Regions↗

PubMedDate not supplied

Indian ethnic populations characterized by dopamine (D4) receptor VNTR polymorphism.

BACKGROUND: The human dopamine receptor D4 gene (DRD4) contains a 48-bp tandem repeat in exon 3 and shows alleles varying between repeats 2 and 11. The gene shows a high level of expression in the prefrontal cortex of the brain and association of particular alleles of this locus with various neuropsychiatric and personality disorders have been reported. OBJECTIVE: The present study reports allele frequency distribution at the DRD4 variable number tandem repeat (VNTR) locus among five ethnic populations of India. This background information is fundamental to the field of pharmacogenetics for disease susceptibility and association studies. SUBJECTS AND METHODS: Three hundred and thirty two healthy unrelated adult individuals belonging to five ethnic groups: Konkanastha Brahmins, Marathas, Ezhavas, Nairs and Muslims, have been typed. Genomic DNA, extracted from peripheral blood, was PCR amplified using a two-enzyme system. The use of ALF Express DNA sequencer was found to be helpful for large-scale population genotyping. Statistical analysis was performed using the POPGENE and DISPAN programs. RESULTS: A total of eight alleles ranging from repeat 2 to repeat 9 were observed. Allele 4 was the predominant allele among all the five populations, consistent with the data on other world populations. A rare allele 9 was detected exclusively among Marathas. The observed heterozygosity was low, ranging from 0.38 to 0.54 while other parameters like Polymorphism Information Content (PIC) and Power of Discrimination (PD) showed moderate values. The populations were in genetic equilibrium when tested under Hardy-Weinberg expectations. CONCLUSION: The allele frequency estimates for DRD4 provided here will contribute towards developing an informative database for this functionally relevant locus. This will prove useful when studying the association between genetic factors and pathogenesis of disease in Indian populations and will address the concern of biased results of association due to population admixtures.

Adult↗

PubMed1995

Lack of association between dopamine D4 receptor gene and schizophrenia.

An intriguing property of the dopamine D4 receptor gene is a hypervariable segment in the coding region characterized by a varying number of direct imperfect 48 bp repeats (2-8 or 10 repeats) in the third exon of the gene [Lichter et al., 1993: Hum Mol Genet 2:767-773]. The authors analyzed 70 unrelated schizophrenics and 70 normal controls to determine the allele and genotype frequencies created by length polymorphism of dopamine D4 receptor gene. All patients and controls were unrelated and from the Japanese population. Patients were divided into three groups with regard to age at onset, familial loading, and severity of symptoms assessed strictly with Manchester scale. There were no statistically significant differences if the distributions of alleles and genotypes were analyzed for schizophrenia as a whole or analyzed in consideration of those clinical subtypes. Lichter and colleagues [1993] have reported that at least 25 haplotypes exist for this polymorphic region of the dopamine receptor D4 gene. In this study only the alleles created by length polymorphism were analyzed, and further investigation to determine the haplotypes of patients and controls on using a much larger sample size will be required.

Adolescent↗