Volume 28, Issue 7 (10-2021)                   RJMS 2021, 28(7): 75-82 | Back to browse issues page

Research code: مقاله حاصل ازپایان نامه است
Ethics code: IR.Arakmu.1397.75
Clinical trials code: این مطالعه کارآزمایی بالینی نمی باشد

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Nomoradi H, Mohajerani H R. Evaluation of the relative frequency of alleles associated with drug addiction and violent behavior in dopamine neurotransmission genes among addicts with a history of violent crime. RJMS 2021; 28 (7) :75-82
URL: http://rjms.iums.ac.ir/article-1-6525-en.html
department of biology ,Arak branch, Islamic Azad University ,Arak, Iran , hr-mohajerani@iau-arak.ac.ir
Abstract:   (1668 Views)
Criminal delinquency includes disruption of family relationships, substance use disorders, failure in educational and professional fields, and constant participation in violent criminal acts, which results in resentment of the victims of these criminal acts, as well as their families and relatives in the community. Clinically, relying on medical findings can deepen human understanding of the causes of these crimes and prevent them. Mental danger from the perspective of psychopathology has a very long history (1).
In connection with violent crime, four types of neurotransmitters have been studied more than others: serotonin, norepinephrine, epinephrine, dopamine (monoamines), genes involved in dopaminergic neurotransmissions, such as dopamine. And dopamine-2 receptor carriers are candidate genes to justify the causes of antisocial behaviors. Polymorphism in dopaminergic genes has been linked to psychiatric and developmental disorders such as ADHD and autism. Also, dopaminergic antagonist drugs are used to control aggressive human behavior (4).
To examine the genetic aspects of a crime, the technique of determining the genetic structure is a process in which differences in a person's genetic makeup are determined by examining a person's DNA sequence by comparing it to another personal sequence or a reference sequence. The relative frequency of alleles associated with drug addiction and violent behavior in dopamine neurotransmission genes has been studied among addicts with a history of violent crime (5).
Materials and methods:
 In this study, by available sampling method, 50 people were selected from among the thieves of violent behaviors, including bags and mobile phones, and participants in street fights who had a history of at least one of these crimes. None of the participants had a history of schizophrenia and/or antisocial personality disorder, aggression, child trauma, child abuse, or various types of abuse (based on diagnostic criteria (DSM-IV TR). The scope and method of study for all participants Were given and informed oral and written consent was obtained from them.Intravenous blood samples were taken from the study participants. DNA was extracted from venous blood using a DNA extraction kit (Sinagen, Iran) according to the prepared protocol. The DNA concentration of the obtained sample was between 15 and 200 ng / μl. The isolated DNA of the samples was kept at 20 ° C until the time of analysis. All laboratory steps were performed in double-blind. Using appropriate primers of 40 bp VNTR polymorphism related to the DAT-1 gene, as described by Vandenberg et al., Was genotyped (5). Polymorphisms of all individuals for TaqI A marker in dopamine D2 receptor were genotyped according to the method used by Qadir, which was examined by RFLP analysis. The frequency of alleles and genotypes was shown as numbers (percent) which were determined by direct counting.
In the present study, the frequency ratio of different alleles of the studied genes has been investigated. DAT-1 40 bp VNTR polymorphisms include R9, R 10, R99 R /, 10R / 10R.
The results show the highest frequency for the 10R allele (72%). The next order was 9 R (30%) and the lowest relative frequency with a large difference belonged to 10R / 10R (4%).
Therefore, the pattern of relative abundance of alleles in the studied samples was as follows: 10R> 9R> 9R / 9R> 10R / 9R> 10R / 10R.
The other gene understudy was DRD2 TaqI A (SNP). The results show the highest frequency for the A2 allele (66%), followed by A2 / A2 and finally A1 / A1 with the lowest relative frequency (6%). The alleles in the studied samples were as follows:
A2> A2 / A2> A1> A2 / A1> A1 / A1.
Discussion and conclusion:
DAT-1 40 bp VNTR has been suggested as a gene responsible for various psychiatric disorders. Previous studies have shown that gene polymorphism (VNTR) is associated with aggressive and antisocial behavior that is consistent with the results of this study.
 Yang et al. Found the 9R allele of the DAT-1 polymorphism as a significant risk factor for extroverted behavior in a sample size of young children. Similarly, the 9R minor allele of the DAT-1 VNTR as a risk allele is involved in cocaine poisoning and alcohol dependence (7) .
In contrast, other studies have reported an association between ADHD and violent delinquency and the prevalence of the 10R DAT-1 VNTR allele. A similar study did not show a role for the same DAT-1 VNTR in the extraversion of behavior and communication problems in a general population. Due to the existence of multiple control groups in previous studies that have a reference sentence (as a group that has not committed a crime of violence) and due to the limitations of this study, if we compare the many ratios in the samples of this study with control groups of previous studies, it will become clear that a similar pattern, In other words, the order of the frequency ratios of alleles in violent and addicted criminals is different from that of normal individuals (10).
 The dopamine D2 receptor, encoded by the DRD2 gene, is a receptor coupled to the presynaptic as well as postsynaptic G protein located in dopaminergic neurons. In the population of East Uttar Pradesh, India, the frequency of the A2 allele was higher than the A1 allele, which is not consistent with the results of the present study. Some heterogeneity between study results and biases may be due to differences in the race population. The results of a meta-analysis study showed that the frequency of A1 minor alleles related to Taq1A polymorphism varied significantly in different populations. In European control subjects, the frequency of the A1 allele was about 19% (6% - 44%). It was significantly lower than the equivalent in Asian control subjects (about 38%).) Also, European and Asian alcoholics both had high doses above the A1 allele (12).
Showed that it is consistent with the results of this study which indicate the high frequency of A2 allele in drug addicts and perpetrators of violent crimes. In vivo and in vitro tests have shown that DRD2 is a gene predisposing to alcohol consumption. Dopamine receptor (DRD2) D2 gene variability is strongly associated with opioid addiction. DRD2 polymorphisms, located in intron 2 (TaqI B), are significantly associated with multidrug addiction, but so far the relative abundance of alleles of this gene in addicted individuals Drugs (treated with methadone) have not been studied. Therefore, it was not possible to compare the results of the present study with similar studies in this field (13).
As a result, the pattern of the superiority of the A2 allele over the other alleles in the present study does not necessarily mean that it is consistent or inconsistent with the findings of other studies, but it can also show the importance of this gene in its indirect effect on drug addiction or committing violent crimes (14).
Conclusion: Although the relative frequency pattern of alleles of genes responsible for dopamine receptor transport in the present study is very similar to the gene pattern of individuals with mental disorders leading to violent behaviors associated with violence, a causal relationship between the frequency of specific alleles cannot be deduced.
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Type of Study: Research | Subject: Clinical Psychiatry

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