Veterinary/zoology session

Heroin dependence is a serious social and public health problem. It is influenced by multiple genetic and environmental factors. Although previous studies have shown that many genes could be risk factors for heroin dependence, these genes are expected to have a small impact individually. The dopaminergic pathway is a part of the brain reward system, so its neurotransmitter receptors are thought to be candidate genes of addiction. Our case-control study reports genotyping of 16 polymorphisms in 7 dopamine and serotonin related genes in 300 heroin dependent subjects and 500 sex-matched healthy Caucasian (Hungarian) individuals. The analyzed polymorphic sites include the coding region (exon 3 VNTR) and the 5’ upstream region (-521CT, -616CG, -615AG and 120 bp duplication) of the dopamine D4 receptor (DRD4) gene; the dopamine transporter (DAT) 3’ VNTR and intron 8 VNTR; the 5’ upstream region (5-HTTLPR) and the intron 2 polymorphisms (STin2) of the serotonin transporter (SERT); the 158AG SNP in the catechol-o-methyl transferase (COMT); the 5’ VNTR of the monoamino oxidase A (MAO-A); the K-variant and 1914 polymorphisms of the butyryl cholinestherase (BCHE) gene and the TaqIA, TaqIB and TaqID polymorphisms of the dopamine D2 receptor (DRD2). My study is mainly focused on these three Taq polymorphisms. The samples from the heroin-dependent patients were collected from the Nyírő Gyula Hospital, the National Institute of Psychiatry and Neurology and from the Dr. Farkasinszky Terézia Youth Drug Centre. The analysis of the DNA was made in Semmelweis University Institute of Medical Chemistry, Molecular Biology and Pathobiochemistry. Significant association was found between the DRD2 TaqIA, TaqIB and heroin dependence (p<0.05). Our results indicate that the genotypes and alleles of the DRD2 TaqIA and TaqIB polymorphisms contribute to the risk of heroin dependence in Hungarian individuals.