We have studied polymorphism of the dopamine receptor gene DRD2 and of the dopamine transporter gene DAT1 in Russians and in Tatars, according to age of onset of opiate use: 16 years old and younger (early onset) and over 16 years old (late onset), and to duration of narcoti­zation experience, 4 years and less and more than 4 years. We established that genotype N2/N2 (NcoI) of DRD2 is a marker of resistance to opiate addiction in patients, while the genotype N1/N1 (NcoI) of DRD2 is a marker of risk to opiate addiction in patients. The allele N1 (NcoI) of DRD2 associates with early onset of narcotic use in Russians. Association of allele N1 (NcoI) of DRD2 with opiate addiction was determined in Tatars in all investigated groups and with late onset. Our results on the TaqI A polymorphism of DRD2 indicate no association with opiate addiction either in Russians or in Tatars.

      Key words: dopamine receptor gene (DRD2), dopamine transporter gene (DAT1), genetic polymorphism, opiate drug addiction