Lack of association of the dopamine D4 receptor gene polymorphism with alcoholism in a Brazilian population

The dopaminergic system has been implicated in alcoholism, but most of the past investigations concentrated on the dopamine D2 receptor (DRD2), with c onflicting results. The dopamine D4 receptor gen (DRD4) is in the same clas s as DRD2, bur presents different pharmacological properties. This gene has an expressed highly variable 48 base pair (bp) tandem repeat polymorphism (VNTR), which could be of functional relevance. We screened 100 Caucasians and 100 Afro-Brazilians to determines the allele distribution of this polym orphism in a southern Brazilian population. The allele frequencies observed are significantly, different from those described in the literature except when Afro-Brazilians and African Bantus ale compared. A group of 136 male alcoholics, classified according to DSM-III-R criteria for alcohol dependen ce, was also ascertained. The results of the association study were negativ e for comparisons between white and black alcoholics and controls, and no a ssociation was disclosed wizen either subtypes of alcoholics and different aspects of this condition were considered. These results, together with tho se available in the literature for other ethnic groups, suggest a minor rol e, if any of the DRD4 gene in the susceptibility to alcoholism.