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

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Abstract
The dopaminergic system has been implicated in alcoholism, but most of the past investigations concentrated on the dopamine D2 receptor (DRD2), with conflicting results. The dopamine D4 receptor gene (DRD4) is in the same class as DRD2, but 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 determine the allele distribution of this polymorphism 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 are compared. A group of 136 male alcoholics, classified according to DSM-III-R criteria for alcohol dependence, was also ascertained. The results of the association study were negative for comparisons between white and black alcoholics and controls, and no association was disclosed when either subtypes of alcoholics and different aspects of this condition were considered. These results, together with those available in the literature for other ethnic groups, suggest a minor role, if any, of the DRD4 gene in the susceptibility to alcoholism.