Lack of association between schizophrenia and alleles of the dopamine D1, D2, D3 and D4 receptor loci

The dopamine system is a preferred object of biological research in schizophrenia. The evolving delineation of distinct multiple human dopamine receptors and the increasing availability of polymorphic DN A probes from the receptor loci allows to test for the involvement of the dopamine receptor genes in the etiology of the disease. Sixty schizophrenic patients and 60 control subjects were examined for association of genetic polymorphisms at the Dl, D2, D3 and D4 dopamine receptor gene loci. No significant differences of genotype or allele frequencies could be found between patients and controls. Our findings do not support the hypothesis that a single mutant form of one of the dopamine receptor genes under study is commonly involved in the etiology of schizophrenia. In addition, no significant differences in the prevalence of a glycine to serine substitution at position 9 in the extracellular N-terminal part of the dopamine D3 receptor gene were observed between schizophrenics and controls. Therefore, this substitution can be regarded as a protein variation with no major effect on susceptibility to schizophrenia.