Lack of association between schizophrenia and alleles in the dopamine D3 receptor gene

Dopamine receptor dysfunction has been implicated in the pathophysiology of schizophrenia. Schizophrenic patients (n = 76) and control subjects (n = 53) were examined for allele frequencies in a 2-allele BalI polymorphism, causing a serine-->glycine amino acid substitution in the coding sequence of the dopamine D3 receptor gene. No statistical significant differences of allele frequencies or genotype frequencies could be found between the two groups. Neither were there any significant relationships between allele frequencies and a number of clinical variables within the schizophrenic subsample. However, if not corrected for multiple testing, an association was found between homozygosity and positive response to neuroleptic drugs. The present study does not provide evidence that the BalI polymorphism in the dopamine D3 receptor gene is involved in the pathophysiology of schizophrenia. Further investigations with an increased number and variety of patients concerning response to neuroleptic drugs and expression of the receptor in human brain should be performed to definitively exclude this hypothesis.