Effects of the dopamine D3 receptor (DRD3) gene polymorphisms on risperidone response: a pharmacogenetic study

Previous observations of the anatomical distribution and pharmacological profile of the dopamine D(3) receptor (DRD3) have indicated its potential role in antipsychotic drug action. Risperidone, an effective first-line atypical antipsychotic agent, exhibits a relatively high affinity for this receptor. Recent studies have reported an association of the Ser9Gly polymorphism in the DRD3 gene with therapeutic response to risperidone, but the results were inconsistent. We therefore postulated that the Ser9Gly polymorphism might be in linkage disequilibrium with an undetected variant that exerts a direct influence on risperidone efficacy. The present study genotyped eight single nucleotide polymorphisms (SNPs) distributed throughout the DRD3 gene and examined five of these for association with treatment outcome, following an 8-week period of risperidone monotherapy in 130 schizophrenic patients from mainland China. Clinical symptoms were assessed before and after the treatment period, using the Brief Psychiatry Rating Scale (BPRS). The confounding effects of non-genetic factors were estimated and the baseline symptom score was included as a covariate for adjustment. Neither was any association observed between the five polymorphisms and improvement in total BPRS scores nor was any combined effect of these variants detected in the haplotype analysis. The current results indicate that genetic variations within the DRD3 gene may not contribute significantly to interindividual differences in the therapeutic efficacy of risperidone.