Are single nucleotide polymorphisms in the oxytocin and vasopressin 1A/1B receptor genes likely candidates for variation in ejaculatory function?

OBJECTIVES To investigate associations between single nucleotide polymorphisms (SNPs) linked to the oxytocin, and arginine vasopressin 1A and 1B receptor genes and ejaculatory function. To investigate these associations in a large, population-based sample. PATIENTS AND METHODS In all, 1517 male twins and non-twin brothers of twins aged 18-45 years (mean = 26.43; SD = 4.87) provided questionnaire data regarding ejaculatory function and relevant covariates and saliva samples for genotyping. A Bayesian linear mixed-effects model, which appropriately controls for between subjects dependence, was used to estimate genotype associations. We corrected for multiple testing using a linkage disequilibrium correlation measure. RESULTS We found a heterozygote effect on one SNP in the oxytocin receptor gene (rs75775), so that individuals heterozygous for this SNP had significantly elevated risk for premature ejaculation symptoms compared with carriers of either homozygote. Several SNPs in the arginine vasopressin receptor genes had rare or very rare genotypes. This study may be underpowered to detect potential effects of rare genotypic variants in arginine vasopressin receptor genes. CONCLUSIONS Our results regarding the oxytocin receptor polymorphisms support previous studies that indicate a complex relationship between oxytocin and ejaculatory function. Oxytocin receptor genes are, for example, unlikely suitable targets for pharmacogenetic intervention studies. Rare variants in arginine vasopressin receptor genes may have significant effects on premature ejaculation, but would need larger sample sizes or case-control designs to be detected.