Polymorphism of serotonin transporter gene (SLC6A4) and its relation to tramadol dependence

Abstract

Background Many genes have been proven to be linked to substance use disorder, on top were serotonin receptor and transporter genes. Aim The aim of this study was to determine the frequency of 5-HTTVNTR allele variants of the serotonin transporter gene and the presence of polymorphic serotonin receptor gene (5-HTR1A) in tramadol-dependent patients in comparison with controls and to explore the association between the groups of tramadol dependent with and without psychiatric comorbidity and 5-HTTVNTR allele variants. Patients and methods This was a cross-sectional case–control outpatient study. The study sample consisted of 90 patients, with 60 tramadol dependents (55 males and five females) and 30 healthy controls. All patients fulfilled the Diagnostic and Statistical Manual of Mental Disorders, 4th ed., Criteria for substance dependence (on tramadol). Genotyping of the 5-HTTVNTR gene and 5-HT1A receptor gene promoter was done employing real-time PCR and PCR/RFLP, respectively. Results A significant association was found between the 5-HTT gene 10 allele polymorphism and tramadol dependence. No significant association was observed with the 5-HT receptor gene polymorphism. Conclusion This study detected an association between the presence of 5-HTTVNTR less transcriptional-efficient genotypes and tramadol dependence, and these genotypes increase psychiatric comorbidity with tramadol dependence, which suggests that the modulation of the serotoninergic system might be implied in psychiatric problems in tramadol dependence.