DRD2 Taq 1A allele is associated with pain response in Chinese male heroin-dependent subjects
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This study explored the association between candidate-gene variants and pain response in male Chinese heroin-dependent subjects (fulfilled DSM-IV criteria), divided into those who had abstained from heroin for one year or more after treatment (no-relapse group) and those who were on methadone or heroin for more than one year and had a history of relapse (relapse group). Healthy male subjects with no history of substance use were recruited as controls. The cold-pressor test was administered to all participants to ascertain pain threshold and tolerance. Subjects were genotyped for dopamine D2 (DRD2) Taq 1A, 孯pioid receptor A118G, and catechol-O-methyltransferase (COMT) val158met polymorphisms. The relapse group had the lowest pain tolerance, when compared with the no-relapse and control groups. There was no significant difference between A118G or COMT genotypes with pain response. However, across case-groups, individuals with at least one A1 allele (A1+) had a lower pain threshold and lower pain tolerance than those with no A1 allele (A1-). Heroin-dependent subjects (relapse group: 64%; no-relapse group: 58%) showed a significantly (p=0.003) higher A2 allele frequency than controls (51%). Relapse-group A1- individuals had a significantly (p<0.05) lower pain tolerance than no-relapse and control subjects. Relapse-group A1+ individuals had a significantly higher pain threshold than no-relapse and control A1+ subjects. Backward linear regression analysis of the three polymorphisms studied showed that only DRD2 A1 allele was a significant (p=0.014) predictor of pain threshold in the no-relapse group. In can be concluded that there is a difference in pain tolerance in heroin-dependent subjects related to relapse history. The DRD2 A1 allele may modulate the pain response in heroin dependence in a manner associated with relapse.
Drug and Alcohol Dependence