Effects of COMTval158met and OPRM1A118G genetic polymorphism on preoperative pain sensitivity

Objective To evaluate the effects of COMTval158met and OPRM1A118G genetic polymorphism on preoperative pain sensitivity in patients.Methods ASA physical status Ⅰ or Ⅱ patients of both sexes,with no history of surgery,aged 20-50 yr,with the body mass index within the normal range,scheduled for elective gynecological or general surgery,were enrolled in the study.Blood samples were taken from the peripheral vein for DNA extraction and COMTval158met and OPRM1A118G genotyping using phenol chloroform extracting method and polymerase chain reaction-restriction fragment length polymorphism,respectively.The patients were divided into 9 groups according to combination of their genotypes:group val/val and A/A (group A1B1),group val/met and A/ A (group A2B1),group met/met and A/A (group A3B1),group val/val and A/G (group A1B2),group val/ met and A/G (group A2B2),group met/met and A/G (group A3B2),group val/val and G/G (group A1B3),group val/met and G/G (group A2B3) and group met/met and G/G (group A3B3).The pain threshold and pain tolerance threshold were measured three times using electrical stimulation after admission to the operating room and the average was calculated.Results Two hundred and seventy-seven subjects were genotyped successfully.There were 68 A1B1,50 A2B1,17A3B1,43 A1B2,46 A2B2,17 A3B2,18 A1B3,10 A2B3 and 8 A3B3.There was no significant difference in the general data of patients among the nine groups (P ＞ 0.05).The OPRM1A118G and COMTval158met allele frequency in Chinese was 0.321 and 0.343,respectively.Compared with group A1B1,the pain threshold was significantly decreased in A2B3 and A3B3 groups,and the pain tolerance threshold was decreased in A1B1,A2B3 and A3B3 groups (P ＜ 0.05).Conclusion There is interaction between COMTval158met and OPRM1A118G genetic polymorphism in their effects on preoperative pain sensitivity and preoperative pain sensitivity is higher in the patients who carry mutation homozygote met158met and 118G. Key words: Pain measurement;  Catechol O-methyltransferase;  Receptors, opioid, mu;  Polymorphism, single nucleotide;  Preoperative care