118A>G and IVS2+691G>C polymorphisms of OPRM1 gene have no influence on cold-pain sensitivity among healthy opioid-naive malay males

• Main Authors: Zahari, Z., Siong, L.C., Yeh, L.Y., Ibrahim, M.A., Musa, N., Mohd Yasin, M.A., Choon, T.S., Mohamad, N., Ismail, R.
• Format: Article
• Published: Innovare Academics Sciences Pvt. Ltd 2016
• Subjects: R Medicine
• Online Access: http://eprints.um.edu.my/18723/
• Institution: Universiti Malaya

Objective: Common polymorphisms of the mu-type opioid receptor (OPRM1) including 118A > G and IVS2+691G > C may affect experimental pain responses in healthy subjects, and the effect could be ethnic-dependent. The aim of this study was to investigate the influence of these OPRM1 polymorphisms on cold-pressor pain responses among healthy opioid-naive Malay males. Methods: Pain-threshold, pain-tolerance, and pain-intensity in response to the cold pressor test (CPT) were measured in healthy opioid-naive Malay males. DNA was extracted from the collected venous blood before PCR-genotyping. Repeated measure analysis of variance (RM-ANOVA) was used to compare CPT responses and OPRM1 polymorphisms (118A>G and IVS2+691G>C) according to their genotypes and allelic additive models, genotype dominant and recessive models, haplotypes, and diplotypes. Results: A total of 152 participants were recruited. Both 118A>G and IVS2+691G>C polymorphisms were not associated with cold-pressor pain-threshold, pain-tolerance and pain-intensity despite using genotypes and allelic additive models and genotype dominant and recessive models (all p>0.05). Likewise, there were no significant associations between haplotypes and diplotypes for the 118A>G and IVS2+691G>C polymorphisms and the three cold-pain responses (all p>0.05). Conclusion: The common OPRM1 polymorphisms (i.e., 118A>G and IVS2+691G>C), are not associated with cold-pressor pain responses in healthy opioid-naive Malay males. However, this may be unique for this particular ethnicity. Other polymorphisms may be more relevant for this population, and this should be further investigated.