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

Nasir, Mohamad and Zalina, Zahari and Siong, Lee Chee (2016) 118A>G and IVS2+691G>C polymorphisms of OPRM1 gene have no influence on cold-pain sensitivity among healthy opioid-naive malay males. International Journal of Pharmacy and Pharmaceutical Sciences, 8 (7). pp. 73-80. ISSN 09751491 [P]

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Abstract

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.

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