Variations in the gene encoding catechol-O-methyltransferase (COMT) are linked to individual differences in pain sensitivity. A single nucleotide polymorphism (SNP) in codon 158 (val158met), which affects COMT protein stability, has been associated with the human experience of pain. We recently demonstrated that three common COMT haplotypes, which affect the efficiency of COMT translation, are strongly associated with a global measure of pain sensitivity derived from individuals’ responses to noxious thermal, ischemic, and pressure stimuli. Specific haplotypes were associated with low (LPS), average (APS), or high (HPS) pain sensitivity. Although these haplotypes included the val158met SNP, a significant association with val158met variants was not observed. In the present study, we examined the association between COMT genotype and specific pain-evoking stimuli. Threshold and tolerance to thermal, ischemic, and mechanical stimuli, as well as temporal summation to heat pain, were determined. LPS/LPS homozygotes had the least, APS/APS homozygotes had average, and APS/HPS heterozygotes had the greatest pain responsiveness. Associations were strongest for measures of thermal pain. However, the rate of temporal summation of heat pain did not differ between haplotype combinations. In contrast, the val158met genotype was associated with the rate of temporal summation of heat pain, but not with the other pain measures. This suggests that the val158met SNP plays a primary role in variation in temporal summation of pain, but that other SNPs of the COMT haplotype exert a greater influence on resting nociceptive sensitivity. Here, we propose a mechanism whereby these two genetic polymorphisms differentially affect pain perception.
aCenter for Neurosensory Disorders, University of North Carolina at Chapel Hill, NC, USA
bAustralian Researcher Center for Population Oral Health, Dental School, University of Adelaide, Australia
cDepartment of Oral Medicine, Chulalongkorn University, Bangkok, Thailand
dNIDCR, NIH, DHHS, Bethesda, MD, USA
eNIAAA, NIH, DHHS, Rockville, MD, USA
fDepartment of Pharmacology, University of North Carolina at Chapel Hill, NC, USA
*Corresponding author. Tel.: +1 919 966 3756; fax: +1 919 966 3683.
Submitted September 19, 2005; revised April 12, 2006; accepted May 8, 2006.