Polymorphisms in the GTP cyclohydrolase gene (GCH1) are associated with ratings of capsaicin pain

Though it is clear that genomic variability plays an integral role in accounting for pain sensitivity, controversy exists over which genes are involved. While recent data suggest a "protective" (i.e., less pain) haplotype in the GTP cyclohydrolase (GCH1) gene, other research has failed to confirm this association. Possibly, the effects of single nucleotide polymorphisms (SNPs) vary depending on the pain task. The current investigation analyzed the association of five previously identified GCH1 SNPs with ratings of pain induced by topical high concentration (10%) capsaicin applied to the skin of 39 healthy human volunteers. Each of the GCH1 polymorphisms was associated with lower pain ratings. When combined, three of the five accounted for a surprisingly high 35% of the inter-individual variance in pain ratings. We conclude that SNPs of the GCH1 gene may profoundly affect the ratings of pain induced by capsaicin. (C) 2008 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.