Identification of QTLs for differential capsaicin sensitivity between mouse strains KJR and C57BL/6.

Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is the main compound of hot chili peppers that causes both a pungent sensation and physiological pain. Capsaicin activates vanilloid receptor 1, a multi-functional receptor for pain sensation. In our previous report, it was found that sensitivity for capsaicin varies among mouse strains. In the present study, we conducted a quantitative trait loci (QTL) analysis to characterize the genetic loci involved in the different sensitivities to capsaicin between C57BL/6 and KJR mouse strains. In the study, we generated F2 progeny from the intercross of F1 mice obtained from a cross of C57BL/6 and KJR. We applied a fluid intake test of a capsaicin solution to the F2 progeny and conducted a QTL analysis. In this mapping study, four QTLs for capsaicin sensitivity were detected. Each of these loci contributed to 18.7-27.87% of strain difference of capsaicin consumption between C57BL/6 and KJR at each concentration. Because the sensation for capsaicin is associated with perception of pain, this genetic study on different capsaicin sensitivities will help future analyses of endogenous analgesic pathway.