Scientists already know that a patient's racial or ethnic background can influence the effect of some drugs due to genetic differences. Now they've got a further subdivision: redheaded women.
Female redheads treated with one type of painkiller can stand more heat- or pressure-induced pain, a team at McGill University in Montreal has found. "Women with red hair respond better to the drug than anyone else," including redheaded men, says McGill pain researcher Jeffrey Mogil.
Previous studies have shownthat some painkillers work better in one sex. Kappa-opioids work better in women. In genetic and behavioral studies in mice, Mogil and colleagues found that differences in the analgesic effect of these drugs could be traced to one gene, Mc1r. Intriguingly, this recessive gene is best known for its role in pigmentation: a variant causes red hair and fair skin in people and yellow hair in mice. Mogil then tested 42 human subjects, 40% female and half of them redheaded. Subjects were tested for endurance to heat and pressure pain from a tightened arm tourniquet and given the kappa-opioid drug, pentazocine. Redheaded women showed a heightened analgesic response, suggesting that Mc1r is involved in the female-specific pain modulation pathway, the scientists report in the 24 March Proceedings of the National Academy of Sciences.
"The study demonstrates an unexpected role for the gene," says neuroscientist Maryann Ruda of the National Institutes of Health in Bethesda, Maryland. The work is a "tour de force," she adds, in forging a chain all the way from mouse genetics to human behavior.
