Many animals broadcast important messages--sexual receptivity springs to mind--via chemicals called pheromones. There's been a fierce debate over whether humans do too. Now researchers have discovered what looks to be a pheromone receptor in the human nose, adding to the evidence that people can sniff out steamy messages.
Pheromones spice up animal romance by providing an aphrodisiac. A male salamander, for instance, can smear a daub of pheromones onto a potential mate's nose, making her more receptive to his advances. The overture is picked up--in most amphibians, reptiles, and mammals other than primates--by a chemical detector system called the vomeronasal organ. Located deep inside the nose, the vomeronasal organ shelters specialized receptors that provide a direct line to the brain.
Evidence for humans tuning into pheromones has been mixed. During prenatal development, about a third of humans have a structure like the vomeronasal organ. But this is probably a holdover from some more sensitively nosed ancestor. It's ephemeral; after birth, it fails to develop into a functioning organ. Some mammals, however, including rabbits and pigs, detect pheromones through their main olfactory system, so the lack of a vomeronasal organ doesn't necessarily mean that humans are immune to a little chemistry.
Now a possible human pheromone receptor has come to light. It turned up incidentally during a search for genes that code for human scent receptors. Neurobiologist Peter Mombaerts of The Rockefeller University in New York and his team combed the human genome for sequences similar to that of a gene for a rodent pheromone receptor. Seven close matches turned out to be nonfunctional, but the eighth looked like it could be turned on to produce a receptor. Indeed, when the researchers tested olfactory tissue from the human nose, they found the receptor, they report in the September issue of Nature Genetics.
Wishful thinking aside, there's no guarantee that the new receptor actually detects pheromones. "I would have reservations about it simply because it is a single gene," says molecular biologist Nicholas Ryba of the National Institute of Dental and Craniofacial Research in Bethesda, Maryland. But the receptor is expressed in the nose, he notes, and that makes him feel "a lot more positive" about its pheromone-sensing potential.
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Diagrams of and
information about the vomeronasal organ
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