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American Association for the Advancement of Science

The nose's danger detector

Plants, fish, insects and mammals all emit chemical alarm signals to their fellow species members when they're in distress. These signals are molecules called "pheromones," and they're a real puzzle.

We know they exist, but scientists don't actually know what the pheromones are made of, or how animals produce them. But, thanks to a new study, they do know how mammals detect these signals when they're floating around in the air.

Julien Brechbühl and colleagues at the University of Lausanne have now discovered that a structure called the "Grueneberg ganglion" picks up alarm pheromones produced by other members of the same species.

The Grueneberg ganglion is a tight ball of round cells located near the tip of the nose. It was discovered back in 1973, but its purpose has been a mystery ever since.

In their study, Dr. Brechbühl and his colleagues compared how normal mice and mice lacking a Grueneberg ganglion responded to alarm pheromones.

The normal mice stopped exploring their cage and froze in a corner, but the other mice kept wandering around, seemingly unaware of the danger signals. Both groups were able to sniff out a cookie hidden in the bedding of their cage, however, which suggests that their olfactory system was otherwise working normally.

This research appears in the 22 August 2008 issue of the journal Science.