The mammalian nose contains a specialized sensor that detects chemical alarm signals emitted by fellow animals, Swiss researchers report in the Aug. 21 issue of Science. The so-called "Grueneberg ganglion" is a tight ball of round cells located near the tip of the nose. It was discovered in 1973, but its function has been a matter of controversy ever since. Julien Brechbühl and colleagues show that the Grueneberg ganglion picks up alarm pheromones produced by other members of the same species when they're in distress. Organisms including plants, fish, insects and mammals are known to emit these pheromones, but it's been unclear exactly what the compounds are, how they're produced and how they're detected. Alarm pheromones are extremely volatile and can be captured by collecting the air around the stressed animal. The researchers compared how normal mice and mice lacking a Grueneberg ganglion responded to alarm pheromones secreted by other mice. Whereas normal mice stopped exploring their cage and froze in a corner, 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, indicating that their olfactory system was otherwise working normally. The authors also used electron microscopy to study the morphology of this ganglion, and they determined that these neurons have similar features to other olfactory neurons.
ARTICLE #18: "Grueneberg Ganglion Cells Mediate Alarm Pheromone Detection in Mice," by J. Brechbühl; M. Klaey; M-C. Broillet at University of Lausanne in Lausanne, Switzerland.