Alarm signal: Cells of the 'Grueneberg ganglion' (pictured) pick up alarm pheromones produced by other members of the same species when they’re in distress.
Credit: Science/AAAS
GENEVA: A new study proves that mammals can communicate danger to each other through smell, and reveals exactly how they do it.
Scientists at the University of Lausanne, in Switzerland, found that when mice are placed in an environment where there is a beaker of water containing alarm pheromones emitted by other mice, they immediately sniff out the danger and move away from the beaker.
Maybe humans too
The mice's keen reaction has been attributed to the 300 to 500 cells found at the entrance of their noses, called the Grueneberg ganglion. This ganglion is present also in human beings, according to the scientist Hans Grueneberg who discovered it in 1973.
The Swiss authors of the new study, led by Julien Brechbühl, speculate that "one can imagine that humans have a similar method" of communicating danger to each other. Their findings are detailed today in the U.S. journal Science.
Cells in the Grueneberg ganglion use their own calcium to transmit the danger warning to the brain, they said.
When researchers exposed a mouse to other types of pheromones, smells and even mothers' milk, they did not witness any increase in the concentration of the intra-cellular calcium in the ganglion, suggesting that these substances failed to trigger the cells into action. Only warning pheromones could trigger the warning signal.
Fight or flight response
In another experiment, scientists removed a Grueneberg ganglion from a mouse to see how it reacted without this ganglion. The mouse was found to be able to detect other smells, such as a hidden biscuit, but it failed to react to a warning or alarm pheromone.
The detection of these alert signals spark "specific behaviours" – such as fleeing from danger or predators, said co-author Marie-Christine Broillet. Other species are known to deploy a similar system. Insects of the same species, for instance, send molecular signals to communicate danger to others.
