Pheromones identified that trigger aggression between...(om the vomeronasal organ are required fo...),Health

To study behavior, the researchers swabbed the backs of neutered male mice with the various pheromone candidates and placed them in a cage with a normal male mouse. Neutered males are useful for the study of aggression because they can neither emit nor detect the aggression pheromones. Whereas normal males will begin fighting as soon as they are placed together in a cage, neutered males remain docile around normal males, and vice versa. If a neutered male whose back has been swabbed with a pheromone candidate elicits hostility in a normal male, the researchers know that the pheromone candidate is responsible for the behavior.

Using a technique called calcium imaging, the team also studied whether pheromone candidates were able to directly activate sensory receptor neurons. Receptor neurons were removed from a mouse vomeronasal organ, spread out on a Petri dish, and labeled with a substance that changed color when the neuron was activated.

The researchers discovered that the protein family that comprises the major urinary protein (MUP) complex in mouse urine is one of two pheromones that can elicit the aggression response in male mice. They also found that the MUP protein is recognized exclusively in the vomeronasal organ, not in the main olfactory epithelium, and activates a specific type of sensory receptor neuron. A second pheromone was also found to elicit an aggression response in male mice, however further study needs to be done regarding its make-up and activity.

"There are about 20 members of the MUP family, and each mouse expresses four to six of the members randomly," explains senior investigator Lisa Stowers, Ph.D. "This creates a bar code of individuality for each mouse. And we don't know whether the proteins are actually coding for aggression per se, or whether they're serving as a general cue of individuality for a male."

If the lat
'/>"/>